Increasing the crankcase ventilation flow rate using active flow control

Abstract

A method for an engine, comprising: electrically controlling a crankcase ventilation valve based on desired engine air and fuel flow rates, current engine air flow rate contributions from a brake booster, and current engine air and fuel flow rate contributions from a fuel vapor purge system to selectively enable crankcase ventilation flow into an engine intake downstream of a throttle valve if the current contributions to the engine air flow rate from the brake booster exceed the desired engine air flow rate, electrically controlling the crankcase ventilation valve to block crankcase ventilation flow into the engine intake, and electrically controlling a canister purge valve to block flow from the fuel vapor purge system into the engine intake.

Description

Field of InterestThe present description relates generally to methods and systems for coordinating throttle bypass flows into an engine of a vehicle from a fuel vapor purging system, a brake booster, and a crankcase ventilation system.Background / SummaryUnburned fuel and other products of combustion may escape into the crankcase past the piston of an internal combustion engine (e.g., an internal combustion engine of a vehicle). The resulting gases in the crankcase, often referred to as "blowby" gases, may contribute to the formation of sludge deposits in the engine oil supply. Further, the blowby gases may unduly pressurize the crankcase, resulting in undesirable leakage of the oil pan seal and crankcase seals.To avoid these issues, an engine may include a positive crankcase ventilation (PCV) system coupled to the intake for venting blowby gases from the crankcase into the intake. The PCV system may include a PCV valve disposed between the crankcase and the engine intake passage to regulate flow of blowby gases from the crankcase to the intake manifold. In the PCV systems, various types of PCV valves may be used to regulate crankcase ventilation flow. A standard configuration of the PCV valve includes three different sized ports. A large orifice is arranged in series with a variable pressure control valve. The series arrangement of the large orifice and the variable pressure control valve is arranged in parallel with a small orifice. This parallel arrangement is arranged in series with a parallel arrangement of a tiny orifice and a check valve, the check valve being configured to allow flow from the crankcase to the intake manifold to the engine intake passage and restrict flow from the engine intake passage to the crankcase. In the case of low intake manifold vacuum, the variable pressure control valve opens and allows air flow through the large orifice. Under this condition, the engine may assume a greater airflow rate that is near the target crankcase ventilation flow rate. In the case of negative intake manifold negative pressure (positive pressure), the air flow from the intake manifold passes through the minute opening to the crankcase. In the case of high intake manifold vacuum, the variable pressure control valve closes, with the gases flowing from the crankcase through the small opening to the intake manifold. As a result, the PCV valve limits the flow of crankcase ventilation air into the intake manifold during idle conditions to reduce the idle air flow rate and thereby limit idle engine air consumption. The limited flow of crankcase ventilation air into the intake manifold during idle conditions may ensure that an appropriate engine airflow budget is left for other flows entering the engine intake downstream of the throttle, such as fuel vapor purge flow and flow from an aspirator serving to generate brake booster vacuum, so that coordination / arbitration of the various throttle bypass flows is not necessary.The prior art for this purpose is described, for example, in the documents DE 10 2013 106 673 A1, DE 11 2013 003 987 T5, DE 10 2013 223 260 A1 and DE 10 2013 216 998 A1.However, the inventors herein have recognized potential problems with such systems. While the limited crankcase ventilation flow that occurs via the small opening during idle conditions may be appropriate during conditions of minimum engine air flow (e.g., during warm idle conditions with the transmission in the idle position and low front end accessory drive (FEAD) loads), these conditions may be relatively rare. Indeed, in some start / stop engines, these conditions may almost no longer exist. The above-described standard PCV valve design that limits crankcase ventilation flow during all idle conditions to a level suitable for minimum engine air flow conditions may be undesirable for several reasons. The rate of crankcase ventilation flow suitable for the conditions of minimum engine air flow may not provide adequate crankcase ventilation during other idle conditions, e.g., when intake manifold vacuum is in the range of 20-80 kPa. Further, in the context of direct injection gasoline engines, increased crankcase ventilation may be desired due to fuel dilution that may occur during warm-up or during cold weather conditions.During such conditions, crankcase oil may be diluted, for example, by unburned injected fuel entering the crankcase. Additionally, the oil separator efficiency may be highest in a narrow band of flow rate, and thus a constant and appropriate crankcase ventilation flow rate may increase oil separation. Oil separation is typically poor when flowing through the small orifice because this results in a low velocity through the oil separator.In one example, the issues described above may be addressed by a method for an engine including electrically controlling a crankcase ventilation valve based on the desired engine air and fuel flow rates, the current engine air flow rate contributions from a brake booster, and the current engine air and fuel flow rate contributions from a fuel vapor purging system to selectively enable crankcase ventilation flow into an engine inlet downstream of a throttle. In this way, crankcase ventilation flow may be actively controlled via the electric control of the crankcase ventilation valve, rather than limiting crankcase ventilation flow to a level acceptable during conditions of minimum engine air flow, such that higher levels of crankcase ventilation flow are achieved during conditions where such flow does not result in an engine air flow rate and / or fuel flow rate that exceed a desired amount for current engine operating conditions. Stated another way, engine operating conditions where crankcase ventilation flow results in engine excessive air / fuel flow may only occur when the transmission is in the neutral position, the engine and catalyst have been warmed up, and the FEAD load is below a threshold. Accordingly, active crankcase ventilation valve control may result in increased crankcase ventilation flow, which may advantageously increase crankcase ventilation and oil separation and decrease fuel dilution. The electrical control of the crankcase ventilation valve may be achieved via control of a solenoid valve incorporated into the crankcase ventilation valve. The crankcase ventilation valve may further include one or more ports incorporated therein and in some examples may further include a variable pressure control valve.It should be understood that the summary above is provided to introduce in simplified form a selection of the concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Moreover, the claimed subject matter is not limited to implementations that eliminate all of the disadvantages recited above or in any part of this disclosure.Brief Description of the DrawingsFIG. 1 is a schematic diagram of an example engine system. FIG. 2 is a schematic diagram of an example vehicle system including the engine system of FIG. 1. FIGS. 3-4 are flowcharts of two methods for regulating brake booster, fuel vapor purge, and crankcase ventilation flows to an engine intake downstream of a throttle. FIG. 5 is a graph illustrating changes in position of an aspirator shut-off valve, a canister purge valve, and a PCV valve under changing engine operating conditions.DETAILED DESCRIPTIONThe following description relates to systems and methods for coordinating multiple flows entering an intake of a vehicle engine downstream of a throttle. As shown in FIG. 1, the intake manifold of an engine may receive fresh air from an intake passage of the engine, the rate of fresh air supplied to the intake manifold being regulated by the position of a throttle in the intake passage. However, the intake manifold may also receive gases from a vacuum canister of the brake booster, a fuel vapor purge manifold, and an engine crankcase. Each of these gas sources may bypass the throttle and may be directed via various paths to engine intake downstream of the throttle (e.g., to the intake manifold). As such, while the flow of fresh air into the intake manifold may be regulated by the position of the throttle, the gas flows entering the intake may be regulated by valves positioned in each of the various paths. For example, an electrically controlled aspirator shut-off valve (ASOV) may be positioned in a flow path between the vacuum reservoir of the brake booster and the engine inlet downstream of the throttle. Further, an electrically controlled canister purge valve (CPV) may be positioned in the flow path between the purge canister and the intake manifold, and a PCV valve (alternatively referred to herein as a positive crankcase ventilation valve) may be positioned in the flow path between the crankcase and the intake manifold. The PCV valve may include a variable pressure control valve (e.g., a spring-operated valve), one or more ports, one or more check valves, and a solenoid for controlling gas flow between the crankcase and the intake manifold. The flows of the brake booster gases, fuel vapor purge gases, and crankcase gases into the intake manifold may all be regulated by an engine controller by adjusting the position of an ASOV, a CPV, and a PCV valve, respectively. Stated another way, the electrically controlled valves may be adjusted to coordinate the flows of the gases to the intake manifold bypassing the throttle. More specifically, as described with respect to FIGS. 3 and 4, the PCV valve, ASOV, and CPV may be individually adjusted to provide a desired air flow rate and a desired fuel flow rate to the intake manifold in conjunction with the throttle regulated flow of fresh air. The ASOV may be opened whenever a level of vacuum stored in the vacuum reservoir of the brake booster falls below a threshold vacuum level, as discussed with respect to FIG. 5. If a concentration of fuel vapors stored in a fuel vapor canister exceeds a threshold concentration, then the CPV may be opened to allow the gases to flow from the purge canister to the intake manifold. However, the CPV may remain closed if its opening would cause the air or fuel flow rates entering the intake manifold to exceed the desired rates. Further, if the ASOV is open, the CPV may be opened only if its opening would not result in a rate of airflow entering the intake manifold exceeding a desired rate and / or a rate of fuel flow entering the intake manifold exceeding a desired rate. The PCV valve may be preset to an open position (e.g., at which a solenoid valve incorporated therein is open). During conditions where boost replenishment and / or fuel vapor purge occurs, the PCV valve may be closed if the flow of crankcase gases into the intake manifold causes the air and / or fuel flow rates entering the engine to exceed the desired rates. Because the opening durations of the CPV and the ASOV may be relatively short, the fraction of engine operation during which the PCV valve is open may be increased via active control of the throttle bypass flows described herein. In another example, the PCV valve may also be closed during conditions where the engine air flow rate is at or below a minimum engine air flow rate, such as when a vehicle transmission (shown in FIG. 2 ) is in neutral and the engine and one or more catalysts of the engine have been warmed up and an FEAD load is below a threshold. These conditions may occur rarely, particularly in start / stop engines. Thus, by incorporating an electrically controlled valve into the PCV valve, the durability and rate of crankcase ventilation flow into the intake manifold during engine operation may be increased. Increasing the regularity and rate of crankcase ventilation flow may increase fuel efficiency during idling, oil separator performance, and engine performance in cold weather or during short periods of engine use.FIG. 1 shows aspects of an example engine system 100 for a motor vehicle. The engine system is configured to combust fuel vapor accumulated in at least one component thereof. The engine system 100 includes a multi-cylinder internal combustion engine, generally shown at 10, which may be included in a propulsion system of a motor vehicle. The engine 10 may be controlled at least in part by a control system including a controller 12 and by input from an operator 130 of the vehicle via an input