Abstract: Methods and systems are provided for combusting an air-fuel mixture in a pre-chamber of a cylinder during an exhaust stroke of the cylinder responsive to fouling of the pre-chamber. In one example, a method may include injecting air into the pre-chamber during the exhaust stroke, injecting fuel into the pre-chamber during the exhaust stroke, and actuating a pre-chamber spark plug in order to combust the air-fuel mixture during the exhaust stroke. In this way, a temperature of the pre-chamber may be increased, which may decrease a soot load of one of a pre-chamber air-injector, a pre-chamber fuel injector, and the pre-chamber spark plug.

Abstract: Methods and systems are provided for combusting an air-fuel mixture in a pre-chamber of a cylinder during an exhaust stroke of the cylinder responsive to fouling of the pre-chamber. In one example, a method may include injecting air into the pre-chamber during the exhaust stroke, injecting fuel into the pre-chamber during the exhaust stroke, and actuating a pre-chamber spark plug in order to combust the air-fuel mixture during the exhaust stroke. In this way, a temperature of the pre-chamber may be increased, which may decrease a soot load of one of a pre-chamber air-injector, a pre-chamber fuel injector, and the pre-chamber spark plug.

Abstract: Methods and systems are provided for tracking a fuel puddle mass in the intake port of a deactivated engine cylinder. The difference in fuel evaporation rate in the deactivated cylinder intake is accounted for by applying distinct time constant and gain values to a transient fuel compensation model. A fuel vapor content is clipped once the intake vapor pressure in the intake port of the deactivated cylinder reaches a saturation pressure limit.

Abstract: Methods and systems are provided for improving engine torque response during transient condition. In one example, a method may include adjusting intake throttle and exhaust waste-gate valve based on the operator torque demand and concurrently, scheduling exhaust gas recirculation (EGR) and variable cam timing (VCT) based on a predicted torque shortfall ratio. The scheduling of EGR and VCT is independent of the actual position of intake throttle and exhaust waste-gate valve.

Abstract: Methods and systems are provided for improving calibration of a variable compression ratio engine. Cylinder-to-cylinder compression ratio variations are detected and accounted for by comparing cylinder fuel flow and IMEP at each compression ratio setting. Dilution parameters including EGR and VCT schedule are also calibrated to account for the cylinder-to-cylinder compression ratio variations.

Abstract: Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, the engine system may be installed in a hybrid vehicle, and, in response to a request to restart the engine while the vehicle is being propelled via motor torque only, the engine may be rotated unfueled via the motor torque at less than cranking speed while at least partially opening a valve disposed in a passage coupled between the first exhaust manifold and the intake passage. In another example, in response to the request to restart the engine, all exhaust valves of a second set of exhaust valves coupled to the second exhaust manifold may be deactivated.

Abstract: Methods and systems are provided for improving fuel efficiency and tailpipe emissions of a variable displacement engine. Fueling is initially disabled in cylinders selected to be deactivated while pumping air through the cylinders to an exhaust after-treatment catalyst, and then valve operation is disabled. On reactivation, if manifold vacuum is dissipated, one bank of cylinders are reactivated while the other bank is operated in DFSO with valves pumping air until manifold vacuum is reestablished.

Abstract: Methods and systems are provided for improving fuel efficiency and tailpipe emissions of a variable displacement engine. Fueling is initially disabled in cylinders selected to be deactivated while pumping air through the cylinders to an exhaust after-treatment catalyst, and then valve operation is disabled. On reactivation, if manifold vacuum is dissipated, one bank of cylinders are reactivated while the other bank is operated in DFSO with valves pumping air until manifold vacuum is reestablished.

Abstract: Methods and systems are provided for adjusting an amount of water injected upstream of a group of cylinders based on a determined maldistribution of water among cylinders during a water injection event. In one example, a method may include injecting a first amount of water upstream of a first group of cylinders and a different, second amount of water upstream of a second group of cylinders based on operating conditions of the respective cylinder groups. Further, the method may include adjusting water injection and engine operating parameters in response the evaporated and/or condensed portion of water.

Abstract: Methods and systems are described for controlling fuel injection in an engine equipped with a dual injector system including a port injector and a direct injector. A ratio of port injected fuel to direct injected fuel is adjusted based at least on intake valve temperature. The proportion of fuel port injected into a cylinder is increased as the intake valve temperature for the given cylinder increases to improve fuel vaporization in the intake port.

Abstract: Methods and systems are provided for coordinating water usage with spark usage based on the effect on an engine torque ratio. Water is injected based on torque ratio at a current spark timing relative to torque ratio at borderline knock to improve the impact of the water injection on the engine performance. Manifold water injection and direct water injected are coordinated based on intake manifold humidity.

Abstract: Methods and systems are provided for tracking a fuel puddle mass in the intake port of a deactivated engine cylinder. The difference in fuel evaporation rate in the deactivated cylinder intake is accounted for by applying distinct time constant and gain values to a transient fuel compensation model. A fuel vapor content is clipped once the intake vapor pressure in the intake port of the deactivated cylinder reaches a saturation pressure limit.

Abstract: Systems and methods for activating and deactivating cylinders of an engine that may activate and deactivate one cylinder independent of other cylinders are presented. In one example, an engine cylinder firing fraction and a remainder value that is based on the engine cylinder firing fraction are a basis for activating and deactivating engine cylinders. The systems and methods also provide for transitioning between different cylinder firing fractions.

Abstract: Methods and systems are provided for tracking a fuel puddle mass in the intake port of a deactivated engine cylinder. The difference in fuel evaporation rate in the deactivated cylinder intake is accounted for by applying distinct time constant and gain values to a transient fuel compensation model. A fuel vapor content is clipped once the intake vapor pressure in the intake port of the deactivated cylinder reaches a saturation pressure limit.

Abstract: Methods and systems are provided for using compression heating to heat a cylinder piston before cylinder combustion is resumed. Cylinder heating is achieved using combinations of slow unfueled engine rotation where the engine cylinders are heated via compression stroke heating, and slow compressor rotation where the cylinders are heated via compression heating. One or more intake or exhaust heaters may be concurrently operated to expedite cylinder heating.

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 improving calibration of a variable compression ratio engine. Cylinder-to-cylinder compression ratio variations are detected and accounted for by comparing cylinder fuel flow and IMEP at each compression ratio setting. Dilution parameters including EGR and VCT schedule are also calibrated to account for the cylinder-to-cylinder compression ratio variations.

Abstract: Methods and systems are provided for improving calibration of a variable compression ratio engine. Cylinder-to-cylinder compression ratio variations are detected and accounted for by comparing cylinder fuel flow and IMEP at each compression ratio setting. Dilution parameters including EGR and VCT schedule are also calibrated to account for the cylinder-to-cylinder compression ratio variations.

Abstract: Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, the engine system may be installed in a hybrid vehicle, and, in response to a request to restart the engine while the vehicle is being propelled via motor torque only, the engine may be rotated unfueled via the motor torque at less than cranking speed while at least partially opening a valve disposed in a passage coupled between the first exhaust manifold and the intake passage. In another example, in response to the request to restart the engine, all exhaust valves of a second set of exhaust valves coupled to the second exhaust manifold may be deactivated.

Abstract: Methods and systems are provided for improving calibration of a variable compression ratio engine. Cylinder-to-cylinder compression ratio variations are detected and accounted for by comparing cylinder fuel flow and IMEP at each compression ratio setting. Dilution parameters including EGR and VCT schedule are also calibrated to account for the cylinder-to-cylinder compression ratio variations.