Detection of engine abnormal combustion with ion current method

To obtain the information about combustion in cylinder, and diagnose the abnormal combustion, abnormal combustion in a spark-ignition engine is experimentally investigated with ion current method. Eight ion current sensors are located symmetrically in the gasket. The ion current signals generating during normal combustion, knock and misfire are collected, and a diagnostic criterion for knock and misfire is established by analyzing the ion current signals. The results show that when knock occurs, the peak of ion current detected by the fourth ion current sensor exceeds 1 μA, and the ion current detected by seventh ion current sensor is advanced to the top dead center (TDC); when misfire occurs, the ion currents detected by the fifth and sixth ion current sensor are very week (less than 0.2 μA), and the appearance of the two ion currents are postponed to 30°-40° CA ATDC.