Systems and methods for a split exhaust combustion engine system

Abstract

Method for an engine, comprising: in response to a request to switch off the internal combustion engine (10): Closing an intake throttle (62) and opening a first valve (32) arranged in a secondary flow passage (30) coupled between an intake manifold (44) downstream of the intake throttle (62) and a first exhaust manifold (80) coupled to a first set of exhaust valves (6) to direct unburned hydrocarbons to a catalyst (72) arranged in an exhaust passage (74) coupled to a second set of exhaust valves (8).

Description

Area

[0001] The present description generally relates to methods and systems for a split exhaust gas internal combustion engine incorporating exhaust gas recirculation. General state of the art / brief description

[0002] Internal combustion engines can utilize boosting devices, such as turbochargers, to increase engine power density. However, engine knock can occur due to elevated combustion temperatures. Knock is particularly problematic under conditions exacerbated by high charge temperatures.

[0003] An exemplary internal combustion engine with exhaust gas recirculation comprising an engine with a plurality of cylinders and an exhaust gas turbocharger is known from document DE 100 84 733 T5. Specifically, it is disclosed that each cylinder has at least two exhaust valves and at least one intake valve, such that each cylinder is connected via a first exhaust valve to a first exhaust manifold and thus to the inlet of the turbine of a turbocharger, and via a second exhaust valve to a second exhaust manifold, which is coupled to the exhaust system of the engine downstream of the turbine.

[0004] Furthermore, DE 102015 116 999 A1 discloses an engine system with a first and a second cylinder group, a turbine coupled to an exhaust duct, and an EGR duct that conducts exhaust gas only from the first cylinder group, the dedicated EGR cylinder group, to an engine intake, which in turn supplies air charge to each of the first and second cylinder groups. It is known from DE 10 2016 101 104 A1 that a throttle valve is closed upon a shutdown request of an internal combustion engine in order to mitigate shutdown vibration.

[0005] The inventors of the present invention have recognized that using an internal combustion engine system with a split exhaust system, wherein a first exhaust manifold directs exhaust gas recirculation (EGR) to an engine inlet upstream of a turbocharger compressor and wherein a second exhaust manifold directs exhaust gas to a turbocharger turbine at an engine outlet, can reduce knock and increase engine efficiency. In such an internal combustion engine system, each cylinder may include two intake valves and two exhaust valves, wherein a first set of cylinder exhaust valves (e.g., scavenge exhaust valves) coupled exclusively to the first exhaust manifold may be operated at a different time than a second set of cylinder exhaust valves (e.g., blowdown exhaust valves) coupled exclusively to the second exhaust manifold, thereby isolating a scavenging portion and a blowdown portion of exhaust gases.The timing of the first set of cylinder exhaust valves may also be coordinated with a timing of the cylinder intake valves to create a positive valve overlap period where fresh intake air (or a mixture of fresh intake air and EGR), also referred to as blowby, can flow through the cylinders and back to the intake upstream of the compressor via an EGR passage coupled to the first exhaust manifold. Blowby air can remove residual exhaust gases from within the cylinders (also referred to as scavenging). The inventors of the present invention have recognized that combustion temperatures can be increased by flowing a first portion of the exhaust gas (e.g., higher pressure exhaust) through the turbine and a higher pressure exhaust passage and by flowing a second portion of the exhaust gas (e.g.,lower pressure exhaust gas) and blow-by air to the compressor inlet can be reduced, while improving turbine working efficiency and engine torque.

[0006] However, the inventors here have recognized potential problems with such systems. For example, when the engine is shut down (either during a key-off event or as an engine start / stop event), hydrocarbons may result from unburned gases, and reversal of the engine's rotation may occur (leading to engine shaking).

[0007] In one example, the problems described above may be addressed by a method for an internal combustion engine, comprising closing an intake throttle and opening a first valve disposed in a secondary flow passage coupled between an intake manifold downstream of the intake throttle and a first exhaust manifold coupled to a first set of exhaust valves to direct unburned hydrocarbons to a catalyst disposed in an exhaust passage coupled to a second set of exhaust valves. For example, the request to shut down the internal combustion engine may be a key-off request. As a result of this action, unburned hydrocarbons may be directed to the catalyst, thereby reducing hydrocarbons in the internal combustion engine system and maintaining catalyst stoichiometry.Additionally, closing the intake throttle reduces engine reversing. Additionally, opening the second valve and the intake throttle after the engine has stopped running allows less exhaust gas recirculation (EGR) to be drawn back into the intake.

[0008] As another example, the examples described above may be addressed by a method for an internal combustion engine, comprising: in response to a request to shut down the internal combustion engine: deactivating all valves of a first set of exhaust valves configured to flow exhaust gas to an exhaust passage via a first exhaust manifold; and opening a first valve disposed in a flow passage coupled between an intake passage and a second exhaust manifold, wherein a second set of exhaust valves is coupled exclusively to the second exhaust manifold. For example, the request to shut down the internal combustion engine may be a start / stop request generated in response to the vehicle in which the internal combustion engine is installed being stopped.By deactivating the first set of exhaust valves, gases can be recirculated through the second set of exhaust valves, reducing intake manifold pressure. This can improve engine operation upon restart, at which point the first set of exhaust valves can be reactivated.

[0009] It should be understood that the foregoing summary is provided to introduce, in a simplified form, a selection of concepts further described in the detailed description. It is not intended to identify important or significant features of the claimed subject matter, the scope of which is defined solely in the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1A shows a schematic representation of a turbocharged internal combustion engine system with a split exhaust system. Fig. 1B shows an embodiment of a cylinder of the internal combustion engine system of Fig. 1A. Fig. 2A shows a block diagram of a first embodiment of an engine air-fuel ratio control system for an internal combustion engine and an air-fuel ratio flowing into an exhaust emission device. Fig. 2B shows a block diagram of a second embodiment of an engine air-fuel ratio control system for an internal combustion engine and an air-fuel ratio flowing into an exhaust emission device. Fig. 3A shows example cylinder intake valve and exhaust valve timing for an engine cylinder of a split exhaust engine system. Fig. 3B shows example intake valve and exhaust valve timing adjustments for an engine cylinder of the split exhaust engine system for various engine operating modes. Fig. 4A-4B show a flow diagram of a method of operating a split exhaust engine system, wherein a first exhaust manifold directs exhaust and blowby air to an inlet of the engine system and a second exhaust manifold directs exhaust to an outlet of the engine system, under various vehicle and engine operating modes. Fig. 5 shows a flowchart of a method for operating the split exhaust engine system in a cold start mode. Fig. 6 shows a flowchart of a method for operating the split exhaust engine system in a deceleration fuel cut mode. Fig. 7A-7B show a flow diagram of a method for operating the split exhaust engine system in a gas reaction mode. Fig. 8 shows a flow diagram of a method for operating the split exhaust engine system in an electric boost mode. Fig. 9 shows a flow diagram of a method for operating the split exhaust engine system in a compressor threshold mode. Fig. 10 shows a flow diagram of a method for operating the split exhaust engine system in a baseline blowthrough combustion cooling (BTCC) mode. Fig. 11 shows a flowchart of a method for diagnosing one or more valves of the split exhaust engine system based on purge manifold pressure. Fig. 12 shows a flow diagram of a method for controlling EGR flow and blow-by air from a scavenging manifold to an intake port by adjusting operation of one or more valves of the exhaust engine system. Fig. 13 shows a flow diagram of a method for selecting between operating modes to adjust a flow of exhaust gases from the engine cylinders to an intake port via purge exhaust valves and a purge exhaust manifold of the split exhaust engine system. Fig. 14 shows a flow diagram of a method for operating a hybrid electric vehicle including the split exhaust engine system in an electric mode. Fig. 15 shows a flow diagram of a method for operating the split exhaust engine system in a shutdown mode. Fig. 16 shows an exemplary diagram of changes in engine operating parameters while operating the split exhaust engine system in a cold start mode. Fig. 17 shows an exemplary diagram of changes in engine operating parameters while operating the split exhaust engine system in a fuel fuel cut-off (DFSO) mode. Fig. 18A-18B show an exemplary graph of changes in engine operating parameters while operating the split exhaust engine system in a gas response mode. Fig. 19 shows an exemplary graph of changes in engine operating parameters while operating the split exhaust engine system in an electric boost mode. Fig. 20 shows an exemplary graph of changes in engine operating parameters while operating the split exhaust engine system in a compressor threshold mode. Fig. 21 shows an exemplary graph of changes in pressure and oxygen content of a scavenging exhaust manifold over a single engine cycle of the split exhaust engine system. Fig. 22 shows an exemplary diagram for controlling one or more engine actuators to adjust exhaust gas recirculation (EGR) flow and blow-by flow from the purge exhaust valves of the engine cylinders to an intake passage of the split exhaust engine system. Fig. 23 shows an exemplary diagram for operating a hybrid electric vehicle in an electric mode to heat the split exhaust engine system prior to starting the engine. Fig. 24 shows an exemplary graph of changes in engine operating parameters while operating the split exhaust engine system in a shutdown mode. Fig. 25 shows an exemplary diagram of the operation of the split exhaust engine system from start-up to shutdown. Detailed description

[0010] The following description relates to systems and methods for operating a split exhaust gas internal combustion engine with blow-by and exhaust gas recirculation (EGR) via a first exhaust manifold to an intake. As described in Fig. 1A, the split exhaust engine may include a first exhaust manifold (referred to herein as a scavenging exhaust manifold) coupled exclusively to a scavenging exhaust valve of each cylinder. The scavenging manifold is coupled to the intake passage upstream of a turbocharger compressor via a first EGR passage including a first EGR valve (referred to herein as a BTCC valve). The split exhaust engine also includes a second exhaust manifold (referred to herein as a blowdown exhaust manifold) coupled exclusively to a blowdown exhaust valve of each cylinder. The blowdown manifold is coupled to an exhaust passage of the engine, wherein the exhaust passage includes a turbocharger turbine and one or more emission control devices (which may include one or more catalysts).In some embodiments, the split exhaust engine system may include additional passages coupled between the scavenging manifold and either the intake or exhaust passage, as shown in FIG. Fig. 1A. Additionally, in some embodiments, the split exhaust engine system may include various valve actuation mechanisms and may be installed in a hybrid vehicle, as shown in Fig. 1B. Due to the multiple exhaust manifolds and various couplings of the scavenging manifold to the intake and exhaust passages, the split exhaust engine may include a unique air-fuel control system, as shown in the Fig. 2A-2B. The scavenging exhaust valves and blow-off exhaust valves open and close at different times in an engine cycle for each cylinder to isolate scavenging and blow-off portions of the combusted exhaust gases and route these portions separately to the scavenging manifold and blow-off manifold, as shown in Fig. 3A. The timing of the intake valve, the scavenge exhaust valve, and the blow-off exhaust valve of each engine cylinder can be adjusted to increase EGR and / or blow-by to the intake and / or to optimize engine performance under various engine operating modes, as shown in Fig. 3B shown.

[0011] The parts of various valves and timing of the cylinder intake and exhaust valves of the split exhaust engine system can be controlled differently under different engine operating conditions, as shown in the Fig. 4A-4B. For example, various operating modes of the split exhaust engine system may include an electric mode (a method for this mode is shown in Fig. 14 and a corresponding exemplary time course diagram is shown in Fig. 23), a cold start mode (a method for this is described in Fig. 5 and a corresponding exemplary time course diagram is shown in Fig. 16), a deceleration cut-off mode (a method for this mode is described in Fig. 6 and a corresponding exemplary time course diagram is shown in Fig. 17), a gas reaction mode (a method for this mode is described in Fig. 7A-7B and a corresponding exemplary time course diagram is shown in the Fig. 18A-18B), an electrical amplification mode (a method for this mode is shown in Fig. 8 and a corresponding exemplary time course diagram is shown in Fig. 19), a compressor threshold mode (a method for this is described in Fig. 9 and a corresponding exemplary time course diagram is shown in Fig. 20), a shutdown mode (a method for this mode is shown in Fig. 15 and a corresponding exemplary time course diagram is shown in Fig. 24) and an output blow-through combustion cooling (BTCC) mode (a method for this mode is described in the Fig. 10-13 and corresponding exemplary time course diagrams are shown in the Fig. 21 and Fig. 22). During an operating period of the engine (e.g., from an ignition key-on start to an ignition key-off shutdown), the split exhaust engine system may transition between several of the operating modes described above. An example of such an engine operating period from engine start to shutdown is shown in Fig. 25. In this way, engine actuators of the split exhaust engine system may be controlled differently based on a current operating mode of the engine system to increase engine efficiency and reduce engine emissions in each engine operating mode.

[0012] In the following description, a valve that is operable or enabled indicates that it is open and / or closed according to specific times during the combustion cycle for a given set of conditions. Similarly, a valve that is disabled or inoperative indicates that the valve remains closed unless otherwise specified.

[0013] Fig. 1A shows a schematic representation of a multi-cylinder internal combustion engine 10 that can be integrated into a drive system of a motor vehicle. The internal combustion engine 10 includes a plurality of combustion chambers (i.e., cylinders), which can be covered on top by a cylinder head (not shown). Fig. 1A, the engine includes 10 cylinders 12, 14, 16, and 18 arranged in an in-line configuration. However, it should be understood that, although Fig. 1A shows four cylinders, the internal combustion engine 10 may include any number of cylinders in any configuration, e.g., V-6, I-6, V-12, opposed 4, etc. In addition, the cylinders shown in Fig. 1A may have a cylinder configuration such as that shown in Fig. 1B, as described further below. Each of the cylinders 12, 14, 16, and 18 includes two intake valves, including the first intake valve 2 and the second intake valve 4, and two exhaust valves, including the first exhaust valve (referred to herein as a blow-off exhaust valve or blow-off valve) 8 and the second exhaust valve (referred to herein as a scavenging exhaust valve or scavenging valve) 6. The intake valves and exhaust valves may be referred to herein as cylinder intake valves and cylinder exhaust valves, respectively. As described further below with reference to Fig. 1B, a timing (e.g., opening timing, closing timing, opening duration, etc.) of each of the intake valves may be controlled via different camshaft timing systems. In one embodiment, both the first intake valves 2 and the second intake valves 4 may be controlled to a same valve timing (e.g., so that they open and close at the same time in the engine cycle). In an alternative embodiment, the first intake valves 2 and the second intake valves 4 may be controlled to a different valve timing. Additionally, the first exhaust valves 8 may be controlled to a different valve timing than the second exhaust valves 6 (e.g., so that a first exhaust valve and a second exhaust valve of a same cylinder open at different times and close at different times than the other), as discussed further below.

[0014] Each cylinder receives intake air (or a mixture of intake air and recirculated exhaust gas, as discussed below) from an intake manifold 44 via an intake passage 28. The intake manifold 44 is coupled to the cylinders via intake ports (e.g., ducts). For example, the intake manifold 44 shown in Fig. 1A, the intake manifold 44 is coupled to each first intake valve 2 of each cylinder via first intake ports 20. Furthermore, the intake manifold 44 is coupled to each second intake valve 4 of each cylinder via second intake ports 22. In this manner, each cylinder intake port can selectively communicate with the cylinder to which it is coupled via one of the first intake valve 2 or the second intake valve 4. Each intake port can supply air and / or fuel to the cylinder to which it is coupled for combustion.

[0015] One or more of the intake ports may include a charge motion control device, such as a charge motion control valve (CMCV). As in Fig. 1A, each first intake port 20 of each cylinder includes a CMCV 24. CMCVs 24 may also be referred to as swirl control valves or tumble control valves. CMCVs 24 may restrict the air flow entering the cylinders via the first intake valves 2. In the example from Fig. 1A, each CMCV 24 may include a valve plate; however, other valve designs are possible. For the purposes of this disclosure, it should be noted that the CMCV 24 is in the "closed" position when fully activated, and the valve plate may be fully tilted into the corresponding first intake port 20, resulting in maximum airflow obstruction. Alternatively, the CMCV 24 is in the "open" position when deactivated, and the valve plate may be fully rotated to be substantially parallel to the airflow, thereby significantly minimizing or eliminating the airflow obstruction. The CMCVs may generally be held in their "open" position and may only be activated "closed" when swirl conditions are desired. As shown in Fig. 1A, only one intake port of each cylinder includes the CMCV 24. However, in alternative embodiments, both intake ports of each cylinder may include a CMCV 24. The controller 12 may actuate the CMCVs 24 (e.g., via a valve actuator that may be coupled to a rotating shaft directly coupled to each CMCV 24) to move the CMCVs to the open or closed position, or a plurality of positions between the open and closed positions, as discussed further below, in response to engine operating conditions (such as engine speed / load and / or when blowby via the second exhaust valves 6 is active). As referred to herein, blowby air or blowby combustion cooling may refer to intake air that is forced between the intake valves and the second exhaust valves 6 during a valve opening overlap period (e.g.,a period when both the intake valves and the exhaust valves 6 are open at the same time) from one or more intake valves of each cylinder to the second exhaust valves 6 (and into the second exhaust manifold 80).

[0016] A double-stage high-pressure fuel system (such as the one in Fig. 1B) may be used to generate fuel pressures at the injectors 66. Thus, fuel may be injected directly into the cylinders via the injectors 66. A distributorless ignition system 88 provides an ignition spark to cylinders 12, 14, 16, and 18 in response to the controller 12 via the spark plug 92. The cylinders 12, 14, 16, and 18 are each coupled to two exhaust ports for separately directing the blowdown and scavenging portions of the combustion gases. In particular, as shown in Fig. 1A, cylinders 12, 14, 16, and 18 exhaust the combustion gases (e.g., scavenging portion) to the second exhaust manifold (referred to herein as a scavenging manifold) 80 via second exhaust conduits (e.g., ports) 82) and the combustion gases (e.g., blowdown portion) to the first exhaust manifold (referred to herein as a blowdown manifold) 84 via first exhaust conduits (e.g., ports) 86. The second exhaust conduits 82 extend from cylinders 12, 14, 16, and 18 to the second exhaust manifold 80. Additionally, the first exhaust manifold 84 includes a first manifold section 81 and a second manifold section 85. The first exhaust conduits 86 of cylinders 12 and 18 (referred to herein as the outer cylinders) extend from cylinders 12 and 18 to the second manifold section 85 of the first exhaust manifold 84.In addition, the first exhaust passages 86 of cylinders 14 and 16 (referred to herein as the inner cylinders) extend from cylinders 14 and 16 to the first manifold portion 81 of the first exhaust manifold 84.

[0017] Each exhaust conduit can selectively communicate with the cylinder to which it is coupled via an exhaust valve. For example, second exhaust conduits 82 communicate with their corresponding cylinders via second exhaust valves 6, and first exhaust conduits 86 communicate with their corresponding cylinders via first exhaust valves 8. Second exhaust conduits 82 are isolated from first exhaust conduits 86 when at least one exhaust valve of each cylinder is in a closed position. Exhaust gases cannot flow directly between exhaust conduits 82 and 86. The exhaust system described above may be referred to herein as a split exhaust manifold system, wherein a first portion of the exhaust gases from each cylinder is exhausted to first exhaust manifold 84 and a second portion of the exhaust gases from each cylinder is exhausted to second exhaust manifold 80, and wherein the first and second exhaust manifolds do not directly communicate with each other (e.g.,no channel directly couples the two exhaust manifolds to each other and thus the first and second parts of the exhaust gases do not mix within the first and second exhaust manifolds).

[0018] The internal combustion engine 10 includes a turbocharger having a double-stage exhaust turbine 164 and an intake compressor 162 coupled on a common shaft. The double-stage turbine 164 includes a first turbine 163 and a second turbine 165. The first turbine 163 is directly coupled to the first manifold section 81 of the first exhaust manifold 84 and receives exhaust gases only from cylinders 14 and 16 via first exhaust valves 8 of cylinders 14 and 16. The second turbine 165 is directly coupled to the second manifold section 85 of the first exhaust manifold 84 and receives exhaust gases only from cylinders 12 and 18 via first exhaust valves 8 of cylinders 12 and 18. The rotation of the first and second turbines drives the rotation of the compressor 162, which is disposed within the intake passage 28. Thus, the intake air is amplified (e.g., pressurized) at the compressor 162 and moves downstream to the intake manifold 44.The exhaust gases exit both the first turbine 163 and the second turbine 165 into the common exhaust passage 74. A wastegate may be coupled to the dual-stage turbine 164. In particular, the wastegate valve 76 may be included in a bypass 78 coupled between each of the first manifold section 81 and the second manifold section 85 upstream of an inlet to the dual-stage turbine 164 and the exhaust passage 74 downstream of an outlet of the dual-stage turbine 164. In this manner, a position of the wastegate valve (referred to herein as a turbine wastegate) 76 controls an amount of boost provided by the turbocharger. In alternative embodiments, the internal combustion engine 10 may include a single-stage turbine where all exhaust gases from the first exhaust manifold 84 are directed to an inlet of a same turbine.

[0019] Exhaust gases exiting the dual-stage turbine 164 flow downstream in exhaust passage 74 to a first emissions control device 70 and a second emissions control device 72, with the second emissions control device 72 being located downstream in exhaust passage 74 from the first emissions control device 70. In one example, the emissions control devices 70 and 72 may include one or more catalyst modules. In some examples, the emissions control devices 70 and 72 may be three-way catalysts. In other examples, the emissions control devices 70 and 72 may include one or a plurality of a diesel oxidation catalyst (DOC) and a selective catalytic reduction catalyst (SCR). In another example, the second emissions control device 72 may include a gasoline particulate filter (BPF).In one example, the first emission control device 70 may include a catalyst, and the second emission control device 72 may include a BPF. After flowing through the emission control devices 70 and 72, the exhaust gases may be directed out to a tailpipe.

[0020] The exhaust passage 74 further includes a plurality of exhaust sensors in electronic communication with the controller 12 of the control system 15, as described below. As in Fig. 1A, the exhaust passage 74 includes a first oxygen sensor 90 disposed between the first emissions control device 70 and the second emissions control device 72. The first oxygen sensor 90 may be configured to measure an oxygen content of exhaust gas entering the second emissions control device 72. The exhaust passage 74 may include one or more additional oxygen sensors positioned along the exhaust passage 74, such as the second oxygen sensor 91 positioned between the dual-stage turbine 164 and the first emissions control device 70, and / or the third oxygen sensor 93 positioned downstream of the second emissions control device 72.Thus, the second oxygen sensor 91 may be configured to measure the oxygen content of the exhaust gas entering the first emissions control device 70, and the third oxygen sensor 93 may be configured to measure the oxygen content of the exhaust gas exiting the second emissions control device 72. In one embodiment, the one or more oxygen sensors 90, 91, and 93 may be wideband (Universal Exhaust Gas Oxygen - UEGO) sensors. Alternatively, the oxygen sensors 90, 91, and 93 may be replaced with a binary exhaust gas oxygen sensor. The exhaust passage 74 may include various other sensors, such as one or more temperature and / or pressure sensors. For example, as shown in FIG. Fig. 1A, a pressure sensor 96 is positioned within the exhaust passage 74 between the first emission control device 70 and the second emission control device 72. Thus, the pressure sensor 96 may be configured to measure the pressure of exhaust gas entering the second emission control device 72. Both the pressure sensor 96 and the oxygen sensor 90 are disposed within the exhaust passage 74 at a point where a flow passage 98 couples to the exhaust passage 74. The flow passage 98 may be referred to herein as a scavenge manifold bypass passage (SNMP) 98. The scavenge manifold bypass passage 98 is coupled directly to and between the second exhaust (e.g., scavenge) manifold 80 and the exhaust passage 74.A valve 97 (referred to herein as the scavenge manifold bypass valve (SMBV)) is disposed within the scavenge manifold bypass passage 98 and is operable by the controller 12 to adjust an amount of exhaust flow from the second exhaust manifold 80 to the exhaust passage 74 at a location between the first emission control device 70 and the second emission control device 72.

[0021] The second exhaust manifold 80 is directly coupled to a first exhaust gas recirculation (EGR) passage 50. The first EGR passage 50 is directly coupled between the second exhaust manifold 80 and the intake passage 28 upstream of the compressor (e.g., turbocharger compressor) 162 (and thus may be referred to as a low-pressure EGR passage). Thus, exhaust gases (or blow-by air, as explained further below) are routed from the second exhaust manifold 80 to the intake passage 28 upstream of the compressor 162 via the first EGR passage 50. As shown in Fig. 1A, the first EGR passage 50 includes an EGR cooler 52 configured to cool exhaust gases flowing from the second exhaust manifold 80 to the intake manifold 28 and a first EGR valve 54 (which may be referred to herein as the BTCC valve). The controller 12 is configured to actuate and adjust a position of the first EGR valve 54 to control an amount of airflow through the first EGR passage 50. When the first EGR valve 54 is in a closed position, no exhaust gases or intake air can flow from the second exhaust manifold 80 to the intake passage 28 upstream of the compressor 162. Additionally, when the first EGR valve 54 is in an open position, exhaust gases and / or blow-by air from the second exhaust manifold 80 may flow to the intake passage 28 upstream of the compressor 162.The controller 12 may additionally position the first EGR valve 54 in a variety of positions between fully open and fully closed.

[0022] A first ejector 56 is positioned at an outlet of the EGR passage 50 within the intake passage 28. The first ejector 56 may include a restriction or venturi that provides a pressure boost at the inlet of the compressor 162. As a result, EGR from the EGR passage 50 may be mixed with fresh air flowing through the intake passage 28 to the compressor 162. Thus, EGR from the EGR passage 50 may act as the motive flow at the first ejector 56. In an alternative embodiment, there may be no ejector positioned at the outlet of the EGR passage 50. Instead, an outlet of the compressor 162 may be shaped as an ejector that lowers gas pressure to assist with EGR flow (and thus, in this embodiment, air is the motive flow and EGR is the secondary flow).In another embodiment, EGR from the EGR passage 50 may be introduced at the trailing edge of a blade of the compressor 162, thereby allowing air to be blown through the EGR passage 50 to the intake passage 28.

[0023] A second EGR passage 58 is coupled between the first EGR passage 50 and the intake passage 28. In particular, as shown in Fig. 1A, the second EGR passage 58 is coupled to the first EGR passage 50 between the EGR valve 54 and the EGR cooler 52. In alternative embodiments, when the second EGR passage 58 is included in the internal combustion engine system, the system may not include an EGR cooler 52. Additionally, the second EGR passage 58 is directly coupled to the intake passage 28 downstream of the compressor 162. Due to this coupling, the second EGR passage 58 may be referred to herein as an intermediate-pressure EGR passage. Furthermore, as shown in Fig. 1A, the second EGR passage 58 is coupled to the intake passage 28 upstream of a charge air cooler (CAC) 40. The CAC 40 is configured to cool intake air (which may be a mixture of fresh intake air from outside the engine system and exhaust gases) as it passes through the CAC 40. Thus, recirculated exhaust gases from the first EGR passage 50 and / or the second EGR passage 58 may be cooled via the CAC 40 before entering the intake manifold 44. In an alternative embodiment, the second EGR passage 58 may be coupled to the intake passage 28 downstream of the CAC 40. In this embodiment, an EGR cooler 52 may not be disposed within the first EGR passage 50. Additionally, as shown in Fig. 1A, a second ejector 57 may be positioned within the intake passage 28 at an outlet of the second EGR passage 58.

[0024] A second EGR valve 59 (e.g., medium-pressure EGR valve) is disposed within the second EGR passage 58. The second EGR valve 59 is configured to adjust an amount of gas flow (e.g., intake air or exhaust) through the second EGR cooler 58. As described further below, the controller 12 may actuate the EGR valve 59 to an open position (thereby allowing flow through the second EGR passage 58), a closed position (thereby blocking flow through the EGR passage 58), or a plurality of positions between fully open and fully closed based on (e.g., as a function of) engine operating conditions.For example, actuating the EGR valve 59 may involve the controller 12 sending an electronic signal to an actuator of the EGR valve 59 to move a valve plate of the EGR valve 59 to an open position, a closed position, or a position between fully open and fully closed. As further explained below, based on system pressures and positions of alternative valves in the engine system, air may flow to either the intake passage 28 within the second EGR passage 58 or the second exhaust manifold 80 within the second EGR passage 58.

[0025] The intake passage 28 further includes an electronic intake throttle 62 in communication with the intake manifold 44. As in Fig. 1A, the intake throttle 62 is positioned downstream of the CAC 40. The position of a throttle plate 64 of the throttle 62 may be adjusted by a control system 15 via a throttle actuator (not shown) communicatively coupled to the controller 12. By modulating the air intake throttle 62 while operating the compressor 162, an amount of fresh air from the atmosphere and / or an amount of recirculated exhaust gases from the one or more EGR passages may be drawn into the engine 10, cooled by the CAC 40, and delivered at compressor (or boosted) pressure to the engine cylinders via the intake manifold 44. To reduce compressor surge, at least a portion of the air charge compressed by the compressor 162 may be recirculated to the compressor inlet.A compressor recirculation passage 41 may be provided for recirculating compressed air from the compressor outlet upstream of the CAC 40 to the compressor inlet. The compressor recirculation valve (CRV) 42 may be provided for adjusting an amount of recirculation flow recirculated to the compressor inlet. In one example, the CRV 42 may be commanded to open in response to actual or expected compressor surge conditions.

[0026] A third flow passage 30 (which may be referred to herein as a hot pipe) is coupled between the second exhaust manifold 80 and the intake passage 28. Specifically, a first end of the third flow passage 30 is directly coupled to the second exhaust manifold 80, and a second end of the third flow passage 30 is directly coupled to the intake passage 28 downstream of the intake throttle 62 and upstream of the intake manifold 44. A third valve 32 (e.g., hot pipe valve) is disposed within the third flow passage 30 and configured to adjust an amount of airflow through the third flow passage 30. The third valve 32 may be actuated to a fully open position, a fully closed position, or a plurality of positions between fully open and fully closed in response to an actuation signal sent from the controller 12 to an actuator of the third valve 32.

[0027] The second exhaust manifold 80 and / or the second exhaust conduits 82 may include one or more sensors (such as pressure, temperature sensors, and / or oxygen sensors) disposed therein. For example, as shown in Fig. 1A, the second exhaust manifold 80 includes a pressure sensor 34 and an oxygen sensor 36 disposed therein and configured to measure a pressure and oxygen content, respectively, of exhaust gases and blowby (e.g., intake) air exiting the second exhaust valves 6 and entering the second exhaust manifold 80. In addition or alternatively to the oxygen sensor 36, each second exhaust conduit 82 may include an individual oxygen sensor 38 disposed therein. Thus, an oxygen content of exhaust gases and / or blowby air exiting each cylinder via second exhaust valves 6 may be determined based on an output of the oxygen sensor 38.

