Ionization current measurement: Notes
Trionic T8 does not have a conventional knock sensor and instead uses the spark plugs as sensors for ionization current measurement.
A voltage of 120V is continuously applied across the spark plugs. As the pressure and temperature are very high in conjunction with combustion, the gases in the combustion chamber will be electrically conductive so that electric current can flow across the spark plug gap without causing a spark.
The degree of ionization (current) is reflected in the conditions in the combustion chamber. By analyzing the ionization current, ECM can determine whether combustion is normal or misfiring and whether there is knocking.
The ignition coils of the respective cylinders generate an ionization voltage, measure the ionization current and send the results to CDM for initial processing of the ionization signal from the respective ignition coil.
CDM generates a knock signal from the ionization information from the four cylinders and the signal is used by ECM to determine whether the engine is knocking. Once the spark has ignited, ECM will "listen" to the knock signal of each cylinder for a specific number of crankshaft degrees, a so-called window.