Methods and systems are provided for a boosted engine having a split exhaust system. In one example, a method comprises directing exhaust from a first cylinder group to one or more of a pre-compressor location, a post-compressor location, and an exhaust turbine, and directing exhaust from a second cylinder group to one or more of the pre-compressor location, and the exhaust turbine. Engine efficiency and knock control may be enhanced by directing exhaust gases to different locations based on engine operating conditions.

Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.

Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.

In this invention, an EMF oxygen sensor is subjected to an activation process applying unidirectional voltage between an atmosphere electrode and an exhaust electrode thereof. A control device controlling the oxygen sensor in which a voltage was applied with the atmosphere electrode being positive, additionally applies unidirectional voltage between the electrodes to make the atmosphere electrode positive, for example, when the oxygen sensor was used under an environment in which the air-fuel ratio of the internal combustion engine was rich relative to the theoretical air-fuel ratio. Conversely, a control device controlling the oxygen sensor in which a voltage was applied to make the atmosphere electrode negative, additionally applies unidirectional voltage between the electrodes to make the atmosphere electrode negative, for example, when the oxygen sensor was used under an environment in which the air-fuel ratio was lean relative to the theoretical air-fuel ratio.

In a control device for an internal combustion engine, when a fuel-supply cutoff process ends and fuel injection restarts, an increase ratio based on which a base injection amount is increased is set such that the increase ratio when a duration of the fuel-supply cutoff process is long is higher than the increase ratio when a duration of the fuel-supply cutoff process is short. In addition, the increase ratio is decreased with a lapse of time after fuel injection restarts. Further, a decrease rate that is an amount by which the increase ratio is decreased within a prescribed period of time is set such that the decrease rate in the case where the duration of the fuel-supply cutoff process is long is higher than the decrease rate in the case where the duration of the fuel-supply cutoff process is short.

A variety of methods and arrangements are described for operating an engine in a skip fire manner so that engine requirements, such as exhaust temperature, exhaust flow, torque and NVH, are met.

A variety of methods and arrangements are described for operating an engine in a skip fire manner so that engine requirements, such as exhaust temperature, exhaust flow, torque and NVH, are met.

A method and system for operating a vehicle that includes an integrated starter/generator and a driveline disconnect clutch is described. In one example, the method estimates engine torque as a function of engine temperature during cold engine starts so that if an estimate of engine torque is in error, the integrated starter/generator may still successfully start the engine.

A method and system for operating a vehicle that includes an integrated starter/generator and a driveline disconnect clutch is described. In one example, the method estimates engine torque as a function of engine temperature during cold engine starts so that if an estimate of engine torque is in error, the integrated starter/generator may still successfully start the engine.

A vehicle control device is configured to execute a fuel cut control for stopping fuel supply to an internal combustion engine in response to a deceleration request to a vehicle; disengage a lock-up clutch and open a throttle of the vehicle during execution of fuel cut control; execute motor assist in a case where there is an acceleration request to a vehicle while the lock-up clutch is disengaged and the throttle is opened; and execute a motor torque reduction control for temporarily reducing an output from an electric motor based on a rotation speed of the internal combustion engine and a rotation speed of a main shaft during the execution of the motor assist.