Method and system for a variable displacement engine

Abstract

The present invention relates to methods and systems for variable displacement engines. Methods and systems are provided for monitoring torque delivery of a variable displacement engine using air flow metered via a throttle body model. During operating conditions when air flow estimates are inaccurate, such as at wide open throttle, the air ratio applied to the engine is constrained to 1.0 even if the operator torque demand is low. VDE degradation is inferred based on the commanded air ratio relative to the actual air ratio based on the torque delivery estimate.

Description

Technical Field

[0001] The present description generally relates to methods and systems for torque monitoring of a variable displacement engine. Background Art

[0002] The engine can be configured to operate with a variable number of active or deactivated cylinders to increase fuel economy, while optionally maintaining the total exhaust mixture air-fuel ratio at about the stoichiometric ratio. Such engines are referred to as variable displacement engines (VDE). Among them, a portion of the engine cylinders can be disabled during selected conditions defined by parameters such as engine speed / load windows, as well as various other operating conditions including operator torque requirements. Conventional VDE control systems can disable a selected group of cylinders, such as a cylinder group, by controlling multiple cylinder valve deactivators that affect the operation of the intake and exhaust valves of the cylinders or by controlling multiple selectively deactivatable fuel injectors that affect cylinder fueling. Newer skip-fire or variable (rolling) VDE systems can be configured to activate / deactivate individual cylinders on a continuously changing basis based on a specified control algorithm to provide a specific ignition mode.

[0003] The VDE system may utilize a variety of torque monitoring methods for ensuring proper torque delivery and diagnosing potential degradation of the VDE system. Examples of attempts to address torque monitoring include comparing two independent sources of torque estimates to the torque requested by the operator. An example method is shown by Light et al. in U.S. Patent No. 6,705,286. Therein, a torque monitoring algorithm compares the driver torque demand with two independent torque estimates, one of which is estimated based on throttle position and the other is estimated based on mass airflow (MAF) to the intake manifold. If one of the two actual torque estimates exceeds the torque demanded by the driver, the monitoring algorithm logic intervenes in the engine torque generation and sets a diagnostic code. Other methods of torque monitoring include fuel injection-based methods, in which valve degradation can be assessed based on the duration of the spark event.

[0004] However, the inventors have recognized the potential problems of such systems. As an example, torque monitoring based on fuel injection may not be suitable for use with a variable VDE system because the number of active cylinders may often be overestimated, and packaging constraints may limit the feasibility of including a fuel injector that is used for all cylinder sensing alone. As another example, a MAP-based method for torque estimation relies on a comparison of air flow metering determined via MAF sensor output and the dynamic effects of the intake cylinder determined via changes in MAP. However, relying on a MAF sensor for air flow metering and a MAP sensor for manifold pressure changes increases the cost and complexity of the vehicle system. In addition, the sensor itself may be prone to degradation. Other methods for air flow metering may model the air flow through the throttle body under selected engine operating conditions. However, such models may be inaccurate at or near wide open throttle (WOT) conditions. As a result of the inaccuracy, the actual torque provided by the VDE system may exceed the torque required by the driver, resulting in a loss of fuel economy and driving performance issues that are unpleasant to the driver. For example, the vehicle may "jump". Inaccuracies in air flow estimation can also cause the actual induction ratio to be incorrectly estimated and the VDE mechanism to be incorrectly indicated as being degraded. If the VDE mechanism is disabled in response to this indication, the engine operating time in VDE mode is unnecessarily reduced, resulting in a loss of fuel economy. Summary of the invention

[0005] The inventors have recognized that torque inaccuracy can be reduced by constraining the intake ratio during conditions when the engine is operating at or near wide open throttle (WOT). For example, a VDE system can be constrained to operate at an intake ratio of 1 to reduce over-torque issues. The resulting temporary reduction in fuel economy may be acceptable to the vehicle driver in view of the improved vehicle drivability. Therefore, in one example, the above-mentioned problem can be at least partially solved by the following method, which includes operating a variable displacement engine with an intake ratio based on an operator torque demand; and in response to the throttle position being within a threshold distance of wide open throttle, independent of the operator torque demand, increasing the intake ratio. In this way, a more accurate torque estimate can be used to more reliably infer the actual intake ratio of the VDE system.

[0006] In one example, a variable displacement engine may be operated with one or more engine cylinders selectively deactivated in response to an operator torque demand. For example, at higher engine speeds and loads, the engine may operate at a higher intake ratio with fewer cylinders deactivated, and at lower engine speeds and loads, the engine may operate at a lower intake ratio with more cylinders deactivated. If the desired intake ratio is within a threshold of 1.0, the applied intake ratio may be constrained to 1.0 while overriding the desired intake ratio. In addition, during engine operating conditions where the desired intake ratio is outside the threshold of 1.0, but the intake throttle is at or within a threshold distance of WOT, the applied intake ratio may increase toward 1.0 (e.g., by incrementally moving to the next most likely intake ratio and gradually increasing toward 1.0), while overriding the desired intake ratio. By constraining the applied intake ratio during conditions when air flow metering may be inaccurate, torque inaccuracy may be reduced. During other conditions, the actual induction ratio may be inferred via the throttle body model used to infer air flow and the rate of change of manifold pressure across the throttle. If the actual induction ratio is significantly different from the commanded induction ratio, degradation of the VDE system may be inferred and mitigating measures may be taken.

[0007] In this way, by relying on a throttle body model for metering air flow, reliance on the MAF sensor is reduced without compromising the accuracy of torque estimates or identification of potential VDE degradation. The technical effect of selectively constraining the applied intake ratio during operating conditions where air flow estimates and torque estimates may be inaccurate is to reduce the likelihood of excessive torque delivery. By increasing the reliability of the actual intake ratio estimate, the likelihood of misdiagnosing VDE degradation and prematurely disabling VDE operation is reduced. By enabling the engine to operate with VDE for longer durations of engine operation, the fuel economy and engine performance benefits of VDE can be extended.

[0008] It should be understood that the above summary is provided to introduce selected concepts in a simplified form, which will be further described in the specific examples. It is not meant to establish key or essential features of the claimed subject matter, the scope of which is solely defined by the appended claims. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An example embodiment of an engine system layout is shown.

[0010] Figure 2 A partial engine view is shown.

[0011] Figure 3An example routine is shown that may be implemented to operate an engine, including controlling an intake ratio in response to a throttle position.

[0012] Figure 4 An example procedure that may be implemented to diagnose VDE degradation based on measured suction ratio is shown.

[0013] Figure 5 Predicted operation of an engine including controlling intake ratio in response to throttle position according to the present disclosure is shown.

[0014] Figure 6 An example block diagram of a torque monitoring method according to the present disclosure is shown. DETAILED DESCRIPTION

[0015] The following description relates to systems and methods for torque monitoring of an engine configured for selected individual cylinder deactivation (also referred to herein as variable VDE), such as for Figure 1 to Figure 2 Engine system. Figure 6 As shown, by utilizing a throttle body model to estimate actual airflow in addition to data from an existing MAP sensor, an independent torque estimate may be determined and compared. The engine controller may be configured to execute a control routine such as Figure 3 The controller may be further configured to perform diagnostic routines such as Figure 4 An example routine is provided to identify degradation of the VDE mechanism when an actual induction ratio estimated based on an independent torque estimate deviates significantly from a desired induction ratio estimated based on an operator torque request. Additionally, the controller may limit the applied induction ratio during conditions when air flow estimates may be susceptible to inaccuracies, such as when the throttle position is close to wide open throttle (WOT). Figure 5 Example engine operation with VDE diagnostics is shown in FIG.

[0016] Now go to Figure 1 , an example engine system 100 is shown. The engine system 100 includes an engine 10 having a first cylinder bank 13 and a second cylinder bank 14. In the depicted example, the engine 10 is a V-8 engine having two cylinder banks, each of which has four cylinders 15. However, in alternative examples, the engine may have an alternative configuration, such as an alternative number of cylinders (e.g., V-6, V-4, etc.), or cylinders arranged in-line (e.g., I-3, I-4, etc.). The engine 10 has an intake manifold 17, and an exhaust manifold 18 coupled to an emission control system 30, the intake manifold 17 having an intake throttle 20. The emission control system 30 includes one or more catalysts and air-fuel ratio sensors, such as for Figure 2As depicted, engine 10 may operate on a variety of substances, which may be delivered via fuel system 8. As a non-limiting example, engine 10 may be included as part of a propulsion system for a passenger vehicle.

[0017] The engine 10 may be a variable displacement engine (VDE) having one or more cylinders 15 with selectively deactivatable intake valves 50 and selectively deactivatable exhaust valves 56. Selected cylinders may be deactivated by closing the corresponding cylinder valves, as described in detail below. In one example, the intake valves 50 and the exhaust valves 56 are configured for electric valve actuation (EVA) via electric individual cylinder valve actuators. While the depicted example shows a single intake valve and a single exhaust valve per cylinder, in an alternative example, Figure 2 As described in detail, each cylinder may have a plurality of selectively deactivatable intake valves and / or a plurality of selectively deactivatable exhaust valves.

[0018] In some examples, engine 10 may additionally have selectively deactivatable (direct) fuel injectors 66 , and selected cylinders may be deactivated by turning off corresponding fuel injectors while maintaining operation of intake and exhaust valves so that air may continue to be pumped through the cylinders.

