RPM Control, Function - GF07.10-P-1008MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Function requirements, general
- Engine runs
The ME-SFI [ME] control unit (N3/10) detects the engine running by evaluating the signals of the crankshaft Hall sensor (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.
RPM control, general
The RPM control stabilizes the engine speed in neutral and limits the engine speed to protect the engine, the drive train and the vehicle. For RPM limitation, the ME-SFI [ME] control unit reads in signals from the following components:
- Crankshaft Hall sensor
- Left throttle valve actuator (M16/60)
- Actual value potentiometer 1, left (M16/60r1)
- Actual value potentiometer 2, left (M16/60r2)
- Right throttle valve actuator (M16/61)
- Actual value potentiometer 1, right (M16/61r1)
- Actual value potentiometer 2, right (M16/61r2)
The ME-SFI [ME] control unit also evaluates the following signals:
- Wheel speeds
The Electronic Stability Program control unit (N30/4) transmits the wheel speeds via the chassis FlexRay (Flex E), the powertrain control unit (N127) and the drive train CAN (CAN C1) to the ME-SFI [ME] control unit.
- Drive position
The fully integrated transmission control unit (Y3/8n4) sends information on the gear range engaged via the drive train CAN to the ME-SFI [ME] control unit.
The ME-SFI [ME] control unit limits the engine RPM by taking the following measures:
- Adjusting the opening angle of the throttle valves
- Adaptation of the injection period for the fuel injection system
- Advanced or retarding the ignition angle
The ME-SFI [ME] control unit actuates the following components for this purpose:
- Left throttle valve actuator
- Left throttle valve actuator motor (M16/60m1)
- Right throttle valve actuator
- Right throttle valve actuator motor (M16/61m1)
- Fuel injection system
- Cylinder 1 fuel injector (Y76/1)
- Cylinder 2 fuel injector (Y76/2)
- Cylinder 3 fuel injector (Y76/3)
- Cylinder 4 fuel injector (Y76/4)
- Cylinder 5 fuel injector (Y76/5)
- Cylinder 6 fuel injector (Y76/6)
- Cylinder 7 fuel injector (Y76/7)
- Cylinder 8 fuel injector (Y76/8)
- Ignition system
- 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)
- Cylinder 1+2 ignition coil (T4)
RPM limitation
In order to protect the engine from the consequences of impermissibly high engine revs, the maximum engine speed is limited to approx. 6800 RPM.
Driving operation is defined via the wheel speeds.
In the event of defective throttle valve actuator motors, the maximum engine speed is limited in idle to approx. 1400 RPM and in driving mode to approx. 1800 RPM.
Maximum vehicle speed limit
Upon reaching maximum speed, the opening angle of the throttle valve and the injection period of the fuel injectors are reduced by the ME-SFI [ME] control unit. The engine torque is thereby reduced and the speed is limited.
Idle speed control
The idle speed control regulates the idle speed depending on the operating conditions and the engine load.
For idle speed control, the ME-SFI [ME] control unit reads in the signals of the following sensors:
- Coolant temperature sensor (B11/4)
- Pressure sensor downstream of left throttle valve (B28/22)
- Pressure sensor downstream of right throttle valve (B28/23)
The ME-SFI [ME] control unit also evaluates the on-board electrical system voltage and the requests of the air conditioning system. The front SAM control unit (N10/6) sends information about the on-board electrical system voltage via interior CAN (CAN B), electronic ignition lock control unit, chassis FlexRay, powertrain control unit and drive train CAN to the ME-SFI [ME] control unit. The climate control unit (N22/1) transmits the requests for RPM increase via the interior CAN (CAN B), the electronic ignition lock control unit (N73), the chassis FlexRay, the powertrain control unit and the drive train CAN to the ME-SFI [ME] control unit.
The ME-SFI [ME] control unit controls the idle speed by:
- Adjusting the opening angle of the throttle valves
- Adaptation of the injection duration of the fuel injectors
- Ignition angle setting (up to 36° crank angle towards retarded or 20° crank angle towards advanced)
Intervention by setting the ignition angle reacts more quickly than intervention by adjusting the throttle valves.
The ME-SFI [ME] control unit regulates the idle speed under the following operating conditions and engine loads:
- Warming-up phase
- Undervoltage in the on-board electrical system
- Purging
Warming-up phase
In the warm-up phase, the ME-SFI [ME] control unit controls the idle speed dependent on the coolant temperature, in order to bring the catalytic converters up to operating temperature more quickly after the engine has been started.
Additional function requirements in the warm-up phase:
- Coolant temperature less than 40°C
- Gear range "N" or "P" engaged
The ME-SFI [ME] control unit raises the idle speed for about 20 s to about 1100 to 1300 RPM. The idle speed is then increased by about 50 to 100 RPM at a coolant temperature of less than 70°C for approx. 50 s by the ME-SFI [ME] control unit.
Undervoltage in the on-board electrical system
If the ME-SFI [ME] control unit detects an undervoltage through circuit 30, the idle speed is raised by about 100 RPM when gear range "D" or "R" is engaged, until the ignition is switched off.
Purging
The idle speed control prevents any change in the engine speed due to purging.
The basic setting of the idle speed can be read out and modified using the diagnostic tester.
| Electrical function schematic for RPM control | Engine 177.9 in model 205, 253 | PE07.10-P-2708-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE07.10-P-2708-97DBG | ||
| 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 |