device 132. In this example, the input device 132 includes a brake pedal. A pedal position sensor 134 generates a proportional pedal position signal PP. The control system may include a powertrain control module (PCM).The engine 10 includes an air intake throttle 20 fluidly coupled to an engine intake manifold 144 along an intake passage 142. The air entering the intake passage 142 from the periphery of the vehicle may pass through an air cleaner 33 disposed upstream of the throttle 20. A position of the throttle 20 may be changed via a signal provided to an electric motor or actuator included in the throttle 20 by the controller 12, a configuration generally referred to as an electronic throttle control (ETC). In this way, throttle 20 may be actuated to vary the intake air provided to intake manifold 144 and the plurality of cylinders therein. A mass airflow sensor 58 may be coupled into the intake passage 142 to provide a signal regarding mass airflow (MAF). A throttle inlet pressure sensor 161 may be coupled immediately upstream of throttle 20 to provide a signal regarding throttle inlet pressure (TIP). A manifold air pressure sensor 162 may be coupled to the intake manifold 144 to provide a signal regarding manifold air pressure (MAP) to the controller 12.Engine system 100 may further include a turbocharger compressor 14 for providing a boosted intake air charge to intake manifold 144. The compressor 14 may be mechanically coupled to and driven by a turbine driven by the hot exhaust flowing from the engine. In the configuration illustrated in FIG. 1, the turbocharger compressor draws fresh air from the air filter 33, compressing the air and flowing the compressed air through an intercooler 18. The intercooler cools the compressed air, which then flows to the intake manifold 144 depending on a position of the throttle valve 20.A compressor bypass 135 may be coupled via the compressor 14 to bypass a portion of the intake air compressed by the compressor 14 back to a location upstream of the compressor. An air rate diverted through bypass 135 may be controlled by opening a compressor bypass valve (CBV) 106. In some examples, the CBV 106 may be a continuous compressor recirculation valve. By controlling the CBV 106 to vary an air rate diverted through the bypass passage 135, boost pressure downstream of the compressor may be regulated. This enables the supercharging pressure control and the pumping control. A compressor inlet pressure sensor 160 is coupled immediately upstream of the compressor to provide a compressor inlet pressure (CIP) signal to the controller 12.The engine system 100 may include one or more vacuum consumption devices that are vacuum actuated. As one example, an ejector 116 may be positioned in a conduit 138 coupled to the intake passage upstream of the compressor and downstream of the compressor. More specifically, a portion of intake air may flow to the intake passage via conduit 138 from a location downstream of intercooler 18 and a location upstream of throttle 20 at a location upstream of compressor 14. In another example, the end of the conduit 138 may be coupled to the intake passage proximal to the intake manifold downstream of the compressor and upstream (rather than downstream) of the intercooler. During flow through conduit 138, the air may pass through ejector 116, producing a vacuum at the ejector vacuum inlet. As shown in FIG. 1, the ejector 116 may be arranged such that air flowing from the intake passage downstream of the compressor to the intake passage upstream of the compressor first enters a converging portion of the ejector and then exits a diverging portion of the ejector. As will be further described below, an intake inlet of ejector 116 may be coupled to a conduit that directs the fuel vapor purge gases from a fuel vapor purge system to the engine inlet. In this manner, during conditions when motive flow is moving through conduit 138 and thus through the motive portion of ejector 116, a portion of the fuel vapor purge gases may flow into the intake inlet of ejector 116 and then into the intake passage upstream of the compressor.The engine system 100 may also include a brake booster 140 coupled to brakes (not shown) of vehicle wheels. A vacuum reservoir 184 of the brake booster 140 may be coupled to the engine inlet via a brake booster vacuum line 85 along with a line 86 and / or a line 87, depending on engine operating conditions. As shown, conduit 85 branches into conduits 86 and 87. a first end of conduit 87 is coupled to conduit 85, while a second end of conduit 87 downstream of the throttle is coupled to the engine intake (e.g., to the intake manifold as shown in FIG. 1 ). A check valve 73 coupled into conduit 87 allows air to flow from brake booster 140 to the engine inlet while limiting air flow from the engine inlet to brake booster 140. A first end of conduit 86 is coupled to conduit 85, while a second end of conduit 86 is coupled to an intake inlet of an aspirator 30, described in more detail below. A propulsion outlet of aspirator 30 is fluidly connected to conduit 87 downstream of check valve 73 and upstream of the engine inlet (e.g., intake manifold).Vacuum reservoir 184 may be disposed behind a diaphragm 183 of the brake booster to boost a force provided by vehicle operator 130 via input device 132 for applying the brakes (not shown) of the vehicle wheels. In one embodiment, the brake pedal 132 may be mechanically coupled to the brake booster 140. Depression of brake pedal 132 may open a valve (not shown) in brake booster 140, allowing outside air to flow into brake booster 140 only on one side of diaphragm 183. As such, the force applied to the brake pedal 132 may be boosted by the brake booster 140, which reduces the amount of force required by the vehicle operator 130 to depress the brake pedal 132. Alternatively or additionally, conduit 85 may supply other vacuum actuators.In another embodiment, two adjustable valves 191 and 193 may be fluidly coupled to the brake booster 140. As shown in FIG. 1, the valves 191 and 193 are disposed in a passage communicating with an air source (e.g., the atmosphere). A first end of the conduit is coupled to the vacuum reservoir 184, while a second end of the conduit may be coupled to the air source. Valve 191 is positioned proximal to vacuum reservoir 184, whereas valve 193 is positioned proximal to the air source. An additional passage may couple the other side of the brake booster (e.g., the opposite side of the vacuum reservoir from the brake booster) to the passage at a location between valves 191 and 193. Valves 191 and 193 are electrically controlled valves, wherein controller 12 may send signals to independently change the positions of valves 191 and 193 from an open position (or a high flow position) to a closed position (or a low flow position) or vice versa, or to any position therebetween. When the brake pedal 132 is depressed, the valve 193 may be opened and the valve 191 may be closed to allow air to enter the brake booster 140 only on one side of the diaphragm (e.g., the side other than the vacuum reservoir) and thereby boost the force provided by the vehicle operator 130. In contrast, valve 191 may be opened to reduce the braking force provided by the brake booster, such as when the vehicle operator releases brake pedal 132. Opening the valve 191 applies the same air pressure to both sides of the diaphragm 183 causing no pneumatic force increase at the brake hydraulic master cylinder.The vacuum reservoir 184 may receive vacuum from an aspirator system 59 having valves and the intake manifold 144. The valved aspirator system 59 may include the aspirator 30, an aspirator shut-off valve (ASOV) 60, a check valve 73, and a check valve 56. In the illustrated example, the ASOV 60 and the aspirator 30 are disposed in a conduit 137. A first end of conduit 137 is coupled to the intake passage upstream of the compressor, while a second end of conduit 137 is coupled to the engine intake (e.g., to the intake manifold as shown) downstream of the throttle. The controller may send a signal to open the ASOV 60 to redirect a portion of intake air from a location upstream of the compressor 14 into the intake manifold 144 conduit 137, thereby creating a vacuum at the intake inlet of the aspirator 30, which may contribute to replenishing vacuum in the vacuum reservoir of the brake booster. As the air flows through conduit 137, it may pass through aspirator 30 and generate a vacuum at the intake inlet of the aspirator. As shown, the aspirator 30 is disposed in the conduit 137 such that its converging portion is proximal to the first end of the conduit while its diverging portion is proximal to the second end of the conduit. A portion of intake air diverted by aspirator 30, and thus an amount of vacuum generated at aspirator 30, may be controlled by aspirator shut-off valve (ASOV) 60. The ASOV 60 may be an electrically controlled valve, such as a solenoid valve. The controller 12 may command a signal to change a position of the ASOV 60 from an open position (or a high flow position) to a closed position (or a low flow position) or vice versa, or to any position therebetween. Further, the check valve 56, coupled between the aspirator intake inlet and the vacuum reservoir of the brake booster, may prevent backflow of air from the aspirator intake inlet to the vacuum reservoir of the brake booster. A vacuum level in the vacuum reservoir of the brake booster may be measured by a pressure sensor 146 disposed therein, as shown in FIG. 1. As will be discussed in greater detail below with respect to FIG. 5, the ASOV may be opened to replenish the vacuum stored in the vacuum reservoir of the brake booster. The replenishment of the brake booster vacuum may be desired, for example, when the movement of the diaphragm 183 takes place or when the valves 191 or 193 are opened.The intake manifold 144 is configured to supply intake air or an air-fuel mixture to a plurality of combustion chambers of the engine 10. The combustion chambers may be disposed over a lubricant-filled crankcase 114 (schematically shown in FIG. 1 ) in which the reciprocating pistons of the combustion chambers rotate a crankshaft. The reciprocating pistons may be substantially isolated from the crankcase via one or more piston rings that suppress the flow of the air-fuel mixture and the combustion gases into the crankcase. Nevertheless, a significant rate of fuel, unburned air, and exhaust gases may 'flow past' the piston rings over time and enter the crankcase. To reduce the degradation effects of the fuel (liquid or vapor) on the viscosity of the engine lubricant and to reduce the venting of vapor to the atmosphere, the crankcase may be continuously or periodically vented, as further described below. In the configuration shown in FIG. 1, the PCV valve 28 (alternatively referred to herein as the crankcase ventilation valve 28) controls the venting of crankcase gases into the intake manifold via the crankcase ventilation line 80.It will be appreciated that the flow of crankcase gases as used herein refers to the flow of fuel vapor and gases from the crankcase along vent line 80 to the intake manifold. Similarly, crankcase recirculation, as used herein, refers to the flow of fuel vapors and gases from the intake manifold along vent line 80 to the crankcase. Recirculation may occur when intake manifold pressure is higher than crankcase pressure (e.g., during boosted engine operation).In a non-limiting example, the PCV valve 28 may include a first port 143, a second port 145, and a third port 147. Each orifice serves to restrict the flow rate of the gases passing therethrough to an extent proportional to a size of the orifice. The first opening 143 may be larger than the second opening 145, which in turn may be larger than the third opening 147. Accordingly, a greater flow rate / flow rate of crankcase gases may pass through the first opening as compared to the second opening, and a greater flow rate / flow rate of crankcase gases may pass through the second opening as compared to the third opening.The crankcase ventilation valve 28 may additionally include a one-way check valve 149 positioned parallel to the third port 147. The one-way check valve 149 allows flow from the crankcase to the intake manifold and limits backflow from the intake manifold to the crankcase. As such, any crankcase return flow from the intake manifold 144 to the crankcase 114 may be forced through the third opening 147. This may occur during conditions where there is lower pressure in crankcase 114 than in the intake manifold (also referred to herein as negative manifold vacuum).In the embodiment shown in FIG. 1, the PCV 28 additionally includes a pneumatically controlled valve 141 disposed in series with the first port 143. This series arrangement of the valve 141 and the first port 143 is arranged in parallel with the second port 145. Further, the parallel arrangement of the valve 141 and the first port 143 to the second port 145 is arranged in series with the parallel arrangement of the third port 147 to the check valve 149.The valve 