[0019] During selected operating conditions, such as when the full torque capacity of the engine is not required, one or more cylinders in the engine 10 may be selected for selective deactivation (also referred to herein as individual cylinder deactivation). This may include selectively deactivating one or more cylinders on the first cylinder bank 13, and / or selectively deactivating one or more cylinders on the second cylinder bank 13. The number and identity of cylinders deactivated on the cylinder banks may be symmetrical or asymmetrical. The engine controller 12 may continuously analyze the individual cylinders to determine whether to activate or deactivate each cylinder based on the driver's pedal position input and torque demand to provide what we refer to as a skip fire or variable VDE operating mode. In other examples, entire cylinder banks or subsets of cylinders may be deactivated.

[0020] During deactivation, selected cylinders may be deactivated by closing individual cylinder valve trains (e.g., VDE trains), such as intake valve trains, exhaust valve trains, or a combination of both. Cylinder valves may be selectively deactivated via hydraulically actuated lifters (e.g., lifters coupled to valve pushrods), via cam profile switching mechanisms in which cam lobes without lift are used to deactivate valves, or via electrically actuated cylinder valve trains coupled to each cylinder. Additionally, fuel flow to the deactivated cylinders may be stopped, such as by deactivating cylinder fuel injectors 66. In some examples, spark to the deactivated cylinders may also be stopped, such as by selectively controlling the vehicle ignition system to deliver spark only to active cylinders.

[0021] When the selected cylinder is disabled, the remaining enabled or active cylinders continue to perform combustion with fuel injectors 66 and cylinder valve train activity and continue to operate. To meet the torque demand, the engine produces the same amount of torque on the active cylinders. This requires a higher manifold pressure, resulting in reduced pumping losses and increased engine efficiency. Also, the lower effective surface area exposed to combustion (from only the enabled cylinders) reduces engine heat losses, thereby improving the thermal efficiency of the engine.

[0022] Based on the specified control algorithm, the cylinder can be deactivated to provide a specific ignition (e.g., skip ignition or variable VDE) mode. More specifically, the selected "skip" cylinder will not be ignited, while other "active" cylinders are ignited. Optionally, the spark timing associated with the selected ignition of the selected working chamber can also be adjusted based on the ignition order or ignition history of the selected working chamber. As used herein, the ignition mode or deactivation mode may include the total number of deactivated cylinders to the total number of remaining active cylinders and the identity of the deactivated cylinders and active cylinders. The ignition mode may further specify the total number of combustion events that each deactivated cylinder remains deactivated and / or the number of engine cycles in which the mode is operated. As described below, the engine controller 12 may be configured with suitable logic for determining the cylinder deactivation (or skip ignition) mode based on the engine operating conditions. For example, the controller may select the desired intake ratio to be applied based on the engine operating parameters including the operator torque demand, and then select the cylinder deactivation mode that can provide the desired intake ratio. As used herein, aspiration ratio is defined as the number of actual cylinder aspiration events (eg, cylinder firings) that occur divided by the number of cylinder aspiration event opportunities (eg, total engine cylinders).

[0023] The engine controller 12 may include a drive pulse generator and a sequencer for determining a cylinder mode that provides a desired intake ratio based on a desired engine output under current engine operating conditions. For example, the drive pulse generator may use adaptive predictive control to dynamically calculate a drive pulse signal that indicates which cylinder will be ignited and at what interval to obtain the desired output (i.e., cylinder ignition / skip ignition mode). The cylinder ignition mode may be adjusted to provide the desired output without generating excessive or inappropriate vibrations in the engine. Thus, the cylinder mode may be selected based on the configuration of the engine, such as based on whether the engine is a V-type engine, an in-line engine, the number of engine cylinders present in the engine, and the like. Based on the selected cylinder mode, the individual cylinder valve mechanisms of the selected cylinders may be closed, while stopping the fuel flow and sparks to the cylinders, thereby enabling the desired intake ratio to be provided.

[0024] Since the best efficiency for a given cylinder is close to full output, a lower frequency of firing events may be selected to reduce output. For example, skipping every other cylinder will produce half the power on average. Additionally, the spacing between firing events may be adjusted to minimize NVH. Whether all cylinders are included in the skip fire mode may depend on the fraction of full engine output desired, which itself depends on various operating conditions, such as cam timing, cylinder temperature, etc.

[0025] In this way, by adjusting the cylinder pattern of individual cylinder valve trains and individual cylinder fuel injectors, it is possible to provide a desired engine output by more efficiently operating fewer cylinders, thereby improving fuel economy.

[0026] Engine 10 may be controlled at least partially by a control system including controller 12. Controller 12 may receive signals from a controller coupled to engine 10 (and referenced to Figure 2 16) and sends control signals to various actuators 81 (such as reference 16) connected to the engine and / or vehicle. Figure 2 The various sensors may include, for example, various temperature, pressure, and air-fuel ratio sensors. In addition, the controller 12 may receive an indication of the throttle position from a throttle position sensor. Now turning to Figure 2 , showing an internal combustion engine 10 (such as Figure 1 Example embodiment 200 of a combustion chamber or cylinder of an engine 10). Figure 1 Components described in the drawings may be similarly numbered. Engine 10 may be coupled to a propulsion system, such as a vehicle 5 configured for road travel. Engine 10 may receive signals from a controller 12 (such as Figure 1 The engine 10 may be controlled by a controller 12 of the vehicle 10 and input from a vehicle operator 130 via an input device 132. In this example, the input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The cylinder (also referred to herein as a "combustion chamber") 15 of the engine 10 may include combustion chamber walls 136 in which a piston 138 is positioned. The piston 138 may be coupled to a crankshaft 140 so that reciprocating motion of the piston is translated into rotational motion of the crankshaft. The crankshaft 140 may be coupled to at least one drive wheel (not shown) of a passenger vehicle via a transmission system.

[0027] Cylinder 15 can receive intake air via a series of intake passages 142, 144, and 146. Intake passage 146 may communicate with other cylinders of engine 10 in addition to cylinder 15. In some embodiments, one or more of the intake passages may include a boost device, such as a turbocharger or a supercharger. For example, Figure 2An engine 10 is shown configured with a turbocharger, the turbocharger including a compressor 174 disposed between intake passages 142 and 144 and an exhaust turbine 176 disposed along exhaust passage 148. Compressor 174 may be at least partially powered by exhaust turbine 176 via shaft 180, wherein the boosting device is configured as a turbocharger. However, in other examples, such as where engine 10 is provided with a supercharger, exhaust turbine 176 may be optionally omitted, wherein compressor 174 may be powered by mechanical input from a motor or engine. A throttle 20 including a throttle plate 164 may be disposed along an intake passage of the engine for varying the flow rate and / or pressure of intake air provided to the engine cylinders. For example, throttle 20 may be disposed downstream of compressor 174, or alternatively may be disposed upstream of compressor 174.

[0028] Exhaust passage 148 may receive exhaust gases from other cylinders of engine 10 in addition to cylinder 15. Exhaust gas sensor 128 is shown coupled to exhaust passage 148 upstream of emission control device 178, such as Figure 1 The exhaust gas sensor 128 is shown as part of the emission control system 30. The exhaust gas sensor 128 may be selected from various suitable sensors for providing an indication of the exhaust gas air-fuel ratio, such as a linear oxygen sensor or UEGO (Universal or Wide Range Exhaust Gas Oxygen), a two-state oxygen sensor or EGO (Exhaust Gas Oxygen) (as depicted), HEGO (Heated EGO), nitrogen oxides (NOx), hydrocarbons (HC), or carbon monoxide (CO) sensors. The emission control device 178 may be a three-way catalyst (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0029] Each cylinder of engine 10 may include one or more intake valves and one or more exhaust valves. For example, cylinder 15 is shown including at least one poppet-type intake valve 150 and at least one poppet-type exhaust valve 156 located at an upper region of cylinder 15. In some embodiments, each cylinder of engine 10 (including cylinder 15) including cylinder 15 may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder.

[0030] Intake valve 150 may be controlled by controller 12 via cam actuation system 151 through cam actuation. Similarly, exhaust valve 156 may be controlled by controller 12 via cam actuation system 153. Cam actuation systems 151 and 153 may each include one or more cams and may utilize one or more of a cam profile switching system (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) system that may be operated by controller 12 to change valve operation. The operation of intake valve 150 and exhaust valve 156 may be determined by valve position sensors (not shown) and / or camshaft position sensors 155 and 157, respectively. In alternative embodiments, the intake valve and / or exhaust valve may be controlled by electric valve actuation. For example, cylinder 15 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including a CPS and / or VCT system. In other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system.

[0031] As reference Figure 1 To elaborate, engine 10 may be a variable displacement engine in which intake and exhaust valves may be selectively deactivated in response to an operator torque demand to operate the engine at a desired intake ratio with a selected cylinder deactivation (or firing) mode.

[0032] In some embodiments, each cylinder of engine 10 may include a spark plug 192 for initiating combustion. Ignition system 190 may provide an ignition spark to cylinder 15 via spark plug 192 in response to spark advance signal SA from controller 12, under select operating modes. In other embodiments, such as where compression ignition is used to initiate combustion in the cylinder, the cylinder may not include a spark plug.

