RPM Control, Function - GF07.10-P-1008MRD
Engine 274.9 in model 213, 238
up to model year 2021
Function requirements, general
- Engine runs
The ME-SFI [ME] control unit (N3/10) detects the engine running via the evaluation of the crankshaft Hall sensor signals (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 drivetrain and the vehicle. For RPM control, the ME-SFI [ME] control unit reads in the signals of the following components:
- Crankshaft Hall sensor
- Throttle valve actuator (M16/6)
- Actual value potentiometer 1 (M16/6r1)
- Actual value potentiometer 2 (M16/6r2),
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 range (transmission 725)
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 regulates the engine speed via the following measures:
- Adjusting the opening angle of the throttle valve
- Adjusting the injection duration of the fuel injection system
- Advanced or retarding the ignition angle
The engine responds more quickly to the ignition angle setting than to the throttle valve setting.
The ME-SFI [ME] control unit actuates the following components for this purpose:
- Throttle valve actuator
- Throttle valve actuator motor (M16/6m1)
- 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)
- Ignition system
- Cylinder 1 ignition coil (T1/1)
- Cylinder 2 ignition coil (T1/2)
- Cylinder 3 ignition coil (T1/3)
- Cylinder 4 ignition coil (T1/4)
RPM limitation
Transmission 716
To prevent damage to the transmission, the maximum engine speed when the vehicle is stationary is limited to approx. 4000 RPM.
Transmission 725
In selector lever position "N" or "P" (no power transmission), the maximum engine speed is limited to approx 4200 RPM to protect the torque converter against excessively high static internal pressure. In order to protect the engine from inadmissible engine speeds during driving mode, the maximum engine speed is limited to about 6000 RPM.
Driving operation is defined via the wheel speeds.
In the case of a defective throttle valve actuator motor of the throttle valve actuator, the maximum engine speed in idle is limited to approx. 1400 RPM and during vehicle operation to approx. 1800 RPM.
Maximum vehicle speed limit
Once the maximum design speed is reached, the ME-SFI [ME] control unit reduces the opening angle of the throttle valve and the injection duration. The engine torque is thus reduced and the speed is limited.
Idle speed control
The idle speed is regulated depending on the operating conditions and 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 throttle valve (B28/7)
The ME-SFI [ME] control unit also evaluates the on-board electrical system utilization and the air conditioning system requests. The front SAM control unit (N10/6) sends information on the on-board electrical system utilization via the interior CAN (CAN B), electronic ignition lock control unit, suspension FlexRay, powertrain control unit and drive CAN to the ME-SFI [ME] control unit. The climate control unit (N22/1) transmits speed increase requests via the interior CAN, electronic ignition lock control unit, suspension FlexRay, powertrain control unit and drive CAN to the ME-SFI [ME] control unit.
The ME-SFI [ME] control unit regulates the idle speed under the following operating conditions and engine loads:
- Warm-up
- Engaging drive range "D" or "R" (transmission 725)
- Actuating the clutch pedal (transmission 716)
- Undervoltage in the on-board electrical system
- Purging
Additional function requirements for starting the warm-up phase:
- Coolant temperature less than 40°C
- Gear range "N" or "P" engaged
The ME-SFI [ME] control unit increases the idle speed for approx. 20 s to between 1100 and 1300 RPM. The idle speed is subsequently increased for a coolant temperature below 70°C for approx. 50 s by 50 to 100 RPM.
Engaging drive range "D" or "R" (transmission 725)
When gear range "D" or "R" is selected, the idle speed is set to a lower value to reduce the tendency of the vehicle to creep forward.
Actuating the clutch pedal (transmission 716)
When operating the clutch pedal, the idling speed is stabilized. The clutch pedal sensor (B53/1) detects the clutch pedal position. The powertrain control unit directly reads in the clutch pedal sensor and transmits the clutch pedal status via the drive CAN to the ME-SFI [ME] control unit.
Undervoltage in the on-board electrical system
An undervoltage is detected by the ME-SFI [ME] control unit via circuit 30. The idle speed is then, with engaged drive range "D" or "R", increased by approx. 100 RPM until the ignition is switched off.
Purging
The idle speed control prevents any change in the engine speed due to purging.
Warm-up
In the warm-up phase, the idle speed is regulated depending on the coolant temperature in order to bring the catalytic converter more quickly to operating temperature after engine start.
The basic setting of the idle speed can be read out and modified via the diagnostic tester.
| Electrical function schematic for RPM control | PE07.10-P-2708-97DBD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 274.9 in model 213 (except 213.050/053/153), 238 up to model year 2021 | GF07.70-P-9998MRD | |
| Engine 274.9 in model 213.050/053/153 up to model year 2021 | GF07.70-P-9998MRP |