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The present paper describes the progress design of microcontrolled three-way catalyst efficiency monitoring system [1]. The system is based on a powerful microprocessor and utilizes the moving average value differential signal from a pair of thermocouples installed at the catalyst outlet and inlet sections. This signal is processed in real time using an appropriate statistical algorithm and the corresponding results are compared to experimentally determined limiting values to assess the current state of the catalyst efficiency during driving conditions. The result of this comparison is presented on a LCD display as A, B, or C catalyst condition signal. The advantages and results of this new algorithm version are presented in this paper. The system has already installed at and operates on new and used cars provided that the type of catalyst used has been experimentally tested to provide the necessary limiting values that characterize its relative levels of efficiency.

The present paper introduces a new method of assessing catalyst performance based on inlet-outlet temperature difference measurements. These preliminary experimental results indicate that at idle speed the age and catalytic efficiency affects this temperature difference reducing outlet temperature as the catalyst ages. The reduced efficiency of the catalyst increases also the time required for the equalization of the inlet and outlet temperature. An additional phenomenon present in these experiments is the gradual appearance of nonlinear time delayed effects as catalyst age increases that are reflected in the autocorrelation function of the temperature difference signal. These effects can be used for a catalyst performance assessment using temperature probes instead of the normal exhaust gas chemical analyzers.