Abstract
To prevent harmful emission, misfire detection is required by regulations. In conventional method, misfire detection was obstructed in high engine speed. To clarify the reason, the torsional vibration of the crankshaft was analyzed. The results of the analysis suggest that the torsional vibration increased in high engine speed and that the misfire effect was hidden in the torsional vibration. We found that the torsional vibration became the most serious when the frequency of the torsional vibration coincides with the frequency of the ignition. To cancel the tosional vibration, we changed the width of the misfire detection window to 120degree (720degree/cylinder number). By this change, misfire detection was enabled at 6000rpm. To realize the misfire detection which is robust to engine acceleration and deceleration, we discussed the constraints for the FIR filter coefficients and designed the detection filter. Misfire detection based on this filter was evaluated by engine test. The results showed that both every cycle misfire and isolated misfire could detected using same method.