[0033] In some embodiments, each cylinder of engine 10 may be configured with one or more injectors for delivering fuel to the cylinder. As a non-limiting example, cylinder 15 is shown including two fuel injectors 166 and 170. Fuel injectors 166 and 170 may be configured to receive fuel from fuel system 8 via a high pressure fuel pump and a fuel rail. Alternatively, fuel may be delivered at a lower pressure via a single stage fuel pump, in which case the timing of direct fuel injection during the compression stroke may be more limited than if a high pressure fuel system was used. Further, the fuel tank may have a pressure sensor that provides a signal to controller 12.

[0034] Fuel injector 166 is shown coupled directly to cylinder 15 for injecting fuel directly therein in proportion to the pulse width of signal FPW-1 received from controller 12 via electronic driver 168. In this manner, fuel injector 166 provides what is known as direct injection (hereafter referred to as "DI") of fuel into combustion cylinder 15. Figure 1 Injector 166 is shown positioned to one side of cylinder 15, but injector 166 may alternatively be located on top of the piston, such as near spark plug 192. Due to the lower volatility of some alcohol-based fuels, this location may improve mixing and combustion when the engine is operated with alcohol-based fuels. Alternatively, the injector may be located on top of and near the intake valve to improve mixing.

[0035] As reference Figure 1 In detail, engine 10 may be a variable displacement engine in which fuel injector 166 may be selectively deactivated in response to an operator torque request to operate the engine at a desired air intake ratio in a selected cylinder deactivation (or firing) mode.

[0036] Fuel injector 170 is shown arranged in intake passage 146 rather than in cylinder 15 in a configuration that provides what is known as a port injector (hereinafter referred to as "PFI") fuel in the intake port upstream of cylinder 15. Fuel injector 170 may inject fuel received from fuel system 8 in proportion to the pulse width of signal FPW-2 received from controller 12 via electronic driver 171. Note that as depicted, a single electronic driver 168 or 171 may be used for both fuel injection systems, or multiple drivers may be used, such as electronic driver 168 for fuel injector 166 and electronic driver 171 for fuel injector 170.

[0037] During a single cycle of the cylinder, fuel may be delivered to the cylinder by two injectors. For example, each injector may deliver a portion of the total fuel injection that is combusted in cylinder 15. Thus, even for a single combustion event, the injected fuel may be injected from the port injector and the direct injector at different timings. Furthermore, for a single combustion event, multiple injections of the delivered fuel may be performed per cycle. Multiple injections may be performed during the compression stroke, the intake stroke, or any suitable combination thereof.

[0038] As mentioned above, Figure 2 Only one cylinder of a multi-cylinder engine is shown. Thus, each cylinder may similarly include its own set of intake / exhaust valves, (one or more) fuel injectors, spark plugs, etc. It should be appreciated that engine 10 may include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Furthermore, each of these cylinders may include reference cylinder 15 by Figure 2 Some or all of the various components described and depicted.

[0039] The engine may also include one or more exhaust gas recirculation passages for recirculating a portion of the exhaust gas from the engine exhaust to the engine intake. Thus, by recirculating some of the exhaust gas, engine dilution may be affected, which may improve engine performance by reducing engine knock, peak cylinder combustion temperature and pressure, throttling losses, and NOx emissions. In the depicted embodiment, the exhaust gas may be recirculated from the exhaust passage 148 to the intake passage 144 via the EGR passage 141. The amount of EGR provided to the intake passage 144 may be changed by the controller 12 via the EGR valve 143. In addition, an EGR sensor 145 may be arranged in the EGR passage and may provide an indication of one or more of the pressure, temperature, and concentration of the exhaust gas.

[0040] In some examples, the vehicle 5 may be a hybrid vehicle with multiple torque sources available to one or more wheels 55. In some examples, the vehicle 5 is a conventional vehicle with only an engine, or an electric vehicle with only (one or more) motors. In the example shown, the vehicle 5 includes an engine 10 and a motor 52. The motor 52 may be a motor or a motor / generator (M / G). When one or more clutches 56 are engaged, the crankshaft 140 of the engine 10 and the motor 52 are connected to the wheels 55 via a transmission 54. In the depicted example, the first clutch 56 is disposed between the crankshaft 140 and the motor 52, and the second clutch 56 is disposed between the motor 52 and the transmission 54. The controller 12 may send a signal to the actuator of each clutch 56 to engage or disengage the clutch so as to connect or disconnect the crankshaft 140 with the motor 52 and the components connected to the motor 52, and / or connect or disconnect the motor 52 with the transmission 54 and the components connected to the transmission 54. The transmission 54 may be a gearbox, a planetary gear system, or other types of transmissions. The powertrain may be configured in a variety of ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0041] The electric machine 52 receives power from the traction battery 58 to provide torque to the wheels 55. The electric machine 52 may also operate as a generator to provide power to charge the battery 58, such as during braking operations.

[0042] Controller 12 is shown as a microcomputer that includes a microprocessor unit (CPU) 106, input / output ports (I / O) 108, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read only memory chip (ROM) 110, a random access memory (RAM) 112, a keep alive memory (KAM) 114, and a data bus. Controller 12 may receive various signals from sensors coupled to engine 10, including, in addition to those previously discussed, a measurement of engine coolant temperature (ECT) from a temperature sensor 116 coupled to a cooling sleeve 118; a surface ignition sensing signal (PIP) from a Hall effect sensor 120 (or other type of sensor) coupled to a crankshaft 140; a throttle position (TPS) from a throttle position sensor; and a manifold absolute pressure signal (MAP) from sensor 124. Engine speed signal RPM may be generated by controller 12 from signal PIP. Manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum or pressure in the intake manifold. Other sensors may include fuel level sensors and fuel composition sensors coupled to the fuel tank(s) of the fuel system.

[0043] Storage medium read-only memory chip 110 can be programmed with computer readable data representing instructions executable by microprocessor unit 106 for performing the methods described below as well as other variants that are anticipated but not specifically listed.

[0044] The controller 12 receives the Figure 1 to Figure 2 The signals of various sensors are used Figure 1 to Figure 2 The controller may control various actuators of the engine to adjust engine operation based on the received signals and indications stored on the memory of the controller. For example, in response to an operator torque command inferred from a pedal position sensor, the controller may send a signal to a throttle actuator to adjust a throttle opening that increases as the torque demand increases. As another example, in response to a desired aspiration ratio determined based on the operator torque demand, the controller may send signals to selected cylinder fuel injectors and valves to selectively deactivate those cylinders according to a cylinder deactivation pattern that provides the desired aspiration ratio.

[0045] During operation of the engine in the VDE mode, with one or more cylinders selectively deactivated, torque may be monitored via one or more monitors to ensure that the actual intake ratio matches the commanded intake ratio. Figure 4As detailed, by comparing the air flow through the throttle estimated via the throttle body model with the change in manifold pressure across the throttle (e.g., from a MAP sensor), the dynamic effects of the actual aspirated cylinder can be learned. This can be used to infer not only the actual aspiration ratio, but also the actual torque provided. By constraining the aspiration ratio applied under engine operating conditions where air flow metering is inaccurate (such as at or near WOT), the possibility of delivering more engine torque than requested by the operator, such as due to operating at an actual aspiration ratio that is greater than the desired aspiration ratio, can be avoided.

[0046] For example, as referenced Figure 3 to Figure 4 and Figure 6 As detailed, controller 12 may employ an air flow-based torque monitoring method to compare the desired amount of torque to the actual amount of torque produced by engine 10 when operating with one or more cylinders selectively deactivated. In one example, the controller may apply a selected cylinder deactivation mode that provides a desired intake ratio based on an operator torque demand, and then estimate the actual intake ratio to characterize the torque produced by the engine. If the difference between the desired intake ratio and the estimated actual intake ratio exceeds a threshold difference, degradation of the VDE mechanism may be inferred and mitigation measures may be implemented, such as by limiting the range of intake ratios that can be provided during subsequent engine operation.

[0047] In this way, Figure 1 and Figure 2The components of the invention provide an engine system, the engine system including a variable displacement engine; a plurality of cylinders, each cylinder having a selectively deactivatable valve train and a selectively deactivatable fuel injector; a manifold pressure sensor; a throttle position sensor; an intake throttle; and a controller. The controller may be configured with computer-readable instructions stored on a non-transitory memory, the instructions being used to: selectively deactivate a plurality of cylinders to provide a commanded air intake ratio based on an operator torque demand; increase the throttle opening in accordance with the increased operator torque demand while maintaining the commanded air intake ratio until the throttle position is at a threshold distance from wide open throttle; and when the throttle position is at a threshold distance from wide open throttle, increase the commanded air intake ratio by selectively reactivating one of a number of deactivated cylinders while reducing the throttle opening to move the throttle position above the threshold distance from wide open throttle. The controller may include further instructions for: in response to an increase in operator torque request when the throttle position is at a threshold distance from wide open throttle and the commanded air ratio increases to 1.0, maintaining all of the plurality of cylinders active; and increasing the throttle opening to move the throttle position to wide open throttle. The controller includes further instructions for: in response to each of the throttle positions being outside the threshold distance from wide open throttle, estimating an actual air ratio of the engine based on a modeled mass air flow through the throttle relative to a rate of change of a sensed manifold pressure across the throttle; estimating a torque error based on the actual air ratio relative to a commanded air ratio; and updating the commanded air ratio based on the torque error, wherein the modeled mass air flow is not based on the output of a mass air flow sensor. The controller includes further instructions for: indicating degradation of a selectively deactivatable valve train or a selectively deactivatable fuel injector in response to a difference between the commanded air ratio and the estimated actual air ratio being above a threshold; and in response to the indication, reactivating one or more of the selectively deactivated plurality of cylinders.

