Knock Control

Knock control prevents knocking. It retards the ignition timing of the affected cylinder(s) (cylinder-selective) only as far as necessary and only if there is an actual risk of knocking. In this way, the ignition angle characteristic map can be adapted to the optimum consumption values (without having to take the knock limit into consideration). A safety distance is no longer necessary. The knock control system carries out all knock-related corrections to the ignition timing and enables perfect operation also with regular grade fuel (minimum RON 91).

The knock control provides:

• Protection against damage resulting from engine knock (also under unfavorable conditions)
• Lower consumption and higher torque over the entire upper load range (corresponding to the fuel quality used).
• High efficiency due to optimized use of the fuel quality and consideration of the relevant engine status

Self-diagnosis of the knock control system includes the following checks:

• Check for disrupted signal, e.g. break in wiring or plug-in connection defective
• Self-test of evaluation circuit
• Check of the noise level picked up by the knock sensor for the engine

The knock control system is switched off if a fault is found during the course of one of these checks. The emergency program adopts the task of controlling the ignition timing. At the same time, the relevant fault is entered in the DME fault memory. The emergency program ensures damage-free operation as from minimum RON 91. It depends on the engine load, speed and engine temperature.