Knock Control, Function - GF07.10-P-1015MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Function requirements, general
- Engine runs
Knock sensor system
Knock control has the task for different fuel grades and for all operating conditions to ensure operation without uncontrolled combustion (knocking) of the engine. If the sensor system detects knocking combustion, the ME-SFI [ME] control unit (N3/10) adjusts the ignition of the affected cylinder in the "retarded" direction.
The ME-SFI [ME] control unit controls the knock control dependent on the signals of the following sensors:
- Knock sensor 1 (A16/1)
- Knock sensor 2 (A16/2)
- Knock sensor 3 (A16/3)
- Knock sensor 4 (A16/4)
- Left intake camshaft Hall sensor (B6/4)
- Right intake camshaft Hall sensor (B6/5)
- Left exhaust camshaft Hall sensor (B6/6)
- Right exhaust camshaft Hall sensor (B6/7)
- Coolant temperature sensor (B11/4)
- Left charge air temperature sensor (B17/14)
- Right charge air temperature sensor (B17/15)
- Pressure sensor downstream of left throttle valve (B28/22)
- Pressure sensor downstream of right throttle valve (B28/23)
- Accelerator pedal sensor (B37)
- Crankshaft Hall sensor (B70)
If a knock sensor fails, the ignition angles of all cylinders are adjusted by up to 12° in the "retarded" direction for safety reasons. The knock control is blocked and a fault is stored in the fault memory.
The requirements of the torque coordination function are also taken into account.
The research octane number (RON) can be changed using the diagnostic tester. The ME-SFI [ME] control unit adapts the knock control accordingly.
Ignition angle setting
Knock control is enabled under the following operating conditions:
- Coolant temperature above 30°C
- Engine load above 34 %
The ME-SFI [ME] control unit evaluates all incoming information and calculates the cylinder-specific ignition angle corrections.
If knocking combustion is detected at a cylinder, the ME-SFI [ME] control unit adjusts the ignition angle at this cylinder by approx. 3° in the "retarded" direction as of the next ignition. If further knocking combustion is then detected, the ME-SFI [ME] control unit adjusts the ignition angle by an additional 3° in the "retarded" direction. The ignition angle can be adjusted by a maximum of 15° in the "retarded" direction. When the combustion is then free of knocking, the ME-SFI [ME] control unit gradually reduces the retarding (steps of approx. 0.75°) until the normal performance map value has been reached or knocking starts again.
The ME-SFI [ME] control unit actuates the following components for the ignition angle setting:
- Cylinder 1+2 ignition coil (T4)
- Cylinder 1 ignition coil (T4t1)
- Cylinder 2 ignition coil (T4t2)
- Cylinder 3+4 ignition coil (T4/1)
- Cylinder 3 ignition coil (T4/1t3)
- Cylinder 4 ignition coil (T4/1t4)
- Cylinder 5+6 ignition coil (T4/2)
- Cylinder 5 ignition coil (T4/2t5)
- Cylinder 6 ignition coil (T4/2t6)
- Cylinder 7+8 ignition coil (T4/3)
- Cylinder 7 ignition coil (T4/3t7)
- Cylinder 8 ignition coil (T4/3t8)
Adaptation of knock control
Adaptation of the knock control becomes active starting from a coolant temperature of about 70°C. The ignition angle corrections required due to combustion knocking are stored continuously in a cylinder-specific way, together with the respective operating state of the engine (engine load and engine RPM). If knocking combustion starts again, the stored adaptation values are taken into account so that the optimal ignition angle can be set immediately for each cylinder.
| Electrical function schematic for knock control | Engine 177.9 in model 205, 253 | PE07.10-P-2715-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE07.10-P-2715-97DBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 177.9 in model 205, 253 | GF07.70-P-9998MNA | |
| Engine 177.9 in model 213 up to model year 2021 | GF07.70-P-9998MNE |