[0048] Now go to Figure 3 The example routine 300 is shown for maintaining the intake throttle at a certain margin from WOT by coordinating throttle adjustment with intake ratio adjustment even when the operator torque demand increases. The routine 300 may be based on instructions stored in the memory of the controller and in conjunction with sensors received from the engine system such as those described above. Figure 1 to Figure 2The sensor signals are executed by the controller for performing routine 300 and instructions for the remaining methods included herein. According to the method described below, the controller may employ an engine actuator of an engine system to adjust engine operation. In one example, the controller may control the engine intake ratio based on a sensor input indicating an operator torque demand. Specifically, based on an input from an accelerator pedal position sensor or other torque requester indicating a decrease in the operator torque demand, the controller may send signals to a selected number of individual cylinder valve mechanisms and fuel injectors to selectively deactivate fuel and valve operation of the selected cylinders while continuing to operate the remaining engine cylinders with fuel and valve operation activity to provide a desired intake ratio and a desired torque.

[0049] At 302 , the routine includes estimating and / or measuring engine operating conditions, including engine speed, operator torque demand, throttle position, barometric pressure (BP), boost pressure, accelerator pedal position (PP), manifold absolute pressure (MAP), mass air flow (MAF), engine dilution (e.g., EGR level), manifold air temperature (MAT), engine coolant temperature (ECT), and ambient humidity.

[0050] At 304, the routine includes determining a desired intake ratio based at least on the operator torque demand. The intake ratio of the engine cylinder is the actual total number of cylinder firing events divided by the actual total number of cylinder compression strokes. In one example, the actual total number of cylinder compression strokes is a predetermined number. As used herein, a cylinder activation event refers to a cylinder firing with the intake and exhaust valves opened and closed during a cylinder cycle, and a cylinder deactivation event refers to a cylinder not firing with the intake and exhaust valves remaining closed during a cylinder cycle. The engine event may be a cylinder stroke (e.g., intake stroke, compression stroke, power stroke, exhaust stroke) occurring, an intake or exhaust valve opening or closing time, an ignition time of an air-fuel mixture in a cylinder, a position of a piston in a cylinder relative to a crankshaft position, or other engine-related events. The engine event number corresponds to a specific cylinder. For example, engine event number one may correspond to a compression stroke of cylinder number one. Engine event number two may correspond to a compression stroke of cylinder number three. The cycle number refers to the engine cycle that includes one event (activated or deactivated) in each cylinder. For example, when each cylinder of the engine completes all 4 stroke events (intake events, exhaust events, compression events, and expansion events), the first cycle is completed in the firing order. When each cylinder of the engine starts another iteration of all 4 stroke events, the second cycle begins. The target or desired intake ratio can be determined by the engine torque requested by the operator. Specifically, the allowable engine cylinder ignition fraction values ​​can be stored in a table or function that can be indexed by the desired engine torque and engine speed. The engine cylinder ignition fraction value that can provide the requested engine torque can be part of a set of available engine cylinder ignition fraction values. Then, based on other vehicle operating conditions, some engine cylinder ignition fractions can be eliminated from the group of available engine cylinder ignition fraction values. For example, if the cylinder ignition fraction provides a higher level of engine vibration, some engine cylinder ignition fractions can be removed from the group. Then, the engine cylinder firing fraction that provides the least number of active engine cylinders during the cycle can be selected from the group of available engine cylinder firing fraction values ​​to provide the desired engine cylinder firing fraction. In this way, a single desired engine cylinder firing fraction can be selected from a large set of engine cylinder firing fractions. It should be understood that the selected engine cylinder firing fraction can then be provided via one of a plurality of possible cylinder deactivation modes, as described in detail below.

[0051] As an example, a target induction ratio of 1 / 2 (or 0.5) means that for every 2 cylinder events, one cylinder is fired and one cylinder is skipped. As another example, a target induction ratio of 1 / 3 (or 0.33) means that for every 3 cylinder events, one cylinder is fired and the remaining two cylinders are skipped.

[0052] At 306, the routine includes selecting a deactivated cylinder pattern for providing a desired intake ratio. As an example, an intake pattern with an intake ratio of 1 / 2 may include selectively not adding fuel to every other cylinder on average to produce half the power. In addition, the same pattern may be applied for each consecutive engine cycle, so that the same cylinder is skipped on consecutive engine cycles, and the remaining cylinders are ignited on each of the engine cycles, thereby producing a fixed pattern. In one example, where cylinders 1 to 8 are arranged in two groups of 4 cylinders each (cylinder group 1 has cylinders 1 to cylinder 4, and cylinder group 2 has cylinders 5 to cylinder 8), the ignition order is 1-5-4-2-6-3-7-8, and an intake ratio of 1 / 2 can be provided by ignition according to the intake pattern S-5-S-2-S-3-S-8, where S represents a skipped cylinder event.

[0053] As another example, an intake pattern with an intake ratio of 1 / 3 may include an average of two cylinders out of every three cylinders being selectively unfueled to produce one-third of the power. In addition, an intake ratio may be provided by skipping different cylinders on each engine cycle, thereby creating a non-fixed pattern. In one example, where cylinders 1 to 8 are arranged in two groups of 4 cylinders each (cylinder bank 1 has cylinders 1 to cylinder 4, and cylinder bank 2 has cylinders 5 to cylinder 8), the firing order is 1-5-4-2-6-3-7-8, and an intake ratio of 1 / 3 may be provided by firing according to the intake pattern 1-SS-2-SS-7-SS-5-SS-6-SS-8-SS-4-SS-3-SS, where S represents a skipped cylinder event.

[0054] In each of the above examples, by evenly spacing the firing events, NVH due to the varying torque output is minimized. In this way, by adjusting the cylinder mode of the individual cylinder valve trains and individual cylinder fuel injectors, it is possible to provide the desired engine output by operating fewer cylinders more efficiently, thereby improving fuel economy.

[0055] Once the cylinder mode corresponding to the desired intake ratio is selected, the controller can deactivate the cylinders according to the selected cylinder mode to provide the target intake ratio. Selective cylinder deactivation includes, for the selected cylinder to be deactivated, keeping the cylinder valve closed while no fuel is injected into the cylinder for the entire engine cycle of 720 crankshaft degrees (i.e., for all 4 strokes of the cylinder).

[0056] In one example, cylinder deactivation may include closing selected individual cylinder valve trains (e.g., VDE mechanisms), such as intake valve trains, exhaust valve trains, or a combination of both, by sending valve closing commands from a controller to valve actuators. Cylinder valves may be selectively deactivated via hydraulically actuated lifters (e.g., lifters coupled to valve pushrods), via cam profile switching mechanisms in which cam lobes without lift are used to deactivate valves, or via electrically actuated cylinder valve trains coupled to each cylinder. Additionally, fuel flow to and spark to the deactivated cylinders may be stopped, such as by deactivating cylinder fuel injectors and disabling spark signals commanded to spark plugs for a given cylinder.

[0057] It should be understood that the decision to activate or deactivate a cylinder and open or close the exhaust and intake valves of a cylinder may be made after a predetermined number of cylinder events (e.g., one cylinder event, or alternatively, one cylinder cycle or eight cylinder events) before the cylinder is activated or deactivated to allow time to begin the process of opening and closing the intake and exhaust valves of the cylinder. For example, for an eight-cylinder engine with a firing order of 1-3-7-2-6-5-4-8, a decision to activate or deactivate cylinder number seven may be made during the intake or compression stroke of cylinder number seven one engine cycle before cylinder number seven is activated or deactivated. Alternatively, a decision to activate or deactivate a cylinder may be made a predetermined number of engine events or cylinder events before the selected cylinder is activated or deactivated. In another example, the number of cylinder events may be adjusted based on hardware capabilities and current engine operating conditions.

[0058] In addition to adjusting the intake ratio, the controller may also set the throttle opening based on operating conditions including torque demand to provide manifold air flow based on the selected intake ratio. In one example, when operating at a lower intake ratio, with a portion of the cylinders deactivated, the engine may be operated with a larger throttle opening to provide a higher air flow to each of the smaller number of active cylinders each operating at a higher displacement. In contrast, the engine may be operated with a smaller throttle opening to provide a smaller air flow to each of the larger number of active cylinders each operating at a smaller displacement.

[0059] At 308, it may be determined whether the operator torque demand has increased. In one example, the torque demand may increase due to the operator applying the accelerator pedal during a tip-in event. As another example, the torque demand may increase while the vehicle is traveling on an incline. If an increase in torque demand is not confirmed, then at 310, the method includes maintaining the current throttle position and the current intake ratio (IR). That is, a certain degree of throttle opening may be maintained, and the engine may continue to operate with one or more cylinders selectively deactivated.

[0060] If an increase in torque demand is confirmed, at 312, the method includes increasing the throttle opening as the torque demand increases until the intake throttle position is within a certain margin from WOT. That is, as the torque demand increases, the controller can meet the torque demand by moving the intake throttle to a more open position to increase the air flow to the cylinder while maintaining the intake ratio and the selected one or more cylinders that are selectively deactivated. The throttle opening can be increased (such as via a lookup table, model, or algorithm) according to the increased operating torque demand until the throttle position is within a threshold distance from WOT, the threshold distance defining the margin from WOT. If the intake throttle opens beyond the margin (and moves to or toward the WOT position), the air flow metering modeled according to the throttle position may be prone to inaccuracy, resulting in potential torque errors. In addition, the actual intake ratio may be inaccurately determined. The threshold distance may be a predefined value. In addition, the threshold distance may vary with engine speed.

