ENGINE PERFORMANCE MONITORING BY MEANS OF THE SPARK PLUG

The importance of measuring 'what is going on' inside a spark ignition engine is well recognized. Knocking combustion, cyclic variation, mis firing and plug fouling are some of the processes to be monitored and controlled. In this work, a new system capable of monitoring these pro cesses using the spark plug is described. The technique relies on a ne w design of the spark plug ionization detection circuit incorporated i n the secondary winding of an ignition coil. It avoids the use of high -voltage diodes that are expensive and unreliable. It can be built int o 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 re ported for investigations of knock detection and engine cyclic variati ons in a spark ignition engine.