141, in one example, may include an internal restrictor (e.g., a cone or ball) and / or may be a spring-operated valve. The position of the internal flow restrictor and thus the flow through the valve may be regulated by the pressure difference between the intake manifold and the crankcase. For example, if there is no vacuum in the intake manifold, e.g., during engine off conditions, a spring may keep a base of the internal flow restrictor located against an end of a housing of the valve communicating with the crankcase such that the valve is at a fully closed position. In contrast, when there is a high level of intake manifold vacuum, e.g., under engine idle or deceleration conditions, the internal flow restrictor moves upward toward the intake manifold end of the valve housing due to the increase in intake manifold vacuum within the valve housing. At this time, the valve 141 is substantially closed. When intake manifold vacuum is at a lower level, such as during part load operation, the internal flow restrictor moves closer to the crankcase end of the valve housing, with PCV flow moving through a larger annular opening between the internal flow restrictor and the valve housing. At this time, the valve 141 is partially open. Finally, a further decrease in intake manifold vacuum (while the intake manifold vacuum is still greater than zero), e.g., during high load conditions, moves the internal flow restrictor even closer to the crankcase end of the valve housing, such that PCV flow moves through an even larger annular opening between the internal flow restrictor and the valve housing. At this time, valve 141 is considered fully open so that PCV flow through the valve is maximized. In this manner, the opening state of the valve 141 is affected by the manifold negative pressure, and the flow rate through the valve 141 is proportional to the manifold negative pressure.When the valve 141 is closed, during conditions where an electrically controlled valve 153, described further below, is open, the gases may still flow through the second opening between the crankcase and the intake manifold. In the case of high manifold vacuum, the valve 141 moves to a closed position where the gases may flow from the crankcase to the intake manifold at a relatively low rate via the second orifice 145. This feature may limit crankcase ventilation flow during engine idling. In the case of low manifold vacuum, the spring-operated valve may open and allow a greater second air rate to flow from the crankcase to the intake manifold. Under this condition, the engine may take the large air flow rate. Further, the greater second rate of airflow may be closer to a desired crankcase ventilation flow rate than the smaller first flow. Thus, the valve may be closed under light engine loads, which reduces the rate of crankcase gases flowing to the intake manifold.The addition of the valve 153 may allow the aperture 145 to be enlarged. This may advantageously result in increased crankcase ventilation flow during high manifold vacuum conditions, which in turn may increase oil separation efficiency. The electrically controlled valve 153 may be positioned between the parallel arrangement of the third port 147 and the one-way check valve 149 and the crankcase. The controller 12 may command a signal to change a position of the valve 153 from an open position (e.g., a high flow position) to a closed position (e.g., a low flow position or no flow position), or vice versa, or to any position therebetween. At the closed position, the electrically controlled valve may not allow fluid communication between the intake manifold 144 and the crankcase 114. For example, the gases may only flow from the crankcase to the intake manifold when the valve 153 is open. Similarly, valve 153 is positioned such that during reverse flow conditions, the gases may only flow from the intake manifold to the crankcase when valve 153 is open. Thus, when the valve 153 is closed, the crankcase and intake manifold are not in fluid communication. As will be described in more detail below with respect to the methods shown in FIGS. 3 and 4, the position of the valve 153, and thus the flow of crankcase gases to the intake manifold 144, may be adjusted by the controller based on a rate of scavenge gas flow into the intake, a rate of brake booster flow into the intake, a difference between a desired engine air flow rate and a measured / estimated current engine air flow rate, and a difference between a desired engine fuel flow rate and a measured / estimated engine fuel flow rate, among other factors. In the embodiment of the PCV valve 28 shown in FIG. 1, the electrically controlled valve 153 is physically contained within the PCV valve 28 so as to be integrated with the PCV valve 28 and integral with the PCV valve 28. However, in other embodiments, electrically controlled valve 153 may be coupled to a vent line 80 external to PCV valve 28. For example, valve 153 may be positioned upstream of PCV valve 28 with respect to positive crankcase ventilation flow between crankcase 114 and PCV valve 28, or downstream of PCV valve 28 with respect to positive crankcase ventilation flow between intake manifold and PCV valve 28.In another embodiment, the PCV valve 28 may not include a pneumatically controlled valve (e.g., a variable pressure control valve). Instead, the PCV valve 28 may include only one or more ports, one or more one-way check valves, and an electrically controlled valve, such as valve 153. In such examples, the flow of crankcase gases to the intake manifold may be regulated solely by the electrically controlled valve 153 and the three ports.References herein to opening or closing the PCV valve may specifically refer to opening and closing the electrically controlled valve (e.g., electrically controlled valve 153) integrated with the PCV valve (or in other examples, arranged in series with the PCV valve).The crankcase 114 may include one or more oil separators 96 and 98 for separating the oil from the crankcase vapors (or the "blowby" gases) before purging the vapors to the intake manifold 144. Oil separators 96 and 98 allow for bidirectional crankcase ventilation as described below. A pressure level in the crankcase 114 may be determined by a pressure sensor 62 disposed in the crankcase.When the atmospheric pressure (BP) is greater than the MAP (e.g., during non-boosted conditions), fresh air is drawn into the crankcase 114 from a location downstream of the air filter 33 and upstream of the compressor 14 along the vent tube 178. Crankcase fuel vapors and gases may then be vented from the crankcase via electrically controlled valve 153 and crankcase ventilation valve 28 to the intake manifold in vent line 80 when valve 153 is open. Under some engine operating conditions, such as when the MAP is greater than the BP (e.g., during boosted conditions) and crankcase pressure is greater than the BP, crankcase fuel vapors may be drawn along the vent tube 178 (a reverse flow). However, under such conditions, the controller may be configured to send a signal to actively close the valve 153 if no reverse flow is desired.The engine system 100 further includes a fuel tank 26 storing a volatile liquid fuel that is burned in the engine 10. To avoid the emission of fuel vapors from the fuel tank and into the atmosphere, the fuel tank is vented to the atmosphere through an adsorbent canister 22. The adsorbent canister may have significant capacity for storing hydrocarbon, alcohol, and / or ester-based fuels; for example, it may be filled with activated carbon granules and / or other high surface area material. Nevertheless, extended adsorption of fuel vapor may eventually reduce the capacity of the adsorbent canister for further storage. Therefore, the adsorbent canister may be periodically purged of the adsorbed fuel, as further described below. In the configuration shown in FIG. 1, a state of a solenoid 118 integrated with a CPV 126 may be controlled by the controller to control purging of fuel vapors from the canister along purge line 82 into the intake manifold. As shown, the CPV 126 is disposed in the purge line 82, with the purge line 82 coupled at its first end to the canister and at its second end to the intake manifold. The check valve 52, coupled into the purge line 82, prevents backflow from the intake manifold 144 into the canister 22.As shown in FIG. 1, the CPV 126 includes a series arrangement of the solenoid 118 and a flow restrictor 119. The flow restrictor 119 serves to restrict the flow of purge vapors from the canister 22 to a flow level that is below a predetermined threshold. The combination of the solenoid 118 and the flow restrictor 119 results in a valve, sometimes referred to as a sonic valve, that operates as a low pressure air and fuel injector. Stated another way, the flow restriction 119 may prevent flow from the canister 22 at a level that exceeds the predetermined threshold.The solenoid 118 of the CPV 126 may be a continuously adjustable valve, and may be duty cycle controlled (e.g. at 10 Hz). The fraction of the time it is open and the pressure drop across it can determine the total molar flow across the CPV. For example, a small duty cycle may be used at low engine flow rates or high canister purge charges. In a loaded canister, the first portion of the molar flow rate has a high concentration of fuel. As the canister fuel charge level falls, the fuel concentration falls, with the valve continuing to open (increased duty cycle) to allow for approximately the same fuel flow rate therethrough. For a full canister, the fuel rate limits the duty cycle of the CPV. For a nearly empty canister, the air flow rate limits the duty cycle of the CPV.When purge conditions are met, such as when the canister is saturated, the measured engine air flow rate is below a desired engine air flow rate and the measured engine fuel flow rate is below a desired engine fuel flow rate (as will be discussed in greater detail below with respect to FIGS. 3 and 4 ), where vapors stored in fuel vapor canister 22 may be purged to intake manifold 144 by actively opening solenoid 118. When the CPV 126 is open, fuel vapors may be drawn from the canister via two paths into intake manifold 144. First, due to the presence of intake manifold vacuum, fuel vapors may be drawn from canister 22 along purge line 82 directly into intake manifold 144 (e.g., into the intake system downstream of the throttle). The purge vapor flow along conduit 82 to intake manifold 144 may occur during conditions when BP>MAP holds (e.g., during non-boosted conditions) and when the CPV is at least partially open. The purge fuel vapors may also flow indirectly to intake manifold 144 along a purge line 83. As shown, a first end of the scavenge conduit 83 may be coupled to the scavenge conduit 82 downstream of the CPV 126 and upstream of the intake manifold, while a second end of the scavenge conduit 83 may be coupled to the intake inlet of the ejector 116. If TIP>BP holds (e.g., during boosted conditions), motive flow moving from the intake passage downstream of the compressor through ejector 116 to the intake passage upstream of the compressor may cause a suck flow of fuel vapors from canister 22 into the intake opening of the ejector and then into intake passage 142 upstream of the compressor. Fuel vapors may then flow into intake manifold 144 via intake passage 142. The one-way check valve 115 coupled to the scavenging line 83 can prevent the motive flow moving through the ejector from entering the scavenging line 83 via the suction port. Accordingly, the flows of both crankcase gas and fuel vapor purge into the intake manifold may be independently controlled.As shown, a vapor blocking valve (VBV) 124 may optionally be included in a conduit between the fuel tank 26 and the canister 22. The VBV 124 may alternatively be referred to as a fuel tank shut-off valve. In some embodiments, the VBV 124 may be a solenoid valve, and operation of the VBV 124 may be regulated by adjusting a drive signal (or pulse width) of the dedicated solenoid. During normal engine operation, the VBV 124 may be maintained closed to limit the rate of fuel tank vapor directed from the fuel tank 26 to the canister 22. During refueling operations and selected purging conditions, the VBV 124 may be opened to route fuel vapors from the fuel tank 26 to the canister 22. By opening the valve during conditions where fuel tank pressure is higher than a threshold (e.g., is above a fuel tank mechanical pressure limit above which the fuel tank and other components of the fuel system may suffer mechanical damage), the refueling vapors may be released into the canister and fuel tank pressure may be maintained below the pressure limits. While the illustrated example shows the VBV 124 positioned in a passage between the fuel tank and the canister, in alternative embodiments, the isolation valve may be attached to the fuel tank 26.As shown, a fuel tank pressure sensor 163 may be disposed in the line coupling fuel tank 26 to VBV 124. Fuel tank pressure sensor 163 may measure a pressure level in fuel tank 26 and provide a