The interdependency between the maximal pressure and ion current in a spark-ignition engine

An experimental investigation on the interdependency between the maximal pressure and ion current in a spark-ignition engine was conducted in this work. Eight ion current sensors were located centrally symmetric in a gasket between the cylinder and its head. The measurements of the ion current and the start timing, peak timing and end timing of the ion current were compared and the optimized interdependency between the maximal pressure and characteristic parameter of ion current was investigated. Experimental results show that the peak timing and the end timing of the ion current depend strongly on the start timing of the ion current for each ion sensor. The interdependency between the maximal pressure and start timing detected from the sensors near the intake port is better than that of the exhaust port. Furthermore, interdependency between the maximal pressure and average start timing from sensors 3 to 7 were found to give the best performance regardless the engine test conditions. The maximum pressure and average start timings were found to vary inversely with increasing intake pressure, ignition timing and excess air fuel ratio.