A system and method for slowing a vehicle. Road conditions around the vehicle are monitored, and determined if those road conditions are hazardous. An engine control unit is informed of the hazardous road conditions and alters the operation of the engine control unit in response to the hazardous road conditions. When an operator of the vehicle desires to slow the vehicle down, an indication is received indicating the intent to slow the vehicle down. The vehicle is then slowed based upon the altered operation of the engine control unit by applying a vacuum to increase a manifold vacuum of the engine.

Engine combustion mode-switching transitions are controlled through a coordination control of an electric machine and a multi-combustion mode engine coupled to each other with a hybrid propulsion system by following predetermined combustion mode-switching strategies and control algorithms.

A method of reducing cold start emissions in a series mode hybrid electric vehicle, including an internal combustion engine with an exhaust duct having a catalyst and a downstream oxygen sensor, an output of the combustion engine being connected to an electric generator with a power output of at least 10 kW that is connected to an electric motor which is coupled to a drive shaft of two or more wheels. The method includes detecting a cold start condition, injecting fuel into the engine such that combustion at a lambda value, λ, is achieved for which λ>1, running the engine at a speed of 1000 rpm or higher, determining if the efficiency of the catalyst reaches a first level, setting λ to about 1 after the predetermined efficiency level of the catalyst has been reached, and reducing the speed to working conditions when the catalyst efficiency reaches a second level.

An MG1 torque at a time of decreasing an engine speed of an engine is made larger when a turbocharging pressure by a turbocharger is higher than when the turbocharging pressure is lower. In this way, even if the losses of pumps of the engine differ due to the remaining turbocharging pressure during a transition of stopping the engine in turbocharging, it is possible to appropriately reduce the engine speed. Therefore, when the engine is being brought to a stop, it is possible to appropriately suppress vibration generated in the vehicle.

When an acceleration request is issued, an electronic control unit for a hybrid vehicle performs control for producing an acceleration feeling of setting a target engine rotation speed to an initial rotation speed (=basic initial value+initial value correction value) which is lower than an optimal-fuel-efficiency rotation speed at which required engine power is able to be most efficiently output and increasing the engine rotation speed from the initial rotation speed to the optimal-fuel-efficiency rotation speed at a rotation speed increase rate (=basic increase rate+increase rate correction value) based on the elapse of time. When the target supercharging pressure is high, the initial value correction value is set to a greater value and the increase rate correction value is set to a greater value than when the target supercharging pressure is low.

Systems and methods for operating a vehicle that includes an engine and an integrated starter/generator are described. In one example, torque generated via the engine is based on a requested driveline torque and a torque of an electric machine when degradation of an engine sensor is present. The torque generated via the engine may be adjusted responsive to a requested engine torque and a feedback engine torque that is based on output of an engine airflow sensor.

A vehicle control device is configured to: execute a fuel cut control for stopping fuel supply to the internal combustion engine in response to a deceleration request to the vehicle; engage the lock-up clutch and open a throttle of the vehicle during the execution of the fuel cut control; close the throttle and execute the motor assist in a case where there is an acceleration request to the vehicle while the lock-up clutch is engaged, the throttle is opened, and the fuel cut control is executed; end the fuel cut control and resume fuel supply to the internal combustion engine when an intake pressure of the internal combustion engine reaches a predetermined startable negative pressure after the throttle is closed; and disengage the lock-up clutch when the fuel supply to the internal combustion engine is resumed.

A variety of methods and arrangements for implementing a start/stop feature in a skip fire engine control system are described. In one aspect, the implementation of the start/stop feature involves automatically turning off an internal combustion engine under selected circumstances during a drive cycle. A determination is made that the engine should be restarted. During the engine startup period, the engine is operated in a skip fire manner such that a desired engine speed is reached.

When a travel mode in which an engine is not used as a drive power source for travel is switched to a travel mode in which the engine is used as a drive power source for travel in response to an acceleration request from a driver, it is determined whether an assist torque which is able to be output from a second rotary machine is sufficient for a required assist torque for compensating for an output shortage of the engine due to a supercharging response delay in a supercharger. When it is determined that the assist torque is not sufficient for the required assist torque, an engine rotation speed is increased to a predetermined target rotation speed by an MG1 torque of a first rotary machine.

A method of reducing cold start emissions in a series mode hybrid electric vehicle, including an internal combustion engine with an exhaust duct having a catalyst and a downstream oxygen sensor, an output of the combustion engine being connected to an electric generator with a power output of at least 10 kW that is connected to an electric motor which is coupled to a drive shaft of two or more wheels. The method includes detecting a cold start condition, injecting fuel into the engine such that combustion at a lambda value, λ, is achieved for which λ>1, running the engine at a speed of 1000 rpm or higher, determining if the efficiency of the catalyst reaches a first level, setting λ to about 1 after the predetermined efficiency level of the catalyst has been reached, and reducing the speed to working conditions when the catalyst efficiency reaches a second level.