P01.20-A037-79
Example illustration of crankcase ventilation system |
1 | Cylinder head bleed line | 2 | Oil separator |
Overview
This document contains information on:
General
Function requirements
Function
General
The crankcase ventilation system regulates the pressure ratios in the crankcase. The aim is to dissipate overpressure and excess combustion gases from the crankcase. The crankcase ventilation system feeds the cleaned air through the intake air system to the combustion engine.
Function requirements
Engine management ON (circuit 87M)
Engine in operation
Function
Crankcase ventilation system
Leaked gases enter the crankcase via the annular gap of the piston rings and the clearance between the piston and cylinder barrel. The crankcase ventilation system is tasked with reducing the overpressure in the crankcase and guiding the cleaned air into the intake air system. The oil separator filters oil residue out of the air before this residue is fed into the intake air system. An expansion line offsets the overpressure through engine ventilation. The amount of air led back differs in partial- and full-load operation.
Partial load operation
In partial-load operation, air is removed from the oil separator to the charge-air distributor via a valve in the bleed line. In overrun mode, the valve is actuated by the combustion engine control unit and closes the bleed line for partial-load operation. The valve remains open as long as the combustion engine control unit does not actuate the valve.
Full load operation
In full-load operation, ventilation takes place from the oil separator to the air intake pipe. The cleaned combustion gases are guided into the air intake pipe upstream of the exhaust gas turbocharger for ventilation. To prevent freezing of the crankcase ventilation system in full-load operation, a heating element is integrated in the bleed line. The heating element heats the bleed line as of an outside temperature of approx. 7 °C.