Importance

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Abstract

An electronic engine controller monitors the operability of a catalytic converter upon ignition of the engine by sensing the temperature of the exhaust gas entering the converter and of the exhaust gas exiting the converter for a period of time after the engine has been started. The electronic engine controller calculates the rate of heat transfer from the exhaust gas to the catalyst material within the converter. This value is then used to calculate the temperature of the catalyst material. Subsequent rates of heat transfer and subsequent temperatures of the catalyst material are calculated and the rate of change of temperature of the catalyst material is determined for each time step. A ratio is formed from the rate of heat transfer and the rate of change of temperature of the catalyst material. The electronic engine controller determines the ratio of the rate of heat transfer and the rate of change of temperature of the catalyst material for the period of time from engine ignition to catalyst light-off. This period of time, the light-off time, is checked against a predetermined trend in the ratio and a converter inoperative condition is set if the light-off time is greater than the threshold value.

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First Claim