Multiple ion current detection by two spark-plugs with fast emission measurements on a 1.6-liter PFI engine during knocking combustion

In this report the results of an experimental study carried out on a Twin Spark 1.6-liter PFI gasoline engine running at different speeds and air load conditions are presented. Engine tests were carried out both in absence and presence of light and heavy knock. Experiments were aimed to test two electronic circuit prototypes implemented for detecting the Ionization Current (IC) by means of spark plug. One of these circuits was able to drive the ignition prior to ionization current measurement (we referred to this circuit as Active Spark Plug, shortened with ASP-IC) through the electrodes of the spark plug housed at the center of the pentroof cylinder head. The other circuit was designed for only ionization detection (we referred to this one as Passive Spark Plug, shortened with (PSP-IC) between the electrodes of a secondary spark plug (M10x1 thread) in side position. In-cylinder pressure was measured through a miniaturized sensor integrated in the secondary spark plug. Engine out emission as total HC, NO, CO and CO2 have been furthermore measured by using fast response gas analyzers (Cambustion). The engine was controlled by a laboratory Electronic Control Unit (EFI Technology). Cycle resolved data are shown for the mentioned and other variables for 27 different operating conditions. Relative air/fuel ratio was calculated based on measured emissions and compared with corresponding lambda measurement obtained with a UEGO sensor.