[0028] In some embodiments, as in Fig. 1A, the intake passage 28 may include an electric compressor 60. The electric compressor 60 is disposed in a bypass passage 61 coupled to the intake passage 28 upstream and downstream of an electric compressor valve 63. Specifically, an inlet to the bypass passage 61 is coupled to the intake passage 28 upstream of the electric compressor valve 63, and an outlet to the bypass passage 61 is coupled to the intake passage 28 downstream of the electric compressor valve 63 and upstream of where the first EGR passage 50 couples to the intake passage 28. Additionally, the outlet of the bypass passage 61 is coupled upstream in the intake passage 28 from the turbocharger compressor 162. The electric compressor 60 may be electrically driven by an electric motor using energy stored in an energy storage device. In one example, the electric motor may be part of the electric compressor 60, as shown in Fig. 1A. When additional boost (e.g., increased intake air pressure above atmospheric pressure) is requested above an amount provided by compressor 162, controller 12 may activate electric compressor 60 to rotate and increase a pressure of intake air flowing through bypass passage 61. Additionally, controller 12 may actuate electric compressor valve 63 to a closed or partially closed position to direct an increased amount of intake air through bypass passage 61 and electric compressor 60.

[0029] The intake passage 28 may include one or more additional sensors (such as additional pressure, temperature, flow rate sensors and / or oxygen sensors).

[0030] For example, as in Fig. 1A, the intake passage 28 includes a mass air flow (MAF) sensor 48 located upstream of the compressor 162, the electric compressor valve 63, and where the first EGR passage 59 couples to the intake passage 28. An intake pressure sensor 31 and an intake temperature sensor 33 are positioned in the intake passage 28 upstream of the compressor 162 and downstream of where the first EGR passage 50 couples to the intake passage 28. An intake oxygen sensor 35 and an intake temperature sensor 43 may be located in the intake passage 28 downstream of the compressor 162 and upstream of the CAC 40. An additional intake pressure sensor 37 may be positioned in the intake passage 28 downstream of the CAC 40 and upstream of the throttle 28. In some embodiments, as in Fig. As shown in Figure 1A, an additional intake oxygen sensor 39 may be positioned in the intake passage 28 between the CAC 40 and the throttle 28. Additionally, an intake manifold pressure (e.g., MAP) sensor 122 and an intake manifold temperature sensor 123 are positioned within the intake manifold 44 upstream of all engine cylinders.

[0031] In some examples, the internal combustion engine 10 may be connected to an electric motor / battery system (as in Fig. 1B) in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, a series configuration, or a variation or combination thereof. Furthermore, in some embodiments, other internal combustion engine configurations may be used, for example, a diesel engine.

[0032] The internal combustion engine 10 may be controlled at least in part by a control system 15 including the controller 12 and by an input from a vehicle operator via an input device (in Fig. 1A not shown). As shown, the control system 15 receives information from a plurality of sensors 16 (various examples of which are described herein) and sends control signals to a plurality of actuators 81. As one example, the sensors 16 may include pressure, temperature sensors, and oxygen sensors located within the intake passage 28, intake manifold 44, exhaust passage 74, and second exhaust manifold 80, as described above. Other sensors may include a throttle inlet pressure (TIP) sensor for estimating a throttle inlet pressure (TIP) and / or a throttle inlet temperature sensor for estimating a throttle air temperature (TCT) coupled downstream of the throttle in the intake passage. Additional system sensors and actuators are described below with reference to Fig. 1B. As another example, the actuators 81 may include fuel injectors, the valves 63, 42, 54, 59, 32, 97, 76, and the throttle 62. The actuators 81 may further include various camshaft timing actuators coupled to the cylinder intake and exhaust valves (as described further below with reference to Fig. 1B). The controller 12 may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on the instruction or code programmed in a memory of the controller 12 according to one or more routines. Example control routines (e.g., methods) are described herein in the Fig. 4-15. For example, adjusting the EGR flow from the second exhaust manifold 80 to the intake passage 28 may include adjusting an actuator of the first EGR valve 54 to adjust an amount of exhaust flow flowing from the second exhaust manifold 80 to the intake passage 28 upstream of the compressor 162. In another example, adjusting the EGR flow from the second exhaust manifold 80 to the intake passage 28 may include adjusting an actuator of a camshaft of exhaust valves to adjust an opening timing of second exhaust valves 6.

[0033] In this way, the first and second exhaust manifolds can be Fig. 1A may be configured to separately direct the blowoff and scavenge portions of the exhaust gas. The first exhaust manifold 84 may direct the scavenge pulse of the exhaust gas to the dual-stage turbine 164 via the first manifold section 81 and the second manifold section 85, while the second exhaust manifold 80 may direct the scavenge portion of the exhaust gas to the intake passage 28 via one or more of the first EGR passage 50 and the second EGR passage 58 and / or to the exhaust passage 74 downstream of the dual-stage turbine 164 via the flow passage 98. For example, the first exhaust valves 8 direct the blow-off portion of the exhaust gases through the first exhaust manifold 84 to the dual-stage turbine 164 and both the first and second emission control devices 70 and 72, while the second exhaust valves 6 direct the scavenge portion of the exhaust gases through the second exhaust manifold 80 and either to the intake passage 28 via one or more EGR passages or to the exhaust passage 74 and the second emission control device 72 via the flow passage 98.

[0034] It should be noted that while Fig. 1A shows the engine 10 including each of the first EGR passage 50, second EGR passage 58, flow passage 98, and flow passage 30. In alternative embodiments, the engine 10 may include only a portion of these passages. For example, in one embodiment, the engine 10 may include only the first EGR passage 50 and flow passage 98 and not the second EGR passage 58 and flow passage 30. In another embodiment, the engine 10 may include the first EGR passage 50, the second EGR passage 58, and flow passage 98, but not the flow passage 30. In another embodiment, the engine 10 may include the first EGR passage 50, the flow passage 30, and flow passage 98, but not the second EGR passage 58. In some embodiments, the internal combustion engine 10 may not include the electric compressor 60.In further embodiments, the internal combustion engine 10 may use all or only a portion of the functions shown in . Fig. 1A shown sensors.

[0035] With reference to Fig. 1B shows a partial view of a single cylinder of the internal combustion engine 10 that can be installed in a vehicle 100. Thus, components that are already in Fig. 1A, are shown with the same reference numerals and are not introduced again. The internal combustion engine 10 is shown with the combustion chamber (cylinder) 130, the coolant sleeve 114 and the cylinder walls 132 with the piston 136 positioned therein and connected to the crankshaft 140. As shown, the combustion chamber 130 communicates with the intake port 146 and the exhaust port 148 via a corresponding intake valve 152 and exhaust valve 156. As already described in Fig. 1A, each cylinder of the internal combustion engine 10 may discharge combustion products along two conduits. In the illustrated view, the exhaust passage 148 represents the first exhaust conduit (e.g., orifice) leading from the cylinder to the turbine (such as the second exhaust conduit 86 of Fig. 1A), while the second exhaust pipe is not visible in this view.

[0036] As in Fig. 1A, each cylinder of the internal combustion engine 10 may include two intake valves and two exhaust valves. In the illustrated view, the intake valve 152 and the exhaust valve 156 are located in an upper region of the combustion chamber 130. The intake valve 152 and the exhaust valve 156 may be controlled by the controller 12 using corresponding cam actuation systems, including one or more cams. The cam actuation systems may use one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems to vary valve operation. In the example shown, each intake valve 152 is controlled by an intake cam 151 and each exhaust valve 156 is controlled by an exhaust cam 153.Intake cam 151 may be actuated via intake valve timing actuator 101, and exhaust cam 153 may be actuated via exhaust valve timing actuator 103 according to the set of intake and exhaust valve timings, respectively. In some examples, the intake and exhaust valves may be deactivated via intake valve timing actuator 101 and exhaust valve timing actuator 103, respectively. For example, the controller may send a signal to exhaust valve timing actuator 103 to deactivate exhaust valve 156 so that it remains closed and does not open at its set timing. The position of intake valve 152 and exhaust valve 156 may be determined by valve position sensors 155 and 157, respectively. As introduced above, in one example, all exhaust valves of each cylinder may be controlled on a same exhaust camshaft.Thus, timing of both the (second) scavenging exhaust valves and the (first) blowoff exhaust valves may be adjusted together via one camshaft, but they may each have different timings relative to each other. In another example, the scavenging exhaust valve of each cylinder may be controlled on a first exhaust camshaft, and a blowoff exhaust valve of each cylinder may be controlled on a different, second exhaust camshaft. In this way, the valve timing of the scavenging valves and the blowoff valves may be adjusted separately. In alternative embodiments, the cam or valve timing system(s) of the scavenging and / or blowoff exhaust valves may utilize a cam-in-cam system, an electro-hydraulic system on the scavenging valves, and / or electromechanical valve lift control on the scavenging valves.

[0037] For example, in some embodiments, the intake and / or exhaust valves may be controlled by electric valve actuation. For example, cylinder 130 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation, including CPS and / or VCT systems. In still other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or system, or a variable valve timing actuator or system.

[0038] In one example, intake cam 151 includes separate and distinct cam lobes that provide different valve profiles (e.g., valve timing, valve lift, duration, etc.) for each of the two intake valves of combustion chamber 130. Similarly, intake cam 153 may include separate and distinct cam lobes that provide different valve profiles (e.g., valve timing, valve lift, duration, etc.) for each of the two exhaust valves of combustion chamber 130. In another example, intake cam 151 may include a common lobe or similar lobes that provide a substantially similar valve profile for each of the two intake valves.

[0039] Additionally, different cam profiles may be used for the different exhaust valves to separate exhaust gases exhausted at low cylinder pressure from exhaust gases exhausted at exhaust pressure. For example, a first exhaust cam profile may open the first exhaust valve (e.g., blowoff valve) from the closed position just before BDC (bottom dead center) of the combustion chamber 130 expansion stroke and close the same exhaust valve well before TDC (top dead center) to selectively exhaust blowoff gases from the combustion chamber. Additionally, a second exhaust cam profile may be positioned to open a second exhaust valve (e.g., scavenge valve) from closed before a midpoint of the exhaust stroke and close it after TDC to selectively exhaust the scavenging portion of the exhaust gases.

[0040] Thus, the timing of the first exhaust valve and the second exhaust valve can isolate cylinder blow-off gases from the scavenging portion of the exhaust gases, while cleaning residual exhaust gases in the cylinder dead space with fresh intake air blow-by during the positive valve overlap between the intake valve and the scavenging exhaust valves. By flowing a first portion of the exhaust gas leaving the cylinders (e.g., higher pressure exhaust gas) to the turbine(s) and a higher pressure exhaust passage, and flowing a later, second portion of the exhaust gas (e.g., lower pressure exhaust gas) and blow-by air to the compressor inlet, engine system efficiency is improved. Turbine energy recovery can be enhanced, and engine efficiency can be improved via increased EGR and reduced knock.

[0041] Continue at Fig. 1B, the exhaust gas sensor 126 is shown coupled to the exhaust passage 148. The sensor 126 may be disposed in the exhaust passage upstream of one or more emission control devices, such as the devices 70 and 72 of Fig. 1A. The sensor 126 may be selected from various suitable sensors for providing an indication of exhaust air-fuel ratio, such as a linear oxygen sensor or UEGO (Universal Exhaust Gas Oxygen Sensor; wideband or wide-range oxygen sensor), a dual-state oxygen sensor or EGO (as shown), a HEGO (Heated EGO) sensor, a NOx, HC, or CO sensor. The downstream emission control devices may include one or more of a three-way catalyst (TWC), a NOx trap, GPF, various other emission control devices, or combinations thereof.

[0042] The exhaust temperature may be estimated by one or more temperature sensors (not shown) disposed within the exhaust passage 148. Alternatively, the exhaust temperature may be inferred based on engine operating conditions such as engine speed, load, air-fuel ratio (AFR), spark retard, etc.

[0043] Cylinder 130 may have a compression ratio that is the volumetric ratio between piston 136 at bottom dead center and top dead center. Conventionally, the compression ratio is in the range of 9:1 to 10:1. However, in some examples where other fuels are used, the compression ratio may be increased. This may occur, for example, when using higher octane fuels or fuels with a higher latent heat of vaporization. The compression ratio may also be increased when using direct injection due to its effect on engine knock.

[0044] In some embodiments, each cylinder of the internal combustion engine 10 may include a spark plug 92 to initiate combustion. The ignition system 188 may provide an ignition spark to the combustion chamber 130 via the spark plug 92 in response to a spark advance (SA) signal from the controller 12 under selected operating modes. However, in some embodiments, the spark plug 92 may be omitted, such as when the internal combustion engine 10 can initiate combustion through auto-ignition or by injecting fuel, which may be the case with some diesel engines.

[0045] In some embodiments, each cylinder of the internal combustion engine 10 may be configured with one or more fuel injectors to supply fuel thereto. As a non-limiting example, the cylinder 130 is shown as including a fuel injector 66. A fuel injector 66 is shown coupled directly to the combustion chamber 130 to inject fuel directly therein in proportion to the pulse width of a signal FPW received from the controller 12 via the electronic driver 168. In this manner, the fuel injector 66 provides so-called direct injection (hereinafter also referred to as "DI") of fuel into the combustion cylinder 130. While Fig. 1B depicts the injector 66 as a side injector, however, it may also be located above the piston, such as near the position of the spark plug 92. Such a position may improve mixing and combustion when the engine is operating on an alcohol-based fuel, as some alcohol-based fuels have lower volatility. Alternatively, the injector may be located above and near the intake valve to improve mixing. In an alternative embodiment, the injector 66 may be a port injector that provides fuel into the intake port upstream of the cylinder 130.

[0046] The fuel may be delivered to the fuel injector 66 from a high-pressure fuel system 180, which includes fuel tanks, fuel pumps, and a fuel rail. Alternatively, the fuel may be delivered at a lower pressure by a single-stage fuel pump, in which case the timing of the direct fuel injection during the compression stroke may be more limited than when using a high-pressure fuel system. Further, although not shown, the fuel tanks may include a pressure transducer that provides a signal to the controller 12. The fuel tank in the fuel system 180 may contain fuel with different properties, for example, with different fuel compositions.These differences may include different alcohol contents, different octane ratings, different vaporization temperatures, different fuel brands, and / or combinations thereof, etc. In some embodiments, fuel system 180 may be coupled to a fuel vapor recovery system, including a canister for storing fuel for refueling and everyday fuel vapors. The fuel vapors may be purged from the canister to the engine cylinders during engine operation when purge conditions are met. For example, the purge vapors may be naturally drawn into the cylinder via the first intake port at or below atmospheric pressure.

[0047] The internal combustion engine 10 may be controlled at least partially by the controller 12 and by input from a vehicle operator 113 via an input device 118, such as an accelerator pedal 116. The input device 118 sends a pedal position signal to the controller 12. The controller 12 is in Fig. 1B as a microcomputer, including a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, illustrated in this specific example as read-only memory 106, random access memory 108, keep-alive memory 110, and a data bus. The storage medium of read-only memory 106 can be programmed with computer-readable data representing instructions executable by the microprocessor 102 for performing the methods and procedures described below, as well as other variations that are anticipated but not specifically listed.The controller 12 may receive various signals from sensors coupled to the engine 10, in addition to the signals previously discussed, including measurements of inducted mass air flow (MAF) from a mass air flow sensor 48; engine coolant temperature (ECT) from a temperature sensor 112 coupled to a coolant sleeve 114; a profile ignition pickup (PIP) signal from a Hall effect sensor 120 (or other type) coupled to the crankshaft 140; throttle position (TP) from a throttle position sensor; a manifold absolute pressure (MAP) signal from sensor 122, cylinder AFR from the EGO sensor 126, and abnormal combustion from a knock sensor and a crankshaft acceleration sensor. An engine speed signal, RPM, may be generated by the controller 12 from the PIP signal.The manifold pressure signal MAP from a manifold pressure sensor can be used to provide an indication of vacuum or pressure in the intake manifold.

[0048] Based on contributions from one or more of the aforementioned sensors, the controller 12 may adjust one or more actuators, such as the fuel injector 66, the throttle 62, the spark plug 92, the intake / exhaust valves and cams, etc. The controller may receive contribution data from the various sensors, process the contribution data, and trigger the actuators in response to the processed input data based on instructions or code programmed therein according to one or more routines.

[0049] In some examples, the vehicle 100 may be a hybrid vehicle with multiple torque sources available to one or more vehicle wheels 160. In other examples, the vehicle 100 may be a conventional vehicle with only an internal combustion engine or an electric vehicle with only an electric machine(s). In the Fig. 1B, the vehicle 100 includes an internal combustion engine 10 and an electric machine 161. The electric machine 161 may be a motor or a motor / generator and thus may also be referred to herein as an electric motor. The crankshaft 140 of the internal combustion engine 10 and the electric machine 161 are connected to the vehicle wheels 160 via a transmission 167 when one or more clutches 166 are engaged. In the depicted example, a first clutch 166 is provided between the crankshaft 140 and the electric machine 161, and a second clutch 166 is provided between the electric machine 161 and the transmission 167. The controller 12 may send a signal to an actuator of each clutch 166 to engage or disengage the clutch to rotate the crankshaft 140 with or without the clutch.to connect or disconnect the electric machine 161 and its associated components and / or to connect or disconnect the electric machine 161 to or from the transmission 167 and its associated components. The transmission 167 may be a manual transmission, a planetary gear system, or another type of transmission. The powertrain may be configured in a variety of ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0050] The electric machine 161 receives electrical power from a traction battery 170 to provide torque to the vehicle wheels 160. The electric machine 161 can also be operated as a generator, for example, to provide electrical power to charge the battery 170 during braking.

[0051] Referring to FIG. 2A, a block diagram of an engine air-fuel ratio control system 200 for an internal combustion engine 10 and an air-fuel ratio flowing into an exhaust emission device is shown. At least portions of the system 200 may be implemented in a system as shown in FIGS. Fig. 1A-1B, as executable instructions stored in non-volatile memory. Other portions of the system 200 may be actions performed via the controller 12, as shown in the Fig. 1A-1B to transfer states of devices or actuators in reality. The air-fuel control of the internal combustion engine described herein can operate in cooperation with previously described sensors and actuators.

[0052] A baseline desired engine air-fuel ratio is entered at block 202. Block 202 contains empirically determined air-fuel ratios for a variety of engine speed and load pairs. In one example, the empirically determined air-fuel ratios are stored in a table in controller memory. The table can be updated using existing engine speed and load values. The table outputs a desired engine air-fuel ratio (e.g., 14.6:1) for the current engine speed and load. Block 202 outputs the desired engine air-fuel ratio to summing point 204 and dividing point 203.

[0053] The air mass flow of the internal combustion engine, as measured by an air mass flow sensor or an intake manifold pressure sensor (such as in Fig. 1A-1B, is input to control system 200 at block 201. The engine mass air flow is divided by the desired engine air-fuel ratio from block 202 at division point 203 to provide a desired engine fuel mass flow rate. The fuel mass flow rate is output to multiplication point 208.

[0054] At summing junction 204, the actual engine air-fuel ratio, as determined by oxygen sensor 91, is subtracted from the desired engine air-fuel ratio to provide an air-fuel ratio error. Additionally, an air-fuel ratio deviation or offset value is added to the desired engine air-fuel ratio and the actual engine air-fuel ratio to improve catalyst efficiency. The air-fuel ratio deviation is output by summing junction 248. Summing junction 204 outputs an air-fuel ratio error to proportional / integral controller 206.The proportional / integral (PI) controller 206 integrates the error and applies proportional and integral gains to the air-fuel ratio error to output a fuel mass control correction or adjustment to the multiplication point 208. The desired engine fuel mass flow rate from the division point 203 is multiplied by the fuel mass control correction at the multiplication point 208. The output of the multiplication point 208 is an adjusted fuel flow rate, which is converted to a fuel injector pulse width via a fuel injector transfer function at block 210. Block 210 outputs a fuel pulse width to control engine fuel injectors (e.g., in . Fig. 2A not shown, in the Fig. 1A-1B as fuel injectors 66), and the engine fuel injectors inject the adjusted fuel flow rate or corrected fuel flow rate into the engine 10.

[0055] The internal combustion engine 10 outputs exhaust gases to the turbocharger turbine (e.g. 163 / 165 Fig. 1A). The exhaust gases pass through the turbocharger turbine 163 / 165 and into the emissions control device 70. The emissions control device 70 may be a three-way catalyst. The exhaust gases pass from the emissions control device 70 into the emissions control device 72. The emissions control device 72 may be a three-way catalyst, a particulate filter, an oxidation catalyst, or a combination of a catalyst and a particulate filter. Processed exhaust gases flow to the atmosphere after passing through the emissions control device 72. As explained above, the turbocharger turbine 163 / 165, the emissions control device 70, and the emissions control device 72 may be part of an exhaust system of the internal combustion engine and may be positioned along an exhaust passage of the internal combustion engine.

[0056] Exhaust gases from the internal combustion engine may be sensed via the lambda sensor 91 to provide an actual air-fuel ratio of the internal combustion engine. The actual air-fuel ratio of the internal combustion engine may be used as feedback in the control system 200. The actual air-fuel ratio of the internal combustion engine is input to the summing junction 204. Exhaust gases downstream of the emissions control device 70 and downstream of the emissions control device 72 may be sensed via the lambda sensor 90 to determine an air-fuel ratio within the exhaust system. The lambda sensor 90 is positioned in an exhaust passage extending between the emissions control device 70 and the emissions control device 72. Alternatively, exhaust gases may be sensed via a lambda sensor positioned downstream of the emissions control device 72 (e.g., in Fig. 1A), instead of the oxygen sensor 90. The output of the oxygen sensor 90 or 93 is routed to switch 222, where it is then sent to the summing point 248 or the summing point 232 based on the state of the switch 222, which is determined via the mode switching logic 224.

[0057] The mode switching logic 224 determines an operating state of the engine and may change the position or state of the switch 222 based on the operating mode of the engine. In particular, the mode switching logic commands the switch 222 to its home position when the engine airflow falls below a threshold and when there is no request to regenerate the exhaust emission devices. The mode switching logic 224 also commands the valve 97 to Fig. 1A, positioned in the purge manifold bypass passage 98, via a first actuator reference function 226 when the engine airflow falls below a threshold and when there is no request to regenerate exhaust emission devices. The switch 222 is shown in its home position. In its home or first position, the switch 222 sends output data from the oxygen sensor to the summing junction 248. Air (e.g., blow-by) is not supplied to the exhaust system (via the purge manifold bypass passage 98) when the switch 222 is in the first position.

[0058] The mode switching logic 224 moves the switch 222 to a second position, as indicated by arrow 250, as directed by the mode switching logic 224 when the engine airflow rate exceeds a threshold or when an exhaust emission device is to be regenerated. In its second position, the switch 222 directs the output of the oxygen sensor 90 to the summing junction 232. The mode switching logic 224 opens the valve 97 via a control signal output from the first reference function 226 to the valve 97 when the engine airflow rate exceeds a threshold or when an exhaust emission device is to be regenerated. A rate of airflow provided to the exhaust system via the scavenging manifold bypass passage 98 is an open loop, adjusted via the second reference function 228.In one example, the second reference function 228 outputs a valve position command, an amount of intake and exhaust valve overlap (e.g., crankshaft angular duration where both the intake and exhaust valves are open simultaneously), a boost pressure command, or another airflow adjustment command based on the engine air-fuel ratio and the mass flow rate of fuel and air combusted within the engine. For example, the engine air-fuel ratio and mass flow rate of fuel and air combusted within the engine may be used to index a table or function that outputs a valve position command, an amount of intake and exhaust valve overlap command, or a boost pressure command.The rate of airflow provided to the exhaust system via the scavenging manifold is a closed-loop controlled via the air-fuel ratio input to summing junction 232. The valve opening amount, intake and exhaust valve overlap duration, boost pressure, or actuation of other actuators that adjust airflow through the scavenging manifold are adjusted at engine 10 according to the control adjustment output from summing junction 236. Thus, PI controller 234 adjusts engine airflow actuators by modifying the output of second reference function 228.

[0059] Alternatively, the rate of airflow provided to the exhaust system via the scavenging manifold may be an open loop that may be controlled based on an estimate of the soot loading stored in the emissions control device 72 or a temperature estimate of the emissions control device 72 instead of the oxygen sensor output. The soot estimate may be based on a pressure differential across the emissions control device 72 or other engine operating conditions known in the art. The temperature of the emissions control device 72 may be estimated based on engine operating conditions, such as engine speed and load. Additionally, the airflow rate may be a closed loop that is controlled based on the temperature of the emissions control device 72 or a pressure differential across the emissions control device 72.In such examples, the temperature or pressure differential is substituted for the oxygen sensor input at summing junction 232, and the air-fuel reference is replaced with a temperature or pressure reference. The air flowing to the exhaust system was not involved in combustion in the internal combustion engine.

[0060] In one example, the second reference function 228 issues a control command to a variable valve timing actuator (e.g., in Fig. 1B) to adjust an amount of valve opening overlap between an intake valve and a purge exhaust valve of a same cylinder and thus of blow-by air (e.g., an amount of blow-by air) directed to the emissions control device 72. Alternatively, the second reference function 228 outputs a control signal to a valve, such as the valve 32 of Fig. 1A or valve 97 from Fig. 1A, each of which can adjust airflow to the exhaust system and emissions control device 72. Additionally, in some examples, the second actuator reference function 228 outputs a control signal to a turbocharger wastegate actuator used to adjust boost pressure, which can also be applied to adjust airflow to emissions control device 72 by adjusting blowby air by increasing or decreasing boost pressure.

[0061] The timing of air supply to the exhaust system from the scavenging manifold may be as follows: a stoichiometric or lean engine air-fuel ratio is enriched to a rich or stoichiometric engine air-fuel ratio, and air supplied to the exhaust system is delivered to the downstream emission device 72 one engine cycle earlier, before exhaust gases produced from the rich or stoichiometric engine air-fuel ratio reach the position of the downstream emission device 72. The air supply to the exhaust system may be terminated before the rich or stoichiometric engine air-fuel ratio is leaned.

[0062] When switch 222 is in its second position, oxygen sensor data from oxygen sensor 90 or 93 is output to summing junction 232 instead of summing junction 248. An actual exhaust air-fuel ratio from oxygen sensor 90 or 93 is subtracted from a desired exhaust air-fuel ratio provided by reference block 230. The desired exhaust air-fuel ratio output from reference block 230 may differ from the desired engine air-fuel ratio output from block 202. In one example, the desired exhaust air-fuel ratio is determined empirically and stored in a table indexed by engine speed and load.The desired exhaust air-fuel ratio output from block 230 may be a stoichiometric air-fuel ratio when the engine air-fuel ratio is rich at high engine speeds and loads, with engine airflow exceeding the threshold. The desired exhaust air-fuel ratio output from block 230 may have a lean stoichiometry when the exhaust emissions device is requested to regenerate while the engine air-fuel ratio is stoichiometric. Subtracting the actual exhaust air-fuel ratio from the desired exhaust air-fuel ratio provides an engine exhaust air-fuel ratio error, which is input to a second PI controller 234.The exhaust air-fuel ratio error is processed by the PI controller and a control correction is fed to summing point 236.

[0063] The engine speed (N) and load values ​​are used to index air-fuel error values ​​in table 244. The air-fuel error values ​​are empirically determined values ​​stored in control memory, and the air-fuel error values ​​provide adjustment of the air-fuel mixtures in the exhaust system for the purpose of improving catalyst efficiency. The air-fuel error and the air-fuel ratio in the exhaust system are added to the desired exhaust air-fuel ratio and the engine output air-fuel ratio at summing junction 204 when switch 222 is in the home position. When switch 222 is not in its home position, the output of summing junction 248 may be adjusted to a predetermined value, such as zero.

[0064] In a first example of how control system 200 may operate, the control adjustment output from summing junction 236 may be an adjustment of an amount of intake and exhaust valve overlap that results in air passing through the engine without having participated in combustion within the engine. By increasing the intake and exhaust valve overlap, airflow through the engine and across the scavenging manifold bypass passage (e.g., in Fig. 1A) into the exhaust system. In contrast, airflow can be reduced by reducing intake and exhaust valve overlap through the engine and into the exhaust system via the scavenging manifold bypass passage.

[0065] In a second example of how the control system 200 may operate, the control adjustment output from the summing point 236 may provide an adjustment of the valve (e.g., 97 from Fig. 1A) positioned in the flushing manifold bypass channel, or a valve (e.g. 32 from Fig. 1A) which is in a hot tube (e.g. 30 from Fig. 1A). When the internal combustion engine 10 is operating at high loads using high boost pressure, the intake manifold pressure may be greater than the purge manifold pressure and the exhaust system pressure, allowing fresh air that did not participate in combustion to pass through the hot pipe to the purge manifold and into the exhaust system to lean exhaust gases and provide oxygen to the emission control device 72. Alternatively, fresh air may pass through the engine cylinders and into the purge manifold 80 without having participated in combustion. The air may then be routed to the emission control device 72 via the purge manifold bypass passage 98 to lean the exhaust gases and provide oxygen to the emission control device 72. Air may similarly be routed to the emission control device 72 in response to a request to regenerate the emission control device.In one example where the emissions control device is a particulate filter, a request to regenerate the particulate filter may be made in response to a pressure drop across the particulate filter exceeding a threshold pressure.

[0066] In this way, system 200 may control an engine air-fuel ratio observed by oxygen sensor 91 and an exhaust air-fuel ratio observed by oxygen sensor 90 or 93 without directing air to the exhaust system in a first mode. System 200 may also control an engine air-fuel ratio observed by oxygen sensor 91 and an exhaust air-fuel ratio observed by oxygen sensor 90 or 93 when air is directed to the exhaust system via a purge manifold. The amount of air provided to the exhaust system that is not involved in combustion in the internal combustion engine may be a closed loop feedback controlled based on the output from the oxygen sensor 90 or 93 and adjustments to the valves coupled to a scavenging manifold, intake and exhaust valve overlap, or boost pressure.

[0067] With reference to Fig. 2B, a block diagram of another embodiment of an engine air-fuel ratio control system 250 for an internal combustion engine 10 and an air-fuel ratio flowing into an exhaust emission device is shown. At least portions of the control system 250 may be implemented in a system as shown in FIGS. Fig. 1A-1B, as executable instructions stored in non-volatile memory. Other portions of the control system 250 may be actions performed via the controller 12, as shown in the Fig. 1A-1B to transfer states of devices or actuators in reality. The air-fuel control of the internal combustion engine described herein can operate in cooperation with previously described sensors and actuators.

