Ion-Gap Sense in Misfire Detection, Knock and Engine Control

The combustion of fuel inside an engine cylinder produces ions. By applying a small DC voltage across the spark gap after ignition, ion current is produced. The ion current wave form contains combustion information and is called Ion-Gap sense. Ion-Gap sense is described and can be used to detect misfire, control knock, obtain cam phasing, and detect pre-ignition. In the future, it will provide air/fuel information.

Test results on nine different engine types are summarized for misfire detection. Knock testing is reviewed for eight engines. Engine tests associated with engine control techniques have been included.