Positive Crankcase Ventilation: Description and Operation

NOTE: Numbers in parentheses ( ) indicate a component or tool in the associated illustration.

Function Of Crankcase Ventilation At Upper Part Load Up To Full Load





Function Of Full Load Breather Compressor (18) Engaged
Bypass flap (22), closed, overpressure in intake area.

The blowby gases (B) flow through the. cylinder head cover (5) to the spiral oil separator (3), the full load breather pipe (2,), to the air cleaner housing (1), the intake area and into the combustion chambers. A check valve (6a) is installed in order to prevent any fresh air (A) (additional throttle quantity and thus additional quantity of oil) being forced through the intake area to the restrictors (6) of the part load breather, and into the crankcase.

The check valve (6a) seals off the breather pipe (10) of the part load-breather when the compressor (18) is engaged.





Function Of Spiral Oil Separator (3) Of Full Load Breather
The blowby gas (B) which is mixed with engine oil (A) enters the spiral from the outside and is guided to the center in a spiral shape. The centrifugal force is increased as the diameter of the spiral narrows.

Engine oil (A) is filtered out as a result of its higher specific density by impinging on the outer walls of the spiral, where it then flows off to the bottom and is forced towards the center by the constant gas flow.

The engine oil (B) flows back to the sump along a drain drilling (3b), the oil return pipe (23) and the dipstick guide tube (24).

A check valve (3a) is installed in the spiral oil separator (3) to enable the engine oil to be extracted through the dipstick guide tube (24).

The check valve (3a) seals off the oil return pipe (23) when a vacuum is produced by the oil extraction device.

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





Function Of Part Load Breather
In the idle speed/part load operating state (compressor not engaged, bypass flap (22) open, vacuum in intake duct), a mixture of blowby gases (B) and fresh air.(A) is drawn out of the crank chamber (12) through the oil separation chamber (11a) in the support of the p cower steering pump (1 i) along the breather pipe (10), to the part throttle breather check valve (6a) and to the restrictors (6) in the cylinder head before entering the combustion chambers.

Engine oil which is filtered out flows out of the oil separation chamber (11a) through a drain drilling and along the oil return pipe (l3) back into the oil sump (14).

Fresh air is drawn through the air cleaner housing (1) of the full throttle breather pipe (2) to the spiral oil separator (3), the cylinder head cover (5) into the crankcase.

Admixing fresh air is an additional measure to prevent engine oil sledging.