Automatic Engine Start/Stop Function - GF07.10-P-1043MMM
ENGINE 276.8 in MODEL 166.063 as of model year 2016
The "automatic engine start/engine stop function" is divided into scopes involving the engine, the 12 V on-board electrical system and the hybrid system. It is viewed and described from the point of view of the engine management of the internal combustion engine.
Information concerning the "functionality of the energy management ECO start/stop function" subfunction for the 12-V on-board electrical system is documented in the "Energy management function" function description.
Information about the partial functions "automatic engine start function" and "automatic engine stop function" from the point of view of the hybrid system can be found over the function description "driving operation function".
The ME-SFI [ME] control unit (N3/10) continuously performs system diagnosis and assesses the function requirements for the "automatic engine start/engine stop function". All of the systems participating in the function continuously check their status and transmit this via the Control Area Network (CAN) network to the ME-SFI [ME] control unit.
If the function requirements are fulfilled, the driver is notified of readiness to operate of the hybrid system from the green "READY" symbol in the instrument cluster (A1).
Further information concerning the required approvals for the "automatic engine start/engine stop function" is described in the following documents:
- Automatic engine stop, function
- Automatic engine start, function
Function requirements for automatic engine start/engine stop function, general
- Engine hood closed
- Hybrid system "READY"
- No Crash event occurred in the driving cycle
- System diagnosis complete and fault-free
Automatic engine start/engine stop function, general
Conventional switching off of the internal combustion engine in request by the driver over the electronic ignition lock control unit (N73) is still possible.
Conventional starting of the internal combustion engine is requested by the driver. The internal combustion engine will only be started however it is necessary from the point if view of system optimization.
The ME-SFI [ME] control unit reads in the following signals for controlling the internal combustion engine:
- Coolant temperature sensor (B11/4), coolant temperature
- Accelerator pedal sensor (B37), accelerator pedal actuation
- Crankshaft Hall sensor (B70), engine rpm
- Fuel system control unit (N118), fuel pressure via the drive train CAN (CAN C)
Automatic engine start/engine stop function, function sequence
The automatic engine start/engine stop consists of the following subfunctions:
- Function sequence for automatic engine stop
- Function sequence for automatic engine start
The automatic engine stop in hybrid vehicles is equivalent to electrical driving.
Additional function requirements for an automatic engine stop
- Hybrid system "READY"
- Internal combustion engine running
- Vehicle speed < 160 km/h
- Transmission oil temperature > 0°C
Function sequence for automatic engine stop
The ME-SFI [ME] control unit makes the request via the drive train CAN to the fully integrated transmission control unit (Y3/8n4) for actuation of the wet clutch in order to disconnect the internal combustion engine from the drive. The fully integrated transmission control unit transmits appropriate feedback over the opened wet clutch to the ME-SFI [ME] control unit.
Further information concerning actuation of the wet clutch is described in the following document:
- Wet clutch, function
The internal combustion engine is switched off by the ME-SFI [ME] control unit if all releases and system conditions of the systems participating in the function are fulfilled.
More precise information about automatic engine stop related to the HD is described in the following document:
- Automatic engine stop, function
Additional function requirements for an automatic engine start
- Hybrid system "READY"
- Internal combustion engine OFF
Function sequence for automatic engine start
An automatic engine start is initiated if the vehicle needs energy for the traction which cannot be delivered purely electrically or changes in system conditions require starting of the internal combustion engine. Start of the internal combustion engine takes place according to the specifications of the aggregate coordinator interface in the ME-SFI [ME] control unit:
- Via the electrical machine (A79/1) (at vehicle standstill), requested via the engine CAN (CAN C1), the powertrain control unit (N127) and the hybrid CAN (CAN L) from the power electronics control unit (N129/1)
or
- Via the starter (M1) (e.g. in electrical operation)
In electrical operation, starting with an opened wet clutch always occurs first over the starter up to a certain rotational speed of the internal combustion engine. The ME-SFI [ME] control unit subsequently requests actuation of the wet clutch via the drive train CAN from the fully integrated transmission control unit in order to connect the internal combustion engine with the transmission.
Further information concerning actuation of the wet clutch is described in the following document:
- Wet clutch, function
After receiving the respective feedback about the closed wet clutch, the ME-SFI [ME] control unit requests actuation of the electrical machine via the engine CAN, the powertrain control unit and the hybrid CAN from the power electronics control unit in order to start the internal combustion engine.
More precise information about automatic engine start related to the HD is described in the following document:
- Automatic engine start, function
The automatic engine start is performed via the electrical machine, preferably when the vehicle is stationary. The internal combustion engine is started over the starter in a vehicle standstill condition if the charge level of the high-voltage battery (A100g1) is not adequate.
The ME-SFI [ME] control unit actuates the following components to start the internal combustion engine:
- Starter
- Ignition coils (T1)
- Fuel injectors (Y76)
- Fuel pump (M3), directly and via the drive train CAN over the FSCU (N118)
Precise information about starting the internal combustion engine with the starter is described in the following document:
- Starting, function
| Electrical function schematic for automatic engine start/engine stop | PE07.10-P-2726-97NBH | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MMM |