[0068] A baseline desired engine air-fuel ratio is entered at block 252. Block 252 contains empirically determined air-fuel ratios for a variety of engine speed and load pairs. In one example, the empirically determined air-fuel ratios are stored in a table in controller memory. The table can be updated using existing engine speed and load values. The table outputs a desired engine air-fuel ratio (e.g., 14.6:1) for the current engine speed and load. Block 252 outputs the desired engine air-fuel ratio to summing junction 254 and dividing junction 253.

[0069] The engine mass air flow, as determined via a mass air flow sensor or an intake manifold pressure sensor, is input to control system 250 at block 251. The engine mass air flow is divided by the desired engine air-fuel ratio from block 252 at division point 253 to provide a desired engine fuel mass flow rate. The fuel mass flow rate is output to multiplication point 258.

[0070] At summing junction 254, the actual engine air-fuel ratio, as determined by oxygen sensor 91, is subtracted from the desired engine air-fuel ratio to provide an air-fuel ratio error. Additionally, an air-fuel ratio deviation or offset value is added to the desired engine air-fuel ratio and the actual engine air-fuel ratio to improve catalyst efficiency. The air-fuel ratio deviation is output by summing junction 278. Summing junction 254 outputs an air-fuel ratio error to proportional / integral controller 256.The proportional / integral (PI) controller 256 integrates the error and applies proportional and integral gains to the air-fuel ratio error to output a fuel mass control correction or adjustment to the multiplication point 258. The desired engine fuel mass flow rate from the division point 253 is multiplied by the fuel mass control correction at the multiplication point 258. The output of the multiplication point 258 is further adjusted at the multiplication point 259 in response to the output from the PI controller 274. These adjustments compensate for the deviation in the exhaust air-fuel ratio within the exhaust system, as determined by the oxygen sensor 90 or 93. The output of the multiplication point 259 (e.g.,A fuel flow adjustment is converted into a fuel injector pulse width at block 260 via a fuel injector transfer function. Block 260 outputs a fuel pulse width to control engine fuel injectors (e.g., in . Fig. 2B not shown, in the Fig. 1A-1B as elements 66), and the engine fuel injectors inject the adjusted fuel flow rate or corrected fuel flow rate into the engine 10.

[0071] The internal combustion engine 10 outputs exhaust gases to the turbocharger turbine (e.g. 163 / 165 Fig. 1A). The exhaust gases pass through the turbocharger turbine 163 / 165 and into the emissions control device 70. The emissions control device 70 may be a three-way catalyst. The exhaust gases pass from the emissions control device 70 into the emissions control device 72. The emissions control device 72 may be a three-way catalyst, a particulate filter, an oxidation catalyst, or a combination of a catalyst and a particulate filter. Processed exhaust gases flow to the atmosphere after passing through the emissions control device 72.

[0072] Exhaust gases from the internal combustion engine may be sensed via the lambda sensor 91 to provide an actual air-fuel ratio of the internal combustion engine. The actual air-fuel ratio of the internal combustion engine may be used as feedback in the control system 250. The actual air-fuel ratio of the internal combustion engine is input to the summing junction 254. Exhaust gases downstream of the emissions control device 70 and downstream of the emissions control device 72 may be sensed via the lambda sensor 90 to determine an air-fuel ratio within the exhaust system. The lambda sensor 90 is positioned in an exhaust passage extending between the emissions control device 70 and the emissions control device 72. Alternatively, exhaust gases may be sensed via a lambda sensor positioned downstream of the emissions control device 72 (e.g., in Fig. 1A), instead of the oxygen sensor 90. The output of the oxygen sensor 90 or 93 is routed to switch 262, where it is then sent to the summing point 278 or the summing point 272 based on the state of the switch 262, which is determined via the mode switching logic 264.

[0073] The mode switching logic 264 determines the operating state of the engine and may change the position or state of the switch 262 based on the operating mode of the engine. In particular, the mode switching logic commands the switch 262 to its home position when the engine airflow falls below a threshold and when there is no request to regenerate the exhaust emission devices. The mode switching logic 264 also commands the valve 97 to Fig. 1A, positioned in the scavenging manifold bypass passage 98, via a first actuator reference function 266 when the engine airflow falls below a threshold and when there is no request to regenerate exhaust emission devices. Switch 262 is shown in its home position. In its home or first position, switch 262 sends output data from the oxygen sensor to summing point 278.

[0074] The mode switching logic 264 moves the switch 262 to a second position, as indicated by arrow 150, as directed by the mode switching logic 264 when the engine airflow rate exceeds a threshold or when an exhaust emission device is to be regenerated. In its second position, the switch 262 directs the output of the oxygen sensor 90 to the summing junction 272. The mode switching logic 264 opens the valve 97 via a control signal output from the first reference function 266 to the valve 97 when the engine airflow rate exceeds a threshold or when an exhaust emission device is to be regenerated. A rate of airflow provided to the exhaust system via the scavenging manifold bypass passage 98 is an open loop, adjusted via the second reference function 268.In one example, the second reference function 268 outputs a valve position command, an amount of intake and exhaust valve overlap (e.g., crankshaft angular duration where both the intake and exhaust valves are open simultaneously), a boost pressure command, or another airflow adjustment command based on the engine air-fuel ratio and the mass flow rate of fuel and air combusted within the engine. For example, the engine air-fuel ratio and mass flow rate of fuel and air combusted within the engine may be used to index a table or function that outputs a valve position command, an amount of intake and exhaust valve overlap command, or a boost pressure command.

[0075] The mode switching logic 264 may also control the path by which air is directed to the exhaust system via the purge manifold bypass passage 98 in response to the output of the oxygen sensor 91, which is positioned in the exhaust system upstream of the emissions control device 70. For example, if the oxygen sensor 91 is a first value (e.g., a first estimate of the air-fuel ratio), air may be provided to the exhaust system at a location upstream of the emissions device 72 and downstream of the emissions device 70 via the engine cylinders, the purge manifold, and the purge manifold bypass pipe. The airflow rate supplied to the exhaust system may be adjusted by adjusting the valve timing. If the output of the oxygen sensor 91 is a second value (e.g.,a second estimate of the air-fuel ratio), air may be provided to the exhaust system at a location upstream of the emissions device 72 and downstream of the emissions device 70 via the hot pipe 30, the purge manifold 80, and the purge manifold bypass pipe 98. The airflow rate supplied to the exhaust system may be adjusted by adjusting the valve 32 and / or the valve 97. By selectively routing air that was not involved in combustion through different paths, it may be possible to provide air to the exhaust system across a wide range of engine operating conditions, thus reducing engine emissions.

[0076] When switch 262 is in its second position, oxygen sensor data from oxygen sensor 90 or 93 is output to summing junction 272 instead of summing junction 278. An actual exhaust air-fuel ratio from oxygen sensor 90 or 93 is subtracted from a desired exhaust air-fuel ratio provided by reference block 270. The desired exhaust air-fuel ratio output from reference block 270 may differ from the desired engine air-fuel ratio output from block 252. In one example, the desired exhaust air-fuel ratio is determined empirically and stored in a table indexed by engine speed and load.The desired exhaust air-fuel ratio output from block 270 may be a stoichiometric air-fuel ratio when the engine air-fuel ratio is rich at high engine speeds and loads. The desired exhaust air-fuel ratio output from block 270 may have a lean stoichiometry when the exhaust emissions device is requested to regenerate while the engine air-fuel ratio is stoichiometric. Subtracting the actual exhaust air-fuel ratio from the desired exhaust air-fuel ratio provides an engine exhaust air-fuel ratio error, which is input to a second PI controller 274.The exhaust air-fuel ratio error is processed by the PI controller 274, which integrates the air-fuel error and applies proportional and integral gains to the output of the summing point 272, and a control correction is provided to the multiplication point 259.

[0077] The timing of air supply to the exhaust system from the scavenging manifold may be as follows: a stoichiometric or lean engine air-fuel ratio is enriched to a rich or stoichiometric engine air-fuel ratio, and air supplied to the exhaust system is delivered to the downstream emission device 72 one engine cycle earlier, before exhaust gases produced from the rich or stoichiometric engine air-fuel ratio reach the position of the downstream emission device 72. The air supply to the exhaust system may be terminated before the rich or stoichiometric engine air-fuel ratio is leaned.

[0078] The engine speed (N) and load values ​​are used to index air-fuel deviation values ​​in table 276. The air-fuel deviation values ​​are empirically determined values ​​stored in control memory, and the air-fuel deviation values ​​provide adjustment of the air-fuel mixtures in the exhaust system for the purpose of improving catalyst efficiency. The air-fuel deviation and the air-fuel ratio in the exhaust system are added to the desired exhaust air-fuel ratio and the engine output air-fuel ratio at summing junction 254 when switch 262 is in the home position. When switch 262 is not in its home position, the output of summing junction 278 may be adjusted to a predetermined value, such as zero.

[0079] In this way, system 250 may control an engine air-fuel ratio observed by oxygen sensor 91 and an exhaust air-fuel ratio observed by oxygen sensor 90 or 93 without directing air to the exhaust system in a first mode. System 250 may also control an engine air-fuel ratio observed by oxygen sensor 91 and an exhaust air-fuel ratio observed by oxygen sensor 90 or 93 when air is directed to the exhaust system via a purge manifold. An amount of fuel delivered to the engine may be a closed loop that is adjusted in response to an amount of air provided to the exhaust system that is not involved in combustion in the engine.The fuel injected into the engine can be adjusted based on the output from the lambda sensor 90 or 93.

[0080] As one example, the technical effect of supplying air via a purge manifold to an exhaust system at a location downstream of an emissions control device, the air not participating in combustion in an internal combustion engine, the purge manifold being in fluid communication with a purge exhaust valve of a cylinder and an intake manifold, the cylinder including a blowoff exhaust valve in fluid communication with a blowoff manifold; adjusting an amount of fuel injected into the internal combustion engine in response to the output of a first oxygen sensor, the first oxygen sensor being positioned in the exhaust system upstream of the emissions control device, is to more precisely control the air-fuel ratio of the exhaust gas downstream of the emissions control device for more efficient engine operation and reduced engine emissions.As another example, the technical effect of flowing air from an intake manifold through a plurality of engine cylinders to a junction of an exhaust passage and a bypass passage in response to a condition wherein the junction is positioned along the exhaust passage between the first and second emission control devices; and flowing exhaust gas to the first emission control device while the air flows to the junction is to increase the amount of oxygen entering the second emission control device, thereby maintaining a stoichiometric mixture entering the second emission control device, and thus increasing the function of the second emission control device and reducing engine emissions.In another example, the increased oxygen content may assist in the regeneration and combustion of soot from the second emission control device, thus also resulting in increased function of the second emission control device and reduced emissions.

[0081] With reference to Fig. 3A, the diagram 300 illustrates exemplary valve timing relative to piston position for an engine cylinder including 4 valves: two intake valves and two exhaust valves, as described above with reference to FIG. Fig. 1A-1B. The example from Fig. Figure 3A is essentially drawn to scale, although each individual point is not labeled with numerical values. Thus, relative differences in timing can be estimated based on the drawing dimensions. However, other relative timings may be used if necessary.

[0082] Continue at Fig. 3A, the cylinder is configured to receive intake air via two inlets and to discharge a first blow-off portion via a first exhaust valve (e.g., the one shown in Fig. 1A shown first, or blow-off, outlet valves 8) to a turbine inlet, a second purge portion via a second outlet valve (e.g. the one shown in Fig. 1A) to an intake port and unburned blow-by air to the intake port via the second exhaust valve. By adjusting the timing of the opening and / or closing of the second exhaust valve with that of the two intake valves, residual exhaust gases in the cylinder dead space can be cleaned and recirculated as EGR along with fresh intake blow-by air.

[0083] Diagram 300 illustrates an engine position along the x-axis in crank angle degrees (CAD). Diagram 302 depicts piston positions (along the y-axis) relative to their location from top dead center (TDC) and / or bottom dead center (BDC), and further relative to their location within the four strokes (intake, compression, power, and exhaust) of an engine cycle.

[0084] During operation of an internal combustion engine, each cylinder typically undergoes a four-stroke cycle, which includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. During the intake stroke, the exhaust valves generally close and the intake valves open. Air is drawn into the cylinder through the corresponding intake port, and the cylinder piston moves to the bottom of the cylinder to increase the volume within the cylinder. The position where the piston is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber has its largest volume) is typically referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake and exhaust valves are closed. The piston moves toward the cylinder head to compress the air within the combustion chamber.The point at which the piston is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber is at its smallest volume) is typically referred to by those skilled in the art as top dead center (TDC). In a process referred to herein as injection, fuel is introduced into the combustion chamber. In a process referred to herein as ignition, the injected fuel is ignited by known ignition means such as a spark plug, resulting in combustion. During the power stroke, the expanding gases push the piston back to BDC. A crankshaft converts this piston movement into torque on the rotating shaft. During the exhaust stroke, the exhaust valves of a conventional design are opened to release the remaining combusted air-fuel mixture to the appropriate exhaust ports, and the piston returns to TDC.In this description, the second exhaust (purge) valves may be opened after the start of the exhaust stroke and remain open after the end of the exhaust stroke, while the first exhaust (blow-off) valves remain closed and the intake valves are opened to purge residual exhaust gases with blow-by air.

[0085] The trace 304 represents a first intake valve timing, lift, and duration for a first intake valve (Int_1), while the trace 306 represents a second intake valve timing, lift, and duration for a second intake valve (INT_2) coupled to the intake port of the engine cylinder. The trace 308 represents an exemplary exhaust valve timing, lift, and duration for a first exhaust valve (Exh_1) that has the Fig. 1A shown first, or blow-off, outlet valves 8) which is connected to a first exhaust manifold (e.g. in Fig. 1A) of the engine cylinder, while the trace 310 illustrates an exemplary exhaust valve timing, lift, and duration for a second exhaust valve (Exh_2, which includes the Fig. 1A shown second, or purge, exhaust valves 6), which is connected to a second exhaust manifold (e.g. in Fig. 1A) of the engine cylinder. As already explained, the first exhaust manifold connects a first exhaust valve to the inlet of a turbine in a turbocharger, and the second exhaust manifold connects a second exhaust valve to an intake port via an EGR passage. The first and second exhaust manifolds can be separated from each other, as explained above.

[0086] In the depicted example, the first and second intake valves are fully opened from a closed position at a common timing (trajectories 304 and 306), beginning near intake stroke TDC, shortly after CAD2 (e.g., at or shortly after intake stroke TDC), and closed after a subsequent compression stroke begins after CAD3 (e.g., after BDC). Additionally, when fully open, the two intake valves may be opened with the same amount of valve lift L1 for the same duration D1. In other examples, the two valves may be operated with different timing by adjusting phasing, lift, or duration based on engine conditions.

[0087] Continuing with the exhaust valves, the timing of the first exhaust valve and the second exhaust valve is staggered relative to one another. In particular, the first exhaust valve is opened from a closed position at a first timing (path 308) that occurs earlier in the engine than the timing (path 310) at which the second exhaust valve is opened from a closed position. In particular, the first timing to open the first exhaust valve is between TDC and BDC of the power stroke before CAD1 (e.g., before the exhaust stroke BDC), while the timing to open the second exhaust valve is shortly after the exhaust stroke BDC after CAD1 but before CAD2. The first (path 308) exhaust valve is closed before the end of the exhaust stroke and the second (path 310) exhaust valve is closed after the end of the exhaust stroke.Thus, the second exhaust valve remains open to overlap slightly with the opening of the intake valves.

[0088] To implement this, the first exhaust valve may be fully opened from a closed position prior to the start of an exhaust stroke (e.g., between 90 and 40 degrees before BDC), remain fully open for a first portion of the exhaust stroke, and remain fully closed before the exhaust stroke ends (e.g., between 50 and 0 degrees before TDC) to capture the blow-off portion of the exhaust pulse. The second exhaust valve (path 310) may be fully opened from a closed position shortly after the start of the exhaust stroke (e.g., between 40 and 90 degrees after BDC), held open for a second portion of the exhaust stroke, and fully closed after the intake stroke begins (e.g., between 20 and 70 degrees after TDC) to discharge the scavenging portion of the exhaust gas. In addition, the second exhaust valve and the intake valves may be configured as shown in Fig. 3A, have a positive overlap phase (e.g., from between 20 degrees BTDC and 40 degrees BTDC to between 40 and 90 degrees BTDC) to enable EGR blow-through. This cycle, with all four valves operational, can repeat itself based on the engine's operating conditions.

[0089] Additionally, at a first timing, the first exhaust valve may be opened with a first amount of valve lift L2, while the second exhaust valve may be opened with a second amount of valve lift L3 (path 310), where L3 is less than L2. Furthermore, at the first timing, the first exhaust valve may be opened for a duration D2, while the second exhaust valve may be opened for a duration D3, where D3 is less than D2. It should be noted that in alternative embodiments, the two exhaust valves may have the same amount of valve lift and / or the same duration of opening, while opening at differently staggered timings.

[0090] In this way, engine efficiency and power can be increased using staggered valve timing by separating exhaust gases released at higher pressure (e.g., expanding blow-off exhaust gases in a cylinder) from residual exhaust gases at lower pressure (e.g., exhaust gases remaining in the cylinder after blow-off) into the various ports. By transporting residual low-pressure gases as EGR along with blow-by air to the compressor inlet (via the EGR port and the second exhaust manifold), combustion chamber temperatures can be lowered, thereby reducing knock and spark retardation from maximum torque. Because the exhaust gases are routed at the end of the stroke either downstream of a turbine or upstream of a compressor, both of which have lower pressures, exhaust pumping losses can be minimized to improve engine efficiency.

[0091] This allows exhaust gases to be used more efficiently than simply directing all of a cylinder's exhaust gas through a single common exhaust port to a turbocharger turbine. Several benefits can be achieved. For example, the average exhaust pressure delivered to the turbocharger can be increased by separating the blow-by pulse and directing it into the turbine inlet to improve turbocharger output. Additionally, fuel efficiency can be improved because blow-by air is routed to the compressor inlet rather than to the catalyst, preventing excess fuel from being injected into the exhaust gases to maintain a stoichiometric ratio.

[0092] Fig. 3A may illustrate initial intake and exhaust valve timing settings for the engine system. Under different engine operating modes, the intake and exhaust valve timing may be adjusted based on the initial settings. Fig. Figure 3B shows example adjustments to the valve timing of the blowdown exhaust valve (BDV), scavenge valve (SV), and intake valve (IV) for a representative cylinder during various engine operating modes. Specifically, plot 320 illustrates engine position along the x-axis in crank angle degrees (CAD). The diagram 320 also illustrates changes in the timing of the BDV, IV, and SV of each cylinder for an exit blow-by combustion cooling (BTCC) mode with higher EGR at plot 322, an exit BTCC mode with lower EGR at plot 324, a first cold start mode (A) at plot 326, a second cold start mode (B) at plot 328, a fuel cut-off (DFSO) mode at plot 330, a BTCC mode in an engine system without a scavenging manifold bypass passage (e.g., in Fig. 1A), an early intake valve closing (EIVC) mode at path 334 and a compressor threshold mode at path 336. In the Fig. In the examples shown in Figure 3B, it is assumed that the SVs and BDVs move together (e.g., via the same cam of a cam timing system). Thus, although the SVs and BDVs open and close at different timings relative to each other, they can be adjusted together by the same amount (e.g., advanced or retarded). However, in alternative embodiments, the BDVs and SVs can be controlled separately and thus can be separately adjustable.

[0093] During the initial BTCC mode with higher EGR, as shown at trace 322, the valve timing controls may be at their initial settings. The SV and BDV are at full advance (e.g., as advanced as the valve timing hardware allows). In this mode, blowby to the intake via the SV can be increased by retarding the SV and / or advancing the IV (increasing IV and SV overlap and thus blowby). By retarding the BDV and SV, EGR is reduced, as shown at trace 324 in the initial BTCC mode with lower EGR. As seen at trace 326, during the first cold start mode (A), the SV may be adjusted to an advanced opening / lift profile. During a second cold start mode (B), as shown at trace 328, the SV may be disabled so that it does not open. Also, the IV may be advanced while retarding the BDV, increasing combustion stability.

[0094] During DFSO mode, the BDV can be deactivated at trace 330 (e.g., so that it remains closed and does not open at its set timing). The IV and SV timing controls can remain at their home positions, or the SV can be retarded to increase the overlap between the SV and the IV, as shown at trace 330. As a result, all combusted exhaust gases are released via the SV to the scavenging exhaust manifold and redirected back to the intake port. Trace 334 shows EIVC mode, where the IV is deactivated and the exhaust cam is staggered to maximum retardation. Thus, the SV and BDV are retarded together. As described further below with reference to Fig. 7A, this mode allows air to be introduced into the engine cylinder via the SV and exhausted via the BDV. Trace 336 shows an example valve timing for a compressor threshold mode. In this mode, the intake cam of the IV is advanced and the exhaust cam of the SV and BDV is retarded to lower EGR and reduce exhaust flow to the compressor inlet. Further details regarding these operating modes are provided below with reference to Fig. 4-15 discussed.

[0095] With reference to the Fig. 4A-4B, a flow diagram of a method 400 for operating a vehicle having a split exhaust engine system (such as that shown in Fig. 1A-1B), wherein a first exhaust manifold (e.g. the one shown in Fig. 1A) directs exhaust gas and blow-by air to an inlet of the engine system and a second exhaust manifold (e.g. the one shown in Fig. 1A) exhaust gas to an outlet of the engine system under various vehicle and engine operating modes. Instructions for performing method 400 and the other methods listed herein may be provided by a controller (such as those described in Fig. 1A-1B) based on instructions stored in a memory of the controller and in conjunction with sensors of the internal combustion engine system, such as those described above in connection with the Fig. 1A-1B. The controller may utilize engine actuators of the engine system to adjust engine operation according to the methods described below. For example, the controller may actuate different valve actuators of different valves to move the valves to the commanded positions and / or actuate different valve timing actuators of different cylinder valves to adjust the timing of the cylinder valves.

[0096] The method 400 begins at 402 by estimating and / or measuring the vehicle and engine operating conditions. Engine operating conditions may include a brake pedal position, an accelerator pedal position, an operator torque demand, a battery charge status (in a hybrid electric vehicle), ambient temperature and humidity, atmospheric pressure, engine speed, engine load, an amount of input to a transmission of a vehicle in which the engine is installed, from an electric machine (e.g., the Fig. 1B) or crankshaft of the internal combustion engine, engine temperature, mass air flow (MAF), intake manifold pressure (MAP), oxygen content of intake air / exhaust gases at various points in the internal combustion engine system, a timing of the cylinder intake and exhaust valves, positions of various valves of the internal combustion engine system, a temperature and / or load level of one or more emission control devices, pressures in the exhaust manifolds, exhaust lines, exhaust passage and / or intake passage, an amount of fuel injected into the internal combustion engine cylinders, an operating state of an electric compressor (e.g., the one in Fig. 1A), a speed of the turbocharger, condensate formation on the turbocharger compressor, a temperature at the turbocharger compressor inlet and / or outlet, etc.

[0097] At 403, the method includes determining whether the vehicle is operating in an electric mode. As explained above, in one embodiment, the vehicle may be a hybrid electric vehicle. A vehicle operating mode may be determined based on the estimated operating conditions. For example, whether to operate the vehicle in an engine-only mode (where the engine drives the vehicle wheels), an assist mode (where the battery assists the engine in driving the vehicle), or an electric-only mode (where only the battery powers the vehicle via an electric motor or generator) may be determined based on at least the estimated driver torque demand and the battery charge status.In one example, when the requested torque can only be provided by the battery, the vehicle may operate in electric-only mode, where the vehicle is propelled using only motor torque. In another example, when the requested torque cannot be provided by the battery, the vehicle may operate in engine mode or assist mode, where the vehicle is propelled using at least some engine torque. The vehicle may operate in the determined operating mode accordingly. If it is confirmed at 403 that the vehicle is operating in electric-only mode, the method proceeds to 405 to operate in electric-only (e.g., electric) mode, which includes propelling the hybrid vehicle using only motor torque (and not engine torque). Details regarding operating in electric mode are discussed further below with reference to FIG. Fig. 14 explained.

[0098] Alternatively, if the vehicle is not operating in electric mode or the vehicle is not a hybrid vehicle, the vehicle may be driven with at least some (or all) of the engine torque and proceed to 404. At 404, the method includes determining whether cold start conditions are met. In one example, a cold start condition may include the engine operating with an engine temperature below a threshold temperature. In one example, the engine temperature may be a coolant temperature. In another example, the engine temperature may be a temperature of a catalyst (e.g., an emissions control device, such as one of the Fig. 1A) positioned in the exhaust passage. If the engine is operating under the cold start condition, the method proceeds to 406 to operate in a cold start mode. Details regarding operation in the cold start mode are discussed below with reference to Fig. 5 explained.

[0099] Otherwise, if cold start conditions are not met (e.g., engine temperatures exceed the specified thresholds), the method proceeds to 408. At 408, the method includes determining whether a fuel shutoff (DFSO) event is occurring (or whether the vehicle is decelerating). As one example, a DFSO event may be initiated and / or indicated when an operator releases a vehicle accelerator pedal and / or presses a brake pedal. In another example, a DFSO event may be indicated when the vehicle speed decreases by a threshold amount. The DFSO event may include terminating fuel injection to the engine cylinders. If the DFSO event occurs, the method proceeds to 410 to operate in a DFSO mode. Details regarding operating in DFSO mode are discussed further below with reference to Fig. 6 explained.

[0100] If DFSO conditions are not met or DFSO does not occur, the method proceeds to 412. At 412, the method includes determining whether the engine load falls below a threshold load. In one example, the threshold load may fall below a lower threshold load at which a gas response condition (e.g., when an intake throttle, such as the one in Fig. 1A, is at least partially closed, such that it is not fully open) and / or an engine idle condition (e.g., when the engine is idling) occurs. In some examples, the threshold load may be based on a load and / or throttle opening at which backflow through the EGR passage (e.g., in Fig. 1A) and the purge exhaust manifold. Backflow may include intake air flowing from the intake port through the EGR port and the purge exhaust manifold and into the engine cylinders via the purge exhaust valves. If the engine load falls below the threshold load (or the throttle is not fully open and thus at least partially closed), the method proceeds to 414 to operate in a gas response mode. Details regarding operation in the gas response mode are discussed further below with reference to the Fig. 7A-7B discussed.

[0101] If the engine load does not fall below the threshold load at 412, the method proceeds to 416. At 416, the method includes determining whether an electric compressor is operating in the engine system. In one example, the electric compressor may be an electric compressor located in the intake passage upstream of where the EGR passage (which is coupled to the scavenging manifold) couples to the intake passage, and upstream of the turbocharger compressor (such as the one shown in Fig. 1A). As an example, the controller may determine that the electric compressor is operating when the electric compressor is electrically powered by energy stored in an energy storage device (such as a battery). For example, an electric motor (coupled to the energy storage device) may drive the electric compressor, and thus, when the electric motor is operating and driving the electric compressor, the controller may determine that the electric compressor is operating. The electric compressor may be turned on and driven by the motor and the stored energy in response to a request for additional boost (e.g., an amount of pressure above that provided via the turbocharger compressor alone at a current turbocharger speed).When the electric compressor is driven and thus operating by the electric compressor's electric motor at 416, the method proceeds to 418 to operate in the electric boost mode. Details regarding operation in the electric boost mode are discussed further below with reference to FIG. Fig. 8 explained.

[0102] If the electric compressor is not operating (e.g., not driven by an electric motor coupled to the electric compressor), the method proceeds to 420. At 420, the method includes determining whether the compressor (e.g., the one in Fig. 1A) is at an operating threshold. The operating threshold (e.g., limit) of the compressor may be one or more of a compressor inlet temperature falling below a first threshold temperature (which may be indicative of condensate formation at the compressor inlet), a compressor outlet temperature exceeding a second threshold temperature (where temperatures at or above this second threshold temperature may result in compressor degradation), and / or a compressor rotational speed (e.g., compressor speed, which is also the turbocharger speed) exceeding a threshold speed (where speeds above this threshold may result in compressor degradation). When the compressor operates above these operating thresholds, compressor degradation and / or reduced performance may occur.In another example, at 420, the method may additionally or alternatively include determining whether the engine speed (RPM) or engine load exceeds the respective thresholds. For example, the engine speed and / or load thresholds may correlate with compressor operation, such that when the engine is operating at these engine speed or engine load thresholds, the compressor may reach one or more of the operating thresholds described above. Thus, at relatively high engine power, speed, and / or load, the compressor may reach one or more of the operating thresholds.If the compressor is at or above one of the operating thresholds, or the engine speed and / or load are at their respective upper thresholds, the method proceeds to 421 to operate in compressor threshold mode (which may also be referred to herein as high performance mode). Details regarding operating in compressor threshold mode are discussed further below with reference to FIG. Fig. 9 explained.

[0103] If the compressor is not operating at one of the operating thresholds (or engine speed and / or load are below their upper thresholds), the method proceeds to 422. At 422, the method includes determining whether a low-RPM transient pedal application condition exists. As one example, the low-RPM transient pedal application condition may include when there is an increase in torque demand above a threshold torque demand when the engine speed is below a threshold speed. For example, if a pedal position signal from an accelerator pedal exceeds a threshold (indicating that the accelerator pedal has been depressed by a threshold amount, thereby indicating a requested increase in engine torque output) while the engine speed is below the threshold speed, the controller may determine that a low-RPM transient pedal application condition exists.If it is determined that the conditions for the low RPM transition pedal application are met, the method proceeds to 423 to determine the amount of opening of the BTCC valve (e.g., the one described in . Fig. 1A) to increase the purge manifold pressure to a desired level, where the desired level is based on the intake manifold pressure (MAP) and the variable cam timing (VCT) of the intake and exhaust valves. For example, at 423, the method may include the controller determining the desired purge manifold pressure based on an estimated or measured MAP and the current timing (e.g., open and close timing) of the intake and exhaust (e.g., purge and blowoff) valves. For example, when the BTCC valve is fully open, the purge manifold operates near the compressor inlet pressure (e.g., ambient pressure). In this mode, EGR and blowby are higher, resulting in higher engine efficiency but low excess reserve throttle. Increasing the desired (e.g.,Setting the (target) purge manifold pressure closer to MAP can reduce EGR and blowby, trapping more charge air in the cylinders. Thus, the BTCC valve can be modulated using feedback of the purge manifold pressure to achieve the desired level of EGR. For example, the target purge manifold pressure for a given level of output torque can be mapped (e.g., in a table or map stored in the controller's memory) against the intake / exhaust valve VCT. In this way, the controller can use a stored relationship of purge manifold pressure versus intake / exhaust valve VCT.

