A method and system for controlling an engine operating over a range of operating conditions.

摘要

A method and system for controlling an engine operating over a range of operating conditions, with differing air-fuel mixtures, the engine producing exhaust gas which is directed through an exhaust treatment system which includes an emission control device 34 and a sensor 40 that generates an output signal indicative of the concentration of a selected exhaust gas component in the exhaust gas exiting the emission control device, the method comprising; determining a first value representative of an instantaneous concentration of the selected component within the engine exhaust gas during a lean operating condition, determining a second value representative of the instantaneous concentration of the selected component exiting the emission control device based on the output of the sensor and, selecting an engine operating condition as a function of the first and second values. The first value my be a function of the engine speed and/or the engine load. During a lean operation, the efficiency of the emission control device may be instantaneously determined and the lean operating condition terminated when the efficiency value falls below a threshold value. A de-sulfating operating condition may be performed, and if the efficiency value does not rise after a predetermined number of such operations then a value for device deterioration may be determined.