signal with this information to the control system.Further, as shown, a vent line 117 may be coupled to the canister 22 to direct the gases from the canister to atmosphere when storing or trapping fuel vapors from the fuel tank 26. Vent line 117 may also allow fresh air to be drawn into fuel vapor canister 22 when purging stored fuel vapors to intake manifold 144 via purge line 82 and CPV 126. While this example shows vent line 117 communicating with fresh, non-heated air, various modifications may also be used. The vent line 117 may include a canister vent valve 120 disposed therein to adjust the flow of air and vapors between the canister 22 and the atmosphere. While a single canister 22 is shown, it will be appreciated that any number of canisters may be coupled to engine system 100.The controller 12 may be configured as a microcomputer including a microprocessor unit, input / output ports, an electronic storage medium for executable programs and calibration values, a random access memory, a keep alive memory, and a data bus. The controller 12 may receive various signals from sensors 16 coupled to the engine 10, such as the MAF sensor 58, the MAP sensor 162, the crankcase ventilation pressure sensor 62, the CIP sensor 160, the TIP sensor 161, the brake booster pressure sensor 146, etc. Additionally, the controller 12 may monitor and adjust the position of various actuators 81 based on the input received from the various sensors. These actuators may include, for example, throttle 20, intake and exhaust valve systems, CPV 126, canister vent valve 120, crankcase vent valve 28, ASOV 60, and compressor 14. The storage medium read-only memory in the controller 12 may be programmed with computer readable data representing the instructions executable by a processor to perform both the methods described below and other variants that are anticipated but not specifically listed. Example methods and routines are described herein with respect to FIGS. 3 and 4.Referring now to FIG. 2, a vehicle system 200 is shown schematically. The vehicle system 200 includes an engine system 100, which may correspond to the engine system 100 of FIG. 1. The vehicle system includes wheels 202. Torque is provided to wheels 202 via engine system 100 and transmission 204. In some examples, an electric motor or a hydraulic motor may also provide torque to wheels 102. As shown, a front end accessory drive (FEAD) 220 may include an alternator 210 and an air conditioning (A / C) compressor 212. Both the alternator 210 and the A / C compressor 212 may be mechanically coupled to the engine system 100 via a respective shaft or pulley 245, 247. Alternatively, alternator 210 and A / C compressor 212 may be mechanically coupled to engine system 100 via a common shaft or pulley. A battery 208 and alternator 210 may provide electrical power to various accessory components of the engine, not shown in FIG. 2. The controller 12 may correspond to the controller 12 described above with respect to FIG. 1, and may include instructions stored in non-transitory memory for controlling and receiving inputs from the alternator 210, the A / C compressor 212, the engine system 100, and the transmission 204.In FIGS. 3 and 4, two methods for coordinating brake booster, crankcase ventilation (PCV), and canister purge flows into an intake manifold (e.g., intake manifold 144 of FIG. 1 ) are shown. As discussed above with respect to FIG. 1, the brake booster, PCV, and canister purge flows may flow into the intake manifold via separate and different flow paths. For example, canister purge vapors may enter the intake manifold via a first conduit (e.g., purge conduit 82), crankcase gases via a second conduit (e.g., crankcase ventilation conduit 80), and brake booster flow via a third conduit (e.g., brake booster vacuum conduit 85). Canister purge vapors may also enter the intake manifold via a fourth conduit (e.g., purge conduit 83) via a vacuum generated at an ejector (e.g., ejector 116). The vacuum generated at the ejector and the resulting flow of purge vapors through the fourth conduit may be dictated by the pressure drop across a turbocharger compressor (e.g., compressor 14) in the intake passage. The positions of a canister purge valve (e.g., CPV 126) disposed in the first conduit and a PCV valve (e.g., PCV valve 28) disposed in the second conduit may each be independently adjusted by a controller (e.g., controller 12) to regulate the purge and PCV flows. Canister purge and PCV flows may thus be independently regulated by adjusting the position of the electrically controlled valves disposed in the first and second conduits. As such, the opening and closing of the PCV valve and canister purge valve (CPV) may be controlled by the controller. The PCV valve may be opened or closed by adjusting the position of an electrically controlled valve (e.g., electrically controlled valve 153). The intake manifold may receive flow from the brake booster (e.g., brake booster 140) that occurs passively when the pressure in the intake manifold is less than the pressure in the brake booster, as explained above with respect to FIG. 1. However, the controller may also cause additional brake booster flow to the intake manifold by adjusting the position of the ASOV 60, thereby generating an additional vacuum source at the aspirator (e.g., the aspirator 30) for evacuating the brake booster. The described methods for regulating PCV, canister purge, and brake booster flows into the intake manifold may be stored in a memory of an engine controller, such as controller 12 shown in FIG. 1.FIG. 3 shows a method 300 for regulating PCV, canister purge, and brake booster flows into the intake manifold. The instructions for executing the method 300 may be stored in memory of an engine controller (e.g., the controller 12). Further, the method 300 may be performed by the controller.At 302 of method 300, the controller estimates and / or measures engine operating conditions. The operating conditions of the engine may include engine speed and load, engine air flow rate, engine fuel flow rate, MAP, TIP, CIP, position of the PCV valve, position of the CPV, etc. After estimating engine operating conditions, the method continues to 304 to enable intentional replenishment of the brake booster. Intentional replenishment of the brake booster may include the controller sending a signal to an actuator to open the ASOV whenever vacuum in the brake booster falls below a threshold level. For example, if the pressure in the brake booster increases above a threshold pressure, then the ASOV may be opened to decrease the magnitude of the pressure / increase the level of the vacuum in the brake booster.The brake booster vacuum may decrease as a result of user input. For example, when an operator of the vehicle (e.g., the operator 130 of the vehicle) moves a brake pedal (e.g., the input device 132), it may be desirable to refill the brake booster, and as such, the controller may open the ASOV. Thus, the replenishment of the brake booster may be controlled by the controller based on input from an operator of the vehicle via the brake pedal, and may be further based on the level of pressure / vacuum in the brake booster.After 304, the controller may proceed to 306 to determine the current and desired engine air flow and fuel flow rates. The controller may estimate current air and fuel flow rates based on outputs from various sensors and actuators. For example, the controller may estimate the air flow rate based on outputs from a mass airflow sensor (e.g., mass airflow sensor 58) positioned in the air intake system (e.g., intake passage 142), a CIP sensor (e.g., CIP sensor 160), a TIP sensor (e.g., TIP sensor 161), and a position of a throttle (e.g., throttle 20). Additionally, the controller may estimate the air flow rate in consideration of the flows into the intake manifold bypassing the throttle, such as gases from a brake booster (e.g., brake booster 140), a scavenge manifold (e.g., scavenge manifold 22), and a crankcase (e.g., crankcase 114). Further, the controller may estimate the fuel flow rate based on engine speed, injector commands, injection pressure, estimated fuel rate within the canister purge flow rate, estimated fuel flow rate within the PCV flow rate. The desired engine air flow and fuel flow rates may be based on input from the vehicle operator. Alternatively, the desired air flow rate and the desired fuel flow rate may be based on a need to operate the engine at idle, such as a commanded idle speed.After estimating the current and desired air and fuel flow rates at 306, method 300 proceeds to 308, wherein the controller determines whether the current engine air flow rate is greater than the desired engine air flow rate. If the current engine air flow rate is greater than the desired engine air flow rate, then the controller proceeds to 310 to close the CPV and PCV valve. Closing the CPV and PCV valve may include moving the valves to a closed position such that the canister purge gases and crankcase gases do not flow into the intake manifold. If the CPV or PCV valve is already closed at 310, the controller may maintain the position of the valve at a closed position at 310. It will be appreciated that references herein to the air flow rate greater than desired refer to an air flow rate after the engine's intake throttle has already been commanded to its minimum position.Next, at 312, the controller may take actions to reduce engine torque. To reduce the net engine braking torque, the controller may load the engine by increasing alternator torque at 313 and / or retarding spark timing at 315. Step 313 stores energy in the battery and thus increases torque consumption, whereas step 315 results in the supply of heat to the outlet and thus reduces torque generation. For example, retarding spark timing may include retarding spark timing from a nominal spark timing, where the nominal spark timing is fixed during the engine's compression stroke to provide maximum fuel efficiency. As such, retarding spark timing may reduce efficiency of the engine (e.g., engine 10) and reduce power output from the engine. Increasing the alternator torque may include increasing a voltage and / or current input to the alternator, thereby increasing the load applied to the engine by the alternator. In one example, at 312, the controller may execute only 313 and increase alternator torque and not proceed to 315 and retard spark timing. In another example, at 312, the controller may only proceed to 315 and retard spark timing and not proceed to 313 and increase alternator torque. In another example, at 312, the controller may proceed to both 313 and 315 and increase alternator torque and retard spark timing. The controller may execute 313 and 315 simultaneously or may execute one before the other. After 312, the method 300 ends.Returning to 308, if the controller determines that the current engine air flow rate is not greater than the desired engine air flow rate, the controller may proceed to 314 and determine whether the current engine fuel flow rate is greater than the desired engine fuel flow rate. If the current engine fuel flow rate is greater than the desired engine fuel flow rate, then the controller may proceed to 316 and close the CPV and PCV valve. Closing the PCV valve may include adjusting the position of the electrically controlled valve (e.g., electrically controlled valve 153) to a more closed position that reduces the cross-sectional area through which crankcase gases may flow. In one embodiment, closing the PCV valve may provide a fluid seal between the crankcase and the intake manifold that prevents the flow of gases therebetween.However, if the controller determines at 314 that the current engine fuel flow rate is less than the desired engine fuel flow rate, the controller may proceed to 318 and determine if the fuel vapor purge conditions are present. The controller may determine whether fuel vapor purge conditions are present based on both a concentration of fuel vapor in the fuel vapor canister / the measured pressure level in the fuel vapor canister and current pressures in the fuel vapor canister and intake manifold. For example, if the fuel vapor concentration in the fuel vapor canister is greater than a threshold concentration, then fuel vapor purge conditions may be present. The threshold concentration may be a known fuel vapor concentration stored in memory of the controller. In one example, the threshold fuel vapor concentration may be twenty percent. Stated another way, fuel vapor purge conditions may be present when one or more of the following conditions are present: fuel vapor concentration in the fuel vapor canister exceeds a threshold concentration; and pressure in the intake manifold is less than pressure in the fuel vapor canister by more than a threshold amount. Regarding the latter condition, the controller may determine whether the pressure in the intake manifold is lower than the pressure in the fuel vapor canister by more than a threshold. The threshold pressure difference may be a pressure difference between the fuel vapor canister and the