Abstract: Methods and systems for adjusting fuel injector operation according to changes in fuel pressure during inter-injection periods are described. The inter-injection period may be before and after fuel is injected to an engine. The methods and systems described herein may be suitable for direct and port fuel injectors.

Abstract: Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include, during a cold start condition, operating an engine with a first number of cylinders unfired and a remaining number of cylinders fired during an engine cycle, opening an intake valve of an unfired cylinder of the first number of cylinders during an expansion stroke of the unfired cylinder, and opening an exhaust valve of the unfired cylinder during a compression stroke of the unfired cylinder. In this way, the unfired cylinders may provide the secondary air to the exhaust system during a stroke that increases mixing of the secondary air with burned exhaust gas from fired cylinders, thus increasing exotherm production in the exhaust system to increase a temperature of the catalyst.

Abstract: Methods and systems are provided for balancing fuel delivery amongst all engine fuel injectors. In one example, a method may include selectively adjusting an injection timing of one or more fuel injectors of a plurality of fuel injectors to increase an inter-injection period between two consecutive fuel injections in response to a request to balance amounts of fuel injected by the plurality of fuel injectors.

Abstract: Methods and systems for adjusting fuel injector operation according to changes in fuel pressure during inter-injection periods are described. The inter-injection period may be before and after fuel is injected to an engine. The methods and systems described herein may be suitable for direct and port fuel injectors.

Abstract: Systems and methods for improving accuracy of an amount of fuel injected to an engine are disclosed. In one example, a maximum fuel injector holding current value is adjusted from a higher value to a lower value within a predetermined amount of time of an end of fuel injection. By adjusting the maximum fuel injector holding current value, it may be possible to reduce variation in an amount of fuel that is injected via the fuel injector.

Abstract: Systems and methods for improving accuracy of an amount of fuel injected to an engine are disclosed. In one example, a maximum fuel injector holding current value is adjusted from a higher value to a lower value within a predetermined amount of time of an end of fuel injection. By adjusting the maximum fuel injector holding current value, it may be possible to reduce variation in an amount of fuel that is injected via the fuel injector.

Abstract: Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include operating an engine in a thermactor mode responsive to a cold start condition, the thermactor mode including skipping a first number of engine cylinders and producing torque via a remaining number of the engine cylinders, and differently adjusting a cylinder valve of at least one of the first number of the engine cylinders relative to the remaining number of the engine cylinders while operating in the thermactor mode. In this way, exotherms may be generated by the secondary air reacting with fuel in exhaust gas, thus increasing a temperature of the catalyst.

Abstract: Methods and systems are disclosed for operating an engine that includes a knock control system that may determine contributions of individual noise sources to an engine background noise level. The contributions of the individual noise sources may be the basis for establishing the presence or absence of knock in one or more engine cylinders.

Abstract: Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include, during a cold start condition, operating an engine with a number of cylinders deactivated and a remaining number of cylinders active, and adjusting a first air charge within a deactivated cylinder of the number of cylinders relative to relative to a second air charge within an active cylinder of the remaining number of cylinders. In this way, an amount of secondary air provided to the exhaust system of the engine may be more robustly controlled, thus decreasing cooling of the exhaust system during the cold start condition that may otherwise occur due to excess secondary air.

Abstract: Methods and systems are provided for providing secondary air to an exhaust system during catalyst warm-up. In one example, a method may include, responsive to a cold start of an engine: operating the engine with a number of unfired cylinders and a remaining number of fired cylinders each engine cycle, and adjusting exhaust mixing by adjusting an exhaust valve parameter of at least one unfired cylinder of the number of unfired cylinders. In this way, the unfired cylinders may provide the secondary air as well as increased mixing of the secondary air with burned exhaust gas from fired cylinders, thus increasing exotherm production in the exhaust system to increase a temperature of the catalyst.

Abstract: Methods and systems are provided for transferring hot, compressed gases from one cylinder to another cylinder while fuel injection in both cylinders is deactivated. In one example, a method may include during a fuel shut-off event, opening a first pre-chamber injector of the first cylinder undergoing late compression or early expansion and opening a second pre-chamber injector of the second cylinder undergoing a late expansion and/or exhaust stroke or undergoing an intake stroke to allow a hot, compressed gas from the first cylinder to transfer to the second cylinder through the first and second pre-chamber injectors.

Abstract: Methods and systems are provided for balancing a plurality of fuel injectors. In one example, a method includes adjusting direct injector parameters in response to a learned direct injector fueling error. The pulse-width supplied to the direct injectors is adjusted to balance cylinder fueling.

Abstract: Methods and systems are provided for balancing fuel delivery amongst all engine fuel injectors.

Abstract: Methods and systems are provided for balancing injector fueling. In one example, a method includes learning portions of a transfer function shape by firing a plurality of injectors at PWs of a set of PWs following a reference injection.

Abstract: Methods and systems are provided for balancing a plurality of fuel injectors. In one example, a method includes determining a fuel injector error shape and applying a fueling correction to all injectors based on the fuel injector error shape.

Abstract: Methods and systems are provided for balancing a plurality of fuel injectors via a diagnostic. In one example, a method may include adjusting a fuel injection pattern to increase an occurrence of a fuel injection being preceded by a same-cylinder bank fuel injection. The method may further include skipping fuel injections resulting in the fuel injection being preceded by an opposite-cylinder bank fuel injection.

Abstract: Methods and systems are provided for reducing emissions during an engine cold start. In one example, a method may include, during emission control device heating, initiating combustion in a cylinder via a spark plug directly coupled to the cylinder and providing secondary air via a turbulent jet ignition system. In this way, an amount of hydrocarbons in feedgas provided to the emission control device prior to the emission control device reaching its light-off temperature may be reduced.

Abstract: Methods and systems for operating an engine that includes adjustable poppet valve timing and an exhaust gas recirculation valve are described. In one example, the exhaust gas recirculation valve is opened and the timing of the poppet valves is retarded so that an amount of fresh air that is pumped by the engine to an after treatment device may be reduced.

Abstract: Systems and methods for improving accuracy of an amount of fuel injected to an engine are disclosed. In one example, holding current of a fuel injector is adjusted to follow a fixed period and timing of a fuel injector off command is adjusted according to attributes of fuel injector holding current so that a fuel injector may provide a requested fuel amount. The fuel injector off command may be adjusted according to an amount of holding current that is expected to be flowing through the fuel injector at a time when the fuel injector is commanded off.

Abstract: Systems and methods for improving accuracy of an amount of fuel injected to an engine are disclosed. In one example, timing of a fuel injector off command is adjusted according to attributes of fuel injector holding current so that a fuel injector may provide a requested fuel amount. The fuel injector off command may be adjusted according to an amount of holding current that is expected to be flowing through the fuel injector at a time when the fuel injector is commanded off.