Engine Performance Monitoring by Means of the Spark Plug

Abstract

The importance of measuring ‘what is going on’ inside a spark ignition engine is well recognized. Knocking combustion cyclic variation, misfiring arid plug fouling are some of the processes to be monitored and controlled. In this work, a new system capable of monitoring these processes using the spark plug is described. The technique relies on a new design of the spark plug ionization detection circuit incorporated in the secondary winding of an ignition coil. It avoids the use of high-voltage diodes that are expensive and unreliable. It can be built into one unit with an ignition coil and directly applied to the one coil per plug system. By way of demonstration, the system's operation is reported for investigations of knock detection and engine cyclic variations in a spark ignition engine.