Abstract: A system and method is provided for controlling a lean-burn engine whose exhaust gas is directed through an exhaust treatment system which includes an emission control device that alternately stores and releases a selected constituent of the exhaust gas, such as NOx, based on engine operating conditions, and a downstream NOx sensor. The system estimates the concentration of NOx flowing into the device based on engine operating conditions while determining a value for the concentration of NOx flowing out of the device based upon the output signal generated by NOx sensor. A device purge event is scheduled when the device efficiency, calculated based on the NOx concentrations flowing into and out of the device, falls below a predetermined minimum efficiency value. The length of a purge event is determined as a function of an accumulated measure based on the difference between the NOx concentrations into and out of the device.

Abstract: A method and system for controlling the operation of a lean-burn engine whose exhaust gas is directed through an emission control device and a downstream reductant-concentration sensor, wherein a stored value for the device's instantaneous capacity to store a selected exhaust gas constituent, such as NOx, is periodically adaptively updated when the sensor's output signal falls outside a predetermined range during a device purge event. A device purge event is scheduled when an accumulated measure of instantaneous feedgas NOx concentration during lean engine operation exceeds the stored NOx-storage capacity value. The purge event is discontinued when the sensor's output signal exceeds the upper limit of the predetermined range, or when a determined value representing a cumulative amount of excess fuel supplied to the engine during the purge event exceeds a threshold value calculated based upon previous values for stored NOx and stored oxygen.

Abstract: A system and method is provided for controlling a lean-burn engine whose exhaust gas is directed through an exhaust treatment system which includes an emission control device that alternately stores and releases a selected constituent of the exhaust gas, such as NOx, based on engine operating conditions, and a downstream NOx sensor. The system estimates the concentration of NOx flowing into the device based on engine operating conditions while determining a value for the concentration of NOx flowing out of the device based upon the output signal generated by NOx sensor. A device purge event is scheduled when the device efficiency, calculated based on the NOx concentrations flowing into and out of the device, falls below a predetermined minimum efficiency value. The length of a purge event is determined as a function of an accumulated measure based on the difference between the NOx concentrations into and out of the device.

Abstract: A method and system for controlling the operation of a lean-burn engine whose exhaust gas is directed through an emission control device and a downstream reductant-concentration sensor, wherein a stored value for the device's instantaneous capacity to store a selected exhaust gas constituent, such as NOx, is periodically adaptively updated when the sensor's output signal falls outside a predetermined range during a device purge event. A device purge event is scheduled when an accumulated measure of instantaneous feedgas NOx concentration during lean engine operation exceeds the stored NOx-storage capacity value. The purge event is discontinued when the sensor's output signal exceeds the upper limit of the predetermined range, or when a determined value representing a cumulative amount of excess fuel supplied to the engine during the purge event exceeds a threshold value calculated based upon previous values for stored NOx and stored oxygen.