[0104] As one example, the controller may use a first lookup table stored in memory to determine the desired purge manifold pressure with MAP and the intake and exhaust valve timings as inputs and the desired purge manifold pressure as output. The controller may then use a second lookup table with the determined desired purge manifold pressure as input and one or more of a desired BTCC valve position, a duration of fully closing the BTCC valve, or an amount of reducing the amount of BTCC valve opening from output to determine the commanded BTCC valve position. The controller may then send a signal to an actuator of the BTCC valve to move the BTCC valve to the desired position (e.g., fully closed or partially closed) and maintain the BTCC valve in that position for the determined duration. As another example, the controller may make a logical determination (e.g.,The controller may then make a control signal (regarding a position of the BTCC valve) based on logic rules that are a function of MAP; intake valve timing; and exhaust valve timing. The controller may then generate a control signal that is sent to the BTCC valve actuator. In some embodiments, at 423, the method may include closing the BTCC valve until the desired purge manifold pressure is reached and then reopening the BTCC valve. In another example, at 423, the method may include modulating the BTCC valve between open and closed positions to maintain the purge manifold pressure at the desired pressure.Purge manifold pressure may be measured via one or more pressure sensors positioned within the purge manifold or in the exhaust lines of the purge exhaust valves. The measured purge manifold pressure may then be used as feedback by the controller to further adjust the BTCC valve position to maintain the purge manifold at the desired purge manifold pressure. In some examples, the controller may use another lookup table with the measured purge manifold pressure and the desired purge manifold pressures as inputs and an adjusted BTCC valve position as the output.

[0105] If there is no low RPM transition pedal application condition at 422, the method instead exits to 424 Fig. 4B. At 424, the method includes determining whether an engine shutdown is expected or requested. The engine shutdown may include an ignition key-off shutdown (e.g., when the vehicle is placed in park and an operator turns off the engine) or a start / stop shutdown (e.g., when the vehicle is stopped but not parked and the engine automatically turns off in response to being stopped for a threshold duration). Thus, in one example, in response to receiving an ignition key-off signal from an ignition of the vehicle and / or the vehicle being stopped for a threshold duration, the controller may determine that a shutdown is requested. If a shutdown request is received at the controller, the method proceeds to 426 to operate in a shutdown mode.Details on operating in shutdown mode are provided below with reference to . Fig. 15 explained.

[0106] If a shutdown request is not received at 424, the method proceeds to 428. At 428, the method includes determining whether blow-through combustion cooling (BTCC) and EGR are provided to the intake passage via the purge exhaust manifold (e.g., via the purge manifold 80 and the first EGR passage 50, as shown in Fig. 1A), are desired or currently enabled. For example, when the engine load exceeds a second threshold load (e.g., higher than the threshold load at 412), blow-by and EGR to the intake port may be desired or enabled. In another example, when the engine's BTCC hardware (e.g., the BTCC valve 54 and / or the purge exhaust valves 6, as shown in Fig. 1A) is enabled, blowby and EGR may be enabled. For example, the BTCC hardware may be determined to be enabled if the purge outlet valves are operating (e.g., not deactivated) and the BTCC valve is open or at least partially open. If blowby and EGR are desired and / or the BTCC hardware is already enabled, the method proceeds to 430 to operate in the initial BTCC mode. Details regarding operating in the initial BTCC mode are discussed further below with reference to the Fig. 10-13 described.

[0107] At 428, if BTCC is not desired, the method alternatively proceeds to 432 to deactivate the purge exhaust valves and operate the engine without blowby. For example, this may include maintaining the purge exhaust valves in the closed position and directing exhaust gases from the engine cylinders via the blowby exhaust valves only to the exhaust passage. As an example, the controller may send a deactivation signal to the valve actuators of the purge valves (e.g., in Fig. 1A) to deactivate the SVs of each cylinder. Furthermore, at 431, the method may include not operating the engine with EGR. The method then proceeds to 434 to deactivate the charge motion control valves (e.g., in Fig. 1A) in the open position so that intake air is not blocked as it enters the engine cylinders via the intake passages. The method then ends.

[0108] Continue at Fig. 5, a method 500 for operating the internal combustion engine system in a cold start mode is shown. The method 500 may continue from 406 of the method 400, as described above. The method 500 begins at 502 by determining whether the purge exhaust valves (e.g., those shown in Fig. 1A) are activated by default. The purge exhaust valves (SVs) may be activated (e.g., open) by default when the valve actuation mechanism (e.g., various valve lift and / or VCT mechanisms as described above and referred to as exhaust valve timing actuator 103 in Fig. 1B) of the purge outlet valves is activated so that the purge outlet valves are actuated open at their set timing. In some examples, the valve actuation mechanism may be deactivated so that the purge outlet valves do not open (and instead remain closed) at their set timing in the engine cycle. The default setting may be the purge outlet valves on state at engine shutdown. In this way, the purge outlet valves may be either activated or deactivated by default at engine startup and during cold start. If the purge outlet valves are activated by default, the method proceeds to 504 to activate the BTCC valve (e.g., the one shown in Fig. 1A) for the first start (e.g. first rotation of the crankshaft).

[0109] At 506, the method includes, after firing the first cylinder (e.g., after injecting fuel into the first cylinder and combusting the air and fuel within the first cylinder), modulating a position of the BTCC valve to direct the EGR through the EGR passage (e.g., the passage shown in Fig. 1A) and to the inlet of the compressor to a desired EGR flow rate. The desired EGR flow rate may be adjusted based on engine operating conditions (e.g., engine load, MAF, combustion A / F, and / or set emissions thresholds). In one example, modulating the position of the BTCC valve may include alternating the position of the BTCC valve between a fully open and fully closed position to maintain a desired EGR flow rate to the intake passage upstream of the compressor.In an alternative example where the BTCC valve is a continuously variable valve adjustable in more than two positions, modulating the position of the BTCC valve may include continuously adjusting the position of the BTCC valve to a variety of positions between fully open and fully closed to maintain the desired EGR flow rate. Additionally, at 506, the method may include adjusting the position of the BTCC valve to prevent backflow through the EGR passage (e.g., intake airflow from the intake passage through the EGR passage to the purge exhaust manifold). For example, control may be initiated in response to a purge exhaust manifold pressure (e.g., the pressure measured in . Fig. 1A) falls below atmospheric pressure, the controller may actuate the BTCC valve to the fully closed position to block flow through the EGR passage. Thus, in some examples, the method at 506 may include the controller making a logical determination (e.g., regarding a position of the BTCC valve) based on logical rules that are a function of the desired EGR flow and a pressure in the purge outlet valve. As another example, the controller may include a lookup table stored in memory with the desired EGR flow and purge manifold pressure as inputs and the BTCC valve position as an output. The controller may then generate a control signal sent to an actuator of the BTCC valve and result in adjusting the BTCC valve (e.g., adjusting a valve plate of the BTCC valve) to the determined position.When the BTCC valve is closed at 506, the method may further include opening (or at least partially opening) the purge manifold bypass valve (e.g., in an engine system including a purge manifold bypass passage, such as passage 98 and SMBV 97, as shown in FIG. Fig. 1A). In this way, excess pressure in the purge exhaust manifold may be relieved by flowing at least a portion of the exhaust gases discharged from the purge outlet valves to the purge exhaust manifold and then to the exhaust passage via the purge manifold bypass passage.

[0110] At 508, the method includes determining whether it is possible to adjust the on-state of the purge outlet valves. As one example, VCT systems may include hydraulically controlled valves that rely on oil pressure to operate and change an on-state and / or timing profile of the valves. Thus, in some examples, the on-state of the purge outlet valves may only be changed when oil pressure has reached a threshold pressure for changing a timing profile or on-state of the purge outlet valves. In alternative embodiments, the purge outlet valves may be adjusted in response to another variable. If it is determined at 508 that the on-state or timing profile of the purge outlet valves cannot be adjusted, the method proceeds to 510 to keep the purge outlet valves activated and continue modulating the BTCC valve.However, if the purge exhaust valves' on state can be switched, the method proceeds to 512 to determine if the purge exhaust valves are capable of switching between timing profiles. In one example, the purge exhaust valves may be switched between cam timing profiles (e.g., to adjust the opening and closing timing within the engine cycle) rather than being deactivated. If the purge exhaust valves cannot be switched between timing profiles, the method proceeds to 514 to deactivate the purge exhaust valves (e.g., to disable the purge exhaust valve actuation / timing mechanisms so that the purge exhaust valves can remain closed and not open at their intended timing) and close the BTCC valve (e.g., to fully close).In some examples, the method at 514 may include retaining some hydrocarbon emissions during cranking within the purge exhaust manifold until the BTCC valve can be reopened. Adjusting the purge exhaust valves and the BTCC valve in this manner as the engine warms up may increase the low-load stability of the engine while reducing emissions during cold start.

[0111] Alternatively, if the purge outlet valves can be switched between timing profiles, the method may proceed to 516 at 512. At 516, the method includes switching the timing of the purge outlet valves to an early opening / lift profile (as in trace 326 of Fig. 3B, as described above) and closing the BTCC valve. In one example, at 516, the method may include advancing the timing (e.g., the opening timing) of the purge exhaust valves and / or increasing an amount of lift of the purge exhaust valves via changing the cam timing profile. In some examples, at 516, the method may further include opening the purge manifold bypass valve to allow exhaust gases to flow from the purge manifold into the intake passage while the BTCC valve is closed. In this embodiment of the method, the pre-catalyst may be located downstream of where the purge manifold bypass passage couples to the exhaust passage (such as the Fig. 1A). Thus, in this embodiment, no additional pre-catalyst (such as a three-way catalyst) may be present upstream of where the scavenging manifold bypass passage couples to the exhaust passage.

[0112] Both of the methods at 516 and 514 proceed to 530 to determine whether a catalyst disposed in the exhaust passage is at (e.g., has reached) a light-off temperature. In one example, the catalyst may be part of one or more emission control devices positioned in the exhaust (e.g., the Fig. 1A). If the one or more catalysts are at or above their light-off temperatures (e.g., for efficient catalyst operation), the method proceeds to 532 to adjust the timing of the purge exhaust valves based on engine conditions. In one example, at 532, the method may include adjusting the purge exhaust valves to their default or baseline timing (e.g., the timing shown in Fig. 3A). Then the procedure ends.

[0113] Alternatively, if a temperature of the one or more catalysts falls below the light-off temperature, the method proceeds to 534 to further adjust engine operation to increase the temperature of the catalyst. In one example, as shown at 536, the method may include, at 534, deactivating the blow-off exhaust valves of the outer cylinders (e.g., the Fig. 1A), while all purge exhaust valves (for all outer cylinders and inner cylinders) remain active. For example, the inner cylinders may be physically positioned between the outer cylinders. In this way, only exhaust from the inner cylinders may flow to the catalysts within the exhaust passage. The method at 536 may further include maintaining fueling to the cylinders with the deactivated blowback exhaust valves, but not firing those cylinders (however, spark is still provided to the cylinders with non-deactivated blowback exhaust valves). In another example, as shown at 538, the method at 534 may include reducing an opening of the throttle (e.g., the opening shown in Fig. 1A) and opening a valve in a second EGR passage located between the purge exhaust manifold and the intake passage downstream of the compressor and upstream of the throttle (e.g., the throttle shown in Fig. 1A). This may result in air flowing backward through the second EGR passage, from the intake passage to the purge exhaust manifold, and into the cylinders via the purge exhaust valves. This may result in increasing the temperature of blowby gases routed to the exhaust via the purge exhaust manifold, thereby increasing the temperature of the catalyst. The method at 538 may be referred to herein as an idle mode and may be described below with reference to Fig. 7A-7B will be explained in more detail. At 534, one of the methods at 536 and 538 may be selected based on the architecture of the engine system. For example, the method at 538 may be used if the system includes the second EGR passage. Otherwise, the method at 536 may be used. In alternative embodiments, the method at 534 may select between the methods at 536 and 538 based on alternative engine operating conditions.

[0114] Returning to 502, if the purge outlet valves are not enabled by default, they may be disabled (and thus closed) by default. In this case, the method proceeds to 518 to perform a timing control of the intake valves (e.g., the valves shown in Fig. 1A) and retard a timing of the exhaust valves. Advancing the timing of the intake valves may adjust one or more valve timing mechanisms of the intake valves to advance a closing timing of the intake valves. Additionally, retarded the timing of the exhaust valves may include retarded opening timing of both the scavenge exhaust valves and the blowoff exhaust valves together (e.g., when controlled via the cam timing system) or retarded opening timing of only the blowoff exhaust valves. These adjustments may increase combustion stability during cold start. At 520, the method includes determining whether it is possible to adjust the on-state or timing profile of the scavenge exhaust valves (e.g., similar to the method at 508 as described above).If the purge outlet valves cannot be adjusted (e.g., due to oil pressure falling below a threshold for switching the valve on state), the method proceeds to 522 to keep the purge outlet valves deactivated. Otherwise, if the purge outlet valves can be adjusted (or reactivated), the method proceeds to 524 to determine if it is possible to switch the purge outlet valves between timing profiles (e.g., similar to the method at 512 as described above). If the purge outlet valves cannot be switched between profiles, the method proceeds to 526 to activate the purge outlet valves and modulate the BTCC valve to control EGR flow through the EGR passage and to the compressor inlet to a desired amount.However, if the purge exhaust valves can be switched between profiles, the method instead proceeds to 528 to change the purge exhaust valve profile to early open / lift and close the BTCC valve, as described above at 516. Both of the methods at 526 and 528 then proceed to 530, as described above.

[0115] Fig. 16 shows a graph 1600 for operating the split exhaust engine system in cold start mode. In particular, the graph 1600 shows an activation state of the purge outlet valves (where on is enabled and off is disabled) at graph 1602, a position of the BTCC valve at graph 1604, the EGR flow (e.g., an amount or flow rate of EGR flow through the EGR passage 50 and to the compressor inlet, as shown in Fig. 1A) at trace 1606, a temperature of an exhaust catalyst relative to a catalyst light-off temperature at trace 1608, a position of an intake throttle (e.g., the position shown in Fig. 1A) at trace 1610, a position of a second intermediate pressure EGR valve disposed in a second (e.g., intermediate pressure) EGR passage (e.g., the one shown in Fig. 1A, in the second EGR passage 58), at plot 1612, and cam timing of the intake valves at plot 1614 and the exhaust valves (which may include the blow-off exhaust valves and the purge exhaust valves if controlled on the same cam timing system) at plot 1616 relative to their output timings B1 (an example of the output cam timings of the intake and exhaust valves may be shown in Fig. 3B, as described above). All curves are plotted against time along the x-axis.

[0116] Before time t1, the engine starts with the scavenging exhaust valves activated by default. This allows the scavenging exhaust valves to open and close at their set timing in the engine cycle. At time t1, the BTCC valve is opened for the first crank. Thus, EGR flow begins to increase after time t1 (and may increase and decrease over time as the BTCC valve opens and closes, respectively). After the first cylinder fires, the BTCC valve is modulated to control EGR flow to a desired level. Between time t1 and time t2, the intermediate pressure EGR valve is closed, and both the intake and exhaust valve timings are at their initial timings. At time t2, the scavenging exhaust valves may be adjusted (e.g., because oil pressure has reached a threshold to adjust the valves), so the scavenging exhaust valves are deactivated (e.g.,(off). After time t2, the catalyst temperature is still below the light-off temperature T1. Thus, the throttle opening is reduced and the intermediate-pressure EGR valve is opened to reverse the flow through the system and send warmer blow-by air to the catalyst within the exhaust passage. This can lead to the catalyst heating to a temperature above the light-off temperature T1.

[0117] During another cold start in the split exhaust engine system, the engine may start with the purge exhaust valves deactivated (e.g., off) by default, as shown at time t3. At time t4, the intake cam timing is advanced and the exhaust cam timing of the purge exhaust valves is retarded (as shown at trace 328 in Fig. 3B, as described above). At time t5, the purge outlet valves are activated in response to the purge outlet valves being adjustable, and the BTCC valve is modulated to adjust EGR flow.

[0118] In this way, exhaust emissions can be reduced during engine cold start by adjusting an activation state of the purge exhaust valves, while also controlling a position of the BTCC valve based on a desired EGR flow and a pressure in the purge exhaust manifold. As described above with reference to Fig. 5 and Fig. 16, a method may include adjusting a position of a first valve (BTCC valve) disposed in an exhaust gas recirculation (EGR) passage based on an engine operating condition during a cold start, wherein the EGR passage is coupled between a first exhaust manifold (purge manifold) coupled to a first set of exhaust valves (purge exhaust valves) and an intake passage upstream of a compressor, while a portion of the exhaust gases flow via a second set of exhaust valves (blowoff exhaust valves) to an exhaust passage including a turbine.A technical effect of adjusting the first valve and / or the first set of exhaust valves in response to an engine operating condition during a cold start is to reduce cold start emissions while also assisting in warming up the engine, such as increasing a temperature of the engine cylinders and / or pistons and / or one or more exhaust catalysts.In another embodiment, in response to selecting engine operating conditions (such as a cold start and / or catalyst temperature below a light-off temperature), a method may include deactivating one or more valves of a set of first exhaust valves (blow-off exhaust valves) coupled to a first exhaust manifold coupled to an exhaust passage, while maintaining active all valves of a set of second exhaust valves (scavenge exhaust valves) coupled to a second exhaust manifold coupled to an intake passage via an exhaust gas recirculation (EGR) passage.A technical effect of deactivating one or more of the blowoff exhaust valves (such as the blowoff exhaust valves of the outer cylinders, as described above at 536 of method 500) during a cold start is to increase a temperature of the engine during the cold start and thus reduce engine emissions during the cold start (e.g., the catalyst may reach its light-off temperature faster than if all blowoff exhaust valves are activated). In another embodiment, a method may include, while both a first exhaust valve (purge exhaust valve) and a second exhaust valve (blowoff exhaust valve) of a cylinder are open, directing intake air through a flow passage (e.g.,Intermediate-pressure EGR passage) coupled between an intake passage and a first exhaust manifold coupled to the first exhaust valve; and further directing the intake air through the first exhaust valve into the cylinder and out the second exhaust valve to a second exhaust manifold (blow-off exhaust manifold) coupled to an exhaust passage that includes a turbine. A technical effect of directing the intake air in this manner while both the first and second exhaust valves are open in response to a temperature of a catalyst disposed in the exhaust passage downstream of the turbine falling below a threshold temperature is to increase the temperature of the blow-by air to the exhaust passage and thus increase the temperature of the catalyst. As a result, the catalyst may reach its light-off temperature more quickly, and engine emissions during cold start may be reduced.

[0119] Continue at Fig. 6, a method 600 for operating the engine system in a DFSO mode is shown. The method 600 may proceed from 410 of the method 400, as described above. At 602, the method includes stopping fuel supply to all cylinders to initiate the DFSO mode. The method proceeds to 604 to open the blowoff exhaust valve (e.g., the one shown in Fig. 1A) of one or more cylinders and leave all purge exhaust valves active. In one example, the method includes, at 604, deactivating the blowoff exhaust valve of each cylinder so that no exhaust gas is directed to the catalyst(s) disposed within the exhaust passage. As a result, oxygen to the catalyst (e.g., three-way catalyst) may be reduced, thereby preserving catalyst function. In another example, the method includes, at 604, deactivating the blowoff exhaust valve of a selected number of cylinders (e.g., only a portion of all engine cylinders). The selected number may be based on pedal position (e.g., driver torque demand), estimated exhaust temperature, turbine speed of a turbine disposed in the exhaust passage, and / or vehicle deceleration rate (e.g., rate of deceleration of vehicle speed).As an example, the method at 604 may include deactivating all BDVs (e.g., each BDV of each cylinder). However, in this example, the turbine may stop rotating and the catalyst may cool. Thus, the methods at 602 and 604 may alternatively include leaving the BDVs of one or more cylinders active and firing the corresponding one or more cylinders to reduce engine braking, spin up the turbine, and maintain catalyst temperature (e.g., without decreasing catalyst temperature). The spark amount to fire the cylinder(s) may be delayed to reduce torque and increase exhaust heat and engine efficiency. Then, the spark fraction (e.g.,The number of cylinders fired with active BDVs and spark to fire the cylinder(s) may be determined based on pedal position, estimated exhaust temperature, and a vehicle deceleration rate. As another example, if the turbine speed falls below a threshold speed, the selected number of BDVs to deactivate may be smaller than if the turbine speed exceeded the threshold speed. In this way, turbocharger delay may be reduced after the DFSO event. As one example, control may make a logical determination of the number of blowoff exhaust valves to deactivate at 604 and / or the number of cylinders stopping fueling as a function of turbine speed, pedal position, estimated exhaust temperature, and / or vehicle deceleration rate.The controller can then send a control signal to an actuator of the blow-off valves to deactivate the specified number of blow-off valves. As an example, each blow-off valve can include an actuator (such as the one shown in . Fig. 1A) which can be used to deactivate and reactivate the associated blow-off outlet valve.

[0120] At 606, the method includes determining whether it is time to reactivate the blowoff exhaust valves of the deactivated cylinders. As an example, it may be determined that it is time to reactivate the deactivated blowoff exhaust valves at the end of the DFSO event, which may be indicated by an increase in vehicle speed and / or an acceleration pedal depression (e.g., a pedal position depressed beyond a threshold position). If it is not time to reactivate the blowoff exhaust valves, the method proceeds to 608 to continue operating the engine with the deactivated cylinders (e.g., cylinders with the blowoff exhaust valves deactivated). Otherwise, if DFSO has ended and / or it is time to reactivate the cylinders, the method proceeds to 610 to reactivate the blowoff exhaust valves of the deactivated cylinders.As one example, reactivating the blowoff exhaust valves of the deactivated cylinders may include sending a signal to one or more valve actuation mechanisms of the blowoff exhaust valves to resume operating the blowoff exhaust valves at their set timing. Furthermore, reactivating the blowoff exhaust valves may include providing spark to each deactivated cylinder after an intake valve closing event and then opening the deactivated blowoff exhaust valve. At 612, the method includes reactivating fuel injection to the cylinders and reducing the amount of fuel enrichment to the cylinders. In one example, this may include reducing the amount of fuel injected to the cylinders compared to a default fuel injection amount following a DFSO event (e.g., without deactivating the blowoff exhaust valves).Because less oxygen was delivered to the catalyst during the DFSO event due to the deactivation of the blowdown exhaust valve, less fuel enrichment may be required after the DFSO event. Consequently, fuel efficiency is increased compared to conventional DFSO.

[0121] Fig. 17 shows a plot 1700 for operating the split exhaust engine system in DFSO mode. Specifically, plot 1700 shows a pedal position (e.g., accelerator pedal position) at plot 1702, a fuel supply amount (injected into the engine cylinders) at plot 1704, an on-state of a first cylinder scavenge exhaust valve (BDV) at plot 1706, an on-state of a second cylinder scavenge exhaust valve (BDV) at plot 1708, an on-state of a third cylinder scavenge exhaust valve (BDV) at plot 1710, an on-state of a fourth cylinder scavenge exhaust valve (BDV) at plot 1712, turbine speed at plot 1714, and an on-state of all cylinders' scavenge exhaust valves (SVs) at plot 1716.

[0122] Before time t1, the pedal position is relatively constant, and the BDVs and SVs of all four cylinders are activated (e.g., turned on). Thus, each BDV can open and close according to a set timing in the engine cycle. At time t1, the pedal position decreases, indicating a deceleration event. A DFSO event is initiated by cutting off fuel supply to a portion of the engine cylinders. As shown at time t1, fuel supply to cylinders 2-4 can be stopped but maintained to cylinder 1 to maintain engine speed at a threshold speed, keep the turbine spinning, and keep the catalyst warm and at stoichiometry (and thus, fuel supply does not go to zero between time t1 and time t2).In response to the DFSO event and the deactivation of fuel delivery to cylinders 2-4, the BDVs of cylinders 2, 3, and 4 are deactivated, while the SVs for all cylinders remain activated. As a result, no exhaust gas flows from cylinders 2, 3, and 4 to the exhaust port. Instead, exhaust gases from the deactivated cylinders are routed to the intake port via the SVs and the scavenging exhaust manifold. At time t2, the pedal position increases and the DFSO event ends. The BDVs of cylinders 2, 3, and 4 are reactivated, and the amount of fuel delivery to the cylinders may be slightly reduced compared to a DFSO event where no BDVs are deactivated.

[0123] At time t3, another DFSO event occurs. In response to the DFSO event and the turbine speed being at a higher level (e.g., higher than at time t1 during the first DFSO event), the BDVs of cylinders 1, 2, 3, and 4 are deactivated. Thus, all BDVs of all cylinders are deactivated (e.g., due to a higher turbine speed at time t3, a greater number of BDVs are deactivated at time t3 than at time t1). In response to the DFSO event ending at time t3, all BDVs are reactivated.

[0124] In this way, in response to selecting engine operating conditions (such as a DFSO condition where fuel supply to the engine is disabled), one or more valves of a set of first exhaust valves (BDVs) coupled to a first exhaust manifold coupled to an exhaust passage may be deactivated, while all valves of a set of second exhaust valves (SVs) coupled to a second exhaust manifold coupled to an intake passage via an exhaust gas recirculation (EGR) passage are left active. One technical effect of deactivating one or more BDVs during the DFSO event is to reduce the amount of oxygen delivered to a catalyst in the exhaust passage during DFSO. As a result, catalyst performance may be improved and engine emissions may be reduced.Additionally, reducing the amount of oxygen directed to the catalyst during DFSO may allow for a small amount of fuel enrichment at the conclusion of the DFSO event to be used when reactivating the BDVs, thereby increasing the fuel efficiency of the engine system.

[0125] Continue with the Fig. 7A-7B, a method 700 for operating the engine system in a gas response mode is shown. The method 700 may continue from 414 of the method 400, as described above. At 702, the method includes determining whether conditions for operating in a hot pipe mode are met. In one example, the split exhaust engine system may include a passage coupled between the scavenging exhaust manifold and the intake passage downstream of an intake throttle (e.g., the Fig. 1A, referred to herein as a hot pipe). However, in some embodiments, the split exhaust engine system may not include the hot pipe, and thus the conditions for hot pipe mode would not be met. In one example, hot pipe mode may be the default mode for best fuel efficiency when the engine is throttled (e.g., when the amount of throttle opening is less than wide open throttle). Conditions for entering hot pipe mode include the engine system including the hot pipe and may additionally include engine knock not being limited. For example, when the engine load falls below a lower threshold load (e.g.,At low engine loads (e.g., at very light loads) and no more EGR can be tolerated by the engine, the hot pipe valve may be closed and the hot pipe conditions will not be met. In another example, when the engine load exceeds an upper threshold load (e.g., at high engine loads), knock may also occur and thus the hot pipe valve may be closed to push more EGR to the compressor inlet to cool the engine. Thus, the conditions for entering hot pipe mode may include the engine knock being unconstrained (e.g., the possibility of engine knock falls below a threshold) and being able to tolerate increased EGR.

[0126] If conditions for entering hot pipe mode are met, the method proceeds to 704. At 704, the method includes closing (e.g., fully closing) the intake throttle, opening the BTCC valve (e.g., the one in Fig. 1A) and opening the valve of the hot pipe (e.g. the one shown in Fig. 1A). As a result, intake air from the intake duct upstream of the compressor can enter the EGR duct (e.g. the one shown in Fig. 1A), through an EGR cooler (e.g. the one shown in Fig. 1A), into the exhaust manifold, through the hot pipe (e.g. the one shown in Fig. 1A), into the intake manifold downstream of the intake throttle and into the engine cylinders. By flowing through the EGR cooler, the intake air is heated before entering the engine cylinders. This can increase MAP, reduce engine intake pumping work, increase fuel efficiency, and reduce engine emissions. In addition, this operation can also reduce scavenging manifold pressure, thereby increasing EGR flow. This intake air can then be combusted within the engine cylinders. A first portion of the combustion gases is then exhausted from the engine cylinders via the blowdown exhaust valves into the blowdown exhaust manifold. The first portion of the combustion gases then flows through the exhaust passage to the turbine and one or more emission control devices.A second portion of the combustion gases is exhausted from the engine cylinders through the purge exhaust valves into the purge exhaust manifold. The second portion of exhaust gases is mixed with intake air within the purge exhaust manifold, and the mixture is then directed to the intake manifold via the hot pipe. This mixture can reduce the influence of any one cylinder on EGR mixing, thus reducing drag and improving manifold optimization.

[0127] At 706, the method includes adjusting (e.g., adjusting a position) of the hot pipe valve based on a desired MAP and adjusting exhaust cam timing based on engine load. As an example, the method adjusts the amount of opening (or position) of the hot pipe valve based on a desired MAP, which may be determined based on engine operating conditions. For example, the controller may determine a control signal sent to the hot pipe valve actuator based on a determination of the desired MAP. The controller may determine the control signal by a determination that takes a particular desired MAP into account, such as increasing the amount of opening of the hot pipe valve as the desired MAP increases.Alternatively, the controller may determine the amount of hot pipe valve opening based on a calculation using a lookup table with the input being the desired MAP and the output being the hot pipe valve position signal. As another example, the controller may make a logical determination (e.g., regarding an actuator of the scavenging and blowoff exhaust valves cam timing system) based on logical rules that is a function of engine load. The controller may then generate a control signal to send to the exhaust valve cam timing actuator. For example, as engine load increases, the cam timing of the exhaust valves (e.g., blowoff and scavenging exhaust valves if controlled by the same cam system) may be advanced.

[0128] At 708, the method includes determining whether conditions are met for a VDE mode where one or more blowoff exhaust valves are deactivated. In one example, conditions for entering VDE mode may include one or more of a turbine speed above a threshold speed (e.g., which may be based on a speed at which turbocharger retardation may occur upon an increase in torque demand) and / or an engine load below a threshold load. If conditions for operating in VDE mode are met, the method proceeds to 710. At 710, the method includes deactivating the blowoff exhaust valve of one or more cylinders. In one example, the number of cylinders for which the blowoff exhaust valve is deactivated may be based on engine load or torque demand. In particular, as engine load decreases, the number of cylinders with deactivated blowoff exhaust valves may increase.For example, during a first state, at throttle response, when the engine torque demand falls below a lower threshold level, the blowoff exhaust valves of each engine cylinder may be deactivated. During the second state, at throttle response, when the engine torque demand exceeds the lower threshold level, only a portion of the blowoff exhaust valves of the engine cylinders may be deactivated, with the portion (and thus the number of cylinders with deactivated blowoff exhaust valves) decreasing as the torque demand continues to increase above the lower threshold level. Additionally, at 710, all purge exhaust valves of all cylinders are left activated during blowoff exhaust valve deactivation. Furthermore, at 710, the method may include deactivating spark delivery to the cylinders with deactivated blowoff exhaust valves while still supplying fuel.In this way, a firing decision may be made later in the engine cycle (since fuel is still being injected). Additionally, fueling the deactivated cylinders and pumping the mixture to fire the cylinders (e.g., cylinders without deactivated blowoff exhaust valves) may increase fuel vaporization upon cylinder firing (and thereby reduce smoke). Further, at 710, the method may include keeping the hot pipe open and the throttle closed during blowoff valve deactivation. In some examples, at 710, the method may include re-enabling the deactivated blowoff exhaust valves in response to an increase in torque demand above a threshold and / or commanding the throttle to fully open (or opening the throttle). The method may then terminate.