intake manifold sufficient to cause the flow of canister purge gases upon opening the CPV.If, at 318, the fuel vapor purge conditions are not present, the controller may close the CPV, at 320. In one example, closing the CPV may include adjusting the position of the CPV to a closed position, and thereby sealing an opening of the valve so that crankcase gases may not flow through the valve. In another example, closing the CPV may include decreasing the size of the opening of the valve from the current position to a position between the current position and the closed first position, and thus decreasing the flow of crankcase gases through the valve.However, if at 318, the fuel vapor purge conditions are present, then the controller may proceed to 322 and estimate the engine air flow rate and fuel flow rate resulting if the CPV is open. The controller may estimate what would be the air flow rate and the fuel flow rate in the intake manifold upon opening the CPV based on an estimated concentration of fuel vapor in the fuel vapor canister and an estimated flow rate of purge vapors (which may be based on an amount of vacuum present at the ejector and intake manifold). For example, increases in the concentration of fuel vapor in the fuel vapor canister and increases in the vacuum present at the intake manifold may increase the fuel flow rate to the intake manifold upon opening the CPV. After estimating what the engine air flow rate and fuel flow rate would be if the PCV is open, the controller may proceed to 324 and determine if opening the CPV would result in the air flow rate being greater than the desired air flow rate and / or the fuel flow rate being greater than the desired fuel flow rate. If opening the CPV would result in the air flow rate and / or fuel flow rate being greater than desired, the controller may proceed to 320 and close the CPV. However, if the controller determines that opening the CPV would not increase the air flow rate and the fuel flow rate beyond their desired rates, then at 326, the controller may open the CPV. Opening the CPV may include adjusting the position of the CPV to a more open position that increases the cross-sectional area through which canister purge gases may flow. Stated another way, the controller may increase the opening amount of the CPV to increase the rate of canister purge gases flowing from the purge canister to the intake manifold (either directly in a purge line, such as purge line 82, or indirectly by flowing in a purge line, such as purge line 83, leading to an ejector intake inlet, with a propulsion outlet of the ejector leading to the intake passage of the engine upstream of the compressor).Either after closing the CPV at 320 or after opening the CPV at 326, the controller may proceed to 328 and estimate the contributions to the air flow rate and fuel rate that would result if the PCV valve were open. An estimate of the contributions of crankcase gases to the air flow rate and fuel flow rate that would result from opening the PCV may be based on the pressure difference between the MAP and the crankcase pressure, among other factors. In one example, a model of the blowby gases entering the crankcase, the fresh air entering the crankcase, and the mixed effluent exiting the crankcase may be used to estimate the air rate in the gases exiting the crankcase. Such a model may be stored in the memory of the control system, for example, wherein the controller may estimate the air rate in the gases leaving the crankcase by lining the model with the current values of the operating parameters. The total molar gas flow rate may be calculated by the controller based on the crankcase pressure, the intake manifold pressure, and the valve position.After 328, method 300 may proceed to 330, wherein the controller may determine whether the engine air flow rate would be greater than the desired air flow rate and / or whether the engine fuel flow rate would be greater than the desired fuel flow rate if the PCV valve were open. The controller may estimate what the air flow rate and fuel flow rate would be if the PCV were open based on canister purge flow, brake boost flow, intake passage mass air flow, turbocharger pressure drop, throttle position, etc. For example, increases in boost flow of the brake booster may result in increases in engine air flow rate, and similarly increases in scavenge flow may result in increases in engine fuel flow rate.If the controller determines that upon opening the PCV valve, either the engine air flow rate and / or fuel flow rate would be greater than desired, then the controller may proceed to 334 to close the PCV valve. In one example, closing the PCV valve may include adjusting the position of the electrically controlled valve integrated with the PCV valve (e.g., electrically controlled valve 153) to a closed position, whereby an opening of the valve may be sealed so that crankcase gases may not flow through the valve. In another example, closing the PCV valve may include decreasing the size of the opening of the electrically controlled valve from the current position to a position between the current position and the closed first position, and thus decreasing the flow of crankcase gases through the valve. After 334, method 300 ends.However, if the controller determines that opening the PCV valve would not increase the engine air flow rate or fuel flow rate beyond its desired levels, then at 332, the controller may open the PCV valve. Opening the PCV valve may include adjusting the position of the valve to a more open position that increases the cross-sectional area through which crankcase gases may flow. After 332, the method 300 ends.Thus, according to method 300, a method for an engine may include electrically controlling a crankcase ventilation valve based on the desired engine air and fuel flow rates, the current engine air flow rate contributions from a brake booster, and the current engine air and fuel flow rate contributions from a fuel vapor purge system to selectively enable crankcase ventilation flow into an engine inlet downstream of a throttle. If the current contributions to engine air flow rate from the brake booster exceed the desired engine air flow rate, the method may further include electrically controlling the crankcase ventilation valve to block crankcase ventilation flow into the engine inlet and electrically controlling a canister purge valve to block flow from the fuel vapor purge system into the engine inlet. If the current contributions to engine air flow rate from the brake booster do not exceed the desired engine air flow rate and if fuel vapor purge conditions are present, the method may also include electrically controlling the canister purge valve to enable flow from the fuel vapor purge system into the engine inlet if the estimated engine air and fuel flow rates with fuel vapor purge flow enabled do not exceed the desired engine air and fuel flow rates, respectively. If the current engine air flow rate contributions from the brake booster do not exceed the desired engine air flow rate and if the fuel vapor purge conditions are present, the method may include electrically controlling the crankcase ventilation valve to allow crankcase ventilation flow into the engine inlet if the estimated engine air and fuel flow rates do not exceed the desired engine air and fuel flow rates, respectively, at both allowed fuel vapor purge flow and allowed crankcase ventilation flow. If the current engine air flow rate contributions from the brake booster do not exceed the desired engine air flow rate and if the fuel vapor purge conditions are not present, the method may further include electrically controlling the canister purge valve to block flow from the fuel vapor purge system into the engine inlet and electrically controlling the crankcase ventilation valve to allow crankcase ventilation flow into the engine inlet if the estimated engine air and fuel flow rates do not exceed the desired engine air and fuel flow rates, respectively, when fuel vapor purge flow is blocked and crankcase ventilation flow is allowed. The method may further include taking actions to reduce engine torque if the current contributions to engine air flow rate from the brake booster exceed the desired engine air flow rate. Electrically controlling the positive crankcase ventilation valve according to method 300 may include controlling a solenoid valve integrated with the positive crankcase ventilation valve as described herein.FIG. 4 shows another example method for regulating PCV, canister purge, and brake booster flows to the intake manifold. The instructions for executing method 400 may be stored in memory of an engine controller (e.g., controller 12). Further, the method 400 may be performed by the controller.Method 400 begins at 402, where the controller estimates and / or measures engine operating conditions. Engine operating conditions may include engine speed and load, intake air mass flow, fuel flow rate, MAP, TIP, CIP, solenoid position of the PCV valve, CPV position, etc. After estimating engine operating conditions, the controller may proceed to 404 and enable intentional replenishment of the brake booster. Intentionally replenishing the brake booster may include opening the ASOV whenever vacuum in the brake booster falls below a threshold level. For example, if the pressure in the brake booster increases beyond a threshold pressure, then the ASOV may be opened to decrease an amount of pressure in the brake booster (increase vacuum in the brake booster). The brake booster vacuum may decrease as a result of user input. For example, if an operator of the vehicle (e.g., the operator 130 of the vehicle) releases a brake pedal (e.g., the input device 132), replenishment of the brake booster may be desired, and as such, the controller may open the ASOV. Thus, the replenishment of the brake booster may be controlled by the controller based on an input from an operator of the vehicle via the brake pedal and the level of pressure / vacuum in the brake booster.After 404, the controller may proceed to 406 and determine the current and desired engine air flow and fuel flow rates, e.g., in the manner described with respect to step 306 of method 300. After estimating the current and desired air and fuel flow rates at 406, method 400 may proceed to 408, where the controller may determine whether the current air flow rate is greater than the desired engine air flow rate, e.g., in the manner described above for step 308 of method 300. If the current air flow rate is greater than the desired engine air flow rate, then the controller may proceed to 410 and close the CPV and PCV valve. Closing the CPV and PCV valves may include moving each of the valves to a closed position such that canister purge gases and crankcase gases do not flow to the intake manifold. If at 410, the CPV or PCV valve is already closed, at 410, the controller may maintain the position of the valve at a closed position.Subsequently, at 412, and optionally at 413 and / or 415, the controller may take action to reduce engine torque, e.g., in the manner described above for step 312 of method 300. After 412, method 400 ends.Returning to 408, if the controller determines that the current engine air flow rate is not greater than the desired engine air flow rate, then method 400 may proceed to 414, where the controller may determine whether the vehicle (e.g., vehicle 200) is in an idle position of the transmission with the engine warmed up and catalyst warmed up and with an FEAD load less than a threshold. The threshold load for the FEAD may be a predetermined amount of load that may be stored in the memory of the controller. Further, the FEAD threshold load may be based on the engine air flow rate, wherein the threshold load may be set to a level at which the engine is operable at a minimum first air flow rate at the magnitude of the FEAD threshold load. The controller may determine that the vehicle is in a transmission neutral position if the transmission (e.g., transmission 204) is not converting torque from the engine to deliver it to vehicle wheels. It may be determined that the catalyst and engine have been warmed up based on engine operating conditions (e.g., engine temperature, duration of engine use, number of engine cycles, etc.). For example, if the temperature of the engine is greater than a threshold and / or the engine has run for more than a threshold period of time and / or an emission level measured downstream of the catalyst is below a threshold level, then the controller may determine that the engine and catalyst have been warmed up.If the controller determines that the transmission is in the neutral position, the engine and catalyst have been warmed up, and the FEAD load is less than a threshold, then the controller may proceed to 418 and close the PCV valve, for example, in the manner described above for step 334 of method 300. If the PCV valve is already closed at 418, the controller may maintain the position of the PCV valve at the closed first position at 418.If the controller determines that either the vehicle transmission