GF07.61-P-3007MAS ME-SFI Maximum Engine Speed Limitation, Function

GF07.61-P-3007MAS ME-SFI Maximum Engine Speed Limitation, Function
- as of model year 09


Function requirements maximum engine speed limitation, general points
^ Circuit 87M ON (engine control ON)
^ Engine running

Maximum engine speed limitation, general points
The maximum engine speed is limited to protect the engine and the drivetrain. On the signal from the crankshaft Hall sensor (B70), the ME-SFI control unit (N3/10) detects engine speed. The ME-SFI control unit adjusts the maximum engine speed according to the following sensors and signals:
- Crankshaft Hall sensor, engine speed
- Front and rear throttle valve actuator (M16/3, M16/4), throttle valve positions
- ESP control unit (N47-5), vehicle speed over the chassis CAN (CAN E)
- Electric controller unit (VGS) (Y3/8), selector lever position over the drive train CAN (CAN C)

The ME-SFI control unit limits the maximum engine speed through the following measures:
- Reducing the opening angle of the front and rear throttle valves
- Shifting the ignition angles of the ignition coils (T1) to "retard"
- Switching off the fuel injection valves (Y62)

Maximum engine speed limitation, function sequence
The ME-SFI control unit controls the maximum engine speed in the following conditions:
^ Torque converter protection function sequence
^ Driving mode function sequence
^ Function sequence fault in front and rear throttle valve actuators
^ Missing variant coding function sequence

Torque converter protection function sequence
In order to protect the torque converter in selector lever positions P or N (no power flow) from excessive static internal pressure, the maximum engine speed is limited to approx. 4200 rpm. The ME-SFI control unit receives the information about the current selector lever position from the electric controller unit (VGS) over the drive train CAN.

Driving mode function sequence
In order to protect the engine from inadmissible engine speeds during driving mode, the maximum engine speed is limited to about 7000 rpm.
The ME-SFI control unit detects the driving mode on the "vehicle speed" CAN signal from the ESP control unit (over the chassis CAN).

Function sequence fault in front and rear throttle valve actuators
If a throttle valve actuator is defective, both throttle valve actuators are switched off and maximum engine speed is limited to about 1400 rpm at idle and about 1800 rpm in driving mode.

Missing variant coding function sequence
If no variant coding exists, maximum engine speed is limited to 2400 rpm.