[0061] Next, at 314, it may be determined whether a further increase in throttle opening is required. For example, during extended vehicle travel on a slope, or where the slope angle is very steep, the increase in torque demand may not be adequately met by increasing the throttle opening to a threshold distance from WOT. Instead, additional air flow may be required, such as may be provided by moving the throttle to WOT. In one example, the controller may reference a lookup table where the operator torque demand is an input and the desired throttle position is an output. If it is determined that the desired throttle position is WOT, the routine may proceed to 318. If a further increase in throttle opening is not required, at 316, the method includes maintaining the selected IR and continuing to adjust the throttle opening based on the torque demand while maintaining the throttle position at a threshold distance from WOT.

[0062] If it is confirmed that the throttle opening is further increased, then at 318, in response to the intake throttle being at a certain threshold distance from WOT, the method includes increasing the intake ratio while reducing the throttle opening to move the throttle to a less open position above the threshold distance from WOT. Thus, the margin from WOT increases. In one example, the intake ratio may be gradually increased to the next possible intake ratio that can be achieved by reactivating one cylinder at a time. As an example, if the engine is a 4-cylinder engine, the engine operates with an intake ratio of 0.5, where 2 cylinders are deactivated and 2 cylinders are active, the engine may reactivate one of the deactivated cylinders and switch to operating with an intake ratio of 0.67, where 1 cylinder is deactivated and 3 cylinders are active. As another example, if the 4-cylinder engine operates with an intake ratio of 0.67, where 1 cylinder is deactivated and 3 cylinders are active, the engine may reactivate the deactivated cylinders and switch to operating with an intake ratio of 1.0, where all cylinders are active.

[0063] Since the average cylinder air flow demand decreases as the number of active cylinders increases, by increasing the intake ratio, the throttle opening can be correspondingly reduced, thereby increasing the distance of the throttle position from WOT. Thus, by increasing the intake ratio, the engine continues to operate at a certain margin from WOT while air flow metering remains reliable. The change in throttle position (and increase in margin) can correspond to an increase (change) in the intake ratio. Referring to the previous example, when the increase in the intake ratio is from 0.5 to 0.67 (the effective change in IR is smaller), the throttle position can change a smaller amount, and when the increase in the intake ratio is from 0.67 to 1.0 (the effective change in IR is larger), the throttle position can change a larger amount.

[0064] In this way, as the operator torque demand changes, the controller can continue to coordinately adjust the intake ratio and throttle opening to maintain a margin of the intake throttle position from WOT. For example, as the operator torque demand increases, the controller may increase the throttle position toward the threshold distance while maintaining the first intake ratio until the throttle position reaches the threshold distance. Thereafter, the controller may reduce the throttle position away from the threshold distance while gradually increasing the intake ratio from the first intake ratio to a second higher intake ratio. As the operator torque demand increases, when at the second intake ratio, the controller may increase the throttle position toward the threshold distance while maintaining the second intake ratio until the throttle position reaches the threshold distance again. Thereafter, the controller may reduce the throttle position away from the threshold distance while gradually increasing the intake ratio from the second intake ratio to a third higher intake ratio (close to / toward 1.0), and so on. At 320 , the method includes diagnosing the VDE mechanism based on an actual IR relative to a commanded IR, the actual IR being measured (or modeled) when the intake throttle is at a distance greater than a threshold distance from WOT. Figure 4As detailed, the controller may more reliably model intake air flow based on throttle position at this position and use the air flow estimate to calculate torque corresponding to the actual IR.

[0065] At 322, it may be determined whether the intake ratio is 1.0, and whether the throttle opening needs to be further increased (exceeding the threshold distance). If not, at 324, the controller may continue to coordinate the intake ratio and throttle opening adjustments. For example, the controller may maintain the applied intake ratio and maintain the throttle at a position with a certain margin from WOT. As previously described, whenever the operator torque demand increases and the throttle opening reaches a certain threshold distance from WOT, the controller may increment the intake ratio and move the throttle position further away from WOT. Once the intake ratio is incremented to 1.0, where all cylinders are active, and the throttle opening reaches the threshold distance, further increases in torque demand cannot be met by further increasing the intake ratio. Therefore, if the intake ratio is 1.0, and the throttle opening needs to be further increased to exceed the threshold distance, at 326, the controller may meet the increased torque demand by maintaining the intake ratio at 1.0 while increasing the throttle opening to WOT. In this way, only when the intake ratio has been incremented to 1.0 (all cylinders active) can the throttle be moved to the WOT position and further increases in torque demand can only be met by throttle adjustments.

[0066] By limiting engine operation with the throttle at WOT, torque delivery is improved. Specifically, when the throttle is at WOT, air flow metering using a throttle-based model may be unreliable. As a result, the engine controller may not be able to reliably determine whether the actual intake ratio applied is the commanded intake ratio. If the actual intake ratio is higher than the commanded intake ratio, more torque than expected may be delivered, resulting in drivability issues that may be objectionable to the driver. For example, the commanded intake ratio may be calibrated so that torque is delivered at an intake pressure of 95% of ambient pressure. However, this causes the throttle position to increase its threshold. In this case, the intake ratio will be increased to the next higher available intake ratio to avoid operating in an area where the throttle model is inaccurate. By maintaining the throttle at a threshold distance from WOT via intake ratio adjustment even when torque demand changes, the actual intake ratio can be more reliably measured and calculated. In addition, excessive torque can be avoided. In addition, as Figure 4 Detailed description enables earlier detection of VDE degradation and timely resolution.

[0067] Now go to Figure 4, method 400 is capable of diagnosing a VDE engine based on reliable and accurate air flow estimation performed when the throttle is far from WOT. By limiting the engine intake ratio based on throttle position to reduce inaccuracies in air flow measurement and air flow-based torque measurement, VDE diagnosis can be performed with a higher degree of confidence. In one example, Figure 4 As a method Figure 3 A portion of the method is performed, such as at 320 .

[0068] At 402, it may be confirmed that the throttle is at a threshold distance from WOT or in a position exceeding a threshold distance from WOT. For example, it may be confirmed that a desired margin from WOT is maintained. When this margin is provided, air flow metering via the throttle body model may be more reliable and, therefore, may be used for VDE diagnosis. If the throttle is not at a threshold distance, such as when the throttle is already at or near WOT, the method moves to 403 where the actual intake ratio is not estimated based on the throttle body model and the MAP sensor output. For example, torque and intake ratio adjustments are not performed in a closed loop based on the throttle body model. Additionally, VDE diagnosis is not initiated. The method then ends.

[0069] At 404, the routine includes estimating the actual intake ratio based on an air flow estimate based on a throttle body model and MAP sensor output, as referenced Figure 6 The throttle body model may be based on the orifice flow equation for compressible flow (see Equation 1 shown below) and include parameters such as throttle angle to determine the cross-sectional area of ​​the orifice, ambient conditions to characterize airflow, engine speed to determine flow rate, and manifold absolute pressure sensor output to characterize upstream and downstream pressures across the throttle.

[0070]

[0071] in:

[0072] qm = mass flow rate (at any cross section), kg / s

[0073] C = orifice flow coefficient, dimensionless

[0074] A2 = cross-sectional area of ​​the hole, m 2

[0075] p1 = upstream pressure of the fluid, dimension is kg / (m·s 2 )

[0076] p2 = downstream pressure of the fluid, dimension is kg / (m·s 2 )

[0077] k = ratio of specific heats, dimensionless

[0078] qv,1 = volume flow rate under upstream conditions, m 3 / s

[0079] ρ1 = actual gas density at upstream conditions, kg / m 3

[0080] It should be appreciated that averaging of MAP data and airflow estimates (such as based on the output of the engine's existing MAP and / or MAF sensors) for one or more cylinder events may be used to improve the robustness of the throttle body model to pressure pulsations. By using a throttle body model to estimate air flow through the system during conditions when air flow metering is not prone to inaccuracies, torque and aspiration ratio estimates can be accurately performed with reduced reliance on MAF, thereby reducing costs.

[0081] At 406, the routine includes comparing the desired aspiration ratio to the estimated actual aspiration ratio and determining whether the absolute difference between the desired aspiration ratio and the estimated actual aspiration ratio is greater than a threshold. In some examples, the threshold may be determined based on an acceptable error in the estimated actual aspiration ratio. The acceptable error in the aspiration ratio may correspond to an acceptable torque error that is imperceptible or objectionable to the vehicle operator. As an example, if the acceptable error in torque is 10% of the maximum torque, the acceptable aspiration ratio error may be 0.1. Alternatively, the threshold may be based on an expected degradation condition of the VDE mechanism, such as based on an acceptable level of VDE wear and tear.

[0082] It should be appreciated that although the routine depicts determining whether the absolute difference between the desired aspiration ratio and the estimated actual aspiration ratio is greater than a threshold, in an alternative example, it may be determined whether the estimated actual aspiration ratio is greater than the desired aspiration ratio in order to mitigate an over-torque condition in which more engine torque is delivered than desired.