is not in the neutral position or the engine and catalyst have not been warmed up or the FEAD load is greater than a threshold, then the controller may proceed to 416 and open the PCV valve, e.g., in the manner described above for step 332 of method 300. Either after closing the PCV valve at 418, or after opening the PCV valve at 416, method 400 may then proceed to 420, where the controller may determine whether fuel vapor purge conditions are present, e.g., in the manner described above for step 318 of method 300.If it is determined at 420 that the fuel vapor purge conditions are not present, the controller may proceed to 432 and close the CPV, e.g., in the manner described above for step 320 of method 300. If the CPV is already closed at 432, the controller may maintain the position of the CPV at the closed first position at 432. After 432, method 400 ends.Otherwise, if the controller determines at 420 that the fuel vapor purge conditions are present, then the controller may then estimate at 422 what the engine air flow rate and fuel flow rate would be if the CPV is opened, e.g., in the manner described above for step 322 of method 300.After estimating what the engine air flow rate and fuel flow rate would be if the CPV is opened, the controller may proceed to 424 and determine if opening the CPV would result in the air flow rate being greater than the desired air flow rate and / or the fuel flow rate being greater than the desired fuel flow rate. If, at 424, the controller determines that opening the CPV valve would not increase the air flow rate and fuel flow rate beyond their desired rates, then at 428, the controller may subsequently open the CPV, e.g., in the manner described for step 326 of method 300. After 428, method 400 ends.However, if opening the CPV would result in the air flow rate and / or fuel flow rate exceeding their respective desired rates, then the controller may proceed to 426 and close the PCV valve, and then determine the resulting engine air flow and fuel flow rates. For example, the PCV valve may be open at 424 (e.g., if the determination at 414 is negative). If opening the CPV would cause either the air or fuel flow rate to exceed their desired rates (e.g., due to contributions to air / fuel flow from the PCV flow entering the intake manifold), then the PCV valve may be closed to prioritize fuel vapor purge over crankcase ventilation. After closing the PCV valve, the controller may determine the resulting engine air flow and fuel flow rates.Next, at 430, the controller may determine if opening the CPV would result in an air flow rate greater than the desired air flow rate and / or a fuel flow rate greater than the desired fuel flow rate. If, at 430, the controller determines that opening the CPV valve would not increase the air flow rate and fuel flow rate beyond their desired rates, then at 434, the controller may subsequently open the CPV, e.g., in the manner described for step 326 of method 300. However, if opening the CPV would result in the air flow rate and / or the fuel flow rate exceeding their respective desired rate, then the controller may proceed to 432 and close the CPV, e.g., in the manner described for step 320 of method 300. If at 430, the CPV is already closed, then at 432, the controller may maintain the CPV closed position.Accordingly, if an engine transmission is in the neutral position, the engine and exhaust catalyst have been warmed up, and a front end accessory drive load is below a threshold, an electrically controlled positive crankcase ventilation valve may be closed to block positive crankcase ventilation flow into an inlet downstream of a throttle, according to method 400. Otherwise, the crankcase ventilation valve may be opened. When boost is requested, the crankcase ventilation valve may be closed if the engine air flow rate exceeds a desired engine air flow rate during boost when the crankcase ventilation valve is open. When boost and fuel vapor purge are requested, fuel vapor purge may be delayed by maintaining a canister purge valve at a closed position if the engine air flow rate exceeds the desired engine air flow rate during boost with the canister purge valve open and crankcase ventilation valve closed. However, the crankcase ventilation valve may be opened during brake booster replenishment and fuel vapor purge concurrent if the engine air flow rate does not exceed the desired engine air flow rate during brake booster replenishment and fuel vapor purge concurrent with the crankcase ventilation valve open. It will be appreciated that during boost replenishment, an electrically controlled isolation valve arranged in series with an aspirator may be opened, the aspirator having a propulsion inlet coupled to the inlet upstream of a turbocharger compressor, a propulsion outlet coupled to the inlet downstream of the throttle, and an intake inlet coupled to a vacuum reservoir of the boost. Further, the crankcase ventilation valve may be closed during brake booster replenishment and fuel vapor purge concurrent if an engine fuel flow rate exceeds a desired engine fuel flow rate during brake booster replenishment and fuel vapor purge concurrent with the crankcase ventilation valve open.According to methods 300 and 400, the minimum PCV flow rate may be increased relative to the PCV flow rate in the systems using conventional PCV control strategies. Thus, when the engine is in the minimum air flow rate condition, the PCV valve is closed because an open PCV valve would cause the target air flow rate to be exceeded during this condition. Whereas previous systems have assumed that the three flows (PCV flow, fuel vapor purge flow, and aspirator flow) should all exist continuously and simultaneously adjacent to one another, enabling the PCM to control all of these flows provides other options, as in methods 300 and 400. Further, such control enables the increase of the minimum PCV flow rate, thus recovering an increase in oil separation. The oil deposit advantageously retains the engine oil in the crankcase rather than losing it for engine combustion.During engine idle conditions, as in methods 300 and 400, PCM control of the fuel sources may advantageously assist in ensuring minimum fuel flow. For example, more fuel flow rate than desired may be obtained from the fuel vapor storage canister, and when ethanol sprays from the engine oil, more fuel flow rate than desired may be obtained from the crankcase ventilation system. The fuel injectors have a minimum fuel mass that they can dose with precision, which fact tends to limit the extent to which the fuel supplied by the fuel injector can be reduced.Shown in FIG. 5 is a graph illustrating how an ASOV, a CPV, and a PCV valve may be adjusted under varying engine conditions. Specifically, plot 500 shows changes in engine air flow at plot 504 and engine fuel flow at plot 506 as a result of changes in throttle position at plot 502. The position of the throttle may be adjusted between closed and open positions by a controller (e.g., controller 12). The throttle may thus be adjusted from a closed first position to an open second position or any position therebetween. Adjusting the throttle to a more open position may increase the rate of air flow to the intake manifold. As discussed above with respect to FIGS. 3 and 4, the engine air flow rate may be measured by a mass air flow sensor (e.g., mass air flow sensor 58). The engine air flow rate may also be based on the flows to the intake manifold bypassing the throttle (e.g., throttle 20), such as the flows from a brake booster (e.g., brake booster 140), a fuel vapor purge manifold (e.g., adsorbent canister 22), and a crankcase (e.g., crankcase 114). The fuel flow rate may be estimated based on the measurements of the engine air flow rate and a known ratio of air flow to fuel flow stored in the memory of the controller. Further, fuel flow rate may also be estimated based on flows from the fuel sources that may bypass the throttle, such as flows from the fuel vapor canister and the crankcase. The throttle position may be adjusted by the controller to regulate an air rate flowing to the intake manifold.Plot 500 also shows changes in brake booster vacuum at plot 508 and fuel vapor canister load at plot 510. The brake booster vacuum may be an amount of vacuum (e.g., a lower pressure than BP) present in the brake booster. Consequently, the pressure in the brake booster decreases as the levels of the negative pressure increase. The amount of vacuum in the brake booster may be measured by a pressure sensor, such as pressure sensor 146 of FIG. 1. The fuel vapor canister load in plot 510 is an estimate of the concentration of fuel vapor in the fuel vapor canister. While fuel vapor canister load may decrease monotonically during a drive cycle and increase only during a refueling event, an increase in fuel vapor canister load is shown at plot 510 to illustrate how the various valves may be controlled as fuel vapor canister load increases above a threshold. For example, if the fuel vapor canister charge increases above a first threshold, F 1, CPV may be opened during certain conditions to allow fuel vapors to flow to the intake manifold. Thus, F 1 may represent a concentration level of fuel vapors in the fuel vapor canister above which purging of the fuel vapor canister is desired. For example, the concentration of fuel vapor in the fuel vapor canister may be estimated based on a pressure in the fuel vapor canister.Graph 500 also shows changes in the position of the ASOV at 512, the CPV at 514, and the PCV valve at 516. As discussed above with respect to FIGS. 1-4, the ASOV, CPV, and PCV valve may all be controlled by the controller. The controller may adjust the valves between open and closed positions depending on engine operating conditions.As specifically worked out above with respect to FIGS. 3 and 4, the ASOV may be adjusted from a closed first position to an open second position when it is desired to increase the vacuum level in the brake booster. As one example, it may be desirable to increase the vacuum level in the brake booster after a user (e.g., the vehicle operator 130) releases a brake pedal (e.g., the input device 132). The CPV may be adjusted between a closed first position and an open second position based on fuel vapor canister charge, intake manifold pressure, brake booster flow to the engine, and engine air flow and fuel flow rates.Further, the PCV valve may be adjusted between a closed first position and an open second position based on engine air flow and fuel flow rate, brake booster flow to the engine, pressure in the intake manifold, and scavenge flow to the intake manifold.The respective closed first positions of the ASOV, CPV, and PCV valve may be positions where the respective openings of the valves are sealed so that gases cannot flow through the valves. The respective open second positions of the ASOV, CPV, and PCV valve may be positions where the respective openings of the valves are increased to a maximum value. Stated differently, the gases may flow through the ASOV, the CPV, and the PCV valve when the valves are at their respective open second positions.The ASOV may be opened if the brake booster vacuum level decreases below a lower first threshold B 2. Thus, the lower first threshold B 2 may represent a vacuum level in the brake booster below which additional vacuum in the brake booster is desired. Further, if the vacuum level in the brake booster increases above a higher second threshold, B 1, the ASOV may be closed to reduce the amount of vacuum provided to the brake booster.As described above with respect to FIGS. 3 and 4, in some examples, the vehicle system may be controlled such that the PCV gases may flow to the intake manifold only via opening of the PCV valve if the flow of the PCV gases were not to increase the air flow rate or the fuel flow rate above their respective desired rates. As a result, with respect to systems in which PCV flow is not actively controlled (e.g., electrically controlled), the amount of time that the PCV valve remains open may be increased. Further, PCV flow to the intake manifold may not only be increased, but may also be more uniform. A more constant PCV flow rate may increase the efficiency of the oil separators (e.g., oil separator 96), wherein an overall increase in PCV flow may increase engine performance during short trips and / or cold weather. Similarly, the system may be controlled to allow the purge gases to flow to the intake manifold only via opening of the CPV valve if the flow of the purge gases were not to increase the air flow rate or the fuel flow rate above their respective desired rates.Accordingly, the system described herein may enable coordination and arbitration of the three flows entering the intake manifold downstream of the throttle. For example, brake booster, scavenge, and PCV flows to the intake manifold may be regulated by the controller via active control of the respective valves, and may be coordinated such that one or more flows do not impede one or more other flows to the intake manifold. The condition under which