[0129] Returning to 702, if the conditions for hot pipe mode are not met, the method proceeds to 712 to determine if the conditions for an EIVC (early intake valve closing) mode are met. In one example, the decision to enter EIVC mode may be a function of MAP, engine speed, and engine temperature when the engine load is below a threshold load. In one example, conditions for entering EIVC mode may include the engine load being below a threshold load and the MAP being at atmospheric pressure (e.g., when the engine is not boosted). If conditions for EIVC mode are met, the method proceeds to 714.At 714, the method includes deactivating the intake valves and opening the scavenging exhaust valves (at the timing set for each cylinder) to introduce air into the engine cylinders via the scavenging exhaust valves, rather than via the intake valves. Specifically, at 714, the method may include deactivating the intake valves (e.g., both intake valves) of all engine cylinders so that no intake air is introduced into the cylinders via the intake valves. The method at 714 may further include opening (e.g., fully opening) the BTCC valve (if not already open).

[0130] At 716, the method includes retarding the timing of the blowoff exhaust valve and the scavenge exhaust valve to reverse the direction of intake air into the cylinder (e.g., to enter the cylinder via the scavenge exhaust valves). In one example, at 716, the method may include operating both the scavenge exhaust valves and the blowoff exhaust valves at a maximum amount of exhaust cam retard (e.g., when controlled by the same cam system). As another example, at 716, with a cam-in-cam type control system, the method may include adjusting the closing of the blowoff exhaust valves to TDC and advancing the scavenge exhaust valves to reduce the overlap between the scavenge and blowoff exhaust valves of each cylinder. As yet another example, at 716, with a cam profiling system, the method may include changing the cam profiles (e.g.,The timing of the purge exhaust valves and blow-off exhaust valves is optimized for EIVC. As a result of this process, in EIVC mode, intake air is drawn into the engine cylinders from the intake port via the EGR port, purge exhaust manifold, and the purge exhaust valves. After combustion within the engine cylinders, exhaust gases are discharged to the exhaust port via the blow-off exhaust valves. This reduces cylinder pumping during low load. Furthermore, charge motion is improved for increased combustion stability.

[0131] Referring again to 712, if conditions for EIVC mode are not met, the method proceeds to 718 to determine if conditions exist to close a charge motion control valve (CMCV) coupled to an intake port of a manifold of each cylinder (such as in Fig. 1A) are met. In one example, the conditions for closing the CMCVs may include an engine load being below a lower threshold load. If the conditions for closing the CMCVs are met, the method proceeds to 720 to close the CMCV coupled to the intake port of the intake valve of each cylinder (such as in Fig. 1A). For example, at 720, the method may include adjusting the CMCVs to control intake flow to the intake valves (e.g., an intake valve as shown in Fig. 1A) of each cylinder. As a result, the turbulence (or swirl) of the intake airflow entering the engine cylinders may increase, allowing the intake air to scavenge an increased amount of exhaust gas from inside the engine cylinders and scavenge the exhaust manifold.

[0132] Otherwise, if conditions to close the CMCV are not met (or they are already closed), the method proceeds to 722 to determine if conditions for an idle boost mode are met. In one example, the condition to enter idle mode includes when the engine is idling (e.g., when the vehicle speed is below a threshold vehicle speed, which may be zero, and / or when the engine speed is below a threshold engine speed). As one example, operating in idle boost mode may allow pressurization of the scavenging manifold, resulting in air scavenging a portion of the exhaust gases trapped in the cylinders. This may increase combustion stability and / or increase heating of one or more catalysts disposed in the exhaust passage.Thus, in one example, a condition for entering idle boost mode includes when purging gases from the engine cylinders is desired. If the conditions at 722 are met, the method proceeds to 724.

[0133] At 724, the method includes closing the turbocharger wastegate (e.g., in Fig. 1A) to increase the boost pressure and open a valve in an idle boost pipe (e.g. valve 59 in the second EGR channel 58, in Fig. 1A). The idle boost pipe may also be referred to as a second or intermediate-pressure EGR passage and may be coupled between the scavenging exhaust manifold and the intake passage downstream of the compressor. By opening the valve in the idle boost pipe while the engine load is below a threshold, intake airflow from downstream of the compressor may flow through the idle boost pipe and into the scavenging exhaust manifold. Thus, when both the scavenging exhaust valve and the blowoff exhaust valve of a same cylinder are open, intake air may flow from the idle boost pipe via the scavenging exhaust valve into the engine cylinder and then via the blowoff exhaust valve to the exhaust passage. This may be referred to as blowby to exhaust.This allows for the purging of exhaust residues from within the engine cylinders to the exhaust passage during idle conditions, thereby increasing engine stability. At 724, the method may further include modulating the BTCC valve position to achieve a desired blowby amount during an overlap (e.g., port overlap) period between the blowoff exhaust valve and the scavenge exhaust valve of each cylinder. As one example, the desired blowby amount during the overlap period may be determined based on engine stability. For example, purging exhaust from the cylinders may improve the combustion rate and allow for richer fueling of the cylinders, which may increase stability. However, too much blowby may decrease fuel efficiency and reduce catalyst temperatures.For example, modulating the BTCC valve position includes opening and closing the BTCC valve to control a purge exhaust manifold pressure to a level that produces a desired amount of blowby from the purge outlet valve to the blowby outlet valve while the purge and blowby outlet valves are both open. As one example, decreasing the amount of BTCC valve opening and / or closing the BTCC valve for an extended period of time may increase the pressure within the purge exhaust manifold (e.g., above the pressure in the exhaust passage) and increase the amount of blowby to the exhaust. As yet another example, the controller may control the purge manifold bypass valve (e.g., SMBV 97, shown in FIG. Fig. 1A) and adjust a BTCC valve position to increase the purge exhaust manifold pressure above the exhaust pressure. The excess air in the exhaust created by the purge may allow rich in-cylinder conditions, increasing engine stability while maintaining an overall stoichiometric air-fuel ratio downstream of a catalyst for reduced emissions. In some examples, the method may additionally include decreasing an amount of opening (or fully closing) of the intake throttle at 724.

[0134] The method proceeds to 726 and includes controlling exhaust and intake valve overlap to regulate flow to the intake manifold from the scavenging exhaust manifold. For example, at 726, the method may include adjusting the timing of a cylinder's scavenging exhaust valve and intake valve to adjust an amount of valve overlap between the intake valve and the scavenging exhaust valve and control airflow from the scavenging exhaust manifold to the intake manifold to a desired level. The desired air level for the intake manifold may be varied based on engine load. For example, in response to increasing engine load, the controller may send signals to timing actuators of the scavenging exhaust valves and intake valves to increase the amount of valve overlap between the intake valve and the scavenging valve of each cylinder, thereby increasing airflow from the scavenging manifold to the intake manifold.As one example, the controller may make a logical determination regarding the timing of the purge exhaust valve and intake valve based on logic rules that are a function of engine load. The controller may then generate a control signal to send to the intake and exhaust valve timing actuators.

[0135] The method may then proceed to 728 to further increase boost and blow-by to desired levels by one or more of turning on (and operating) an electric compressor (e.g., electric compressor 60 shown in Fig. 1A), increasing the opening of the turbocharger wastegate, adjusting spark retard, and / or adjusting cam timing to adjust the purge valve and blowoff valve overlap. As one example, the method may include, at 728, increasing an amount of wastegate opening in response to a request to decrease a pressure of the purge exhaust manifold and reduce an amount of blowby air flowing from the purge exhaust manifold to the blowoff exhaust manifold. As another example, operating the electric compressor may improve blowby capability by providing increased pressure to the purge exhaust manifold. In yet another example, increased spark retard may be used in response to a request for more blowby to the exhaust. In yet another example, in systems in which the blowoff and purge exhaust valve overlap can be varied (e.g.,via a cam-in-cam type system) the overlap can be increased to increase blow-through.

[0136] Referring again to 722, if the idle boost mode conditions are not met, the method proceeds to 730 Fig. 7B. As an example, the conditions for idle boost mode may not be met when it is determined that it is time to measure EGR retraction into a purge outlet valve conduit. At 730, the method includes determining whether the engine is idling (e.g., when an accelerator pedal is not applied and / or the engine is decoupled from the vehicle's powertrain). If the engine is idling, the method proceeds to 732 to determine the amount of EGR that has retracted into the conduit (e.g., exhaust port) of each purge outlet valve based on the oxygen level measured via an oxygen sensor positioned in the exhaust conduit of each purge outlet valve. For example, an oxygen sensor may be positioned in the exhaust conduit of each purge outlet valve (such as the oxygen sensors 38 shown in Fig. 1A), and thus, an output of each oxygen sensor may provide an estimate of EGR retraction for each cylinder. At 734, the method includes adjusting exhaust valve timing (e.g., purge exhaust valves and blowoff exhaust valves) to adjust EGR flow based on the estimated amount of EGR retraction for each engine cylinder. This may include, for example, advancing exhaust valve timing to increase EGR flow in response to increasing EGR retraction. As another example, control may make a logical determination (e.g., regarding exhaust valve timing) based on logic rules that are a function of EGR retraction into the purge exhaust valve lines. Control may then generate a control signal to be sent to the exhaust valve timing actuators. Alternatively, if the engine is not idling at 730, the method ends.

[0137] The Fig. 18A-18B show a graph 1800 for operating the split exhaust engine system in a gas response mode. In particular, graph 1800 shows the engine load at plot 1802, a position of an intake throttle (e.g., intake throttle 62 shown in Fig. 1A) at trace 1804, a BTCC valve position (e.g. valve 54, shown in Fig. 1A) at trace 1806, a position of the hot tube valve (e.g., valve 32, shown in Fig. 1A) at trace 1808, MAP relative to atmospheric pressure (ATM) at trace 1810, an activation state (e.g., on and operating or off and deactivated) of the intake valves at trace 1812, an activation state of the purge exhaust valves (e.g., valves 6, shown in Fig. 1A) at course 1814, a position of the CMCVs (e.g. CMCVs 24, shown in Fig. 1A) at curve 1816, a position of the idle boost tube valve (e.g., valve 59, shown in Fig. 1A) at curve 1818, a position of the turbocharger wastegate (e.g. wastegate 76, shown in Fig. 1A) at curve 1820, an operating state of an electric compressor (the electric compressor 60, shown in Fig. 1A, where a indicates that the electric compressor is driven by an electric motor of the electric compressor), a pressure in the purge exhaust manifold (e.g., output of pressure sensor 34 shown in Fig. 1A) at trace 1824, a pressure at the compressor inlet of the turbocharger compressor (e.g., output of pressure sensor 31, shown in Fig. 1A) at trace 1826, an activation state of a first blow-off exhaust valve (BDV) of a first cylinder at trace 1828, and an activation state of the blow-off exhaust valves (BDVs) of a second, third, and fourth cylinders at trace 1830. Although the valve positions in the Fig. 18A-18B can be shown as open and closed, the valves can be adjusted to a variety of positions between fully open and fully closed.

[0138] Before t1, the engine load is above a lower threshold load L1 and the throttle is fully open. An engine load below the lower threshold load L1 may indicate a low load condition in which the throttle is at least partially closed (e.g., not fully open). Thus, the engine load is above this low load threshold before time t1. At time t1, the engine load decreases below the lower threshold load and the throttle position is reduced (e.g., the amount of throttle opening decreases). The engine may also be boosted at time t1 (e.g., MAP greater than ATM). In response to this low load condition at time t1, immediately after time t1, the throttle is closed, the BTCC valve is open, and the hot pipe valve is open to operate the engine in a hot pipe mode.The CMCVs may be kept closed during the low load condition at time t1. Further, the BDV of the first cylinder may be deactivated immediately after time t1 in response to the engine load being below the lower threshold load. However, the BDVs of the second, third, and fourth cylinders may remain activated. As a result, no exhaust gas moves from the first cylinder to the exhaust port while the BDV of the first cylinder is deactivated. In alternative embodiments, additional BDVs of additional cylinders may be deactivated in response to the low load condition. For example, if the engine load were to continue to be below the lower threshold load L1 between times t1 and t2, the controller may deactivate the BDVs of two or more cylinders (instead of just one, as shown at time t1).

[0139] At time t2, the engine load increases above the lower threshold load L1, and the throttle position gradually returns to the fully open position (e.g., wide-open throttle). Thus, one hot pipe valve is closed at time t2. Further, the CMCVs are opened, and all BDVs are turned on at time t2. The electric compressor is also turned on at time t2 to increase the boost. In response to the compressor inlet pressure being above the purge exhaust manifold pressure at time t2, the BTCC valve is also closed. The BTCC valve is opened again before time t3. In response to the BTCC valve being opened, the CMCVs are closed.

[0140] At time t3, the engine load again drops below the lower threshold load L1. In response to this low load condition and the conditions for EIVC mode being met, the intake valves of all engine cylinders are deactivated at time t3. In some examples, the exhaust cam timing of the BDVs and SVs may be retarded to allow intake air to be introduced into the engine cylinders via the SVs and expelled from the BDVs during EIVC mode. At time t4, the engine load increases above the lower threshold load L1. As a result, the intake valves are reactivated. Before time t5, the wastegate opens. In one example, the wastegate may open in response to the turbine speed increasing above a threshold turbine speed.For example, a turbine speed above the threshold turbine speed may result in a compressor outlet temperature higher than an upper threshold (e.g., to reduce turbocharger degradation).

[0141] At time t5, the engine load again drops below the lower threshold load L1. In response to this low load condition and the idle boost mode conditions being met, the idle boost pipe valve is opened and the wastegate is closed. Additionally, the BTCC valve is modulated to achieve a desired blow-by amount during the BDV and SV overlap period. At time t6, the engine load increases above the lower threshold load, and the idle boost pipe valve is closed.

[0142] In this way, the reverse flow through the EGR passage to the engine cylinders via the purge exhaust valves can be reduced during a gas reaction condition, which can cause reduced mixing and cylinder balance. As one embodiment of a method during a gas reaction condition, a method includes directing intake air from an intake passage to a first exhaust manifold (purge manifold) coupled to a first set of cylinder exhaust valves (purge exhaust valves) via an exhaust gas recirculation (EGR) passage; heating the intake air as it passes through an EGR cooler in the EGR passage; directing the heated intake air to an intake manifold downstream of an intake throttle via a flow passage (hot pipe) coupled between the first exhaust manifold and the intake manifold; and expelling combustion gases via a second set of cylinder exhaust valves (blow-off exhaust valves) to a second exhaust manifold.which is coupled to the exhaust passage. A technical effect of directing intake air in this manner, through the hot pipe, during a gas reaction condition (or when the engine load is below a threshold load) is to improve the mixing of EGR from each cylinder with incoming intake air, reduce cylinder pumping, heat the intake air via the EGR cooler to increase MAP, further reduce intake pumping, and improve fuel efficiency and reduce emissions. As another embodiment of a method during a gas reaction condition, a method includes, in response to engine load below a threshold, deactivating all intake valves of an engine cylinder while operating a first exhaust valve (purge exhaust valve) coupled to an exhaust gas recirculation (EGR) passage.a second exhaust valve (blowoff exhaust valve) coupled to an exhaust passage at different times; and directing intake air from the intake passage through the EGR passage and into the engine cylinder via the first exhaust valve. A technical effect of deactivating all intake valves during the gas response state is to warm the intake air via an EGR cooler disposed in the EGR passage, reducing pumping work, and improving fuel efficiency. As yet another embodiment of a method during the gas response state, a method includes, in response to an engine load below a lower threshold load, adjusting a first set of swirl valves (e.g., CMCVs) coupled upstream of a first set of intake valves to at least partially block intake airflow to the first set of intake valves, wherein each cylinder has two intake valves,including one of the first set of intake valves, and two exhaust valves. A technical effect of adapting the first set of swirl valves to at least partially block intake airflow to the first set of intake valves is to increase the turbulence of the intake airflow entering the cylinders via the first set of intake valves, thereby improving the scavenging of residual combusted exhaust gases from the combustion chambers. As a result, engine emissions may be reduced and engine efficiency may be increased. As yet another embodiment of a method during the gas response state, a method includes, in response to engine load below a threshold and while a first set of exhaust valves and a second set of exhaust valves are simultaneously open: directing intake air through a secondary flow passage (idle boost passage),coupled between an intake passage downstream of a compressor and a first exhaust manifold, the first exhaust manifold being coupled to the first set of exhaust valves; heating the intake air directed through the secondary flow passage via an EGR cooler coupled to the first exhaust manifold; and directing the heated intake air through engine cylinders and to a second exhaust manifold, the second exhaust manifold being coupled to the second set of exhaust valves and an exhaust passage including a turbine, via the first set of exhaust valves and the second set of exhaust valves. The technical effect of directing the intake air through the secondary flow passage in this manner while the engine load is below the threshold,consists in allowing the remaining exhaust gas to be forced out of the cylinder and into the exhaust passage before the second exhaust valve closes. As a result, engine efficiency and fuel efficiency can be improved even under gas reaction conditions.

[0143] Fig. 8 shows a method 800 for operating the engine system in an electric boost mode. Method 800 may continue from 418 of method 400, as described above. Thus, during method 800, the electric motor of the electric compressor may drive the electric compressor (e.g., driving a rotor of the electric compressor to increase the pressure of the intake air). At 802, the method includes determining whether a compressor inlet pressure is above a scavenging manifold pressure. As one example, the compressor inlet pressure may be a pressure at the inlet (or directly upstream) of the turbocharger compressor (e.g., compressor 162, shown in Fig. 1A). As another example, the compressor inlet pressure may be a pressure at an outlet of the EGR passage (e.g., where the passage 50 joins the intake passage in Fig. 1A upstream of the compressor 162). In one example, the compressor inlet pressure may be measured via a pressure sensor positioned in the intake passage upstream of the turbocharger compressor (e.g., pressure sensor 31, shown in Fig. 1A). In an alternative example, the compressor inlet pressure may be estimated by the controller based on one or more alternative engine operating parameters (such as a pressure upstream of the location where the electric compressor couples to the intake port). Additionally, the purge manifold pressure may be a pressure of the purge exhaust manifold (e.g., purge exhaust manifold 80, shown in Fig. 1A). In one example, the purge manifold pressure may be measured by a pressure sensor disposed in the purge manifold (e.g., pressure sensor 34 shown in Fig. 1A). In another example, purge manifold pressure may be estimated or measured via a plurality of pressure sensors positioned in exhaust conduits of the purge outlet valves.

[0144] If the compressor inlet pressure is above the purge manifold pressure, the method proceeds to 804 to determine a position of the BTCC valve (e.g., valve 54 shown in Fig. 1A) and / or the purge outlet valves (SVs, e.g. outlet valves 6, shown in Fig. 1A) to reduce blowby to the exhaust. In one example, the method at 804 may include one or more of decreasing the amount of opening of the BTCC valve and shutting off the SVs in response to a scavenge manifold pressure being below a turbocharger compressor inlet pressure while the electric motor is driving the electric compressor. In one example, the BTCC valve may be a two-position valve that can be adjusted to a fully open position and a fully closed position. In another example, the BTCC valve may be a continuously adjustable valve that can be adjusted to a fully open position, a fully closed position, and a plurality of positions between fully open and fully closed.In this example, an amount of decreasing the amount of BTCC valve opening may increase as the amount of purge manifold pressure decreases below the compressor inlet pressure. In another example, the controller may deactivate the SVs when the purge manifold pressure is below the compressor inlet pressure by a threshold amount. As one example, the method adjusts the amount of reducing the opening of the BTCC valve based on the purge manifold pressure. For example, the controller may determine a control signal to send to the BTCC valve actuator (or the SV actuator that controls an on state of the SVs) based on a determination of the purge manifold pressure.The controller may determine the BTCC valve position (open, closed, or a position between fully open and fully closed) through a determination that directly takes a particular position into account, such as decreasing the amount of opening as purge manifold pressure decreases. Alternatively, the controller may determine the BTCC valve position or an SV turn-on state based on a lookup table calculation where the input is purge manifold pressure and the output is the BTCC valve position (or SV turn-on state). As another example, the controller may make a logical determination (e.g., regarding a BTCC valve position) based on logic rules that are a function of purge manifold pressure. The controller may then generate a control signal sent to the BTCC valve (and / or SV) actuator.Adjusting the BTCC valve and / or the SVs in this manner at 804 reduces the reverse flow of gases from the scavenging manifold to the exhaust manifold and exhaust passage via the SVs and BDVs, which may occur due to the scavenging manifold being at a lower pressure than the intake passage at the compressor inlet.

[0145] The method proceeds to 808 to determine if the electric motor has stopped driving the electric compressor (e.g., the electric compressor is operating and no longer boosting the intake air). If the electric motor has stopped driving the electric compressor, the method proceeds to 812 to turn the SVs back on (if they were turned off at 804) and / or to open the BTCC valve (if it was closed or the amount of opening was reduced at 804). The method further includes, at 812, adjusting the position of the BTCC valve based on a desired EGR flow amount. As one example, the controller may make a logical determination (e.g., regarding a BTCC valve position) based on logic rules that are a function of a particular desired EGR flow amount. The controller may then generate a control signal to send to the BTCC valve actuator.Additionally or alternatively, the method at 812 may include returning to 420 from method 400.

[0146] Referring again to 808, if the electric motor is still driving the electric compressor, the method proceeds to 810 to further adjust the BTCC valve and the SVs based on the purge manifold pressure, as described above and below. The method may then return to 802 to again check the purge manifold pressure relative to the compressor inlet pressure. If the compressor inlet pressure is no longer greater than the purge manifold pressure, the method may proceed to 806 to reopen the BTCC valve if it was closed and / or re-enable the SVs if they were disabled. The BTCC valve is then controlled (e.g., adjusted) to deliver the requested (e.g., desired) EGR flow and / or blowby to the intake port.In this way, reverse flow through the EGR passage, through the scavenging manifold, through the engine cylinders, and to the exhaust passage can be reduced while the electric compressor is operating to boost the intake air and when the intake air pressure at the compressor inlet (and at the point where the EGR passage couples to the intake passage) is above the scavenging manifold pressure.

[0147] Fig. 19 shows a diagram 1900 for operating the split exhaust engine system in electric boost mode. In particular, the diagram 1900 shows an operating state of an electric compressor (e.g., the electric compressor 60 shown in Fig. 1A) at trace 1902, a pressure in the purge exhaust manifold (e.g., the output of pressure sensor 34 shown in Fig. 1A, referred to here as the scavenging manifold pressure) at trace 1904, a pressure at the turbocharger compressor inlet (e.g., the output of pressure sensor 31, shown in Fig. 1A, referred to here as compressor inlet pressure) at trace 1906, an on-state of the purge outlet valves (SVs) at trace 1908, and a position (open, closed, or anywhere between fully open and fully closed) of the BTCC valve (e.g., valve 54, shown in Fig. 1A) for the 1910 course.

[0148] Before time t1, the electric compressor is off (e.g., not driven by the electric motor) and the scavenging manifold pressure is above the compressor inlet pressure. At time t1, the electric motor begins driving the electric compressor, and as a result, the compressor inlet pressure (of the turbocharger compressor) begins to rise. However, since between time t1 and time t2 the scavenging manifold pressure is above the compressor inlet pressure, the BTCC valve and the SVs are adjusted based on a desired EGR flow rate and blow-by level relative to the intake port (e.g., based on the engine operating conditions). At time t2, while the electric compressor is operating, the scavenging manifold pressure decreases below the compressor inlet pressure. In response, the amount of BTCC valve opening is decreased. As shown in Fig. 19, the amount of BTCC valve opening is decreased, but the BTCC valve is not fully closed. In alternative embodiments, the BTCC valve may be fully closed or the SVs may be deactivated in response to the compressor inlet pressure increasing above the purge manifold pressure. At time t3, the purge manifold pressure increases above the compressor inlet pressure. As a result, the amount of BTCC valve opening returns to a required level based on a desired EGR flow amount. In one example, as shown at time t3, this may include the fully open position. After time t3 (and after the BTCC valve has been fully opened), the electric compressor is no longer driven by the electric motor.

[0149] At time t4, the electric compressor is again driven by the electric motor. However, at this time, the compressor inlet pressure is below the purge manifold pressure, so the current position of the BTCC valve and the activation state of the SVs are maintained. In response to the compressor inlet pressure rising above the purge manifold pressure at time t5, the SVs (of all engine cylinders) are deactivated. At time t5, the electric compressor ceases operation. In response to the electric compressor no longer being driven by an electric motor, the SVs are reactivated. Shortly thereafter, the compressor inlet pressure decreases below the purge manifold pressure.

[0150] In this way, the position of the BTCC valve and / or the energization state of the purge outlet valves can be controlled in response to the operation of an electric compressor to reduce reverse flow through the EGR passage via the purge outlet valves to the exhaust passage. A technical effect of adjusting a BTCC valve position in response to an electric motor driving the electric compressor based on the pressure in the purge exhaust manifold is to reduce reverse flow through the EGR passage via the purge outlet to the exhaust passage while the compressor inlet pressure is above the purge manifold pressure, thereby improving engine efficiency and reducing engine emissions.

[0151] Fig. 9 shows a method 900 for operating the engine system in a compressor threshold mode. The method 900 may proceed from 421 of the method 400, as described above. The method begins at 902 by determining whether the conditions for intermediate pressure EGR are met. In one example, the engine system may include an intermediate pressure EGR passage (e.g., the second EGR passage 58 shown in Fig. 1A) located between a low-pressure EGR passage (e.g., the first EGR passage 50 shown in Fig. 1A) and an intake passage downstream of the turbocharger compressor. Flowing exhaust gases from the scavenging manifold to the intake passage via the intermediate-pressure EGR passage may provide intermediate-pressure EGR to the intake system of the internal combustion engine. Because the exhaust gases are discharged downstream of the compressor via the intermediate-pressure EGR passage, a temperature at the compressor and / or the compressor speed may be reduced while directing exhaust gases from the scavenging exhaust manifold to the intake via the intermediate-pressure EGR passage. In one example, the conditions for enabling medium-pressure EGR (e.g., conditions for flowing exhaust gases from the scavenging manifold to the intake passage, downstream of the compressor via the medium-pressure EGR passage) may include one or more of the EGR demand (e.g., desired EGR flow) being above a threshold level (e.g., high EGR demand), no EGR cooler present in the EGR system (e.g.,no EGR cooler in the first EGR passage, such as EGR cooler 52 shown in . Fig. 1A), from any compressor bypass present in the engine system (e.g. compressor recirculation channel 41, shown in Fig. 1A), a temperature of the exhaust gas from the purge outlet valves above an upper threshold temperature and / or compressor flow conditions (e.g., if flow through the compressor is above an upper threshold, EGR cannot be added to the compressor inlet without degraded compressor operation / efficiency). If one or more conditions for enabling intermediate pressure EGR are met, method 904 transitions to deactivate the BTCC valve (e.g., valve 54 shown in Fig. 1A) and the medium pressure EGR valve (e.g. valve 59, shown in Fig. 1A) located in the intermediate-pressure EGR valve. For example, opening the intermediate-pressure EGR valve may include a controller sending a signal to an actuator of the intermediate-pressure EGR valve to fully open the intermediate-pressure EGR valve or increase the amount of opening of the intermediate-pressure EGR valve (e.g., from a fully closed position). Closing the BTCC valve may include fully closing the BTCC valve such that no exhaust gases are directed to the intake passage upstream of the compressor. In an alternative embodiment, the method at 904 may include opening the intermediate-pressure EGR valve and decreasing the amount of opening of the BTCC valve (but not fully closing it) or keeping the BTCC valve open. For example, both the BTCC valve and the intermediate pressure EGR valve may be opened in response to compressor surge conditions.In yet another embodiment, the method may include, at 904, increasing the amount of opening of the intermediate pressure EGR valve while decreasing the amount of opening of the BTCC valve, where the amount of increasing and decreasing the amount of opening of these valves is based on compressor conditions (e.g., inlet temperature, outlet temperature, and rotational speed). For example, the controller may determine a control signal to be sent to the BTCC valve and intermediate pressure EGR valve actuators based on a determination of the compressor inlet temperature, compressor outlet temperature, and / or compressor rotational speed. These compressor conditions may be detected via one or more sensors in the system (as shown in FIG. Fig. 1A) or determined based on operating conditions, such as engine speed and load and / or combustion air-fuel ratio. The controller may determine the desired position of the BTCC and intermediate pressure EGR valves by a determination that directly takes into account the determined compressor conditions, such as increasing the amount of intermediate pressure EGR valve opening and decreasing the amount of BTCC valve opening as the compressor outlet temperature increases, decreasing the compressor speed, and / or decreasing the compressor inlet temperature (e.g., above / below the values ​​discussed above with respect to 420 in Fig. 4A). Alternatively, control may determine the valve positions based on a calculation using a lookup table, where the compressor conditions are the input and the signal sent to the valve actuators is the output, which corresponds to a valve position of the BTCC valve and the intermediate pressure EGR valve. After 904, the method ends. In alternative embodiments, the method may transition from 904 to 906 to determine whether additional engine actuator adjustments are desired to move the compressor away from operating at the operating thresholds.

