ME-SFI anti-knock control, function - GF07.61-P-4030SM
ENGINE 113.986
ENGINE 113.987
ENGINE 113.988
ENGINE 113.989
The task of the anti-knock control (AKC) is to ensure 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 antiknock control function is integrated in the ME-SFI [ME] control unit (N3/10).
Input signals:
- Knock identification → Knock sensor(A16/1, A16/2)
- Engine speed → crankshaft position sensor (L5)
- Ignition circuit identification → Crankshaft position sensor and camshaft Hall sensor (B6/1)
- Engine temperature → coolant temperature sensor (B11/4)
- Air mass → hot film MAF sensor(B2/5)
- Engine load → Accelerator pedal sensor(B37)
- Pre-setting (programming) → STAR DIAGNOSIS
Output signals:
- Cylinder specific ignition angle correction on the calculated map value of the ME control unit.
- Ignition angle emergency mode if knock sensor fault is detected
The anti-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 retardation is achieved.
If knocking-free combustion exists, the retardation is reduced in stages after a few ignitions (depending on the engine speed) until the normal performance map value is achieved or knocking once again occurs.
If the anti-knock control specifies retardation of the ignition angle for a lengthy period, the engine control system reduces the engine power output as a protection of the engine.
Faults if knocking detected
If no signals are received from the knock sensor, the ignition angle of all cylinders is retarded by as much as 15° crank angle for safety reasons, depending on engine speed and temperature. The anti-knock control and its adaptation are deactivated and a fault is stored in the fault memory.
Adaptation of anti-knock control
The adaptation of the anti-knock control is active as of 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 calculating the individual ignition angles, the saved adaptation values are taken into consideration, so that the optimum ignition angle can be determined immediately for each cylinder.
In the event of abrupt acceleration, no values are stored for approx. 2 seconds in order to avoid incorrect adaptation values.
A default setting for the RON correction can be programmed using the STAR DIAGNOSIS.
The ignition angle corrections of the overheating or knocking protection and the anti-knock control are added depending on the performance map.
| Crankshaft position sensor component description | L5 | GF07.04-P-6010SM |
| Camshaft Hall sensor component description | B6/1 | GF07.04-P-6020SM |
| Knock sensor, component description | A16/1, A16/2 | GF07.04-P-6030SM |
| Coolant temperature sensor component description | B11/4 | GF07.04-P-6040SM |
| Hot film MAF sensor component description | B2/5 | GF07.07-P-6000SM |
| ME-SFI [ME] control unit component description | N3/10 | GF07.61-P-6000SM |
| Component description of ignition coil | T1/1-T1/8 | GF15.10-P-2100SM |
| Accelerator pedal sensor, component description | B37 | GF30.20-P-2010SM |