enabling all three flows (crankcase ventilation, aspirator, and fuel vapor purge) is desired, but under which opening all three valves would result in an air flow rate or a fuel flow rate above a target, is generally idle when air consumption and fuel consumption are low. The system described herein prioritizes use of each. While the first priority is given to brake booster vacuum, replenishment, canister purge, and crankcase ventilation are also important. At high canister load, canister purge is given the second priority, while crankcase ventilation is given the third priority, so that it can take the air or fuel flow that is left behind.Beginning before time t 1 the throttle is open (plot 502), with the engine air flow rate (plot 504) and the engine fuel flow rate (plot 506) each fluctuating by higher first levels. As shown, at this time, the fuel vapor canister load (plot 510) may be less than the first threshold F 1. As such, the CPV may be closed 1 prior to time t. The brake booster vacuum level (plot 508) may be greater than the lower first threshold B 2, but less than the upper second threshold B 1 prior to time t 1. Accordingly, the ASOV may be closed before time t 1. Prior to time t 1 the PCV valve may be open as long as the flow of the PCV gases to the intake manifold does not cause the air flow rate or fuel flow rates to increase above their respective threshold rates.At time t 1 the throttle valve is closed. The throttle may be closed as a result of the vehicle operator depressing the brake pedal. As a result of closing the throttle, at time t 1 both the engine air flow rate and the engine fuel flow rate may decrease. Specifically, as a result of closing the throttle, airflow to the engine may decrease, and the controller may correspondingly decrease the fuel flow rate to correspond to a desired ratio of airflow to fuel flow. Further, at time t 1 the brake booster vacuum level may decrease below the lower first threshold, B 2. The brake booster vacuum level may decrease due to the vehicle operator depressing the brake pedal. Responsive to the brake booster vacuum level decreasing below B 2 at time t 1 the ASOV may be opened. In addition, due to the decrease in the target fuel flow rate at time t 1 the PCV valve may be closed. The PCV valve may thus be closed at time t 1 to reduce the likelihood of exceeding the desired fuel flow rate. At time t 1 the CPV may remain closed.From time t 1 to time t 2 the throttle, CPV, and PCV valve may remain closed. The ASOV may remain open, and fuel vapor canister charge may continue to decrease monotonically. Due to the ASOV remaining open during the time interval from t 1 to t 2 the brake booster vacuum level may increase from below the first threshold B 2 to above the lower first threshold B 2. However, the brake booster negative pressure level does not increase above the upper second threshold value B 1. Due to the throttle remaining at the closed position, the engine air flow rate and the engine fuel flow rate may continue to be lower than their upper first levels before time t 1.Continuing to t 2 the throttle is opened again. Responsive to the throttle opening at t 2 the engine air flow rate and the engine fuel flow rate may increase at similar levels as before time t 1. Due to the brake booster level increasing above the lower first threshold B 2 the ASOV may be closed at time t 2. Further, the PCV valve may be opened at time t 2. At t 2 the CPV may remain closed since the fuel vapor canister charge remains below the first threshold F 1.From time t 2 to time t 3 the throttle and PCV valve may remain open. The ASOV may remain closed and fuel vapor canister charge may continue to decrease. Due to the ASOV remaining closed during the time interval from t 2 to t 3 the brake booster vacuum level may decrease but remain 2 above the lower first threshold B. Due to the throttle remaining at the open position, the engine air flow rate and the engine fuel flow rate may continue to fluctuate around their upper first levels as before time t 1.Proceeding to time t 3 the brake booster vacuum level may decrease below the lower first threshold B 2. In response to the brake booster vacuum level decreasing below B 2 the ASOV may be opened at time t 3. At time t 3 the throttle remains open. Due to the throttle remaining at an open position, the engine air flow rate and the engine fuel flow rate remain at similar levels as before time t 1. Further, at time t 3 the PCV valve may remain open. At time t 3 the CPV may remain closed since the fuel vapor canister charge remains below the first threshold F 1.From time t 3 to time t 4 the throttle, ASOV, and PCV valve may remain open. At this time, the fuel vapor canister charge is not above the first threshold F 1, and as such, the CPV may remain closed. However, as shown, canister load is increasing, e.g., due to a refueling event. It will be appreciated that the increase in canister load is shown only to illustrate system behavior and control when canister load is above a threshold; otherwise, the other plots shown in FIG. 5 illustrate conditions during a drive cycle rather than during engine off conditions where refueling would normally occur.Due to the ASOV remaining open during the time interval from t 3 to t 4 the brake booster vacuum level may increase above the lower first threshold B 2 but remain below the upper second threshold B 1. Due to the throttle remaining at the open position, the engine air flow rate and the engine fuel flow rate may continue to fluctuate around their upper first levels as before time t 1.At time t 4 fuel vapor canister charge may increase above first threshold F 1. Responsive to the fuel vapor canister charge increasing above the first threshold F 1( e.g., due to a refueling event), the CPV may be opened at t 4. At time t 3 the throttle remains open. Due to the throttle remaining at an open position, the engine air flow rate and the engine fuel flow rate remain at similar levels as before time t 1. However, due to increased fuel vapors flowing to the intake manifold as a result of opening the CPV, at t 4 the PCV valve is closed. Thus, at t 4 the PCV valve is closed to reduce the likelihood of exceeding the desired fuel flow rate. At t 4 the ASOV may remain open.From time t 4 to time t 5 the throttle, CPV, and ASOV may remain open. Fuel vapor canister charge may decrease below threshold F 1 in response to CPV remaining open from time t 4 to time t 5. Due to the ASOV remaining open during the time interval from t 4 to t 5 the brake booster vacuum level may continue to increase above the first threshold B 2 but remain below the second threshold B 1. Due to the throttle, ASOV, and CPV remaining at the open position, engine mass airflow rate and engine fuel flow rate may increase 4 from their upper first levels before time t.At time t 5 the PCV valve may be opened again. At time t 5 the fuel vapor canister load may continue to decrease below F 1. The CPV may remain open at time t 5. In response to the CPV remaining open, fuel vapor canister charge may continue to decrease below the first threshold F 1. At time t 5 the throttle remains open. The ASOV may also remain open at time t 5. In response to the ASOV remaining open, at time t 5 the brake booster vacuum level may continue to increase but remain below the first threshold, F 1,. Due to the throttle, CPV, and ASOV remaining at open positions, and due to the PCV valve opening, at time t 5 the engine air flow rate and engine fuel flow rate may continue to increase.From time t 5 to time t 6 the CPV and PCV valve may remain open. Additionally, due to the CPV remaining open, fuel vapor canister load may continue to decrease below F 1. Both the throttle and the ASOV remain open. In response to the ASOV remaining open, the brake booster vacuum level may continue to increase but remain below the first threshold, F 1,. Due to the throttle, CPV, PCV valve, and ASOV remaining at open positions, engine air flow rate and engine fuel flow rate may continue to increase.At time t 6 the brake booster vacuum level may increase above the higher second threshold B 1. Responsive to the brake booster vacuum level increasing above B 1 at time t 6 the ASOV may be closed. Responsive to closing the ASOV, the engine air flow rate may decrease at time t 6. At time t 6 the CPV valve remains open. As such, the vapor canister load may continue to decrease below F 1 due to the CPV remaining open. The throttle valve also remains open. Due to the throttle remaining open and the CPV and PCV valve remaining open, engine fuel flow rate may continue to fluctuate at a level similar to that between time t 5 and time t 6.From time t 6 to time t 7 the CPV and PCV valve may remain open. Additionally, fuel vapor canister load may continue to decrease below F 1 due to the CPV remaining open. The throttle remains open. However, the ASOV remains closed. As a result of the ASOV remaining closed, the brake booster vacuum level decreases below the higher second threshold B 1 but may remain above the lower first threshold B 2. Due to the throttle, CPV, and PCV valve remaining at open positions, engine air flow rate and engine fuel flow rate may continue to fluctuate by levels similar to that at time t 6.At time t 7 the fuel vapor canister charge may decrease to a level similar to that as before time t 1. Responsive to the decrease in fuel vapor canister charge, at time t 7 the CPV valve may be closed. Additionally, closing the CPV may reduce the likelihood of increasing the fuel flow rate beyond the desired fuel flow rate because the PCV valve is open at time t 7. The brake booster vacuum level may continue to fluctuate between the lower first threshold, B 2, and the higher second threshold, B 1. As a result, at time t 7 the ASOV may remain closed. At t 7 the throttle and PCV valve may remain open. In response to the throttle and PCV valve remaining open at time t 7 both engine air flow rate and engine fuel flow rate may fluctuate by similar levels to those between time t 6 and time t 7.Thus, plot 500 shows how the flow of gases from a fuel vapor canister, a brake booster, and a crankcase to an intake manifold may be regulated. Specifically, a period that a PCV valve is open may be increased without causing the engine air flow rate and the engine fuel flow rate to exceed the desired rates. The PCV valve may be closed only under conditions where opening the PCV valve would result in an engine air flow rate and an engine fuel flow rate exceeding their respective desired rates.Thus, a method may include adjusting a positive crankcase ventilation (PCV) valve, a canister purge (CPV) valve, and an aspirator shut-off (ASOV) valve based on engine operating conditions. The three valves may be positioned in three different flow paths to the intake manifold bypassing a throttle in an intake passage of the engine. Specifically, the ASOV may be positioned in a first flow path between a brake booster and the intake manifold, the CPV may be positioned in a second flow path between a fuel vapor purge manifold and the intake manifold, and the PCV valve may be positioned in a third flow path between a crankcase and the intake manifold. Each valve may be an electrically controlled valve that may be controlled by a controller of an engine. Thus, by adjusting the position of the three valves, the method may manage three separate flows to the intake manifold bypassing a throttle in an intake passage. Brake booster flow may be regulated by adjusting the position of the ASOV, canister purge fuel vapors may be regulated by adjusting the position of the CPV, and PCV gases may be regulated by adjusting the position of the PCV valve.In cold operation, it may typically be useless to purge a vapor storage canister because attempting to remove the adherent fuel from a cold canister may be nonproductive. Further, in cold operation, crankcase ventilation tends to have priority because a condition of fuel in oil is most likely to occur in cold operation. Any moisture that may be purged from the crankcase during cold weather is also a gain because the water in the oil draws in the NO that forms the nitric acid and the engine mud. The system described herein recognizes that there is little fuel coming from the canister, thus changing priority to crankcase ventilation. Such operation may be particularly advantageous during operation of the cold engine function (e.g., during operation of the engine at 40° F. and below). Canister purge systems are often shut down when operating cold; however, conventional PCV systems do not utilize the additional air flow rate available to them at this time, and instead only continue to use the lower than optimal crankcase ventilation rates. In contrast, the system described herein has the effect of increasing crankcase ventilation flow during cold weather and / or when the canister purge system is off.In this way, a technical effect of increasing the uniformity and rate of PCV flow from a crankcase to an intake manifold is achieved by adjusting the position of an electrically controlled valve positioned in a flow path between the crankcase and the