Ion Current Sensing for Spark Ignition Engines

This paper describes an ion current measurement system with a new, modified inductive ignition system and evaluates the detection quality for misfire and knock detection.

The System uses an ignition circuit with adjustable spark duration limitation. The measurement circuit is located at the low tension side of the secondary ignition coil.

Due to the fact that a lot of influencing factors on misfire detection have been investigated, the estimation of the signal-to-noise-ratio is possible as well as the detection of critical operation points.

Results of a closed-loop knock control with ion current are presented and are compared with the structure borne noise method.