Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, mode changes between deactivating cylinders is based on an amount of time a valve is deactivated, and the longer the valve is deactivated the sooner cylinder valves may be deactivated. If the amount of time the valve is deactivated is short, the time that valves may be deactivated may be delayed.

Systems and methods for controlling a gasoline urea selective catalytic reductant catalyst are described. In one example, an observer is provided that corrects an estimate of an amount of NH.sub.3 that is stored in a SCR. The amount of NH.sub.3 that is stored in the SCR is a basis for generating additional NH.sub.3 or ceasing generation of NH.sub.3.

Systems and methods for operating an engine with deactivating and non-deactivating valves are presented. In one example, engine volumetric efficiency actuators are adjusted in response to a request to activate engine cylinders so that engine intake manifold pressure is drawn down quickly toward its normal state at the engine's present speed and torque.

This disclosure is intended to suppress a noble metal supported by a three-way catalyst from being deteriorated by oxidation with the execution of fuel cut processing in a suitable manner. A control apparatus for a naturally aspirated gasoline engine is provided with a three-way catalyst, a first throttle valve, a second throttle valve arranged in the intake passage at the downstream side of the first throttle valve, an EGR valve, and a controller. When the controller carries out fuel cut processing and the temperature of the three-way catalyst is equal to or higher than a predetermined temperature, the controller introduces the EGR gas into a cylinder of the gasoline engine as intake air by fully closing the first throttle valve and by opening the EGR valve, and further controls an amount of the EGR gas by adjusting the degree of opening of the second throttle valve.

A vehicle control system for an internal combustion engine having a fuel injection valve for injecting fuel directly into a combustion chamber includes a controller configured to perform a fuel cut-off when a predetermined fuel cut-off condition is met during travel of the vehicle to thereby stop fuel injection from the fuel injection valve. The controller is configured to resume the fuel injection from the fuel injection valve when a predetermined fuel cut-off recovery condition is met during the fuel cut-off. The controller is configured, upon elapse of a predetermined time that is required for a wall temperature of the combustion chamber to rise after resuming the fuel injection from the fuel injection valve, to perform a rich spike that temporarily increases the fuel injection amount from the fuel injection valve.

A control device for an internal combustion engine has a controller configured to control a fuel injection valve arranged to directly inject a fuel into a combustion chamber, and a variable compression ratio mechanism arranged to vary an upper dead center position of a piston, and thereby to vary a compression ratio of the internal combustion engine. The controller is configured to control a fuel cut by which the fuel injection from the fuel injection valve is stopped, when a predetermined fuel cut condition is satisfied during a traveling of a vehicle. The fuel injection from the fuel injection valve is restarted when a predetermined fuel cut recovery condition is satisfied during the fuel cut.

An engine device includes: an engine; and a control device that executes a return rich control that controls the engine so that an air-fuel ratio becomes rich over a predetermined period after the engine returns from the fuel cut. When the engine is intermittently stopped during the execution of the return rich control, the return rich control is executed for a period shorter than the predetermined period after the engine is restarted. Thus, when the engine is intermittently stopped during the execution of the return rich control and the engine is restarted thereafter, it is possible to suppress a total period of the return rich control from becoming long. As a result, it is possible to suppress an increase in the amount of hydrocarbons in the exhaust gas and suppress deterioration of emissions.

A control device for an internal combustion engine of a vehicle has a controller that controls a fuel injection valve of the internal combustion engine arranged to directly inject a fuel into a combustion chamber, and a pressure regulator of the internal combustion engine arranged to vary a pressure of the fuel supplied to the fuel injection valve. The controller performs a fuel cut that stops the fuel injection of the fuel injection valve when a predetermined fuel cut condition is satisfied during a traveling of the vehicle. The controller restarts the fuel injection of the fuel injection valve when a predetermined fuel cut recovery condition is satisfied during the fuel cut.

To keep medium purification efficiency at a high level and prevent deterioration of emission performance. An aspect of the present invention includes: a downstream equivalence ratio calculation unit that calculates a catalyst downstream exhaust gas equivalence ratio by using a catalyst statistical model that receives at least a detection value of an air-fuel ratio sensor on an upstream side of a catalyst and outputs a catalyst downstream exhaust gas equivalence ratio; an oxygen output calculation unit that calculates an output value of an oxygen sensor by using an oxygen sensor statistical model that receives the catalyst downstream exhaust gas equivalence ratio and outputs an output value of the oxygen sensor on the downstream side of the catalyst; a downstream equivalence ratio correction unit that corrects the catalyst downstream exhaust gas equivalence ratio calculated by the downstream equivalence ratio calculation unit based on a calculation result of the oxygen output calculation unit and the detection value of the oxygen sensor; and an air-fuel ratio control unit that controls an air-fuel ratio of an air-fuel mixture of an internal combustion engine based on the corrected catalyst downstream exhaust gas equivalence ratio and air-fuel ratio target value.

A reduction method for a catalytic converter in an exhaust system of an internal combustion engine for reducing the oxygen content in the catalytic converter, in particular after an overrun fuel cutoff mode of the internal combustion engine, the method including first injection of fuel into a first cylinder, the first injection taking place after an ignition point in time of a compression stroke of a first working cycle of the cylinder and including an introduction of the injected fuel from the cylinder into the catalytic converter during an exhaust stroke of the first cylinder.