intake manifold of an engine. By increasing the uniformity and rate of PCV flow to the crankcase, oil separator efficiency may be increased. Additionally, engine power may be increased during cold conditions and / or short periods of engine running. The PCV may be closed if engine airflow and / or engine fuel flow rate exceed their respective desired threshold levels. Further, PCV flow to the intake manifold may be increased without restricting flows from a fuel vapor purge manifold or a brake booster to the intake manifold. Specifically, the PCV valve may be closed if a CPV and / or ASOV are open and opening the PCV valve would cause the engine air flow rate or fuel flow rate to increase above the desired levels.In another illustration, the PCV valve may also be closed if an engine transmission is in neutral, an FEAD load is below a threshold level, and the engine and one or more catalysts in the engine are above a threshold temperature or have operated for more than a threshold period of time. A method for an engine may include, for example, determining a desired engine air flow rate based on engine operating conditions. The method may further include maintaining an electrically controlled positive crankcase ventilation valve open to allow positive crankcase ventilation flow to enter an engine intake downstream of an intake throttle while the desired engine air flow rate is above a threshold, and closing the positive crankcase ventilation valve to block positive crankcase ventilation flow if the desired engine air flow rate falls below the threshold. The threshold may correspond to an engine air flow rate suitable during minimum engine air flow conditions that may occur if the engine transmission is in the neutral position, an FEAD load is below a threshold level, and the engine and one or more catalysts are in the engine above a threshold temperature or have operated for more than a threshold period of time.It should be noted that the example control and estimation routines included herein may be used with various configurations of the engine and / or vehicle system. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, the various acts, operations, and / or functions illustrated may be performed in the order illustrated, performed in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and / or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the engine control system, wherein the described acts are performed by executing the instructions in a system including the various components of the engine hardware in combination with the electronic controller.It is understood that the configurations and routines disclosed herein are exemplary in nature and that these specific embodiments are not to be considered in a limiting sense because numerous variations are possible. The above technique can be applied to, for example, V-6, I-4, I-6, V-12, Boxer-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 characteristics disclosed herein.The following claims particularly point out certain combinations and sub-combinations which are considered novel and not obvious. These claims may refer to "a" element or "a first" element or its equivalent. Such claims should be understood to include inclusion of one or more such elements and neither require nor exclude two or more such elements. Further combinations and sub-combinations of the disclosed features, functions, elements and / or characteristics may be claimed through alteration of the present claims or through presentation of novel claims in this or a related application. Such claims, whether broader than, narrower than, or equal to the scope of the original claims, or different from the scope of the original claims, are also considered to be included within the scope of the present disclosure.Explanation of FiguresFIG. 3 301 Beginning 302 Estimate and / or measure 304 engine operating conditions allowing intentional replenishment of the brake booster (e.g., open the ASOV if brake booster vacuum falls below a threshold) + YES - NO 314 Current engine air flow rate > desired engine air flow rate? 306 Determine the current and desired engine air flow and fuel flow rates 308 Current engine fuel flow rate > desired engine fuel flow rate? 310 Close the CPV and PCV 312 measures, To reduce engine torque 313 load the engine (e.g., increase alternator output) 315 retard spark timing 316 Close CPV and PCV 318 If fuel vapor purge conditions are present? 322 Estimate engine air flow rate and fuel flow rate if CPV is open 320 Close CPV 324 Result opening of CPV to air flow rate>set air flow rate 326 and / or fuel flow rate>setrate? The CPV opens 328 Estimate the contributions to the air flow rate and fuel flow rate that result if the PCV is opened 330 The engine air flow rate > target air flow rate and / or the engine fuel flow rate > target fuel flow rate if the PCV is opened? 334 The PCV closes 332 The PCV opens 335 End FIGS. 4 401 Beginning 402 Estimate and / or measure 404 Intentional replenishment of the brake booster enable 406 Determine the current and target engine air flow and fuel flow rates + YES-NO 408 Current engine air flow rate > target engine air flow rate? 410 The CPV and PCV close 412 actions to reduce engine torque 413 Load the engine (e.g., increase alternator output) 415 Retard spark timing 414 Transmission, engine and catalyst 416 neutral and FEAD load < threshold? The PCV opens 418 The PCV closes 420 If fuel vapor purge conditions are present? 422 Estimate engine air flow rate and fuel flow rate if the CPV is open 424 Results in the opening of the CPV to air flow rate>set air flow rate and / or fuel flow rate>setrate? 426 The PCV closes, then determine the resulting engine air flow and fuel flow rates 428 The CPV opens 430 Results in the opening of the CPV to air flow rate>set air flow rate and / or fuel flow rate>setrate? 432 The CPV closes 434 The CPV opens 435 End

Claims

A method for an engine, comprising: electrically controlling a crankcase ventilation valve based on the desired engine air and fuel flow rates, current engine air flow rate contributions from a brake booster, and current engine air and fuel flow rate contributions from a fuel vapor purge system to selectively enable crankcase ventilation flow into an engine inlet downstream of a throttle if the current engine air flow rate contributions from the brake booster exceed the desired engine air flow rate; electrically controlling the crankcase ventilation valve to inhibit crankcase ventilation flow into the engine inlet; and electrically controlling a canister purge valve to inhibit flow from the fuel vapor purge system into the engine inlet.The method of claim 1, further comprising: if the current contributions to engine air flow rate from the brake booster do not exceed the desired engine air flow rate and if the fuel vapor purge conditions are present, electrically controlling the canister purge valve to enable flow from the fuel vapor purge system into the engine inlet if the estimated engine air and fuel flow rates do not exceed the desired engine air and fuel flow rates, respectively, with fuel vapor purge flow enabled.The method of claim 2, further comprising: if the current contributions to engine air flow rate from the brake booster do not exceed the desired engine air flow rate and if the fuel vapor purge conditions are present, electrically controlling the crankcase ventilation valve to enable crankcase ventilation flow into the engine inlet if the estimated engine air and fuel flow rates do not exceed the desired engine air and fuel flow rates, respectively, at both enabled fuel vapor purge flow and enabled crankcase ventilation flow.The method of claim 2, further comprising: if the current contributions to engine air flow rate from the brake booster do not exceed the desired engine air flow rate and if the fuel vapor purge conditions are not present, electrically controlling the canister purge valve to block flow from the fuel vapor purge system into the engine inlet, and electrically controlling the crankcase ventilation valve to allow crankcase ventilation flow into the engine inlet if the estimated engine air and fuel flow rates do not exceed the desired engine air and fuel flow rates, respectively, when fuel vapor purge flow is blocked and crankcase ventilation flow is allowed.The method of claim 1, further comprising taking actions to reduce engine torque if the current contributions to engine air flow rate from the brake booster exceed the desired engine air flow rate.The method of any of claims 1 to 5, wherein electrically controlling the positive crankcase ventilation valve comprises controlling a solenoid valve integrated with the positive crankcase ventilation valve.A system for a vehicle engine, comprising: a brake booster having a vacuum canister fluidly coupled to an intake of the engine downstream of an intake throttle; a fuel vapor purging system fluidly coupled to the intake selectively downstream of the intake throttle based on a state of a canister purge valve; an engine crankcase fluidly coupled to the intake selectively downstream of the throttle based on a state of a solenoid incorporated into a crankcase ventilation valve; an aspirator having a propulsion inlet coupled to the engine intake upstream of a turbocharger compressor, a propulsion outlet coupled to the engine intake downstream of the throttle, and an intake inlet coupled to the vacuum canister of the brake booster; and an electrically controllable shut-off valve arranged in series with the aspirator.The system of claim 7, wherein the crankcase ventilation valve further comprises a first opening, a second opening less than the first opening, and a third opening less than the second opening.The system of claim 8, wherein the first port is arranged in series with a variable pressure control valve, the series arrangement of the first port and the variable pressure control valve is arranged in parallel with the second port, wherein the third port is arranged in parallel with a check valve, and wherein the parallel arrangement of the first port and the variable pressure control valve to the second port is arranged in series with the parallel arrangement of the third port to the check valve.The system of claim 9, wherein the solenoid is arranged in series with the series arrangement of the parallel arrangement of the third port to the check valve and the parallel arrangement of the first port and the variable pressure control valve to the second port.The system of claim 8, wherein the first opening is arranged in parallel with the second opening, wherein the third opening is arranged in parallel with a check valve, and wherein the parallel arrangement of the first opening to the second opening is arranged in series with the parallel arrangement of the third opening to the check valve.The system of claim 11, wherein the solenoid is arranged in series with the series arrangement of the parallel arrangement of the third port to the check valve and the parallel arrangement of the first port to the second port, and wherein the crankcase ventilation valve does not include a variable pressure control valve.A method for an engine, comprising: if an engine transmission is in the neutral position, the engine and an exhaust catalyst have been warmed up, and a front end accessory drive load is below a threshold, closing an electrically controlled positive crankcase ventilation valve to block positive crankcase ventilation flow into an inlet downstream of a throttle; otherwise, opening the positive crankcase ventilation valve.The method of claim 13, further comprising: when a boost is requested, closing the crankcase ventilation valve if the engine air flow rate exceeds a desired engine air flow rate during boost of the crankcase ventilation valve open brake booster.The method of claim 14, further comprising: when boost and fuel vapor purge are requested, retarding fuel vapor purge by maintaining a canister purge valve in a closed position if the engine air flow rate exceeds the desired engine air flow rate during boost with the canister purge valve open and crankcase ventilation valve closed.The method of claim 15, further comprising: opening the crankcase ventilation valve during simultaneous boost and fuel vapor purge if the engine air flow rate does not exceed the desired engine air flow rate during simultaneous boost and fuel vapor purge with the crankcase ventilation valve open.The method of claim 16, further comprising opening an electrically controlled isolation valve disposed in series with an aspirator during boosting, the aspirator having a propulsion inlet coupled to the inlet upstream of a turbocharger compressor, a propulsion outlet coupled to the inlet downstream of the throttle, and an intake inlet coupled to a vacuum reservoir of the brake booster.The method of claim 16 or 17, further comprising closing the crankcase ventilation valve during simultaneous boost and fuel vapor purge if an engine fuel flow rate exceeds a desired engine fuel flow rate during simultaneous boost and fuel vapor purge with the crankcase ventilation valve open.

Images