[0152] Referring again to 902, if the conditions for medium pressure EGR are not met or additional actuator adjustments are desired to move the compressor away from operating at or above the operating thresholds, the method proceeds to 906. At 906, the method includes determining whether condensate is forming at the compressor (e.g., at the compressor inlet). In one example, it may be determined that condensate is forming at the compressor in response to an inlet temperature of the compressor (e.g., a temperature of the gases entering the compressor inlet) being below a first threshold temperature. In another example, it may be determined that condensate is forming or expected to form at the compressor when the ambient humidity is above a threshold humidity value and / or when the ambient temperature is below a threshold temperature.If condensate is forming at the compressor (or is expected to form in some examples), the method proceeds to 908 to retard the exhaust valve cam (e.g., camshaft) timing to reduce the amount of EGR flowing from the purge manifold to the intake passage upstream of the compressor via the EGR passage. Retardant exhaust valve cam timing may include retardant the timing of only the purge exhaust valves or both the purge and blowoff exhaust valves based on the valve timing hardware of the engine system. By retardant the timing of the purge exhaust valves, each purge exhaust valve may open and close later in the engine cycle (e.g., open at -90 crank angle degrees relative to TDC vs. approximately -135 crank angle degrees, as shown in FIG. Fig. 3B, as described above). As described above with respect to the Fig. 1A-1B, various variable camshaft timing (VCT) systems can be used to achieve the retarded timing of the scavenge exhaust valves (and possibly the blowoff exhaust valves). In one example, which may be the basic internal combustion engine system, both the scavenge exhaust valves and the blowoff exhaust valves can be controlled together via a single camshaft system. Thus, retarding the exhaust cam results in retarding the timing of the scavenge exhaust valves and the blowoff exhaust valves (even though the opening and closing timing of the scavenge exhaust valves are different from the blowoff exhaust valves). In this way, the timing of the scavenge exhaust valves and the blowoff exhaust valves can be retarded by the same amount using the single cam system.In another example, the VCT system for the exhaust valves may include a cam-in-cam system in which the timing of the purge exhaust valves and the blowoff exhaust valves can be varied independently of set timings. In yet another example, the VCT system for the exhaust valves may include a MultiAir-type system for the purge exhaust valves. In this system, the opening timing and lift for the purge exhaust valves can be controlled individually and separately from the blowoff exhaust valves (e.g., in this case, only the timing of the purge exhaust valves is delayed). In yet another example, the VCT system for the exhaust valves may include an electric valve lift control on the purge exhaust valves in which the timing of the purge exhaust valves can be set separately from the blowoff exhaust valves (e.g.,delayed while maintaining the timing of the blow-off exhaust valves).

[0153] At 910, the method includes determining whether the exhaust valve timing (of the purge exhaust valves) is at a maximum amount of retard. For example, the timing of the purge exhaust valves may only be retarded by a set number of crank angle degrees. Once the exhaust valve timing reaches the maximum amount of retard (e.g., a maximum amount of adjustment), the exhaust valve timing may not be retarded any further. If the timing of the purge exhaust valves reaches the maximum amount of retard while condensate is present at the compressor (e.g., when the compressor inlet temperature is below the first threshold temperature), the method proceeds to 912 to further retard the exhaust cam timing of the purge exhaust valves. In some examples, this may include retarding the exhaust cam to a maximum amount of retard.In other examples, this may include retarding the exhaust cam to an amount of retarding that is less than the maximum amount of retarding.

[0154] If the maximum amount of retardation for the exhaust cam has been reached at 910 and the scavenge exhaust valve timing cannot be retarded any further, the method proceeds to 914 to determine if the intake cam of the intake valves can be advanced. Advancing the intake valve timing may result in more overlap between an intake valve and a scavenge exhaust valve of each cylinder, thereby increasing an amount of hot blowby air recirculation to the compressor inlet. This may lower the compressor inlet temperature and reduce condensate formation at the compressor. The intake cam may be able to be advanced if it has not already been advanced to its most advanced position (e.g., if it is not already at its maximum advance amount).If the intake cam can be advanced to advance the intake valve timing, the method proceeds to 916 to advance the intake valve timing. This may include actuating the intake cam (e.g., intake cam 151, shown in FIG. Fig. 1B) via an intake valve timing actuator (e.g., the intake valve timing actuator 101 shown in Fig. 1B) to advance the intake valve timing and thus open and close each intake valve earlier or later in the engine cycle. Otherwise, if the intake cam cannot be advanced any further, the method transitions from 914 to 918 to close the BTCC valve. For example, at 918, the method may include fully closing the BTCC valve to block the flow of exhaust gases from the purge manifold (e.g., purge exhaust manifold) to the compressor inlet, thereby reducing low-pressure EGR and reducing condensate formation at the compressor. The method may further include, at 918, opening a purge manifold bypass valve (SMBV) disposed in a bypass passage coupled between the purge manifold and the exhaust passage (e.g., SMBV 97 in bypass passage 98, shown in Fig. 1A). For example, the controller may send a signal to an actuator of the SMBV to open the SMBV in response to the BTCC valve closing. As a result, exhaust gases may be routed from the purge manifold to the exhaust passage while the BTCC valve is closed. In alternative embodiments, at 918, the method may include decreasing the amount of opening of the BTCC valve (without fully closing) and increasing the amount of opening of the SMBV (without fully opening). In some examples, the amount of increasing the amount of opening of the SMBV may be approximately the same as (e.g., proportional to) the amount of decreasing the amount of opening of the BTCC valve.

[0155] Referring again to 906, if condensate is not forming at the compressor or is not expected to form (e.g., if the compressor inlet temperature is not below the first threshold temperature), the method proceeds to 920 to determine whether the compressor outlet temperature is above a second threshold temperature. In one example, the compressor outlet temperature (e.g., a temperature of gases exiting the turbocharger compressor) may be measured via a temperature sensor positioned downstream of or at the outlet of the compressor (e.g., temperature sensor 43, shown in Fig. 1A). In other examples, the compressor outlet temperature may be estimated based on various other sensor outputs and engine operating conditions, such as the compressor inlet temperature and a compressor rotational speed or an intake manifold temperature. If the compressor outlet temperature is above the second threshold temperature, the method proceeds to 922.

[0156] At 922, the method includes modulating the BTCC valve to reduce the amount of exhaust flow to the compressor inlet from the scavenge manifold, opening the SMBV, and / or opening the turbine wastegate (e.g., wastegate 76 shown in Fig. 1A). In one example, modulating the BTCC valve may include switching the BTCC valve between the fully open and fully closed positions to reduce the amount of exhaust flow to the compressor inlet via the EGR passage (compared to if the BTCC valve remained fully open) to a first level. Modulating the BTCC valve may include increasing the amount of time the BTCC module is closed compared to the amount of time the BTCC valve is open. The amount of modulation or the average amount of time the BTCC valve is closed may be based on the compressor outlet temperature and / or a desired EGR flow amount.For example, if the compressor outlet temperature continues to increase above the second threshold temperature, the BTCC valve may be closed for a longer period of time and / or the average amount of time the BTCC valve is closed during the modulation period may increase. In some examples, the method at 922 may include fully closing the BTCC valve. In yet another example, the method at 922 may include decreasing the amount of opening of the BTCC valve (e.g., to a position between fully open and fully closed, without modulation). The method at 922 may additionally include opening the SMBV or increasing the amount of opening of the SMBV while the BTCC valve is closed or modulated between open and closed. Additionally or alternatively, the method at 922 may include opening the turbine wastegate while modulating the BTCC valve.Opening the turbine wastegate valve reduces the turbocharger speed and can thus reduce the load on the compressor.

[0157] The method proceeds to 924 to advance the intake cam of the intake valves to reduce a pressure ratio across the compressor. For example, the intake cam may be advanced while modulating the position of the BTCC valve to reduce EGR flow to the compressor inlet to the first level. The method then proceeds to 926 to retard the exhaust cam to retard the exhaust valve opening timing (e.g., of at least the purge exhaust valves) to further reduce EGR. For example, retardation of the exhaust cam may result in reducing EGR flow to the compressor inlet to a second level that is below the first level. At 928, the method includes reducing cold recirculation via opening the BTCC valve. Since EGR flow may be reduced due to the exhaust valve retardation (e.g.,Purge Outlet Valve) timing at 926 is reduced, opening the BTCC valve at 928 increases the flow of pressurized, cooler air back to the compressor inlet, thereby lowering the compressor temperature.

[0158] Referring again to 920, if the compressor outlet temperature is not above the second threshold temperature, the method proceeds to 930 to determine if the compressor is operating at an alternative compressor constraint (e.g., threshold). For example, the compressor speed (e.g., compressor rotational speed) may be above a threshold speed, which may result in degradation of the compressor's reduced performance. If the compressor is operating at the alternative constraint, such as the compressor speed above the threshold speed, the method proceeds to 932 to close the BTCC valve and open the SMBV. In one example, this may include fully closing the BTCC valve and fully opening the SMBV.In another example, at 932, the method may include decreasing the amount of BTCC valve opening (without fully closing) and increasing the amount of SMBV opening (without fully opening). The amount of decreasing the amount of BTCC valve opening and the amount of increasing the amount of SMBV opening may be based on a desired purge manifold pressure, where the purge manifold pressure is based on intake manifold pressure and timing of the intake and exhaust valves. For example, the amount of overlap between when the purge exhaust valve and the intake valve are both open may determine the time available for blowby air, but the pressure difference between the intake manifold (e.g., MAP) and the purge manifold may determine the driving pressure for the blowby flow.When MAP is above the purge manifold pressure, excess oxygen may flow to the exhaust passage via the purge manifold bypass passage. The desired drive pressure for the blow-by flow may be based on desired oxygen levels in the exhaust, as discussed above with respect to the . Fig.2A-2B. Thus, as intake manifold pressure increases, the desired purge manifold pressure for a set intake and exhaust valve timing and a desired blowby amount may decrease. For example, the controller may determine the desired purge manifold pressure through a determination that directly considers a particular intake manifold pressure and the current intake and exhaust valve timing, and then determine the corresponding BTCC valve and SMBV positions that achieve the desired purge manifold pressure. As another example, the controller may make a logical determination (e.g., regarding a BTCC valve and SMBV position) based on logical rules that are a function of intake manifold pressure, intake valve timing, and exhaust valve timing. The controller may then generate a control signal sent to the BTCC valve and SMBV actuators.

[0159] At 934, the method includes advancing the purge exhaust valve timing (e.g., the opening timing of the purge exhaust valves) while the BTCC valve is closed (or while decreasing the amount of BTCC valve opening). For example, the amount of advance used to open the purge exhaust valve may increase as the amount of blowby to the exhaust passage decreases (e.g., to a second downstream catalyst in the exhaust passage, as in Fig. 1A). The method then proceeds to 936 to increase the opening of the turbine wastegate, thereby decreasing the turbocharger speed.

[0160] Alternatively, if the compressor is not at an alternative constraint, the method proceeds to 938 at 930 to keep the turbine wastegate closed. In some embodiments, the default position of the turbine wastegate may be closed. The wastegate may then only be opened at high turbocharger speeds. The method may include returning to method 400 from the Fig. 4A-4B include.

[0161] Fig. 20 shows a diagram 2000 for operating the split exhaust engine system in compressor threshold mode. Specifically, diagram 2000 shows the engine load at trace 2002, the EGR demand (e.g., desired EGR flow to the intake port) at trace 2004, the compressor outlet temperature at trace 2006, the compressor inlet temperature at trace 2008, the compressor (e.g., turbocharger) speed at trace 2009, a turbine wastegate position at trace 2010, a BTCC valve position at trace 2012, a medium-pressure EGR valve position at trace 2014, a SMBV position at trace 2016, an intake valve timing of the intake valves at trace 2018, and an exhaust valve timing of the scavenging exhaust valves at trace 2020.In an embodiment where the purge exhaust valves and blowoff exhaust valves are controlled by the same cam system, the exhaust valve timing at plot 2020 may be the timing of both the purge exhaust valves and the blowoff exhaust valves. Although the valve positions in . Fig. 20 can be shown as open and closed, the valves can be adjusted to a variety of positions between fully open and fully closed.

[0162] Before time t1, the compressor inlet temperature is above the first threshold temperature T1, the compressor outlet temperature is below the second threshold temperature T2, and the compressor speed is below the threshold speed S1. Thus, the BTCC valve is open, the intermediate pressure EGR valve is closed, and the unloader tube valve is closed. The intake and exhaust valve timings are also at their default timings (as shown by the default line D1) for best fuel efficiency before time t1. At time t1, the compressor inlet temperature drops below the first threshold temperature T1, indicating that the compressor may be experiencing condensate formation.Also, the EGR demand is relatively high at this time point, so in response to the compressor inlet temperature being below the first threshold temperature T1 while the EGR demand is relatively high, the BTCC valve is closed and the intermediate-pressure EGR valve is opened. This can reduce the low-pressure EGR flow to the compressor inlet, thereby reducing condensate formation. At time point t2, the compressor inlet temperature rises above the first threshold temperature T1, so the BTCC valve is opened again, and the intermediate-pressure EGR valve is closed shortly after time point t2.

[0163] At time t3, the compressor outlet temperature rises above the second threshold temperature T2 while the EGR demand is at a relatively low level (e.g., lower than at time t1). In response to these conditions, the BTCC valve is modulated to reduce EGR flow, and the SMBV is correspondingly modulated to be open when the BTCC valve is closed. Furthermore, between time t3 and time t4, the intake valve timing is advanced and the exhaust valve timing is retarded. At time t4, in response to the compressor outlet temperature falling below the second threshold temperature T2, the BTCC valve is opened and the SMBV is closed, and the intake and exhaust valve timing return to their default positions for best fuel efficiency.

[0164] At time t5, the compressor inlet temperature drops below the first threshold temperature T1 again, while the EGR demand is at a lower level (compared to the higher EGR demand level at time t1). Thus, immediately after time t5, the exhaust valve timing is retarded to reduce EGR flow to the compressor inlet. At time t6, the exhaust valve timing reaches the maximum retard amount (e.g., it cannot be retarded any further). In response to reaching this maximum level, the intake valve timing is advanced. At time t7, the compressor inlet temperature rises above the first threshold temperature, and in response, the intake and exhaust valve timing return to their default timings.

[0165] At time t8, the compressor speed increases above the threshold speed S1. In response to this increase in compressor speed, the BTCC valve is closed and the SMBV is opened. Also after time t8, the purge outlet valve timing is advanced and the turbine wastegate is opened. After the turbine speed decreases below the threshold speed S1 at time t9, the BTCC valve is opened, the SMBV is closed, and the purge outlet valve timing returns to the default timing. In this way, the intake valve timing, the exhaust valve timing of the purge outlet valves, and a position of the BTCC valve (and in some examples, the SMBV) can be adjusted in coordination in response to a condition of the compressor (e.g., the compressor reaching one or more operating thresholds, as described above).For example, as shown at time t3, the BTCC valve has been modulated to reduce EGR flow to a first level, and the exhaust valve timing is retarded to reduce EGR flow to a lower, second level. At this time, the intake valve timing is advanced to reduce the pressure ratio across the compressor. As another example of adjusting intake valve timing, exhaust valve timing, and BTCC valve timing in coordination with one another, as shown at times t5 through t7, the purge exhaust valve timing is retarded, and upon reaching its maximum retard amount while the compressor inlet temperature is still above the first threshold temperature, the intake valve timing is advanced.A technical effect of adjusting the intake valve timing, exhaust valve timing of the purge outlet valves, and the position of the BTCC valve in coordination with one another is to reduce EGR flow to the compressor inlet and thus reduce compressor condensate formation, reduce the compressor outlet temperature, and / or reduce compressor speed, thereby reducing compressor degradation. In another embodiment, as shown at time t1, in response to the compressor inlet temperature being below the threshold inlet temperature, the intermediate-pressure EGR valve may be opened to direct exhaust gas from the purge outlet valves to the intake passage downstream of the compressor.A technical effect of directing exhaust gas from the scavenging exhaust valves to the intake passage downstream of the compressor in response to a compressor condition is to reduce EGR flow to the compressor inlet, thereby reducing compressor condensate formation, increasing the compressor outlet temperature, and reducing compressor speed. As a result, compressor degradation may be reduced. In yet another embodiment, as shown at times t3 and t8, the BTCC valve may be closed (or modulated between open and closed) while the SMBV is opened (or modulated) accordingly to reduce EGR flow to the compressor inlet and instead direct exhaust gases from the scavenging manifold to the exhaust passage.A technical effect of reducing gas flow from the scavenging exhaust manifold to the intake passage upstream of the compressor in response to an engine operating condition (such as a compressor outlet temperature above a threshold outlet temperature and / or a compressor speed above a threshold speed) and, in response to reducing gas flow, increasing gas flow from the scavenging manifold bypass passage is to reduce compressor degradation while also reducing pressures in the scavenging exhaust manifold and trapping residual gases in the cylinders.

[0166] Fig. 10 shows a method 1000 for operating the engine system in an initial BTCC mode. Method 1000 may continue from 430 of method 400, as described above. Method 1000 begins at 1002 by adjusting the intake cam timing of the intake valves and the exhaust cam timing of the scavenge exhaust valves and the blowoff exhaust valves for the best fuel efficiency. For example, the timing of the exhaust valves and the intake valves may be adjusted for the best achievable brake specific fuel consumption (BSFC) at the current engine operating conditions. In one example, this may include adjusting the timing of the scavenge exhaust valve, the blowoff exhaust valve, and the intake valve of each cylinder at the Fig. 3A, as described above. In some embodiments, the timing of the exhaust valves and the intake valves may be slightly different from the timing shown in Fig. 3A may be adjusted based on engine speed and load. For example, intake timing may be adjusted to fully retard at lighter engine loads and advanced when the engine is boost-limited or there is a request to increase blowby to reduce knock. In another embodiment, exhaust valve timing may be adjusted so that the exhaust valves open sooner than engine speed increases. Exhaust valve timing may then be retarded when boost decreases (e.g., during low engine speed and high engine load conditions) or when engine speed is high and the EGR temperature is above a threshold temperature.

[0167] At 1004, the method includes determining whether the engine torque output is at a required level. The required torque level may be a vehicle operator torque demand, which in one example is determined based on a position of an accelerator pedal of the vehicle. In one example, the controller may determine the required torque in response to a pedal position signal received from an accelerator pedal position sensor. If the torque is not at the required level, the method proceeds to 1006 to optimize cam timing and BTCC valve position for the required torque. As one example, this may include limiting the purge exhaust valve flow to increase the torque output and modifying the amount of limiting based on a turbocharger compressor surge threshold.For example, limiting purge outlet valve flow may include retarding the cam timing of the purge outlet valves to reduce EGR flow. In yet another example, this may alternatively or additionally include retarding the cam timing of the intake valves to reduce blowby from the purge outlet valves to the intake passage. Further, modifying the amount of limiting purge outlet valve flow may include decreasing the amount of restriction as compressor operation (e.g., flow rate and pressure drop across the compressor) approaches the surge threshold or surge line. In yet another example, the method at 1006 may additionally or alternatively include limiting the amount of opening of the BTCC valve (e.g., closing or decreasing the amount of opening).

[0168] If the engine torque output is at the required level, the method proceeds to 1008 to determine the oxygen content and pressure of gases in the purge manifold (e.g., the purge exhaust manifold 80, shown in Fig. 1A). In another embodiment, the method at 1008 may additionally or alternatively include measuring the oxygen content and pressure of gases in the exhaust conduit of each purge outlet valve. For example, the method at 1008 may include obtaining pressure and oxygen content measurements from one or more pressure sensors and oxygen sensors disposed in the purge manifold and / or the purge outlet valve conduits (e.g., pressure sensor 34, oxygen sensor 36, and oxygen sensors 38 shown in Fig. 1A).

[0169] As described above, both exhaust gases (e.g., EGR after the cylinder is ignited via the combustion of an air-fuel mixture in the cylinder) and blowby air (during an overlap period between the opening of the intake valve and the scavenge exhaust valve) may be expelled into the scavenge manifold from the engine cylinders via the scavenge exhaust valves. Furthermore, each scavenge exhaust valve of each engine cylinder may expel EGR and blowby air at different times than the other engines (e.g., based on an adjusted cylinder firing order during an engine cycle). As used herein, an engine cycle refers to a period of time in which each engine cylinder fires once in the cylinder firing order.For example, if the cylinder firing order includes firing the cylinders in the following order: cylinder 1, cylinder 2, cylinder 3, and then cylinder 4, the purge exhaust manifold may receive four separate EGR pulses and blowthrough from each cylinder in the cylinder firing order during each engine cycle. Therefore, at 1010, the method includes estimating blowthrough (BT, e.g., the amount of unburned gases entering the purge manifold from the purge exhaust valve during an overlap period between the intake valve and the purge exhaust valve of each cylinder) and EGR (e.g., burned exhaust gases).Estimating BT and EGR may include estimating an amount of BT and an amount of EGR expelled into the scavenging exhaust manifold for each cylinder and / or estimating a total amount of BT and EGR entering the intake passage for all cylinders during a single engine cycle (e.g., total BT and EGR amount for four cylinders in a four-cylinder engine or for as many cylinders that have scavenging exhaust valves enabled). In a first embodiment of the method at 1010, the method at 1011 may include estimating the amount of BT and EGR based on crankshaft angle (e.g., engine position) and scavenging manifold pressure (e.g., based on an output of a pressure sensor in the scavenging manifold).In a second embodiment of the method at 1010, the method at 1013 may include estimating the BT and EGR amount based on the crankshaft angle (or a corresponding timing of opening and closing of the intake valve and purge exhaust valve of each cylinder) and the oxygen content of the purge manifold (e.g., based on an output of an oxygen sensor in the purge manifold or in each purge exhaust valve conduit).

[0170] Fig. Figure 21 shows a graph 2100 of changes in scavenging manifold pressure and oxygen content over a single engine cycle that includes firing four cylinders (e.g., cylinders 1-4 shown in Fig. 21). In particular, diagram 2100 illustrates an engine position along the x-axis in crank angle degrees (CAD) for a complete engine cycle (e.g., from -360 CAD to 360 CAD) with four cylinders firing of a representative four-cylinder engine (such as the one shown in the Fig. 1A-1B). For each cylinder, timing, lift, and duration of opening (relative to the engine position) of the intake valve (IV), scavenge exhaust valve (SV), and blow-off exhaust valve (BDV) are shown. Trace 2102 shows the cylinder valve events for a first engine cylinder, cylinder 1; trace 2104 shows the cylinder valve events for a second engine cylinder, cylinder 2; trace 2106 shows the cylinder valve events for a third engine cylinder, cylinder 3; and trace 2108 shows the cylinder valve events for a fourth engine cylinder, cylinder 4. Changes in measured scavenge manifold pressure over the engine cycle are shown at trace 2110, and changes in measured scavenge manifold oxygen content are shown at trace 2112.The measured purge manifold oxygen content can also represent an air-fuel ratio of the gases entering the purge exhaust manifold from the SVs.

[0171] As shown in diagram 2100, each time an SV of one of the cylinders opens, there is a positive pulse in the scavenging manifold pressure and a negative pulse in the scavenging manifold oxygen content. For example, when an SV opens (e.g., at -90 CAD for cylinder 2), burnt exhaust gases are expelled into the scavenging manifold. While the same SV is open and when an IV of the same cylinder opens (e.g., overlap period, as indicated by 2114 for cylinder 2), blowby air is expelled into the scavenging manifold. Thus, when the SV opens, there is an increase in scavenging manifold pressure and the scavenging manifold oxygen content decreases due to the burnt exhaust gases entering the scavenging manifold. While the SV is open and before the IV opens, the scavenging manifold oxygen content represents an air-fuel ratio of the burnt exhaust gases (which may be richer). Then, the scavenging manifold content increases again when the blowby air (e.g.,The oxygen content of the scavenging manifold (i.e., that which contains no combusted gases and is thus richer in oxygen than the exhaust gases) enters the scavenging manifold. While both the SV and IV are open simultaneously for each cylinder, the scavenging manifold oxygen content represents an air-fuel ratio of the blow-by air, which is leaner than the combustion gases.

[0172] Thus, by correlating the pulses in scavenging manifold pressure and / or oxygen content to CAD, the pressure and / or oxygen changes due to the exhaust gases and blowby air can be determined for each cylinder and differentiated between them. By observing the size (e.g., magnitude) of these pulses over known time periods (e.g., CAD and firing order) of the expulsion of exhaust gases and blowby air into the scavenging manifold, the amount of EGR and blowby air flowing to the intake port via the scavenging manifold can be determined for each cylinder or for each engine cycle (e.g., by summing the pulses). As another example, estimating blowby and / or EGR flow from scavenging manifold oxygen content may involve measuring (via an oxygen sensor) a transition between a combustion air-fuel content of the gases (e.g., combustion gases) expelled from each SV (e.g.,the valleys or low points of trace 2112), and a leaner air-fuel ratio of the gases (e.g., blowby air) exhausted from the SV (e.g., peaks or high points of trace 2112). The transition or change between a peak (e.g., maximum) and a valley (e.g., minimum) of the oxygen sensor output for each cylinder may indicate the amount of EGR and blowby air exiting the SV and flowing to the intake for each cylinder. For example, the transition may include an increase in the oxygen level of the blowby air exhausted from the SVs. The increase in oxygen level may be an increase from a lower, first oxygen level (at the valleys) to a higher, second oxygen level (at the peaks).The transition between the combustion air-fuel ratio content of the exhausted gases and the leaner air-fuel ratio of the gases can be determined on a cylinder-by-cylinder basis to determine the EGR flow and blowby air amount for each cylinder. Furthermore, the total amount of blowby air flowing from the scavenging manifold to the intake port during a single engine cycle can be determined for each cylinder based on the second oxygen level for each SV.

[0173] Referring again to 1010 of Fig. 10, in this manner, the BT amount and the EGR amount may be determined based on an output from a pressure sensor and / or an oxygen sensor positioned in the purge manifold (or purge exhaust valve lines) that is correlated with the crank angle degree (e.g., engine position). As an example, the controller may determine the BT amount for a first cylinder based on the received output of the pressure sensor between a time the intake valve of the first cylinder opens and a time the purge exhaust valve of the first cylinder closes. The controller may repeat this process for each engine cylinder and then sum all values ​​to determine a total BT amount to the intake port for a complete engine cycle.As another example, the controller may determine the EGR flow rate for the first cylinder based on the received pressure sensor output between a time the purge exhaust valve of the first cylinder opens and a time immediately before the intake valve of the first cylinder opens (e.g., the time until the intake valve opens, and thus before the BT air enters the purge manifold). The same process may be performed using the output of the oxygen sensor instead of the pressure sensors. As one example, the controller may make a logical determination regarding the EGR or BT flow rate in the purge manifold based on logical rules that are a function of the pressure (or oxygen content) of the purge manifold (for the set BT or EGR period, as discussed above, for each cylinder).

[0174] At 1012, the method includes adjusting the BTCC valve (e.g., adjusting a position of the BTCC valve), the timing of the purge exhaust valve (SV), the timing of the intake valve (IV), and / or the SMBV (e.g., adjusting a position of the SMBV) based on the estimated blowby and EGR flow amount (as determined at 1010), the desired blowby and EGR flow amount, the boost level (e.g., boost pressure downstream of the turbocharger compressor), and the current positions and timing of each of the valves listed above. As one example, the BTCC valve may be opened in response to the engine being boosted (e.g., with the turbocharger compressor operating and resulting in MAP being above atmospheric pressure).As another example, if more or less EGR flow or blowby is desired to the intake passage via the purge manifold and the EGR passage relative to the estimated levels (estimated at 1010), the controller may adjust the positions or timing of one or more of the BTCC valve, SV, IV, and SMBV to achieve the desired EGR flow and blowby flow. Details on adjusting the timing of the BTCC valve, SMBV, and SV to achieve the desired EGR and blowby flow are further described with reference to FIG. Fig. 12-13. Further, adjusting the valve positions and timings at 1012 may include adjusting the valve positions and / or timings relative to each other. For example, if the BTCC valve is closed and the desired purge manifold pressure is below the currently measured purge manifold pressure, the method at 1012 may include opening or increasing the amount of opening of the SMBV to reduce the purge manifold pressure.

[0175] In another example of the method at 1012, the purge manifold pressure may change the control of the BTCC valve, SMBV, and / or intake valve at certain SV timings. For example, the SV timing may be adjusted based on the measured purge manifold pressure. In one example, in response to the measured purge manifold pressure being greater than the desired purge manifold pressure, the method may include retarding the SV timing to reduce the purge manifold pressure. The desired purge manifold pressure may be determined based on (e.g., as a function of) one or more of the intake manifold pressure, exhaust pressure, and / or boost conditions (e.g., whether the engine is boosted or not). Further, in response to adjusting the SV timing based on the measured pressure and in response to the purge manifold pressure, the positions of the BTCC valve and / or SMBV may be adjusted.For example, after adjusting the SV timing, the position of the SMBV may be adjusted to maintain the purge manifold pressure at the desired purge manifold pressure (based on engine operating conditions), and the position of the BTCC valve may be adjusted to maintain the EGR flow at a desired EGR flow (e.g., based on engine operating conditions such as engine load, knock, and compressor operating conditions such as temperature and speed).

[0176] The method proceeds to 1014 to activate the charge movement control valves (e.g., CMCVs 24 shown in Fig. 1A) positioned in at least one intake manifold of each cylinder. As an example, closing the CMCVs may include the controller actuating a valve actuator of the CMCVs to move the CMCVs to the closed position, which restricts airflow entering the cylinder via the intake valves of the intake manifolds to which the CMCVs are internally coupled. For example, the closed position may include when the CMCVs are fully turned on, and the valve plate of the CMCVs may be fully tilted into the corresponding intake manifold (e.g., port), resulting in maximum air charge flow obstruction. This may reduce the bypassing of air from the intake valve directly to the SV without fully purging exhaust gases from inside the cylinders.As a result of closing the CMCVs during operation in the initial BTCC mode, more exhaust purging may result, increasing engine power and torque output during subsequent cylinder combustion events.

[0177] At 1016, the method includes determining whether conditions for performing a valve diagnostic are met for one or more of the BTCC valve, SMBV, or SV. In one example, the conditions for performing the valve diagnostic may include one or more of a period of time elapsed since a previous valve diagnostic, a period of engine operation, and / or a number of engine cycles. For example, a valve diagnostic may be performed at regular intervals (e.g., after a set period of engine operation or a set number of engine cycles), after every shutdown event (e.g., upon engine restart), or in response to a diagnostic flag set in the controller.For example, a diagnostic flag may be set when a measured purge manifold pressure is different than expected by a threshold amount based on the current valve positions and timing of the BTCC valve, SMBV, and / or the SVs. If conditions to perform the valve diagnostics are met, the method proceeds to 1018 to perform the valve diagnostics and diagnose a position or timing of the BTCC valve, SMBC, and the SVs based on the purge manifold pressure. Details for performing this diagnostic routine are discussed below with respect to [ ]. Fig. 11. Alternatively, if conditions for performing the valve diagnostics are not met at 1016, the method proceeds to 1020 to not perform the diagnostics and instead continue engine operation at the current valve positions / timings. Method 1000 then ends.