[0083] If the absolute difference between the desired induction ratio and the estimated actual induction ratio is greater than a threshold, the routine proceeds to 412 where the routine includes indicating degradation of the VDE mechanism. At 414, the routine includes limiting cylinder deactivation during subsequent engine operation when engine operation with cylinder deactivation is possible in response to the indication of degradation. In one example, limiting cylinder deactivation may include operating at a higher induction ratio than desired for a given engine operating condition by maintaining certain cylinders active rather than deactivating them.

[0084] If the absolute difference between the desired aspiration ratio and the estimated actual aspiration ratio is not greater than the threshold, the routine continues to 408 where degradation of the VDE mechanism is not indicated. At 410 , the controller continues to operate the engine in the VDE mode with one or more cylinders deactivated, and the method ends.

[0085] In addition, if there is a condition that causes the throttle to be within the WOT threshold (such as Figure 3 The controller may resume re-evaluation if the operating conditions (discussed in the description above) change, or if the pressure ratio across the throttle (throttle pressure ratio, or TR) is within a threshold pressure ratio. The throttle pressure ratio is defined as the pressure before the throttle divided by the pressure after the throttle, which can be measured by an existing pressure sensor. In some examples, this may include a manifold absolute pressure (MAP) such as Figure 1 The desired intake ratio is controlled using the MAP sensor 124. In one example, the desired intake ratio can be controlled so that MAP remains less than or equal to atmospheric pressure (BP)*(1-throttle pressure ratio). In other words, the desired intake ratio will remain greater than the estimated actual intake ratio to deliver torque when the intake pressure is equal to atmospheric pressure (BP)*(1-throttle pressure ratio).

[0086] If the throttle is within the threshold of wide open throttle or the pressure ratio is within the threshold of 1, then Figure 3 As discussed herein, the controller continues to incrementally increase the intake ratio (such as incrementally increasing in one step or at a time) and / or reactivates one or more cylinders in accordance with the incremental intake ratio. In one example, the reactivation of the cylinders may include selectively reactivating the cylinder valves via a cam profile switching mechanism via a hydraulically actuated lifter. In other examples, the reactivation of the cylinders may include selectively reintroducing spark and / or fuel to the cylinder selected for reactivation. The reactivated cylinder may be the next cylinder in the firing order.

[0087] It should be appreciated that the control may be performed continuously during engine operation as the operator torque demand and engine intake ratio change. Figure 3 to Figure 4 Alternatively, Figure 3 to Figure 4 The method may be triggered in response to a change in operator torque demand requiring a change in throttle position or a change in intake ratio.

[0088] In this way, a variable displacement engine can be operated based on an intake ratio of an operator torque demand; and in response to a throttle position being within a threshold distance of wide open throttle, the intake ratio can be increased independently of the operator torque demand. Operating with an intake ratio based on the operator torque demand includes: operating at a higher intake ratio when the operator torque demand is high, and operating at a lower intake ratio when the operator torque demand is low, providing a higher intake ratio by selectively deactivating fewer engine cylinders, and providing a lower intake ratio by selectively deactivating more engine cylinders. In one example, increasing the intake ratio may include incrementally increasing the number of active cylinders by incrementally reactivating the selectively deactivated cylinders. In another example, increasing the intake ratio includes constraining the intake ratio to 1.0. The intake ratio may be a commanded intake ratio, and the method further includes: estimating an actual intake ratio based on a modeled mass air flow through the throttle relative to a sensed manifold pressure change rate across the throttle; comparing the commanded intake ratio with the estimated actual intake ratio; and indicating degradation of the variable displacement engine mechanism based on the comparison. The indication may include indicating in response to a difference between a commanded intake ratio and an estimated actual intake ratio being higher than a threshold difference. In addition, in response to the indication, selective cylinder deactivation may be disabled independently of an operator torque demand. The modeled mass air flow may be modeled based on a throttle position when the throttle position is outside a threshold distance of a wide open throttle. Specifically, the modeled mass air flow is not based on an output of a mass air flow sensor. Estimating the actual intake ratio may include estimating an actual engine torque output based on a modeled mass air flow through the throttle relative to a sensed manifold pressure change rate across the throttle, estimating a torque error based on the actual engine torque relative to a desired torque based on the commanded intake ratio; and estimating the actual intake ratio based on the commanded intake ratio and the torque error. In addition, in response to the commanded intake ratio being within a threshold of 1.0, the intake ratio may be increased independently of the driver torque demand and the throttle position.

[0089] Now go to Figure 6 , shows an example torque estimation method 600 that can accurately determine torque with reduced reliance on the MAF sensor. The method can compare actual torque to desired torque, so that actual air intake ratio can be compared to commanded or desired air intake ratio, and engine operation can be adjusted to avoid excessive delivery of torque.

[0090] Method 600 includes air flow metering or estimation of mass air flow (MAF) at 602. To reduce reliance on expensive MAF sensors, MAF is determined using a throttle body model based on throttle position, manifold pressure, and barometric pressure (BP). The throttle body model may be based on an orifice flow equation for compressible flow (see equation 1 above) and include parameters such as throttle angle to determine the cross-sectional area of ​​the orifice (through the throttle in this article), ambient conditions that characterize airflow (BP in this article). The method compares the mass air flow with changes in manifold pressure across the throttle measured based on the output of a MAP sensor. The MAP sensor output characterizes the pressure downstream of the throttle, while the BP sensor, compressor outlet pressure sensor, or throttle inlet pressure sensor characterizes the pressure upstream of the throttle. The rate of change of MAP 404 reflects the dynamic effects of the actual intake cylinder of the engine. By calculating an average over one or more cylinder events, the robustness of the torque estimate to pressure pulsations is improved while providing adequate mitigation response. Using this approach, the controller can detect errors between the desired intake ratio and the actual intake ratio. When an error occurs, the controller may indicate degradation of the VDE system. The comparison of air flow and MAP changes is then used along with an estimate of engine speed 406 to determine an actual intake ratio 408. The engine load 410 and actual intake ratio 408 are then used as inputs to an indicated torque lookup table 412. By comparing the desired intake ratio to the output of the indicated torque lookup table, a torque error 414 is obtained, which is then used to output an estimated indicated torque 416. This torque estimate is then used to adjust engine operation and diagnose VDE degradation.

[0091] Now go to Figure 5 , shows an example operating timeline for a variable displacement engine. The engine may have the capability to perform a VDE system diagnostic routine based on a throttle body model, such as Figure 4 In response to a change in torque demand, the VDE system diagnostics routine may be executed by executing a control routine such as Figure 3 A controller of the program coordinates the throttle position and the intake ratio of the engine. Among other things, by selectively constraining the desired intake ratio in response to the throttle position, the possibility of over-delivering torque can be reduced. By using a throttle body model to map the air flow through the throttle, the need for a MAF sensor can be reduced, thereby providing component cost and complexity benefits. Figure 5The mapping graph 500 depicts accelerator pedal position (PP) at curve 502, throttle position (or opening) relative to WOT at curve 504, MAP sensor output at curve 506, commanded air intake ratio at curve 508, and a flag indicating VDE degradation at curve 512. All curves are plotted along the x-axis over time. In addition, as shown, the magnitude of the parameter represented in any given curve increases from bottom to top along the y-axis. Time markers t1 to t8 depict the time when significant events occur.

[0092] Prior to time t1, the accelerator pedal (plot 502) is depressed significantly, indicating an elevated operator torque demand. At this point, the torque demand is met by operating the engine with all cylinders active, as indicated by an intake ratio of 1.0. Additionally, the engine is operated with the throttle in a more open position while still maintaining the throttle opening below level 503. Thus, a margin 505 from WOT being greater than the minimum is provided. MAP reflects the degree of opening of the throttle and is therefore elevated at this point.

[0093] At t1, the operator torque demand decreases, as indicated by a significant release of the pedal. For example, the decrease in operator torque demand may be due to the operator releasing the pedal. The change in torque demand is met by reducing the intake ratio (IR). Specifically, multiple cylinders are selectively deactivated. In the depicted example, the change in torque demand is met by reducing the intake ratio to the lowest possible intake ratio for a given engine configuration. In addition, the throttle opening is reduced, but the change in throttle position is not as large as the change in IR. As a result, the change in MAP is also not significant.

[0094] At t2, the operator torque demand drops further, as indicated by a large release of the pedal, such as due to a vehicle coasting condition. Since it is not possible to further reduce the IR, the change in torque demand can be met by reducing the throttle opening while maintaining the intake ratio (IR) at the lowest setting. At this time, the throttle opening is reduced by a large amount. The change in MAP is proportional to the change in throttle opening.

[0095] At t3, the operator torque demand increases, such as indicated by a significant release of the pedal. For example, the increase in operator torque demand may be due to an operator pedaling event, such as when the vehicle is traveling on an uphill section with a steep grade. The change in torque demand is met by increasing the throttle opening as the torque demand increases while maintaining the (minimum) intake ratio (IR). Due to the change in throttle position, MAP increases.

[0096] At t4, the throttle opening reaches a level 503 that provides a minimum margin 505. However, the pedal is still depressed and the operator torque demand continues to increase. If the throttle moves toward WOT beyond level 503, the torque estimation may be compromised. Therefore, to maintain at least the minimum margin 505, in response to the increase in torque demand, the intake ratio is increased to the next higher acceptable intake ratio while the throttle opening is reduced. In one example, the next higher acceptable intake ratio can be achieved by reactivating one of the previously deactivated cylinders. Alternatively, the next higher acceptable intake ratio can be achieved by operating with a higher number (e.g., a higher amount) of reactivated cylinders. This is because in a variable VDE mechanism, the identity of the deactivated and reactivated cylinders can be continuously adjusted.

