Crankcase Ventilation System, Function - GF01.20-P-0001MRS

Engine 264.9 in model 205, 253 

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.

  Crankcase ventilation system, general 

  The crankcase ventilation system ensures under all operating conditions of the engine that overpressure and excess gases are dissipated from the crankcase and fed back to the engine via the intake air system for combustion. To balance out the pressure ratio, a separate line is attached for engine ventilation.

  The ME-SFI [ME] control unit evaluates the following signals for the implementation of the crankcase ventilation system:

• Engine load

  Pressure and temperature sensor downstream of throttle valve (B28/27)

• Accelerator pedal position

  The powertrain control unit (N127) reads in the accelerator pedal sensor (B37) signals directly, and transmits the accelerator pedal position via the drive CAN (CAN C1) to the ME-SFI [ME] control unit.

• Outside temperature

  The front SAM control unit (N10/6) transmits the outside temperature via the interior CAN (CAN B) electronic ignition lock control unit (N73), suspension FlexRay (Flex E), powertrain control unit and drive CAN to the ME-SFI [ME] control unit

View of engine from the left 

Courtesy of MERCEDES-BENZ USA

Crankcase ventilation system 

In the partial load range, ventilation takes place starting from the oil separator (1) to the charge-air distributor (2). For this purpose, the crankcase ventilation system valve is located in the partial load bleed line (3).

The crankcase ventilation system valve is actuated in overrun mode by the ME-SFI control unit and closes the partial load-bleed line (3) from the oil separator (1) to the charge-air distributor (2).

The inflow of exhaust from the crankcase during the mixture adaptation and disruptive background noise are thus avoided If no actuation by the ME-SFI control unit takes place the valve crankcase ventilation system is permanently open.

In full-load operation ventilation takes place starting from the timing case to the exhaust gas turbocharger.