[0178] In this way, the BTCC valve, SV timing, IV timing, and / or SMBV may be adjusted based on an estimate of blowby and EGR flow determined based on a purge manifold pressure or oxygen content measurement (or estimate). As one example, a method includes adjusting the amount of opening overlap between the intake valves and the purge exhaust valves (e.g., via advancing or retarding the SV and IV timing, as discussed above) in response to a transition from an estimated combustion air-fuel content to a leaner air-fuel content of the blowby air on a cylinder-by-cylinder basis. As discussed above, for each cylinder, there may be a transition from the estimated combustion air-fuel content to the leaner air-fuel content corresponding to an SV opening event for each cylinder.One technical effect of adjusting the port overlap in response to this transition is to deliver the desired amount of blowby to the intake port, thereby increasing engine efficiency and reducing engine knock. As another example, this includes adjusting the BTCC valve, the SMBV, the SV timing, and / or the IV timing based on the measured purge exhaust manifold pressure. One technical effect of adjusting these valves and / or valve timing based on the purge manifold pressure is to increase the accuracy of controlling the amount of blowby and EGR flow to the intake port, thereby increasing engine efficiency, reducing engine emissions, and reducing engine knock.

[0179] With reference to Fig. 11, a method 1100 is shown for diagnosing one or more valves of the split exhaust engine system based on purge manifold pressure. Method 1100 may proceed from 1018 of method 1000, as described above. The method begins at 1102 by determining an expected pressure loss across each of the BTCC valve and the SMBV and determining the expected timing of the purge exhaust valves (SVs). As an example, the expected pressure loss (e.g., differential) across the BTCC valve and the SMBV may be determined based on a commanded position of the BTCC valve and the SMBV and additional engine operating conditions. For example, the commanded position of the valves may include a fully open, a fully closed, or one of a plurality of positions between the fully open and fully closed positions.In the case of the expected pressure drop across the BTCC valve, the additional engine operating conditions may include a pressure in the intake port upstream of the compressor (e.g., at the point where the EGR port couples to the intake port), atmospheric pressure (e.g., when there is no electric compressor upstream of the compressor or the electric compressor is not operating), a position of the SMBV (e.g., open or closed), an exhaust pressure in the exhaust port at the point where the scavenging manifold bypass port couples to the exhaust port, and / or a timing of the SVs.As one example, the controller may determine the expected pressure loss across the BTCC valve based on a lookup table stored in the controller's memory, the lookup table including one or more of the commanded BTCC valve position, intake pressure, atmospheric pressure, exhaust pressure, SMBV position, and SV timing as inputs, and the expected pressure loss across the BTCC valve as output. In another example, the controller may determine the expected pressure loss according to a relationship stored in the controller's memory that is a function of the commanded BTCC valve position, intake pressure, atmospheric pressure, exhaust pressure, SMBV position, and / or SV timing.Similarly, the controller may determine the expected pressure drop across the SMBV based on the commanded SMBV position and engine operating conditions, which may include one or more of a BTCC valve position, timing of the SVs, and the exhaust pressure in the exhaust passage where the scavenging manifold bypass passage couples to the exhaust passage (e.g., using lookup tables or stored relationships as discussed above). In one example, the exhaust pressure in the exhaust passage where the scavenging manifold bypass passage couples to the exhaust passage may be a pressure measured via a pressure sensor disposed in the exhaust passage, such as pressure sensor 96 shown in FIG. Fig. 1A. In another example, the intake pressure where the EGR passage couples to the intake passage may be measured via a pressure sensor located in the intake passage upstream of the compressor, such as pressure sensor 31 shown in Fig. 1A. The expected timing of the SVs can be the currently set (or last commanded) timing of the SVs. For example, the controller can look up or determine the last commanded or output timing for the SVs and use that as the expected SV timing.

[0180] At 1104, the method includes determining the actual pressure losses across the BTCC valve and across the SMBV and determining the actual timing of the SVs based on a measured pressure in the purge manifold. As an example, the purge manifold pressure may be measured via a pressure sensor disposed in the purge manifold (e.g., pressure sensor 34, shown in Fig. 1A). The controller may receive the time-varying purge manifold pressure sensor signal and then measure either an instantaneous or average purge manifold pressure (e.g., averaged over one engine cycle or a plurality of engine cycles). As an example, the actual pressure loss across the BTCC valve may be determined based on the purge manifold pressure sensor output and atmospheric pressure (or based on an output of a pressure sensor located in the intake passage at the location where the EGR passage couples to the intake passage upstream of the compressor).For example, the controller may determine the actual pressure loss across the BTCC valve based on a lookup table stored at the controller, where the lookup table includes the measured purge manifold pressure and atmospheric (or intake) pressure as inputs and the actual BTCC valve position as the output. Similarly, the controller may determine the actual pressure loss across the SMBV based on the output of the pressure sensor positioned in the purge manifold and an output of a pressure sensor positioned in the exhaust passage at an outlet of the purge manifold bypass passage (e.g., pressure sensor 96, shown in FIG. Fig. 1A). In addition, the controller may determine the actual timing (e.g., opening timing) of the SVs based on a peak in the scavenging manifold pressure output during a single engine cycle. For example, as described above with reference to Fig. As described in Figure 21, the purge manifold pressure sensor pressure signal may pulse (or spike) whenever an SV opens. The controller can correlate this pulse with the CAD (or engine position) at which this pulse occurs, thus determining the opening and closing timing of the SVs.

[0181] The method then proceeds to 1106 to determine whether an absolute value of a difference between the actual pressure loss or timing, determined at 1104, and the expected pressure loss or timing, determined at 1102, is above a threshold difference. The method may include determining this difference for each of the BTCC valve, SMBV, and SVs at 1106. The threshold difference may be a non-zero difference and may indicate the valves that are in a different than desired position or at a different than desired timing. For example, this difference may be a difference indicating that the BTCC valve is incorrectly positioned (e.g., open instead of closed or closed instead of open).In another example, the difference may be a difference indicating that the timing of the SVs differs from the desired (or commanded) by a CAD threshold amount. These differences may result in degraded engine performance, such as reduced torque output, increased emissions, and / or degradation of the turbocharger or emissions control devices.

[0182] If the absolute value of the difference between the actual pressure loss or timing and the expected pressure loss or timing is not greater than a threshold difference, the method proceeds to 1110 to continue operating the valves at the set positions and / or timings based on the current engine operating conditions (e.g., according to method 400 described above with respect to the Fig. 4A-4B). For example, if the difference between the actual pressure loss or actual timing and the expected pressure loss or expected timing does not exceed the threshold difference, the valves may not be degraded and they may be in their commanded or set positions.

[0183] Alternatively, if the difference between the actual pressure loss or timing and the expected pressure loss or timing at 1106 is greater than the threshold difference, the method proceeds to 1108 to adjust the commanded position / timing of the identified valve(s), indicate the degradation of the identified valve(s), and / or adjust an alternative valve to deliver the desired EGR and blowby amount to the intake port. As introduced above, method 1100 may be performed for one or more or each of the SVs, the BTCC valve, and the SMBV.Therefore, the method proceeds to 1108 to perform the actions described above for all of the valves for which the difference between the actual pressure loss or actual timing and the expected pressure loss or expected timing is greater than the corresponding threshold difference. In one example, the controller may indicate degradation of the identified valve(s) by setting a diagnostic flag and / or alerting a vehicle operator that the identified valve(s) require service or replacement (e.g., via an audible or visual signal). In another example, the controller may move the identified valve(s) to the desired (e.g., originally commanded) positions or timings.For example, if the BTCC valve is diagnosed as being incorrectly positioned, the method at 1108 may include moving the valve to the desired position (e.g., open or closed), and then the controller may rerun the diagnostics to see if the BTCC valve has been moved to the desired position. In another example, if the identified valve is the SVs, the method at 1108 may include further delaying the SV timing past a desired or previously commanded level if the actual timing is further advanced than the desired timing. In this way, adjusting the valve positions or timings at 1108 may include compensating for the difference identified at 1106 and may thus result in achieving a desired valve position or timing. In yet another example, and as described below with reference to FIG. Fig. 12-13, the method at 1108 may include adjusting an alternative valve different from the identified valve (e.g., one of the non-degraded or correctly positioned valves) to deliver the desired EGR or blowby flow. For example, if the BTCC valve is identified as improperly positioned based on the difference determined at 1106, the method may include adjusting the timing of the SVs to deliver the desired EGR and blowby, rather than adjusting the BTCC valve. In another example, in response to the difference between the actual pressure loss and the expected pressure loss across the BTCC being greater than the threshold difference, the EGR flow to the intake port may be adjusted to the desired level via adjusting the position of the SMBV and / or the timing of the SVs, rather than adjusting the position of the BTCC valve.In yet another example, in response to determining that the SMBV is mispositioned, the controller may instead adjust the BTCC valve to deliver the desired EGR flow and blowby. In yet another example, at 1108, the method may include adjusting the flow of exhaust gases from the SVs to the intake passage via adjusting only the BTCC valve and not the timing of the SVs in response to the actual opening timing of the SVs differing from the expected timing by a threshold amount. In this way, the desired EGR and blowby may still be delivered to the intake passage even if one or more of the valves described above are degraded or mispositioned.

[0184] In this way, a position of one or more of the BTCC valve and the SMBV and / or a timing of the SVs may be diagnosed based on an output of a pressure sensor positioned in the purge exhaust manifold. The valve diagnosed as degraded or mispositioned may then be commanded to a different position and / or an alternative valve may be adjusted to achieve desired operating conditions (such as a desired EGR flow or pressure in the first exhaust manifold). Thus, a technical effect of diagnosing the BTCC valve, the SMBV, and / or the SVs based on purge manifold pressure is to increase the ease of determining valve degradation (e.g.,Determine when a valve needs to be serviced or replaced) and the ability to deliver the desired EGR flow or blow-by amount to the intake port even if one or more of these valves is mispositioned or deteriorated by adapting an alternative valve. This allows engine efficiency and fuel economy to be maintained even if one or more valves are diagnosed as deteriorated or mispositioned.

[0185] In embodiments in which a hot pipe valve or a medium pressure EGR valve is included in the split exhaust engine system (e.g., the hot pipe valve 32 and the medium pressure EGR valve 59 shown in Fig. 1A), method 1100 may further include diagnosing the positions of these valves in a manner similar to diagnosing the BTCC valve and the SMBV as disclosed above.

[0186] With reference to Fig. 12, a method 1200 is shown for controlling EGR flow and blowby air from the purge manifold to the intake port via adjusting the operation of one or more valves of the engine system. Method 1200 may continue from 1012 of method 1000 or from 1108 of method 1100, as described above. For example, method 1200 may be performed in response to changing engine operating conditions (which may include changes in valve positions, cylinder valve timing, system pressures, etc.) that may result in a change in the desired EGR flow amount or rate or the desired blowby flow amount or rate from the purge exhaust manifold (e.g., purge manifold) to the intake port. Method 1200 may additionally or alternatively be performed by one or more of the other methods described herein (e.g., with respect to the Fig. 4-10) which describe changing (e.g., increasing or decreasing) the EGR flow or blow-by flow to the intake port.

[0187] Method 1200 begins at 1202 by determining whether a request to increase EGR is present. In one example, a request to increase EGR (e.g., from the purge manifold 80, via the EGR passage 50, to the intake passage, as shown in Fig. 1A) when an estimated EGR flow rate is below a desired EGR flow rate (as described above with respect to Fig. 10). In another example, a request to increase EGR may be present after an engine cold start where the BTCC valve was closed or at least partially closed. Further, a request to increase EGR may be generated in response to a turbocharger compressor outlet temperature decreasing below a threshold outlet temperature, a turbocharger compressor inlet temperature increasing above a threshold inlet temperature, and / or a compressor speed decreasing below a threshold speed. If a request to increase EGR is present (e.g., increasing the amount of exhaust flow from the engine cylinders to the intake passage via the scavenging exhaust valves (SVs) and the scavenging manifold), the method proceeds to 1204 to adjust one or more engine actuators to increase EGR flow from the scavenging manifold to the intake passage.Increasing EGR at 1204 may include one or more of opening the BTCC valve at 1206, advancing the timing (e.g., opening and closing timing) of the SVs at 1208, and closing the SMBV at 1210. Opening the BTCC valve (e.g., valve 54, shown in . Fig. 1A) may involve the controller sending a signal to an actuator of the BTCC valve to fully open the BTCC valve or to increase the amount of opening (but not full opening) thereof. Similarly, closing the SMBV (e.g., SMBV 97, shown in Fig. 1A) may include the controller sending a signal to an actuator of the SMBV to fully close the SMBV or to decrease the amount of opening (but not fully closing) thereof. Further, advancing the SV timing may include the controller sending a signal to an actuator of the SVs (SVs 6, shown in Fig. 1A) to advance the timing of the SVs alone or all exhaust valves (e.g., when the SVs or BDs are controlled via the same actuator and cam timing system). The method may include, at 1204, selecting the one or more of the adjustments at 1206, 1208, and 1210 to use to increase EGR to a desired level based on engine operating conditions, as described below with respect to Fig. 13 described in more detail.

[0188] If at 1202 there is no request to increase EGR, the method proceeds to 1212 to determine if there is a request to decrease EGR. In one example, a request to decrease EGR (e.g., from the purge manifold 80 via the EGR passage 50, as shown in Fig. 1A) when an estimated EGR flow rate is above a desired EGR flow rate (as described above with respect to Fig. 10). For example, in response to a condition of the turbocharger compressor, including one or more of compressor condensate formation, a compressor inlet temperature below a lower threshold temperature, a compressor outlet temperature above an upper threshold temperature, and a compressor speed above a threshold speed, a request to decrease EGR flow to the intake passage upstream of the compressor may be present. If a request to decrease EGR is present (e.g., decreasing the amount of exhaust flow from the engine cylinders to the intake passage via the scavenging exhaust valves (SVs) and the scavenging manifold), the method proceeds to 1214 to adjust one or more engine actuators to decrease EGR flow from the scavenging manifold to the intake passage.Reducing EGR at 1214 may include one or more of closing (or decreasing the amount of opening) the BTCC valve at 1216, retarding the timing (e.g., opening and closing timing) of the SVs at 1218, and opening (or increasing the amount of opening) the SMBV at 1220. The method may include, at 1214, selecting the one or more of the adjustments at 1216, 1218, and 1220 to use to reduce EGR to a desired level based on engine operating conditions, as described below with respect to FIG. Fig. 13 described in more detail.

[0189] If no request to decrease EGR is present, the method proceeds to 1222 to determine if a request to increase blowby (BT) is present. As described above, increasing blowby may include increasing an amount of fresh, unburned air (or mixed intake air from the intake manifold, where at least a portion of the mixed intake air has not undergone combustion) flowing from the intake port to an SV during a valve overlap period of the intake valve and the SV and then flowing via the scavenging manifold and the EGR port to the intake port. In one example, a request to increase blowby may be present in response to a compressor outlet temperature above a threshold outlet temperature, engine knock, and / or compressor surge.If a request to increase blowby is present, the method proceeds to 1224 to increase blowby via one or more of retarding the timing of the SVs at 1226, advancing the timing of the intake valves (IV) at 1228, and closing the SMBV and / or opening the BTCC valve at 1230. For example, increasing the amount of port overlap between the SV and IV of the same cylinder (e.g., increasing the amount of time both the SV and IV of a same cylinder are open at the same time) may result in increasing the amount of blowby to the intake. In particular, increasing the amount of opening overlap between the IV and the SV may include delaying the SV timing (e.g., delaying the SV closing timing) and / or advancing the IV timing (e.g., advancing the IV opening timing).In one example, increasing the amount of opening (or fully opening) of the BTCC valve and / or decreasing the amount of opening (or fully closing) of the SMBV may increase the amount of blowby air flowing from the engine cylinders to the intake port. However, if the BTCC valve is already fully open and the SMBV is already fully closed, the method at 1224 may include retarding the SV timing and / or advancing the IV timing. Further, if the SV timing is already at the maximum amount of retard, the method at 1224 may include advancing the IV timing to increase blowby to the intake. Similarly, if the intake valve timing is already maximally advanced, the method at 1224 may include retarding the SV timing to increase blowby.Furthermore, at 1224, if the blowby is still not at the requested level when the SV timing reaches the maximum amount of delay, the method may include first retarding the SV timing and then advancing the IV timing. In yet another example, the decision regarding adjusting more than one of the engine actuators at 1224 may be based on the amount of requested change in the amount of blowby. For example, if the requested blowby continues to increase above the current level, the method may include increasing the amount of adjustment of the SV timing, IV timing, and valve position and / or adjusting two or more of the actuators at 1224 (e.g., simultaneously retarding the SV timing and advancing the IV timing to achieve the desired amount of blowby).In this way, increasing the blowby at 1224 may include adjusting one or more of the SV timing, IV timing, SMBV, and the BTCC valve based on the current timings and positions of each other and the amount of the requested blowby increase.

[0190] If there is no request to increase blowby, the method proceeds to 1232 to determine if there is a request to decrease blowby. In one example, a request to decrease blowby may be present in response to a turbine operating below a threshold speed and above a threshold load, and a flow rate through the compressor that is above a threshold flow rate (where the threshold flow rate may be a flow rate at which compressor efficiency decreases and results in charge air heating). If there is a request to decrease blowby, the method proceeds to 1234 to decrease blowby via one or more of advancing the SV timing at 1236, retarding the IV timing at 1238, and opening the SMBV and / or closing the BTCC valve at 1240.For example, decreasing the amount of opening overlap between the SV and IV of the same cylinder (e.g., decreasing the amount of time both the SV and IV of a same cylinder are open simultaneously) may result in decreasing the amount of blowby to the intake. In particular, decreasing the amount of opening overlap between the IV and the SV may include advancing the SV timing (e.g., advancing the SV closing timing) and / or retarding the IV timing (e.g., advancing the IV opening timing). In one example, decreasing the amount of opening (or fully closing) of the BTCC valve and / or increasing the amount of opening (or fully opening) of the SMBV may decrease the amount of blowby air flowing from the engine cylinders to the intake port.However, if the BTCC valve must remain open to deliver the requested amount of EGR to the intake port, the method at 1234 may include advancing the SV timing and / or retarding the IV timing. Further, if the SV timing is already at the maximum amount of advance, the method at 1234 may include retarding the IV timing to reduce blowby to the intake. Similarly, if the intake valve timing is already at the maximum retarded, the method at 1234 may include advancing the SV timing to reduce blowby. Furthermore, if the blowby is still not at the requested level when the SV timing reaches the maximum amount of advance, the method at 1234 may include first advancing the SV timing and then retarding the IV timing.In yet another example, the decision regarding adjusting more than one of the engine actuators at 1234 may be based on the amount of requested change in the amount of blow-by. For example, if the requested blow-by continues to decrease below the current level, the method at 1234 may include decreasing the amount of adjustment of the SV timing and the IV timing, or adjusting both the SV timing and the IV timing simultaneously to achieve the desired amount of blow-by.

[0191] If there is no request to reduce blow-by, the method proceeds to 1242 to maintain the current valve positions and timings. Method 1200 then ends.

[0192] Fig. 13 shows a method 1300 for selecting between operating modes for adjusting the flow of exhaust gases (e.g., EGR flow) from the engine cylinders to the intake passage via the purge exhaust valves and the purge exhaust manifold. Method 1300 may proceed from 1204 and 1214 of method 1200, as described above. Method 1300 begins at 1302 by determining whether conditions for a first mode are met. In one embodiment, conditions for a first mode for adjusting EGR flow may include when a requested change in EGR flow to the intake is above a threshold level. The threshold level may be a non-zero threshold amount of EGR flow that cannot be achieved by adjusting only a single actuator.In another embodiment, conditions for a first mode for adjusting EGR flow for intake may include when none of the BTCC valve and SVs are diagnosed as mispositioned or degraded (such as during method 1100, as described above with respect to FIG. Fig. 11). If the conditions for a first mode are met at 1302, the method proceeds to 1304 to adjust both the BTCC valve and the SV timing to adjust the amount of EGR flow to the intake port. For example, at 1304, the method may include adjusting together, at a same time, the position of the BTCC valve and the timing of the SVs to adjust the EGR flow to the desired level (e.g., to increase or decrease the EGR flow, as described above with respect to Fig. 12). In another example, at 1304, the method may include first adjusting one of the BTCC valve position and the SV timing, and then, immediately after adjusting the first actuator, adjusting the other of the BTCC valve position and the SV timing. In this way, adjusting the BTCC valve (e.g., opening) may adjust EGR flow by a first amount (e.g., increasing or decreasing), and adjusting the SV timing (e.g., advancing or retarding) may adjust EGR flow by a second amount. Thus, by adjusting both the BTCC valve position and the SV timing during the first mode, a greater adjustment to EGR flow may be achieved.

[0193] Alternatively, if at 1302 the conditions of the first mode are not met, the method proceeds to 1306 to determine if conditions for a second mode for adjusting EGR flow are met. In one embodiment, the conditions for a second mode may include one or more of when the timing of the SVs cannot be further adjusted for a currently required direction of EGR flow adjustment, and when the BTCC valve is in a partially open position and there is a request for both increased EGR flow and increased blowby air from the SVs to the intake passage. For example, the SV timing cannot be further adjusted if it is already at its maximum amount of retardation (in the case of decreasing EGR flow) or advancement (in the case of increasing EGR flow).In another embodiment, the conditions for a second mode may additionally or alternatively include when the difference between an actual timing of the SVs and an expected timing of the SVs is above a threshold (e.g., as described above with respect to method 1100 of FIG. Fig. 11). Thus, if the SVs are diagnosed as not at the correct timing or as degraded, they cannot be used to adjust EGR flow. In this case, the BTCC valve may be adjusted to adjust EGR flow to the desired level based on the actual timing of the SVs. If the conditions for a second mode are met at 1306, the method proceeds to 1308 to adjust only the BTCC valve to adjust EGR flow to the desired level. For example, the method at 1308 may include adjusting only the position of the BTCC valve (e.g., increasing or decreasing the amount of opening or modulating the position between fully open and fully closed) to adjust EGR flow to the desired level, and not adjusting the SV timing.

[0194] Alternatively, if at 1306 the conditions of the second mode are not met, the method proceeds to 1310 to determine if conditions for a third mode for adjusting EGR flow are met. In one embodiment, the conditions for a third mode may include when the BTCC valve is already in a fully open position and in response to a request to increase exhaust flow from the SVs to the intake passage. In another embodiment, the conditions for a third mode may additionally or alternatively include when the difference between the actual pressure loss across the BTCC valve and the expected pressure loss across the BTCC valve is above a threshold (e.g., as described above with respect to method 1100 of Fig. 11). Thus, if the BTCC valve is diagnosed as mispositioned or degraded, it cannot be used to adjust EGR flow. If the conditions for a third mode are met at 1310, the method proceeds to 1312 to adjust only the SV timing to adjust EGR flow. For example, at 1312, the method may include advancing or retarding the SV timing to adjust EGR flow to the desired level and not adjusting the BTCC valve. As an example, if the BTCC valve is already fully open and there is a request to increase EGR flow, the method at 1312 includes maintaining the BTCC valve in a fully open position and adjusting the timing of the SVs to adjust EGR flow to the desired level.

[0195] If the conditions for a third mode are not met at 1310, the method proceeds to 1314 to maintain the SV timing and BTCC valve position at the current timings / positions. Method 1300 then ends.

[0196] Fig. 22 shows a diagram 2200 of controlling one or more engine actuators to adjust the EGR flow and blow-by flow from the purge exhaust valves to the intake port. Specifically, chart 2200 shows changes in EGR flow at trace 2202, changes in blowby amount (BT) at trace 2204, changes in a position of the BTCC valve at trace 2206, changes in SV timing at trace 2208 (relative to a standard timing D1 for best fuel efficiency, a maximum amount of advance MA, and a maximum amount of retard MR), changes in a position of the SMBV at trace 2210, changes in IV timing at trace 2212 (relative to a standard timing D2 for best fuel efficiency, a maximum amount of advance MA, and a maximum amount of retard MR), changes in a difference between an actual pressure loss and an expected pressure loss across the BTCC valve (e.g.,B. during valve diagnostics) at trace 2214 and changes in a difference between an actual timing and an expected timing of the SVs at trace 2216.

[0197] Before time t1, the BTCC valve is fully open, the SMBV is fully closed, the IV timing is at its default timing D2, and the SV timing is at its default timing D1. At time t1, a request may be present to increase EGR flow to the intake port to a first level. In response to this request, and due to the BTCC valve already being in the fully open position, the SV timing is advanced to increase EGR flow to the first level. Advancing the SV timing may also decrease BT. Thus, at time t2, a request to increase BT is present. However, because the EGR flow demand is still at the first level, the intake valve timing is advanced at t2 while the SV timing is maintained at the advanced timing.

[0198] Before time t3, the difference between the actual and expected timing of the SVs increases above a threshold T2. Then, at time t3, a request to reduce EGR flow and blowby may be present. Thus, in response to the request and the SV timing diagnosis at time t3, the BTCC valve is closed to reduce EGR flow and BT. Furthermore, since the BTCC valve is closed, the intake valve timing may return to the default timing D2. Between time t3 and time t4, the BTCC valve position may be modulated between fully open and fully closed to obtain the desired EGR flow to the intake.In alternative embodiments where the BTCC valve is a continuously variable valve that can be adjusted to a variety of positions between and including fully open and fully closed, the BTCC valve can be adjusted to and maintained at a partially closed position that delivers the desired EGR flow to the intake (e.g., rather than modulating). Before time t4, the difference between the actual and expected SV timing may reduce back below threshold T2. At time t4, there may again be a request to increase EGR, but to a second level that is above the first level requested at time t1. In response to this higher request, which may be above a threshold increase in EGR flow, the BTCC valve is opened at time t4 and the SV timing is advanced.The IV timing can also be advanced at time t4 to maintain the BT at the desired level. This allows both the BTCC valve and the SV timing to be adjusted simultaneously to adjust the EGR flow to the requested second level.

[0199] At time t5, a request to reduce EGR flow may be present. Immediately before time t5, the difference between the actual and expected pressure drop across the BTCC valve may increase above a threshold T1. In response to the request and the BTCC valve diagnostics, the SV timing is retarded. However, at time t6, the SV timing may reach its maximum amount of retardation, but EGR flow may still need to be further reduced. As a result, the SMBV may be opened to further reduce EGR flow to the intake port. In this way, under different operating modes, one or more actuators (e.g., the BTCC valve, the SV timing, the IV timing, and / or the SMBV) can be adjusted to achieve the desired EGR flow and BT flow.For example, during a first mode, as shown at time t4, both the SV timing and the BTCC valve are adjusted to deliver the desired EGR flow to the intake port. As another example, during a second mode, as shown at time t3, only the BTCC valve is adjusted to deliver the desired EGR flow because the SVs are diagnosed as not being at the correct timing (and possibly exhibiting degraded function). However, at this time, the IV timing is also adjusted to maintain the desired BT flow. Furthermore, during a third mode, as shown at time t5, only the SV timing is adjusted to adjust the EGR flow because the BTCC valve is diagnosed as exhibiting degraded function and / or being mispositioned.However, since the SV timing reaches its maximum retardation amount at time t6, the SMBV is opened in addition to retarding the SV timing to achieve the higher desired EGR level. Adjusting the various actuators in coordination with each other (e.g., based on a current position, timing, and / or degradation or misposition condition of another) can enable the efficient delivery of both the desired EGR flow and BT flow amounts via the SVs to the intake port.A technical effect of adjusting exhaust flow from the purge outlet valves to the intake passage upstream of the compressor via adjusting one or both of the BTCC valve and the purge outlet valve timing in the different modes described above is to deliver the desired EGR flow and blowby flow to the intake, even if one of the BTCC valve or the SV timing cannot be adjusted. Furthermore, controlling EGR flow in the third mode by adjusting only the SV timing may provide more consistent EGR flow, with a fixed amount of EGR being forced to the intake passage in each engine cycle. For example, controlling EGR flow in this manner may allow the EGR valve to be an on / off valve, thereby simplifying EGR valve control and reducing engine system costs.

[0200] Fig. 14 shows a method 1400 for operating the vehicle in electric mode (e.g., all-electric mode). The method 1400 may continue from 405 of the method 400, as described above. The method 1400 begins at 1402 by driving the hybrid electric vehicle solely via engine torque. For example, one or more clutches may be moved to disengage the engine crankshaft from an electric machine and its associated components and connect the electric machine to the transmission and wheels of the vehicle (such as the electric machine 161, the transmission 167, and the clutches 166 shown in Fig. 1B). In this way, the electric machine (e.g., motor) can provide torque to the vehicle wheels (e.g., using electrical power received from a traction battery).

[0201] At 1404, the method includes determining whether an engine start is imminent. As one example, in response to the battery charge state and the driver torque demand, the controller may determine that an engine start is imminent (e.g., wherein the engine needs to be started to begin combustion to provide torque to propel the vehicle). For example, if the required torque cannot be provided by the battery (at the current state of charge), a request to start the engine and operate the vehicle in engine mode may be generated. In another example, if the required torque can only be provided by the battery for a limited period of time, a request to start the engine within that limited period of time may be generated.This period may be based on an amount of time to increase intake manifold pressure and / or piston temperature above threshold levels for starting the engine with reduced emissions, as described in more detail below. However, if the required torque can only be provided by the battery (e.g., for longer than the restricted period of time) and thus an engine start is not imminent, the method may proceed to 1406 to determine if the vehicle is decelerating. In one example, the vehicle may decelerate when an accelerator pedal is released and / or a brake pedal is applied. In another example, the vehicle may decelerate when engine speed decreases. If the vehicle is not decelerating, the method proceeds to 1407 to continue propelling the vehicle solely using engine torque.However, if the controller determines that the vehicle is decelerating, the method proceeds to 1408 to deactivate all of the blowoff exhaust valves (e.g., the first exhaust valves 8 shown in . Fig. 1A) deactivate the engine cylinders and rotate the engine using torque from the vehicle wheels (via the crankshaft) instead of charging the battery. In one example, deactivating all blowoff exhaust valves may include the controller deactivating one or more of the blowoff exhaust valve actuation systems to keep the blowoff exhaust valves closed so that gases do not move via the cylinders into the exhaust passage. As a result, gases cannot move through the exhaust passage, thereby reducing engine emissions. Rotating (e.g., spinning) the engine during deceleration may result in engine warm-up, thereby increasing engine power and reducing engine emissions at engine start-up.

[0202] Referring to FIG. 1404, when an engine start is imminent, the method proceeds to 1410 to determine whether to operate in a blowoff valve deactivation mode prior to engine start (e.g., prior to engine firing). In one embodiment, control may determine to operate the engine in the blowoff deactivation mode in response to an intake manifold pressure above a threshold pressure. The threshold pressure may be based on an intake manifold pressure at which elevated emissions may occur at engine start. In one example, the threshold pressure may be a pressure at or above atmospheric pressure.In another embodiment, the controller may determine not to operate the engine in the blowoff shutdown mode and instead operate in an extended crank mode in response to a piston temperature below a threshold temperature. The threshold temperature may be a threshold temperature for restarting the engine with reduced emissions. For example, if the engine starts with a piston temperature below the threshold temperature, increased emissions may result. In one example, a determination may be made whether to operate in the blowoff shutdown mode or the extended crank mode based on a threshold cylinder (or piston) temperature at which fuel is vaporized. Thus, the decision at 1410 may also be based on fuel type.When the piston (or cylinder) temperature is below the threshold temperature, which is the temperature required to vaporize the current fuel type, the controller may determine to operate the engine in the enhanced crank mode at 1410.