[0097] Between t4 and t5, in response to a further increase in torque demand, the throttle opening is increased while maintaining the most recent (one-step-incremental) intake ratio. At t5, the throttle is again at level 503. Therefore, at t5, as at t4, in response to the pedal continuing to be depressed, the intake ratio is increased by another step by reactivating yet another cylinder while reducing the throttle opening. The same is true between t5 and t6, until all cylinders are reactivated and the intake ratio is 1.0. Each time the throttle opening is reduced, the amount of reduction is based on the corresponding increase in the intake ratio. In addition, as the throttle opening increases and decreases, the MAP increases and decreases accordingly. In this way, between t4 and t6, despite the increase in torque demand, the throttle is maintained at least at the minimum margin 505 from WOT.

[0098] At t6, the air-intake ratio is 1.0 and the throttle opening is at level 503. The accelerator pedal continues to be depressed. At this time, to meet the increased torque demand, the throttle moves to WOT while all cylinders remain activated.

[0099] Between t0 and t6, the actual induction ratio modeled based on the throttle body model matches the commanded induction ratio and the degradation flag is not set. Between t6 and t7, when the throttle is at WOT, the throttle body model is not used and VDE degradation is not determined based on the throttle body model.

[0100] At t7, the reduction in operator torque demand is met by reducing the intake ratio and reducing the throttle opening to increase the margin to WOT. As at t1, the intake ratio is reduced to the minimum intake ratio and the throttle opening is reduced by a smaller amount (compared to the change in intake ratio). Between t7 and t8, the actual intake ratio is determined based on the throttle body model. The actual intake ratio 510 determined based on the throttle body model is significantly different from the command intake ratio. Specifically, the actual intake ratio 510 is higher than the command intake ratio (curve 508) by more than a threshold amount. In response to the difference, it is determined that the VDE mechanism is degraded and a flag is set at t8. The flag may indicate that fewer cylinders than expected are deactivated, resulting in a torque delivery ratio higher than expected. In one example, this may be due to degradation of the VDE mechanism, resulting in the cylinders not being deactivated as expected. In another example, the control system may be degraded, resulting in the VDE mechanism not being activated to deactivate the cylinders. Due to VDE mechanism degradation, the measured MAP is lower than desired or expected when operating with actual induction 510 higher than commanded induction ratio. When all cylinders are subsequently activated, the actual MAP returns to being the same as the desired or expected MAP.

[0101] In addition, in response to the indication of degradation, cylinder deactivation may be limited during subsequent engine operation. Specifically, even during operating conditions suitable for operating the engine in VDE mode (e.g., with one or more deactivated cylinders), cylinder deactivation may still be limited based on the degree of degradation. As an example, a commanded intake ratio may be 0.5, while an actual intake ratio may be determined to be 0.75. Due to the indication of degradation, the commanded intake ratio during subsequent operation may not drop below 0.75, thereby limiting the intake ratio to 0.75 or greater.

[0102] In this way, an engine controller may selectively deactivate one or more engine cylinders to operate the engine at a commanded intake ratio based on an operator torque demand; estimate an actual intake ratio based on a modeled mass air flow through an intake throttle relative to a sensed manifold pressure change across the throttle; and indicate degradation of a selective cylinder deactivation mechanism based on the commanded intake ratio relative to the estimated actual intake ratio. The controller may further constrain the commanded intake ratio to 1.0 independently of the operator torque demand in response to the throttle position being within a threshold distance of wide open throttle. Constraining the commanded intake ratio to 1.0 may include operating the engine with all cylinders active. In this article, the modeled mass air flow may model the throttle position based on the throttle position when the throttle position is outside a threshold distance of wide open throttle, and wherein the sensed manifold pressure change is based on the output of a manifold pressure sensor. The controller may further constrain the commanded intake ratio to 1.0 independently of the operator torque demand and the throttle position in response to the commanded intake ratio being within a threshold distance of 1.0. Indicating degradation may include indicating degradation in response to a difference between a commanded intake ratio and an estimated actual intake ratio being above a threshold. Further, in response to the indication, the controller may reactivate one or more engine cylinders that were selectively deactivated. Further, in response to the throttle opening being within a threshold distance of wide open throttle, the controller may increase the commanded intake ratio to a first intake ratio independently of the operator torque demand while decreasing the throttle opening above the threshold distance of wide open throttle, the first intake ratio being the next available intake ratio from the commanded intake ratio, the first intake ratio being higher than the commanded intake ratio. Further, after increasing the commanded intake ratio to the first intake ratio, adjusting the throttle opening based on the operator torque demand, and in response to the throttle opening being within the threshold distance of wide open throttle after the adjustment, increasing the first intake ratio to a second intake ratio, the second intake being the next available intake ratio from the first intake ratio, the second intake ratio being higher than the first intake ratio.

[0103] In this way, by using a model of the throttle body to characterize the airflow entering the engine under a wider range of engine operating conditions, the need for a MAF sensor for air flow metering during torque estimation is reduced. This provides the benefit of reduced components in terms of cost and complexity. By relying on an air flow estimate based on a throttle body model combined with an indication of pressure changes at both ends of the throttle (e.g., using an existing MAP sensor), independent data for torque monitoring can be provided. This allows the use of fewer sensors to accurately and reliably estimate the actual intake ratio. The technical effect of coordinating throttle adjustment and intake ratio adjustment as torque demand changes is that the throttle position can be maintained at a minimum margin from WOT over a large portion of the driving cycle, thereby allowing a higher accuracy of air flow metering via the throttle body model over a large portion of the driving cycle. Specifically, by reducing the throttle opening while gradually increasing the intake ratio, the engine torque output can be increased without moving the throttle to the WOT position. By comparing the estimated actual intake ratio with the desired intake ratio (based on torque demand), the degradation of the VDE mechanism can be known. The technical effect of constraining the commanded intake ratio during conditions when air flow metering can be inaccurate, such as when the throttle is within a wide open throttle threshold, is that the drawbacks of using a throttle body model can be overcome and the potential for over-delivered torque can be reduced, thereby improving the drivability of a vehicle having a variable displacement engine.

[0104] An example method includes: operating a variable displacement engine with an intake ratio based on an operator torque demand; and increasing the intake ratio independent of the operator torque demand in response to the throttle position being within a threshold distance of wide open throttle. In the foregoing examples, additionally or optionally, operating with an intake ratio based on the operator torque demand includes: operating with a higher intake ratio when the operator torque demand is higher, and operating with a lower intake ratio when the operator torque demand is lower, the higher intake ratio being provided by selectively deactivating fewer engine cylinders, and the lower intake ratio being provided by selectively deactivating more engine cylinders. In any or all of the foregoing examples, additionally or optionally, increasing the intake ratio includes incrementally increasing the number of active cylinders fired on each engine cycle. In any or all of the foregoing examples, additionally or optionally, increasing the intake ratio includes constraining the intake ratio to 1.0 or close to 1.0. In any or all of the foregoing examples, additionally or optionally, the intake ratio is a command intake ratio, and the method further includes estimating an actual intake ratio based on a modeled mass air flow through the throttle relative to a rate of change of a sensed manifold pressure across the manifold, comparing the command intake ratio to the estimated actual intake ratio, and indicating degradation of the variable displacement engine mechanism based on the comparison. In any or all of the foregoing examples, additionally or optionally, the indication is responsive to a difference between the command intake ratio and the estimated actual intake ratio being above a threshold difference, and the method further includes, in response to the indication, disabling selective cylinder deactivation independent of operator torque demand. In any or all of the foregoing examples, additionally or optionally, the modeled mass air flow is modeled based on a throttle position when the throttle position is outside a threshold distance of wide open throttle. In any or all of the foregoing examples, additionally or optionally, the modeled mass air flow is not based on an output of a mass air flow sensor. In any or all of the foregoing examples, additionally or optionally, estimating the actual intake ratio includes estimating the actual engine torque based on a modeled mass air flow through the throttle relative to a sensed rate of change of manifold pressure across the throttle; and estimating the actual intake ratio based on the actual engine torque. In any or all of the foregoing examples, additionally or optionally, the method further includes, in response to the commanded intake ratio being within a threshold of 1.0, increasing the intake ratio independent of the operator torque demand and the position of the throttle. In further representations, increasing the intake ratio includes incrementally increasing the number of activated cylinders by incrementally reactivating selectively deactivated cylinders.

