Monitoring method for NOx storage catalytic convertors

摘要

The method involves having a sensor positioned downstream of the convertor monitoring the exhaust gases. The exhaust gas is influenced so that there is an increase in components which have a reducing effect, and the time delay from the commencement of the influence to a change in the sensor reading is monitored as a measure of the storage capability of the catalytic convertor. The sensor is preferably an oxygen sensor or may also be a hydrocarbon sensor, and the exhaust gas is influenced by either changing the exhaust gas mixture from lean to rich or by adding a reducing agent. Preferably the system has an exhaust gas sensor positioned upstream of the catalytic convertor which can detect the commencement of the influence on the catalytic convertor, so that a delay can be determined by comparing the readings from the two sensors.