Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be determined via two filters that are constructed in parallel. Output of the two filters may be the basis for determining the presence or absence of engine knock.

Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are deactivated to determine the presence or absence of engine knock. Additionally, engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are reactivated such that the engine operates with all cylinder combusting so that the possibility of indicating knock when knock is not present may be avoided.

Abstract: Methods and systems are provided for maintaining a compression ratio of an engine via a brake and while disabling an electric current applied to an actuator of the associated variable compression ratio mechanism. A braking force applied via the brake on a compression ratio control shaft is varied before and during a compression ratio transition to move the control shaft at a desired velocity. Brake torque application is coordinated with motor torque from a VCR actuator and engine torque applied on the control shaft to enable a smooth CR transition.

Abstract: Methods and systems are provided for maintaining a compression ratio of an engine via a brake and while disabling an electric current applied to an actuator of the associated variable compression ratio mechanism. A braking force applied via the brake on a compression ratio control shaft is varied before and during a compression ratio transition to move the control shaft at a desired velocity. Brake torque application is coordinated with motor torque from a VCR actuator and engine torque applied on the control shaft to enable a smooth CR transition.

Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be determined via two filters that are constructed in parallel. Output of the two filters may be the basis for determining the presence or absence of engine knock.

Abstract: Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are deactivated to determine the presence or absence of engine knock. Additionally, engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are reactivated such that the engine operates with all cylinder combusting so that the possibility of indicating knock when knock is not present may be avoided.

Abstract: Systems and methods for operating an internal combustion engine based on output of an intake manifold pressure sensor and output of an in cylinder pressure sensor are described. The systems and methods provide a way of determining cylinder air charge so that a fuel injector has sufficient time to provide a desired amount of fuel to a cylinder during a cycle of the cylinder.

Abstract: Systems and methods for operating an internal combustion engine based on output of an intake manifold pressure sensor and output of an in cylinder pressure sensor are described. The systems and methods provide a way of determining cylinder air charge so that a fuel injector has sufficient time to provide a desired amount of fuel to a cylinder during a cycle of the cylinder.

Abstract: Methods and systems are provided for reducing or avoiding a torque bump resulting from unintended combustion in a deactivated cylinder of a variable displacement engine. In one example, a method includes reducing or avoiding a torque bump associated with an engine of a vehicle while one or more cylinders of the engine are deactivated by reducing a torque output of the engine by an amount substantially equivalent to a torque increase provided to the engine via the unintended combustion event. In this way, undesired torque bumps may be avoided when operating in VDE mode, which may improve customer satisfaction, and which may enable improved fuel economy and engine efficiency.

Abstract: Methods and systems are provided for reducing or avoiding a torque bump resulting from unintended combustion in a deactivated cylinder of a variable displacement engine. In one example, a method includes reducing or avoiding a torque bump associated with an engine of a vehicle while one or more cylinders of the engine are deactivated by reducing a torque output of the engine by an amount substantially equivalent to a torque increase provided to the engine via the unintended combustion event. In this way, undesired torque bumps may be avoided when operating in VDE mode, which may improve customer satisfaction, and which may enable improved fuel economy and engine efficiency.

Abstract: Methods and systems are provided for reducing fouling of a spark plug in a cylinder of a variable displacement engine configured to propel a vehicle. In one example, a method includes in response to deactivation of a cylinder or cylinders of the engine, providing spark to the cylinder or cylinders at a predefined position of a piston or pistons coupled to the cylinder or cylinders, respectively, where the predefined position comprises the piston or pistons being within a threshold of a bottom dead center position. In this way, spark plug fouling may be reduced or eliminated during conditions of cylinder deactivation.

Abstract: A method for selecting compression ratio of a variable compression ratio internal combustion engine when such engine is operating under an idle condition is disclosed. The compression ratio is selected to avoid engine knock, an undesirable phenomenon which is more likely at higher temperatures, higher compression ratios, lower engine speeds, and higher engine torques. The selected compression ratio is based on one or more of engine torque required to drive engine accessories, engine coolant temperature, engine air temperature, and transmission status (neutral idle or drive idle). A normalized airflow parameter is computed or found in a lookup table based on engine coolant temperature and engine air temperature. When actual normalized airflow (that which provides necessary engine torque to drive engine accessories and overcome engine friction) exceeds normalized airflow parameter exceeds, a higher compression ratio is selected.

Abstract: A method for selecting compression ratio of a variable compression ratio internal combustion engine when such engine is operating under an idle condition is disclosed. The compression ratio is selected to avoid engine knock, an undesirable phenomenon which is more likely at higher temperatures, higher compression ratios, lower engine speeds, and higher engine torques. The selected compression ratio is based on one or more of engine torque required to drive engine accessories, engine coolant temperature, engine air temperature, and transmission status (neutral idle or drive idle). A normalized airflow parameter is computed or found in a lookup table based on engine coolant temperature and engine air temperature. When actual normalized airflow (that which provides necessary engine torque to drive engine accessories and overcome engine friction) exceeds normalized airflow parameter exceeds, a higher compression ratio is selected.