Anti-knock control function - GF15.12-P-4024KE
ENGINE 271.921 in MODEL 203
ENGINE 271.940 in MODEL 203, 209
ENGINE 271.941 in MODEL 211
ENGINE 271.944 in MODEL 171
ENGINE 271.946 in MODEL 203
ENGINE 271.948 in MODEL 203
ENGINE 271.955 in MODEL 209
ENGINE 271.956 in MODEL 211
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 anti-knock control is integrated in the 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 MAF 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 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 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 anti-knock control gives an ignition angle adjustment over a longer period, the ME control unit reduces the power to protect the engine.
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 determining the individual ignition angles, the stored adaptation values are taken into account, so that for the optimal ignition angle can be determined for each cylinder.
In the event of abrupt acceleration, no values are stored for approx. 2 seconds in order to avoid incorrect adaptation values.
Errors in knock identification
In the event of failure of the knock sensor signal, for reasons of safety, the ignition angle for all cylinders (dependent on engine speed and temperature) is retarded by up to 15° crankshaft angle. The anti-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 the coolant temperature, intake/charge air temperature and anti-knock control are added in line with the performance map.
| Crankshaft position sensor, component description | L5 | GF07.04-P-6010KE | |
| Camshaft Hall sensor component description | B6/4, B6/7 | GF07.04-P-6020KE | |
| Knock sensor component description | A16 | GF07.04-P-6030KE | |
| Coolant temperature sensor component description | B11/4 | GF07.04-P-6040KE | |
| Pressure sensor component description | B28 | GF07.04-P-6060KE | |
| Intake air temperature sensor, component description | B17 | GF07.04-P-6070KE | |
| Component description of hot film MAF sensor description | B2/5 | GF07.07-P-6000KE | |
| ME-SFI [ME] control unit, component description | N3/10 | GF07.61-P-6000KE | |
| Component description of ignition coil | T1/1-T1/4 | GF15.10-P-2100KE | |
| Accelerator pedal sensor component description | B37 | GF30.20-P-2010KE |