[0203] If the blowoff valve deactivation mode is selected at 1410, the method proceeds to 1412 to deactivate all blowoff exhaust valves prior to cranking the engine (e.g., deactivating the blowoff exhaust valve 8 of each cylinder, as in Fig. 1A). As a result, gases passing through the engine cylinders cannot flow to the exhaust passage. At 1414, the method includes circulating gases through the engine cylinders and back to the turbocharger compressor inlet (e.g., compressor 162, shown in Fig. 1A) via the purge exhaust manifold (e.g. the second exhaust manifold 80, shown in Fig. 1A) and the purge outlet valves (e.g. the purge outlet valves 6, shown in Fig. 1A) to pump down the intake manifold pressure. In this way, gases may enter the engine cylinders via the intake manifold, exit the engine cylinders via the purge exhaust valves of each cylinder, and then flow into the purge exhaust manifold, through the EGR passage to the intake passage, and back to the intake manifold. This may be repeated for multiple rotations of the crankshaft. For example, the method at 1414 may be repeated until the manifold pressure decreases below a lower threshold pressure or until an indication that the engine needs to be started is received. If at 1416 it is determined that it is time to start the engine (e.g.,based on the intake manifold pressure decreasing below the lower threshold pressure for engine start and / or based on the torque demand no longer being able to be supplied by the battery), the method proceeds to 1418 to determine whether a catalyst disposed in the exhaust passage (e.g., the emission control device 70 and / or 72 shown in FIG. Fig. 1A), is at a light-off temperature. If the catalyst is not at the light-off temperature, the method proceeds to 1420 to re-enable the blow-off exhaust valves of the inner cylinders, while the blow-off exhaust valves of the outer cylinders remain deactivated and the cylinders are fired. As an example, the inner cylinders may include the cylinder oriented within and between the outer cylinders of the internal combustion engine (such as in Fig. 1A, cylinders 14 and 16 are inner cylinders and cylinders 12 and 18 are outer cylinders. This may help the catalyst(s) reach its light-off temperature(s) more quickly. Alternatively, if the catalyst is at light-off temperature at 1418, the method proceeds to 1422 to re-enable all blow-off exhaust valves of all cylinders, inject fuel into each of the cylinders, and resume combustion at each of the cylinders. As a result, the vehicle may begin operating in engine (e.g., pure engine or auxiliary) mode and stop operating in pure electric mode.

[0204] Referring again to 1410, if it is determined that the engine should be operated in the extended crank mode rather than the blowoff valve deactivation mode, the method transitions from 1410 to 1424. At 1424, the method includes operating in the extended crank mode by slowly rotating the unfueled engine with the motor (e.g., electric motor). The method may further include, at 1424, heating each cylinder during a compression stroke of the cylinder. For example, at 1424, while propelling the hybrid vehicle solely via engine torque and prior to engine restart, the method may include rotating the unfueled engine via engine torque at less than a threshold speed. Here, the vehicle's electric motor may propel the vehicle and rotate the engine.The threshold speed, in one example, may be an engine crank speed. That is, the engine may be rotated at a speed below the speed at which the engine would be rotated by a starter motor during engine cranking and restarting. For example, during engine cranking without fuel, the engine may be rotated at 150 rpm via a starter motor. In comparison, during slow rotation for cylinder heating, the engine may be rotated at 10-30 rpm via the hybrid vehicle's electric motor / generator. In alternative examples, the threshold speed at or below which the engine is slowly rotated may be higher or lower based on operating parameters such as oil temperature, ambient temperature, or NVH.In one example, slow rotation of the engine may be initiated in a cylinder (e.g., a first cylinder) selected based on proximity to a cylinder piston position relative to a compression stroke TDC. For example, a controller may identify a cylinder with a piston positioned closest to the compression stroke TDC or at a position experiencing at least a threshold level of compression. The engine is then rotated such that each cylinder is sequentially heated during a compression stroke of the cylinder. As rotation progresses, each cylinder may be cooled during a power stroke of the cylinder immediately following the compression stroke.However, the cylinder can be heated more during the compression stroke than the cylinder is cooled during the expansion stroke, allowing for a net heating of each cylinder via a heat pump effect. Therefore, during a compression stroke, each cylinder's air charge is compressed, generating heat. By rotating an internal combustion engine so that a cylinder is kept in the compression stroke, heat can be transferred from the compressed air to the cylinder walls, cylinder head, and piston, increasing the engine temperature.

[0205] With reference to 1426, the method includes throttling the BTCC valve (e.g., the first EGR valve 54 shown in Fig. 1A) or the hot pipe valve (e.g. the third valve 32 shown in Fig. 1A) to increase crank torque and, as a result, further heat the engine. In one example, throttling the BTCC valve or the hot pipe valve may include at least partially closing (or decreasing the amount of opening) the BTCC valve or the hot pipe valve. In some examples, the intake throttle and the BTCC valve may be closed at 1426 to recirculate gases through the cylinders via the hot pipe (and not the EGR passage) while the hot pipe valve is partially closed (e.g., throttled) to increase crank torque. In another example, the intake throttle may remain open and the hot pipe valve may be fully closed to recirculate gases through the cylinders via the EGR passage (e.g., the first EGR passage 50 shown in Fig. 1A) while the BTCC valve is partially closed (e.g., throttled) to increase crank torque. At 1428, the method includes determining whether it is time to start (e.g., restart) the engine. In one example, the engine may not be started until the piston temperature increases above the threshold temperature. If it is not time to start the engine, the method returns to 1424 and 1426 to continue operation in enhanced crank mode. Otherwise, if it is time to start the engine, the method proceeds to 1422 to restart the engine, as described above.

[0206] Fig. 23 shows a graph 2300 for operating the hybrid electric vehicle in the electric mode to heat the engine system prior to starting the engine. In particular, the graph 2300 shows the vehicle speed at plot 2302, the battery state of charge (SOC) at plot 2304, the intake manifold pressure (MAP) at plot 2306, the piston temperature at plot 2308, the catalyst temperature at plot 2310, the engine speed at plot 2312, an activation state of the cylinder bleed exhaust valve (BDVs) at plot 2314, a position of the BTCC valve (e.g., the first EGR valve 54 shown in Fig. 1A) at trace 2316, a position of the hot tube valve (e.g., valve 32 shown in Fig. 1A) at curve 2318 and a position of an intake throttle (e.g. throttle 62, shown in Fig. 1A) at trace 2320. All traces are shown versus time along the x-axis.

[0207] Before time t1, the vehicle may be operating in an electric mode and propelled solely by engine torque. For example, the engine start conditions may not be met before time t1. Between time t1 and t2, as operator torque demand and, accordingly, vehicle speed vary, the battery SOC may vary, with the battery SOC being reduced at a faster rate as vehicle speed increases. While the vehicle is propelled using engine torque between time t1 and t2, the piston temperature may be below the threshold temperature T1 and MAP may be above the threshold pressure P1.

[0208] At time t2, the operator torque demand and vehicle speed increase. As a result, the battery SOC may stop decreasing, or it may be decreased at a slower rate. Shortly after time t2, a vehicle deceleration event occurs. During this event, instead of dissipating wheel torque as heat or using it to recharge the battery, the engine opportunistically rotates the wheels without fuel, and the blowoff exhaust valves of all engine cylinders are deactivated. For example, at least a portion of the wheel torque is applied to the engine rotation via a vehicle motor / generator, temporarily increasing the engine rotation speed.As a result of the engine rotating and the blowoff valves deactivating, air is recirculated through the engine via the purge exhaust valves, the EGR passage, and the open BTCC valve, increasing piston temperature. Once vehicle speed decreases, opportunistic engine rotation is stopped. In alternative embodiments, in an engine system with a hot pipe (e.g., hot pipe 30 shown in FIG. Fig. 1A) coupled between the scavenging exhaust manifold and the intake manifold downstream of an intake throttle, the intake throttle and the BTCC valve are closed while a valve in the hot pipe is opened to allow the recirculation of air through the engine cylinders via the scavenging exhaust valves and the hot pipe.

[0209] At time t3, the deceleration event ends and vehicle speed increases again. At time t4, an indication that an engine start is imminent may be present. In response to the MAP being above threshold pressure P1 and the piston temperature being below threshold temperature T1 during the indication of imminent engine start, all BDVs of all engine cylinders are again deactivated. While the BTCC valve is open, gases are circulated through the engine cylinders and back to the intake passage via the purge exhaust valves, the purge exhaust manifold, and the EGR passage. As a result, intake manifold pressure decreases. At time t5, intake manifold pressure decreases below threshold pressure P1. As a result, the engine may be started.However, since the catalyst temperature is below the light-off temperature T2, only the BDVs of the inner combustion engines can be reactivated, while the BDVs of the outer cylinders remain deactivated. Then, when the catalyst temperature rises above the light-off temperature T2 at time t6, the BDVs of the outer cylinders are reactivated.

[0210] After a period of time (e.g., following an engine shutdown and / or a key-turn vehicle shutdown), the vehicle may again operate in electric mode, powered entirely by engine torque. At time t7, there may be an indication that an engine start is imminent while the piston temperature is below the threshold temperature T1. In response, the vehicle may operate in an extended crank mode, with the engine slowly rotated via the electric motor without fuel supply (e.g., at less than one crank speed). While the engine is rotating, the BTCC valve may be closed, the hot pipe valve may be at least partially open, and the intake throttle may be closed.Furthermore, the hot pipe valve may not be fully open (so it is partially throttled) to increase crank torque and further increase engine heating. As a result of this process, air is heated in the cylinders during the compression stroke and then recirculated through the engine system via the scavenging exhaust valves, the scavenging exhaust manifold, the hot pipe, and the intake manifold, thereby increasing the piston temperature. At time t8, the piston temperature rises above the threshold temperature T1. As a result, the engine is restarted, and the BTCC valve and intake throttle are opened and the hot pipe valve is closed.

[0211] In this way, an engine of a hybrid vehicle using a motor can be slowly cranked during a transition from operation in an electric mode to an engine mode to warm the engine prior to engine start. By slowly rotating the unfueled engine for a period prior to engine start, heat generated by air being compressed in a cylinder during a compression stroke can be transferred to the cylinder walls and pistons and advantageously used to heat the engine. Furthermore, by throttling the hot pipe valve (or the BTCC valve if gases are recirculated via the EGR passage instead of the hot pipe), crank torque is increased, further increasing engine warmup.Thus, a technical effect of rotating the unfueled engine above engine torque at less than crank speed while at least partially throttling the BTCC valve or hot pipe valve is to increase piston temperature and the rest of the engine, thereby reducing cold-start emissions and starting the engine faster. In another example, by deactivating the blowoff exhaust valves and recirculating air through the engine cylinders, scavenge exhaust manifold, and EGR passage, intake manifold pressure may be pumped down and / or engine temperature may be increased. In this way, the engine may start faster, and overall engine cold-start exhaust emissions and engine performance may be improved.Thus, a technical effect of turning off the blow-off exhaust valves and circulating air through the engine cylinders during electric mode is to reduce intake manifold pressure, increase engine temperature, and thus start the engine faster while reducing emissions.

[0212] Fig. 15 shows a method for operating the engine system in a shutdown mode. Method 1500 may proceed from 426 of method 400, as described above. Method 1500 begins at 1502 by determining whether the detected or indicated shutdown event is an ignition key-off shutdown. In one example, in response to the controller receiving a signal that an ignition (operated by a user) has been turned off, it may be determined to be an ignition key-off shutdown event. In another example, in response to the controller receiving a signal that the engine has been turned off (e.g., via an ignition being turned off) and the vehicle being positioned in park mode, it may be determined to be an ignition key-off shutdown event.In this way, an ignition key-off shutdown may be a shutdown during which the engine is expected to be turned off for a threshold period and not restarted for a duration. If the shutdown at 1502 is an ignition key-off shutdown, the method proceeds to 1504 to close the intake throttle (e.g., throttle 62 shown in FIG. Fig. 1A) and the hot pipe valve (e.g. valve 32, shown in Fig. 1A) to direct unburned hydrocarbons to a catalyst (e.g., one of the emission control devices 70 and 72 shown in Fig. 1A) in the exhaust passage of the engine. During this time, the blow-off valves remain deactivated. Furthermore, at 1504, the method may further include closing the BTCC valve (e.g., valve 54 shown in Fig. 1A). As a result, unburned hydrocarbons can be returned from the engine cylinders to the intake manifold via the scavenging exhaust valves, the scavenging exhaust manifold, and the hot pipe (e.g., passage 30, shown in Fig. 1A). The recirculated unburned hydrocarbons can then be pumped from the engine cylinders to the exhaust passage with the catalyst via the blow-off exhaust valves. This can reduce the amount of hydrocarbons in the engine during shutdown and can keep the catalyst at stoichiometry during shutdown and subsequent restart.

[0213] At 1506, when the engine stops rotating, the method includes opening the BTCC valve and opening the throttle. For example, in response to a crankshaft of the engine stopping rotating, the controller may actuate a BTCC valve actuator to open the BTCC valve and a throttle actuator to open the throttle. This may reduce the amount of exhaust gas drawn back into the intake (e.g., intake passage) of the engine. Further, at 1506, the method may first include opening the BTCC valve and then, in response to the BTCC valve opening, opening the throttle.

[0214] Referring again to 1502, if the shutdown is not an ignition key-off shutdown, the method may determine that the shutdown is a start / stop shutdown and thus may proceed to 1508. As an example, in response to the vehicle being stopped for a threshold period but not turned off via the ignition key (e.g., when the vehicle is stopped at a traffic light), the controller may determine that the shutdown is a start / stop shutdown request. At 1508, the method includes initiating the start / stop shutdown. Then, the method proceeds to 1510 to deactivate all blowoff exhaust valves (e.g., valves 8 shown in Fig. 1A) to deactivate (e.g., turn off) the engine and open the BTCC valve after the last of all engine cylinders has fired. In other words, once the last cylinder fires (e.g., the last cylinder to undergo combustion before no further cylinders are fired and the engine shuts down), the controller can deactivate the blowoff exhaust valve actuators such that the blowoff exhaust valves remain closed and do not exhaust gases to the exhaust passage. As a result, gases from all engine cylinders are recirculated to the intake manifold via the scavenge exhaust valves and the EGR passage. This reduces the pressure in the intake manifold during engine deceleration (e.g., while the crankshaft speed decreases and it eventually stops).

[0215] At 1512, the method includes determining whether a request to restart the engine is present. In one example, the request to restart the engine may be generated in response to an increase in torque demand from a stopped position of the vehicle. For example, when a brake pedal is released and / or an accelerator pedal of the vehicle is applied, a restart request may be generated. If a request to restart the engine is present, the method proceeds to 1516 to deactivate the blowoff exhaust valves and maintain the BTCC valve in the open position. Otherwise, if a request to restart the engine is present, the method proceeds to 1514 to re-enable the blowoff exhaust valves upon an initial cranking of the crankshaft. Regular engine operation then resumes.For example, the method may end and / or return to method 400. As discussed above, re-enable the blowoff exhaust valves may include the controller sending a signal to the valve actuators of the blowoff exhaust valves to resume opening and closing the blowoff exhaust valves at their set timing.

[0216] Fig. 24 shows a plot 2400 for operating the vehicle's split exhaust engine system in shutdown mode. Specifically, plot 2400 shows whether a vehicle's ignition is on or off at plot 2402, vehicle speed at plot 2404, a throttle position at plot 2406, a BTCC valve position at plot 2408, a hot pipe valve position at plot 2410, engine speed at plot 2412, and an activation state (e.g., on / off or enabled / disabled) of the blowoff exhaust valves (BDVs) at plot 2414. All plots are shown versus time along the x-axis.

[0217] Before time t1, the engine is operating and the vehicle speed is above a steady-state level (e.g., a level at which the vehicle may be stationary or not moving). Furthermore, before time t1, all BDVs of all engine cylinders are turned on and operating at their set timing (which is different from the opening timing of the scavenge exhaust valves). After time t1, the vehicle speed decreases to approximately zero, indicating that the vehicle has stopped. At time t1, the engine ignition remains on. In response to the vehicle being stopped, a start / stop shutdown is initiated. This may include firing a last engine cylinder at time t2. Then, in response to the last engine cylinder firing, all BDVs (e.g., every BDV of every cylinder) are deactivated at time t2, and the BTCC valve is opened.During this time, the scavenging exhaust valves remain active, and thus gases from the engine cylinders are directed via the scavenging exhaust manifold and the EGR passage to the intake passage. If the BDVs are deactivated, they may remain closed, and thus no gases from the engine cylinders are directed to the engine exhaust passage. Immediately before time t3, a request to restart the engine may be received by the controller (e.g., via an operator releasing a brake pedal and depressing an accelerator pedal, thereby indicating an increase in torque demand from the stopped position). The crankshaft is cranked at time t3, and thus the engine speed begins to increase. During the initial cranking at time t3, the BDVs are reactivated. The cylinders begin firing again, and at least a portion of the exhaust gases may be directed to the exhaust passage via the BDVs.Regular internal combustion engine operation will resume.

[0218] After a period of time, the vehicle speed decreases to essentially zero at time t4, indicating that the vehicle has stopped. At time t5, the engine ignition is turned off (e.g., manually turned off by a vehicle operator). In response to the vehicle being stopped (e.g., in park mode) and the engine being turned off via the ignition (e.g., turned off via the ignition key), the throttle is closed, the BTCC valve is closed, and the hot pipe valve is opened. As a result, engine gases are recirculated via the scavenging exhaust manifold and hot pipe, reducing intake manifold pressure. When the engine stops rotating (engine speed reaches approximately zero), the throttle and BTCC valve are both opened.

[0219] In this way, during a key-on engine shutdown (as shown at time t5) and a start / stop shutdown (as shown at time t1), the throttle valve, BTCC valve, BDVs, and / or hot pipe valve may be adjusted to reduce the amount of hydrocarbons in the engine intake, reduce intake manifold pressure, and bring a catalyst to or near stoichiometry. This may reduce engine emissions during the shutdown and improve engine operation (and reduce emissions) during a subsequent engine start or restart. A technical effect of closing the intake throttle and opening the hot pipe valve in response to a request to shut down the engine (e.g.,The purpose of the ignition key-off request is to reduce engine reversing and direct unburned hydrocarbons to the exhaust catalyst, thereby reducing hydrocarbons in the engine system and maintaining the catalyst at stoichiometry. A technical effect of deactivating the BDVs and opening the BTCC valve is to recirculate gases through the engine, reducing intake manifold pressure prior to engine shutdown.

[0220] Fig. 25 shows a graph 2500 of the operation of the split exhaust engine from start-up to shutdown. In particular, the graph 2500 shows an activation state of the purge outlet valves (SV, where on stands for activated and off stands for deactivated) at graph 2502, a position of the BTCC valve at graph 2504, the EGR flow (e.g., through the EGR passage 50 to the compressor inlet, as I Fig. 1A) at trace 2506, a temperature of an exhaust catalyst (such as a catalyst of one of the emission control devices 70 and 72 shown in Fig. 1A) relative to a light-off temperature T1 at trace 2508, a temperature at an outlet of the turbocharger compressor (e.g., compressor 162, shown in Fig. 1A) relative to a threshold outlet temperature T2 at trace 2509, a position of an intake throttle (e.g., throttle 62 shown in Fig. 1A) at trace 2510, an on state of the blow-off exhaust valves (BDVs) of the outer cylinders (e.g., cylinders 12 and 18, shown in Fig. 1A) at curve 2512, a switch-on state of the BDVs of the inner cylinders (e.g. cylinders 14 and 16, shown in Fig. 1A) at trace 2513, cam timing of the intake valves at trace 2514 and the exhaust valves (which may include the blow-off exhaust valves and the purge exhaust valves if controlled by the same cam timing system) at trace 2516 relative to their output timings B1 (an example of the output cam timing of the intake and exhaust valves may be shown in Fig. 3B, as described above), a position of the hot tube valve (e.g., valve 32 shown in Fig. 1A) at course 2518, a position of the SMBV (e.g. SMBV 97, shown in Fig. 1A), the engine speed at trace 2522, and the engine load at trace 2524. All traces are shown versus time along the x-axis.

[0221] Before time t1, the engine starts (e.g., in response to a vehicle operator turning on the ignition), with the purge exhaust valves switched on by default. This allows the purge exhaust valves to open and close at their set timing in the engine cycle. At time t1, the BTCC valve is opened for the first crank. Thus, EGR flow begins to increase after time t1 (and may increase and decrease over time as the BTCC valve opens and closes, respectively). After the first cylinder fires, the BTCC valve is modulated to control EGR flow to a desired level. Between time t1 and time t2, the hot pipe valve and the SMBV are closed, and both the intake and exhaust valve timings are at their initial timings B1. At time t2, the purge exhaust valves can be adjusted (e.g.,, because the oil pressure has reached a threshold to adjust the valves), so the purge exhaust valves are deactivated (e.g., turned off). After time t2, the catalyst temperature is still below the light-off temperature T1. Thus, the BDVs of the outer cylinders (e.g., cylinders 12 and 18, shown in . Fig. 1A) is deactivated to reduce heat loss during catalyst light-off. Furthermore, compression heat can further heat the cylinder, as airflow to all cylinders is maintained during BDV activation. This can lead to the catalyst heating to a temperature above the light-off temperature T1.

[0222] At time t3, the catalyst temperature rises above its light-off temperature T1, and there may also be a request to increase EGR flow to the intake port via the EGR port and scavenging manifold. In response to the request to increase EGR flow, the BTCC valve is held open and the SV timing is advanced at time t3. Immediately before t4, the engine load decreases below a threshold load L1, and the throttle position is adjusted to a partially closed position (e.g., throttle response). In response to this low load condition at time t4, the throttle is closed, the BTCC valve is open, and the hot pipe valve is open to operate the engine in a hot pipe mode. At time t5, there is an increase in torque demand (and thus, the engine load increases).As a result, an electric compressor may be turned on to increase boost pressure. In response to the electric compressor turning on, the BTCC valve may be closed. At time t6, the electric compressor may be turned off upon reaching the target boost pressure, and there may also be a request for increased EGR. In response to this request (which may be above a threshold amount of EGR flow), both the BTCC valve is opened and the SV timing is advanced to increase EGR flow. The IV timing may also be advanced at time t6 to maintain blowby to the intake at the desired level while the SV timing is advanced to increase EGR flow. Between time t6 and time t7, the engine load continues to increase, and thus, the EGR flow to the intake port upstream of the compressor also increases.

[0223] At time t7, the compressor outlet temperature rises above a threshold outlet temperature T2. In response to this rise, the BTCC valve position is modulated to decrease EGR flow, the SMBV is opened, and the SV timing is retarded and the IV timing is advanced. As a result, EGR flow to the intake port upstream of the compressor decreases, and the compressor outlet temperature decreases. At time t8, there is a sudden reduction in engine load, which may result from an operator removing their foot from an accelerator pedal. Thus, a fuel fuel shutoff (DFSO) event may occur, in which fuel supply to all engine cylinders is stopped. As a result of stopping fuel supply during the DFSO event, all BDVs of all engine cylinders are shut down.In alternative embodiments, only a portion of the BDVs may be deactivated (e.g., the BDVs of only the inner or outer cylinders, or for three of four engine cylinders). In response to the DFSO event ending due to an increase in load at time t9, the BDVs are reactivated and fuel injection to the engine cylinders is reactivated.

[0224] At time t10, the vehicle stops, and thus the engine load decreases to zero. At this time, a driver can position the vehicle in park mode and turn off the engine ignition. As a result of the key-off shutdown event at time t10, the throttle is closed, the BTCC valve is closed, and the hot pipe valve is opened. As a result, engine gases are recirculated via the purge exhaust manifold and hot pipe, reducing intake manifold pressure. When the engine stops rotating at time t11 (engine speed reaches approximately zero), the throttle and BTCC valve are both reopened.

[0225] In this way, a split exhaust gas internal combustion engine may be provided with a first scavenging exhaust manifold directing EGR and blow-by air to an inlet of the internal combustion engine upstream of a turbocharger compressor, and a second blow-off exhaust manifold directing exhaust gas to a turbocharger turbine in an exhaust passage of the internal combustion engine (such as the one shown in Fig. 1A-1B) under different engine operating conditions to reduce emissions, increase torque output, reduce knock, and increase engine efficiency.

[0226] As one embodiment, a method for an internal combustion engine includes, in response to a request to shut down the internal combustion engine, closing an intake throttle and opening a first valve disposed in a secondary flow passage coupled between an intake manifold downstream of the intake throttle and a first exhaust manifold coupled to a first set of exhaust valves to direct unburned hydrocarbons to a catalyst disposed in an exhaust passage coupled to a second set of exhaust valves. In a first example of the method, the method further includes, while closing the intake throttle and opening the first valve, closing a second valve disposed in an exhaust gas recirculation passage coupled between the first exhaust manifold and an intake passage upstream of the intake throttle.A second example of the method optionally includes the first example and further includes, in response to the internal combustion engine ceasing to rotate, opening the second valve and opening the intake throttle. A third example of the method optionally includes one or more of the first and second examples and further includes where opening the second valve and opening the intake throttle includes first opening the second valve and then opening the intake throttle. A fourth example of the method optionally includes one or more of the first through third examples and further includes where the request to turn off the internal combustion engine is an ignition key turn-off request generated in response to an operator turning off a vehicle in which the internal combustion engine is installed.A fifth example of the method optionally includes one or more of the first through fourth examples, and further includes operating the first set of exhaust valves at a different opening and closing time than the second set of exhaust valves. A sixth example of the method optionally includes one or more of the first through fifth examples, and further includes directing the unburned hydrocarbons from the first exhaust manifold through the secondary flow passage into the intake manifold through the engine cylinders and via the second set of exhaust valves to the catalyst while the intake throttle is closed and the first valve is open. A seventh example of the method optionally includes one or more of the first through sixth examples, and further includes the exhaust passage being coupled to a second exhaust manifold, the second exhaust manifold being coupled to the second set of exhaust valves.

[0227] As another embodiment, a method for an internal combustion engine, in response to a request to shut down the internal combustion engine, includes: deactivating all valves of a first set of exhaust valves configured to flow exhaust gas to an exhaust passage via a first exhaust manifold; and opening a first valve disposed in a flow passage coupled between an intake passage and a second exhaust manifold, wherein a second set of exhaust valves is coupled exclusively to the second exhaust manifold. In a first example of the method, deactivating all valves of the first set of exhaust valves and opening the first valve occurs after a last cylinder fires following the request to shut down the internal combustion engine.A second example of the method optionally...

Claims

[1] A method for an engine, comprising: in response to a request to switch off the internal combustion engine (10): Closing an intake throttle (62) and opening a first valve (32) arranged in a secondary flow passage (30) coupled between an intake manifold (44) downstream of the intake throttle (62) and a first exhaust manifold (80) coupled to a first set of exhaust valves (6) to direct unburned hydrocarbons to a catalyst (72) arranged in an exhaust passage (74) coupled to a second set of exhaust valves (8). [2] The method of claim 1, further comprising, during closing the intake throttle (62) and opening the first valve (32), closing a second valve (54) disposed in an exhaust gas recirculation passage (50) coupled between the first exhaust manifold (80) and an intake passage (28) upstream of the intake throttle (62). [3] The method of claim 2, further comprising, in response to the internal combustion engine (10) ceasing to rotate, opening the second valve (54) and opening the intake throttle (62). [4] The method of claim 3, wherein opening the second valve (54) and opening the intake throttle (62) includes first opening the second valve (54) and then opening the intake throttle (62). [5] The method of claim 1, wherein the request to turn off the internal combustion engine (10) is an ignition key turn-off request generated in response to an operator turning off a vehicle in which the internal combustion engine (10) is installed. [6] The method of claim 1, further comprising operating the first set of exhaust valves (6) at a different opening and closing time than the second set of exhaust valves (8). [7] The method of claim 1, further comprising directing the unburned hydrocarbons from the first exhaust manifold (80) through the secondary flow passage (30) into the intake manifold (44) through the engine cylinders (12, 14, 16, 18) and via the second set of exhaust valves (8) to the catalyst (70) while the intake throttle (62) is closed and the first valve (32) is open. [8] The method of claim 1, wherein the exhaust passage (74) is coupled to a second exhaust manifold (84), the second exhaust manifold (84) being coupled to the second set of exhaust valves (8). [9] System for an internal combustion engine (10), comprising: a first exhaust manifold (84) coupled to a first set of exhaust valves (8) and an exhaust passage (74) including a catalyst (70); a second exhaust manifold (80) coupled to a second set of exhaust valves (6) and an intake passage (28) upstream of an intake throttle (62) disposed in the intake passage (28) via an exhaust gas recirculation (EGR) passage (50) including a first valve (54); a secondary flow passage (30) including a second valve (32) and coupled between the second exhaust manifold (80) and an intake manifold (44) downstream of the intake throttle (62); and a controller (12) including a memory with computer-readable instructions to: in response to a request to shut down the internal combustion engine (10), adjusting one or more of an activation state of the first set of exhaust valves (8) and a position of each of the intake throttle (62) and the second valve (32). [10] The system of claim 9, wherein the computer-readable instructions further include instructions, when the request to turn off the internal combustion engine (10) is generated in response to an ignition key-off event where a vehicle in which the internal combustion engine (10) is installed is placed in park and turned off, to close the intake throttle (62) and open the second valve (32). [11] The system of claim 10, wherein the computer-readable instructions further include instructions, after the intake throttle (62) has been closed and the second valve (32) has been opened, in response to the internal combustion engine (10) stopping rotation, to open the first valve (54) and open the intake throttle (62). [12] The system of claim 9, wherein the computer-readable instructions further include instructions, when the request to turn off the internal combustion engine (10) is generated in response to a vehicle in which the internal combustion engine (10) is installed being stopped but the ignition key not being turned off, to deactivate the set of exhaust valves and open the first valve (54). [13] The system of claim 12, wherein the computer-readable instructions further include instructions for reactivating the first set of exhaust valves (8) in response to a request to restart the internal combustion engine (10) and upon engine start-up. [14] The system of claim 9, further comprising a turbocharger including a turbine (164) and a compressor (162), wherein the compressor (162) is positioned in the intake passage (28) between the intake throttle (62) and wherein the EGR passage (50) couples to the intake passage (28), wherein the turbine (164) is positioned in the exhaust passage (74) upstream of the catalyst (70, 72).

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