Abstract: Methods and systems are provided for enabling engine dilution control. One or more engine diluents are combined to provide a desired engine dilution, the various diluents selected based on their respective combustion stability limits. A ratio of the various diluents used is further adjusted based on engine operating limitations.

Abstract: Methods and systems are provided for adjusting a throttle based on an intake oxygen sensor output. In one example, a method may include adjusting a position of a throttle based on a dilution threshold and a total aircharge dilution level, the total dilution aircharge level based on an output of an intake oxygen sensor. Additionally, spark timing may be adjusted based on the total aircharge dilution level.

Abstract: Methods and systems are provided for adjusting a reference voltage for an intake manifold oxygen sensor based on ingestion of hydrocarbons from a fuel system canister and/or an engine crankcase. During conditions when purge or crankcase ventilation hydrocarbons are ingested in the intake aircharge, the intake oxygen sensor is transitioned from operating at a lower reference voltage to a higher reference voltage where the effects of the ingested hydrocarbons on the sensor output are nullified. An EGR dilution of the intake aircharge is estimated based on the output of the sensor at the higher reference voltage while an amount of hydrocarbons ingested is estimated based on a difference between sensor outputs at the higher and lower reference voltages.

Abstract: Methods and systems are provided for improving combustion stability, in particular during transient operations such as tip-out to lower load conditions, when EGR is being purged. Until a desired LP-EGR rate is achieved, fuel may be delivered as a split injection with at least an intake stroke injection and a compression stroke injection. Subsequently, single fuel injection may be resumed.

Abstract: Methods and systems are provided for improving engine knock tolerance, in particular when rapidly ramping in LP-EGR from low levels of EGR. Until a desired LP-EGR rate is achieved, fuel may be delivered as a split injection with at least an intake stroke injection and a compression stroke injection to compensate for the transport delay in EGR filling the intake system. Subsequently, single fuel injection may be resumed.

Abstract: Methods and systems are provided for using compressor recirculation flow via a venturi to enhance low pressure EGR flow. The opening of a compressor recirculation valve can be adjusted based on EGR flow demand to recirculate cooled compressed air through a venturi while generating vacuum for drawing EGR. The approach allows for concurrent EGR control and surge control.

Abstract: Methods and systems are provided for using compressor recirculation flow via a venturi to enhance low pressure EGR flow. The opening of a compressor recirculation valve can be adjusted based on EGR flow demand to recirculate cooled compressed air through a venturi while generating vacuum for drawing EGR. The approach allows for concurrent EGR control and surge control.

Abstract: A method and system for providing a suitable engine torque response during a transient condition is presented. In one example, when a desired inlet manifold pressure is greater than a throttle inlet pressure of a first throttle, a second throttle positioned upstream from the first throttle is opened to increase the throttle inlet pressure. The method may provide an appropriate torque response while minimizing impact on fuel economy.

Abstract: A method may comprise automatically de-choking an engine and cranking the engine in response to an engine flood event, wherein automatically de-choking the engine comprises automatically cutting fuel to the engine while opening an air intake throttle.

Abstract: An engine is provided that includes an exhaust gas recirculation (EGR) conduit in fluidic communication with a first exhaust valve in a cylinder and an intake system, an exhaust conduit in fluidic communication with a second exhaust valve in the cylinder and an emission control device. During operation with the first valve active and the second valve deactivated, a fixed EGR level can be provided. However, during operation with the first valve deactivated and the second valve active, increased engine output can be achieved with reduced EGR without requiring additional exhaust throttling or switching valves.

Abstract: A method for controlling combustion in a cylinder of a turbocharged engine in which intake air is reserved upstream of the cylinder. The method comprises decreasing an internal EGR rate in the cylinder during a tip-out condition if the temperature of the intake air is above a threshold, and increasing the internal EGR rate in the cylinder during a tip-out condition if the temperature of the intake air is below the threshold.

Abstract: Methods and systems are provided for improving fuel usage while addressing knock by adjusting the use of spark retard and direct injection of a knock control fluid based on engine operating conditions and the composition of the injected fluid. One or more engine parameters, such as EGR, VCT, boost, throttle position, and CMCV, are coordinated with the direct injection to reduce torque and EGR transients.

Abstract: Methods and systems are provided for improving engine knock control by accounting for a drop in charge cooling efficiency of a knock control fluid at higher temperatures. In response to the prediction of an elevated temperature of a knock control fluid at a time of release from a direct injector, a pulse width of the injection is adjusted. Any knock relief deficits are compensated for using alternate engine adjustments, such as boost or spark timing adjustments.

Abstract: Methods for operating a flexible fuel engine with a fuel reformer which reforms a fuel into a gaseous fuel reformate are provided. Operating parameters of the fuel reformer and delivery of reformate to the engine are adjusted based on an alcohol content of the fuel.

Abstract: Methods and systems are provided for enabling engine dilution control. One or more engine diluents are combined to provide a desired engine dilution, the various diluents selected based on their respective combustion stability limits. A ratio of the various diluents used is further adjusted based on engine operating limitations.

Abstract: Systems and methods for a twin turbocharged engine with a single exhaust gas recirculation (EGR) system are disclosed. In one example approach a system is provided comprising a first turbocharger in a first intake passage with a low-pressure EGR system fluidically coupling exhaust exiting the first turbocharger to intake air entering the first turbocharger, and a second turbocharger in a second intake passage without a low-pressure EGR system fluidically coupling exhaust exiting the second turbocharger to intake air entering the second turbocharger.

Abstract: Methods and systems are provided for improving fuel usage while addressing knock by adjusting the use of spark retard and direct injection of a knock control fluid based on engine operating conditions and the composition of the injected fluid. One or more engine parameters, such as EGR, VCT, boost, throttle position, and CMCV, are coordinated with the direct injection to reduce torque and EGR transients.

Abstract: Various systems and methods are described for controlling combustion stability in an engine driving a transmission. One example method comprises limiting airflow to the engine in response to a spark timing retarded beyond a spark retard threshold, the limiting airflow to the engine reducing engine torque output and compensating for the reduction in engine torque output by adjusting a transmission operating parameter.

Abstract: Methods and systems are provided for improving fuel usage while addressing knock by adjusting the use of spark retard and direct injection of a knock control fluid based on engine operating conditions and the composition of the injected fluid. One or more engine parameters, such as EGR, VCT, boost, throttle position, and CMCV, are coordinated with the direct injection to reduce torque and EGR transients.

Abstract: Various systems and methods are described for controlling combustion stability in an engine driving a transmission. One example method comprises limiting airflow to the engine in response to a spark timing retarded beyond a spark retard threshold, the limiting airflow to the engine reducing engine torque output and compensating for the reduction in engine torque output by adjusting a transmission operating parameter.