944 Turbo

The knock sensor, which is bolted on the engine block next to the cylinder head, monitors ignition knocking. With the trigger signal for each individual cylinder, the DME ignition signal and the signal from the knock sensor can recognize in which cylinder there has been uncontrolled combustion (knocking).

With the next ignition pulse from the DME control unit for this cylinder, the ignition signal will be delayed in the knock control unit and fed back, so that the ignition for the pertinent cylinder is retarded 3 degrees. If knocking occurs again, the ignition of the cylinder will be retarded again by 3 degrees. If this stops the engine knocking, the ignition will be advanced to the correct value in steps.

If knock pulses continue, the charging air pressure will then be taken back in steps of (.03-.05 degrees).