In the exhaust gas control system, the electronic control unit is configured to execute first air-fuel ratio control for controlling an air-fuel ratio of an air-fuel mixture in a part of cylinders to a lean air-fuel ratio and controlling an air-fuel ratio of an air-fuel mixture in the other part of the cylinders to a rich air-fuel ratio is executed. The electronic control unit is configured to execute second air-fuel ratio control to perform malfunction diagnosis. The electronic control unit is configured to execute second air-fuel ratio control when the execution of the first air-fuel ratio control is interrupted after the temperature of the three-way catalyst becomes equal to or higher than the diagnosis temperature.

A diesel engine system includes a diesel engine, an exhaust line, a particulate filter interposed in the exhaust line and an electronic control unit for controlling fuel injectors associated with cylinders of the engine. When an accumulated particulate mass in said filter reaches a predetermined threshold, a filter regeneration mode is activated, including activating post-injections of fuel by controlling said injectors, to determine a start of an automatic filter regeneration step, which is caused by an increase in temperature of exhaust gases fed to the filter. The temperature increase is sufficient to burn particulate in the filter. The post-injections of fuel are deactivated whenever a critical condition occurs for at least a first period of time, the critical condition being one in which a temperature value upstream of the filter exceeds a first threshold value. In this case, the regeneration mode is resumed following disappearance of the critical condition.

A control system and method utilize an exhaust oxygen (O2) sensor and a controller configured to operate a turbocharged engine in a scavenging mode, and while the operating the engine in the scavenging mode: command a target in-cylinder air/fuel ratio (FA) for achieving a target exhaust gas FA, adjust the measurement of the exhaust O2 sensor based on a scavenging ratio and the target in-cylinder FA to obtain a modified O2 concentration, adjust an exhaust system temperature modeled by a thermal model to obtain a modified exhaust system temperature, and adjust the target in-cylinder FA based on the modified O2 concentration and the modified exhaust system temperature.

Particulate accumulation in a particulate filter in the exhaust line of an engine is calculated by an electronic engine control unit. When the estimated accumulated particulate mass exceeds a predetermined threshold, an automatic regeneration step of the filter is activated. An actual instantaneous burned particulate mass is calculated as a function of values indicative of the state of the filter. A temporary correction factor representing an error between a theoretical value and the actual value is calculated. The temporary correction factor is stored in a second map of correction factors, based on the engine operating conditions. During an accumulation step, the estimated instantaneous particulate mass, calculated according to the first map based on the operating conditions of the engine, is multiplied by a correction factor calculated according to the second map based on the operating conditions of the engine.

In an exhaust gas control system for an internal combustion engine operable at a lean air-fuel ratio, after a request to stop the internal combustion engine has been issued, the internal combustion engine is operated at a stoichiometric air-fuel ratio or lower until an air-fuel ratio in an SCR catalyst becomes lower than or equal to the stoichiometric air-fuel ratio, and then supply of fuel to the internal combustion engine is stopped.

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.

To provide a controller and a control method for an internal combustion engine capable of estimating exhaust gas temperature at any estimation positions of the exhaust pipe with good accuracy by taking into consideration a temperature drop of exhaust gas by heat radiation of the exhaust pipe. A controller for an internal combustion engine is provided with an outlet gas temperature calculator that calculates an outlet gas temperature which is a temperature of exhaust gas at an outlet of a combustion chamber, based on the driving condition; a heat radiation amount calculator that calculates a temperature decrease amount of the exhaust gas by heat radiation of an exhaust pipe from the outlet of the combustion chamber to an estimation position; and an exhaust gas temperature estimation calculator that estimate an exhaust gas temperature at the estimation position by subtracting the temperature decrease amount from the outlet gas temperature.

An upstream integrated value is an integrated value of a difference obtained by subtracting an upstream gas temperature at a starting point in time of integration from the upstream gas temperature after starting of the internal combustion engine. A downstream integrated value is an integrated value of a difference obtained by subtracting a downstream gas temperature at the starting point in time of the integration from the downstream gas temperature after the starting of the internal combustion engine. An anomaly diagnosing process obtains an anomaly determination result indicating that the exhaust purification device is in a removed state when a deviation between the upstream integrated value and the downstream integrated value is smaller than a reference level. The determination threshold is higher than a dew point.

In an opposed-piston engine which includes a catalytic aftertreatment device in its exhaust system an exhaust gas condition indicating a catalyst temperature of the aftertreatment device is monitored. When the catalyst temperature is near or below a light-off temperature, a catalyst light-off procedure is executed to elevate the temperature of the catalyst.

A method for preventing overheating of a diesel particulate filter during regeneration when an engine is idling may include using an electric machine to apply a load to the engine and compensating for the increase in applied load by increasing an engine torque set point to reduce the concentration of Oxygen in the exhaust gas flowing to the diesel particulate filter. Increased engine torque may be provided by adjusting air-fuel ratio by enriching an air-fuel mixture supplied to the engine and the diesel particulate filter. The control may be initiated in response to entering an idle mode during regeneration or in response to a measured or estimated temperature of the diesel particular filter exceeding a threshold or limit. Estimated temperature may be predicted using a soot combustion model.