Patent ID: 6546718
Filing Date: 2003-04-15
Classification: F01N,F02D

Abstract:
A method of controlling an engine that operates at a plurality of engine operating conditions characterized by combustion of air-fuel mixtures having different air-fuel ratios to generate engine exhaust gas, wherein the exhaust gas is directed through an exhaust treatment system including an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected exhaust gas constituent when the exhaust gas is rich, and a sensor operative to generate an output signal representative of a concentration of the selected constituent in the exhaust gas exiting the device, the method comprising:determining a first value representative of an instantaneous concentration of the selected constituent in the engine exhaust gas when operating in the lean operating condition; determining a second value representative of the instantaneous concentration of the selected constituent exiting the device based on the output signal generated by the sensor; and selecting an engine operating condition as a function of the first and second values, wherein selecting includes calculating, during the lean operating condition, an efficiency value based on the first and second values; and terminating the lean operating condition when the efficiency value falls below a minimum efficiency value.