Positive Crankcase Ventilation: Description and Operation

NOTE: Engine 120.980/981/982/983 Shown

OVERVIEW

Overview (Part 1 Of 2):

FUNCTION

Overview (Part 2 Of 2):

The engine has a sealed maintenance-free crankcase ventilation system. Ventilation chambers with an oil separator are positioned in the right cylinder head cover in the timing case cover and in the crankcase (6).
The damper (7a) in the full throttle ventilation line (7) absorbs the pressure vibrations during full throttle ventilation and prevents engine oil being entrained.

PART LOAD VENTILATION

Function Of Crankcase Ventilation At Idle Speed Up To Mid-part-throttle:

Throttle flaps closed, or opened slightly: The air release dome (1) is integrated into the right-hand cylinder head cover and sealed with the shield (2). Crankcase: vapors are extracted out of the ventilation chamber (3) which is produced as a result, through calibrated nozzles or 0 2 mm (4) as as result of the intake manifold vacuum downstream of the throttle flaps. The vacuum which is produced as a result in the crankcase draws in fresh air upstream of the throttle flaps through the shaped lines (9) and (10). Filtered fresh air thus passes along the shaped lines (9) and (10) and through the full throttle ventilation line (7) at the front into the crankcase.

FULL THROTTLE VENTILATION

Function Of Crankcase Ventilation At Upper-part-throttle Up To Wide Open Throttle:

Throttle flaps open:
The engine blow by gases and crankcase vapors flow out of the extraction point in the left-hand cylinder head cover at the front through the ventilation pipe (5), upstream of the left-hand cylinder head, into the ventilation chamber (6) with oil separator. From there, the full throttle ventilation line (7) runs below the intake manifold (in middle of engine) into the damper (7a) and then to a junction piece (8) at the rear of the engine. A shaped line (9) and (10) each run from this junction piece to the left and right throttle flaps. The blowby gases are mixed upstream of the throttle flaps and drawn into the intake manifold and into the combustion chambers.