Method and apparatus for maintaining catalyst efficiency of a nox trap

摘要

An engine control computer (20) estimates the cumulative NOx storage in a NOx trap (32) based on engine operating conditions and enters a NOx purge mode of operation when a maximum storage capacity limit, based on trap temperature, is exceeded. The purge mode is terminated when NOx storage level decreases below a minimum storage capacity limit. The rate of NOx dissipation is also based on trap temperature.