GF07.10-P-1015D Knock Control, Function

GF07.10-P-1015D Knock Control, Function
- up to model year 08

Component Identification:

The task of knock control is to ensure the knock-free operation of the engine with different fuels and in all operating conditions (from idling speed up to maximum engine speed).
For this purpose, if uncontrolled combustion (knocking) occurs, the ignition angle at the relevant cylinder or cylinders is retarded. The knock control is integrated in the ME-SFI [ME] control unit.

Input signals:
^ Knock identification->knock sensor
^ Engine speed->Crankshaft position sensor
^ Ignition circuit detection->Crankshaft position sensor and camshaft Hall sensor
^ Engine temperature->Coolant temperature sensor
^ Air mass->Pressure sensor and hot film mass air flow sensor
^ Intake air temperature->Intake air temperature sensor
^ Engine load->Accelerator pedal sensor
^ Presetting (programming)->STAR DIAGNOSIS

Output signals:
^ Ignition angle correction for specific cylinder (to the map value calculated by the ME-SFI [ME] control unit)
^ Emergency mode ignition angle if knock sensor fault is detected

The knock control is active from engine start. If knocking is detected at a cylinder, the electronic mapped ignition angle of this cylinder is retarded from the next ignition. If knocking continues to be detected, the ignition angle continues to be retarded in stages (depending on the engine speed) until maximum adjustment is achieved.

If knocking-free combustion exists, the retardation is reduced in stages after a few ignitions (depending on engine speed) until the normal performance map value is achieved or knocking once again occurs.

If knock control specifies an ignition angle adjustment over a longer period, the ME-SFI [ME] control unit performs a power reduction to protect the engine.

Adaptation of knock control
The adaptation of the knock control is active from a coolant temperature of approx. 50 °C. Any corrections required to the ignition angle because of knocking combustion are constantly detected for the specific cylinder and stored together with the relevant operating state of the engine (engine load/speed range).

When determining the individual ignition angles, the stored adaptation values are taken into account, so that the optimal ignition angle can be calculated immediately for each cylinder.
During abrupt acceleration, no values are stored for about 2 seconds in order to avoid any incorrect adaptation values.

Failure of the knock sensor signal
If the knock sensor signal is missing, for reasons of safety, the ignition angle for all cylinders (dependent on engine speed and engine temperature) is adjusted delayed by up to 15° crankshaft angle. Knock control and the adaptation are deactivated and a fault is stored in the fault memory.

A default setting for the RON correction can be programmed using the STAR DIAGNOSIS.

The ignition angle corrections of coolant temperature, charge air temperature and knock control are added up according to performance mapping.