Technical Paper
Development of New On-Board Diagnostic (OBD) Methods for Three-Way Catalysts Applicable to Various Driving: Examples of Application to a CNG Vehicle
2012-09-10
2012-01-1676
Cars are highly dependent on catalyst-based aftertreatment technology today due to tighter exhaust emission regulations. Since catalyst performance degradation over long-term operation is a major concern, onboard diagnostic (OBD) technology is becoming increasingly important. This paper presents new three-way catalyst diagnostic methods that can be applied under various driving conditions. Their effectiveness in meeting OBD requirements was evaluated when applied to CNG vehicles, which will be introduced in Europe. In the conventional catalyst diagnostic routine, large variation in the air-fuel ratio is generated when performing diagnosis, and catalyst degradation is determined by evaluating the signal response of an O2 sensor installed downstream of the catalyst. However, this method can only be used in conditions close to steady-state operation. In real-world driving, where a variety of operating conditions are possible, the rate of catalyst monitoring may decrease.