[0105] Another example method includes: selectively deactivating one or more engine cylinders to operate the engine at a commanded intake ratio based on an operator torque demand; estimating an actual intake ratio based on a modeled mass air flow through an intake throttle relative to a sensed manifold pressure change across the throttle; and indicating degradation of a selective cylinder deactivation mechanism based on the commanded intake ratio relative to the estimated actual intake ratio. In the foregoing example, additionally or optionally, the method also includes, in response to a throttle opening within a threshold distance of wide open throttle, independently of the operator torque demand, increasing the commanded intake ratio to a first intake ratio while decreasing the throttle opening to a threshold distance greater than wide open throttle, the first intake ratio being the next available intake ratio from the commanded intake ratio, the first intake ratio being higher than the commanded intake ratio. In any or all of the foregoing examples, additionally or optionally, the method further comprises, after increasing the commanded air ratio to the first air ratio, adjusting the throttle opening based on the operator torque demand, and in response to the throttle opening being within a threshold distance of wide open throttle after the adjustment, increasing the first air ratio to a second air ratio, the second air ratio being the next available air ratio starting from the first air ratio, the second air ratio being higher than the first air ratio. In any or all of the foregoing examples, additionally or optionally, the modeled mass air flow is modeled based on the throttle position when the throttle position is outside the threshold distance of wide open throttle, and wherein the sensed manifold pressure change is based on the output of the manifold pressure sensor. In any or all of the foregoing examples, additionally or optionally, the method further comprises, in response to the commanded air ratio being within a threshold distance of 1.0, independently of the operator torque demand and the throttle position, constraining the commanded air ratio to 1.0. In any or all of the foregoing examples, additionally or optionally, the indication includes responsive to a difference between a commanded induction ratio and an estimated actual induction ratio being above a threshold, indicating degradation, the method further comprising, responsive to the indication, reactivating one or more selectively deactivated engine cylinders.

[0106] Another example engine system includes: a variable displacement engine; a plurality of cylinders, each cylinder having a selectively deactivatable valvetrain and a selectively deactivatable fuel injector; a manifold pressure sensor; a throttle position sensor; an intake throttle; and a controller having computer-readable instructions stored on a non-transitory memory, the instructions being used to: selectively deactivate a plurality of cylinders to provide a commanded intake ratio based on an operator torque demand; increase the throttle opening in response to an increase in the operator torque demand while maintaining the commanded intake ratio until the throttle position is at a threshold distance from wide open throttle; and when the throttle position is at a threshold distance from wide open throttle, increase the commanded intake ratio by selectively reactivating one of the plurality of deactivated cylinders while reducing the throttle opening to move the throttle position to a threshold distance greater than wide open throttle. In any or all of the foregoing examples, additionally or optionally, the controller includes further instructions for, in response to an increase in operator torque demand when the throttle position is at a threshold distance from wide open throttle and the commanded air ratio increases to 1.0, maintaining all of the plurality of cylinders active; and increasing the throttle opening to move the throttle position to wide open throttle. In any or all of the foregoing examples, additionally or optionally, the controller includes further instructions for, in response to each of the throttle positions being outside the threshold distance from wide open throttle, estimating an actual air ratio of the engine based on a modeled mass air flow through the throttle relative to a sensed manifold pressure change across the throttle; estimating a torque error based on the actual air ratio relative to the commanded air ratio; and updating the commanded air ratio based on the torque error, wherein the modeled mass air flow is not based on the output of the mass air flow sensor. In any or all of the foregoing examples, additionally or optionally, the controller includes further instructions for, in response to a difference between the commanded induction ratio and the estimated actual induction ratio being above a threshold, indicating degradation of the selectively deactivatable valvetrain or the selectively deactivatable fuel injector; and in response to the indication, reactivating one or more of the selectively deactivated plurality of cylinders. In further representations, the engine system is coupled in a hybrid vehicle system.

[0107] In another representation, a method for an engine having selectively deactivatable cylinders includes, in response to an increase in operator torque demand, maintaining engine operation at a first intake ratio, while increasing the throttle opening until a certain threshold distance from the throttle is reached in accordance with the increase in torque demand. In the foregoing examples, additionally or optionally, the first intake ratio includes a first number of deactivated cylinders, and wherein the first intake ratio is based on the operator torque demand. In any one or all of the foregoing examples, additionally or optionally, after the throttle opening increases a certain threshold distance from the throttle being fully opened, in response to a further increase in the operator torque demand, operating the engine at a second intake ratio higher than the first intake ratio, while reducing the throttle opening away from the threshold distance from the throttle being fully opened. In any one or all of the foregoing examples, additionally or optionally, the second intake ratio has a second number of deactivated cylinders, the second number being one deactivated cylinder less than the first number. In any or all of the foregoing examples, additionally or optionally, reducing the throttle opening is based on a difference between the first intake ratio and the second intake ratio, wherein the throttle opening is further reduced as the difference increases.

[0108] Note that the example control and estimation procedures included herein can be used with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and can be implemented by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific procedures described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. Thus, the various behaviors, operations, and / or functions described can be executed in the order described, executed simultaneously, or omitted in some cases. Similarly, the order of processing is not necessary to achieve the features and advantages of the example embodiments described herein, but is provided for ease of description and description. Depending on the specific strategy used, one or more of the described behaviors, operations, and / or functions can be repeatedly executed. In addition, the described behaviors, operations, and / or functions can be graphically represented as codes in a non-transitory memory of a computer-readable storage medium that will be programmed into an engine control system, wherein the described behaviors are implemented by executing instructions in combination with an electronic controller in a system including various engine hardware components.

[0109] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be construed in a limiting sense, as many variations are possible. For example, the above techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or properties disclosed herein.

[0110] The accompanying claims particularly point out certain combinations and subcombinations deemed novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope than the original claims, are still deemed to be included in the subject matter of the present disclosure.

Claims

1. A method for a variable displacement engine, comprising: operating the variable displacement engine at an intake ratio based on an operator torque demand; In response to a throttle position being within a threshold distance of wide open throttle, independent of the operator torque request, increasing the induction ratio, wherein the induction ratio is defined as a number of actual cylinder induction events that occurred divided by a number of total engine cylinders, wherein the induction ratio is a commanded induction ratio; and An actual induction ratio is estimated based on a modeled mass air flow through the throttle and a sensed rate of change of manifold pressure across the throttle, the commanded induction ratio is compared to the estimated actual induction ratio, and degradation of a variable displacement engine mechanism is indicated based on the comparison.

2. The method of claim 1 , wherein operating with the induction ratio based on an operator torque request comprises: and operating at a higher intake ratio provided by selectively deactivating fewer engine cylinders when the operator torque demand is higher, and operating at a lower intake ratio provided by selectively deactivating more engine cylinders when the operator torque demand is lower.

3. The method of claim 1 , wherein increasing the suction ratio comprises: Incrementally increases the number of active cylinders firing on each engine cycle.

4. The method of claim 1 , wherein increasing the suction ratio comprises: The aspiration ratio was constrained to 1.

0.

5. The method of claim 1 , wherein the indicating is in response to a difference between the commanded inhalation ratio and the estimated actual inhalation ratio being greater than a threshold difference, the method further comprising: In response to the indication, selective cylinder deactivation is disabled independent of the operator torque request. The method of claim 1 , wherein the modeled mass air flow is modeled based on the throttle position when the throttle position is outside the threshold distance of wide open throttle. The method of claim 6 , wherein the modeled mass air flow is not based on output of a mass air flow sensor.

8. The method of claim 1, wherein estimating the actual suction ratio comprises: estimating actual engine torque based on the modeled mass air flow through the throttle and the sensed rate of change of manifold pressure across the throttle; as well as Based on the actual engine torque, the actual intake ratio is estimated.

9. The method according to claim 1, further comprising: In response to the commanded air ratio being within a threshold of 1.0, the air ratio is increased independent of the operator torque request and the throttle position.

10. The method according to claim 1, further comprising: In response to the indication, one or more selectively deactivated engine cylinders are reactivated.

11. An engine system, comprising: variable displacement engines; a plurality of cylinders, each cylinder having a selectively deactivatable valvetrain and a selectively deactivatable fuel injector; Manifold pressure sensor; Throttle position sensor; Intake throttle valve; as well as a controller having computer readable instructions stored on a non-transitory memory and configured to: selectively deactivating a number of the plurality of cylinders based on an operator torque request to provide an aspiration ratio, wherein the aspiration ratio is defined as a number of actual cylinder aspiration events that occurred divided by a number of total engine cylinders, wherein the aspiration ratio is a commanded aspiration ratio; increasing throttle opening in response to increasing the operator torque request while maintaining the commanded air intake ratio until the throttle position is at a threshold distance from wide open throttle; as well as When the throttle position is at the threshold distance from wide open throttle, increasing the commanded intake ratio by selectively reactivating one of the number of deactivated cylinders while decreasing the throttle opening to move the throttle position above the threshold distance from wide open throttle, estimating an actual intake ratio based on a modeled mass air flow through the throttle and a sensed rate of change of manifold pressure across the throttle; Based on the commanded induction ratio and the estimated actual induction ratio, degradation of the selectively deactivatable valvetrain is indicated.

12. The system of claim 11, wherein the controller is further configured to: In response to an increase in the operator torque request when the throttle position is at the threshold distance from wide open throttle and the commanded intake ratio increases to 1, maintaining all of the plurality of cylinders active; and The throttle opening is increased to move the throttle position to wide open throttle.

13. The system of claim 12, wherein the controller is further configured to: In response to each of the throttle positions being outside the threshold distance of wide open throttle, estimating the actual intake ratio based on the modeled mass air flow through the throttle and a sensed rate of change of manifold pressure across the throttle; estimating a torque error based on the actual intake ratio and the command intake ratio; and The commanded induction ratio is updated based on the torque error, wherein the modeled mass air flow is not based on an output of a mass air flow sensor.

14. The system of claim 12, wherein the controller is further configured to: In response to a difference between the commanded induction ratio and the estimated actual induction ratio being above a threshold, indicating degradation of the selectively deactivatable fuel injector; and In response to the indication, one or more of the selectively deactivated plurality of cylinders are reactivated.

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