Ion Current Combustion Monitoring

The ion current combustion monitoring is also used in the MSS60 for knock identification and misfiring identification. In principle, the method of action is identical to the S85 and its MSS65.

The S85 has two ion current monitoring devices, each of which covers a whole cylinder bank. In the S65, the electronic ion current system is integrated into each ignition coil and the ion current monitoring devices are not required.

During ignition, the measurement current is stored in a capacitor integrated in the ignition coil, and after ignition, is available at the spark plug electrode. In the S65, the ion current measurement and evaluation is also performed exclusively by the MSS60.

The functional range of the ion current electronics has been further refined. There is no longer a need for two measurement control lines, and the ignition current and the ion current measurement signal have been combined into a single transmission route (separate in the S85).

For the purposes of smoothing the voltage and electromagnetic compatibility, an "ignition suppression capacitor" is installed in the wiring harness of each cylinder bank (in the S85 this is in the ion current control device). This is electrically connected using terminal 87 and the vehicle earth.

The same spark plugs are used as in the S85 (basic value approx. 60,000 km).