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Engine Timing Start-Stop Function - GF07.10-P-1041MRH

Engine 274.9 in model 205.047/053/054/147/247/253 

Engine 274.9 in model 253.354/954 

IMPORTANT The ME-SFI [ME] control unit (N3/10) continuously performs a system diagnosis and assesses the function requirements for the start/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 drive system from the "READY" symbol in the instrument cluster (A1).

Function requirements for engine management, start/stop function, general points 

Engine management start-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 front SAM control unit (N10/6) also checks the function of all associated components and sends the status via the interior CAN (CAN B), electronic ignition lock control unit, chassis FlexRay (Flex E), powertrain control unit (N127) and drive train CAN (CAN C1) to the ME-SFI [ME] control unit.

The ME-SFI [ME] control unit reads in the following signals to control the combustion engine for the start/stop function:

Engine management Start-Stop function, function sequence 

The ECO start/stop function consists of the following partial functions:

IMPORTANT The automatic engine stop in hybrid vehicles is equivalent to electrical driving.

Additional function requirements for an automatic engine stop 

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.

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.

Additional function requirements for an automatic engine start 

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:

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.

After receiving the respective feedback over the closed wet clutch, the ME-SFI [ME] control unit requests actuation of the electrical machine via the hybrid CAN from the power electronics control unit in order to start the internal combustion engine.

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 assembly parts to start the internal combustion engine:

Function sequence for forced engine start 

The forced engine start sub-function is available as a protection function. Here the internal combustion engine is force started autonomously (without any action taken by the driver) by the ME-SFI [ME] control unit if one of the following function requirements occurs:

IMPORTANT A maneuvering process is recognized for an engaged gear range "R" and the start/stop function is deactivated.

If the internal combustion engine is stopped it is force started and if it is running, the engine stop function is suppressed.

The start/stop function is subsequently activated again for an engaged gear range "D" and for exceeding a vehicle speed of 15 km/h.

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