Patent ID: 6408616
Filing Date: 2002-06-25
Classification: F01N,G01M,Y02A,Y02T

Abstract:
A method of on-board vehicle monitoring the performance of a catalyst treating the exhaust stream of a diesel engine, comprising a sequence of the following steps:detecting a predetermined engine operating condition; determining the catalyst inlet temperature; introducing reductant from a secondary fuel supply into the exhaust stream after combustion of fuel by said engine in order to maintain a substantially constant concentration of hydrocarbon in the exhaust stream over a predetermined interval of time; calculating a theoretical exotherm based on said substantially constant hydrocarbon concentration; determining the catalyst outlet temperature; calculating the actual exotherm based on the difference between the catalyst input temperature prior to introduction of said reductant and the catalyst output temperature at the end of said predetermined time interval; calculating a current hydrocarbon conversion value from said actual and theoretical exotherms; comparing the hydrocarbon conversion value to a value indicative of a target threshold emittance level; and providing an indication when said target threshold emittance level is exceeded.