Comparison of Misfire Detection Technologies in Spark-ignition Engines for Meeting On-Board Diagnostic Regulation

Misfires in SI engines are one of the major causes for increase in vehicle exhaust emissions beyond the regulatory limit. Misfires have a great potential to destroy catalytic converters due to increased exhaust temperatures caused by unburned fuel from the misfired cylinders. It also leads to decrease in engine efficiency and high fuel consumption. Misfires are majorly caused due to unfavorable spark plug temperatures, low ignition energy, fuel system malfunction, improper air-fuel mixture ratio, flame propagation speed, etc. Monitoring of misfire detection in SI engines is an essential requirement of On-Board Diagnostic (OBD) regulations in many countries. This paper compares the conventional and advanced misfire detection technologies in spark-ignition engines, available and under development for meeting the OBD regulations worldwide. It describes the misfire detection principle. Comparison of the methods is done considering system cost, system accuracy in detecting misfire, ease of implementation and conclusions are drawn.