Positive Crankcase Ventilation: Description and Operation

PURPOSE
The positive crankcase ventilation system prevents blowby gases enter from inside the crankcase into the atmosphere.

OPERATION
Fresh air is sent from the air cleaner into the crankcase through the breather hose to be mixed with the blowby gases inside the crankcase. The blowby gas inside the crankcase is drawn into the intake manifold through the positive crankcase ventilation valve.

The positive crankcase ventilation valve is designed to lift the plunger according to the intake manifold vacuum so as to regulate the flow of blowby gas properly.

In other words, the blowby gas flow is regulated during low load engine operation to maintain engine stability, while the flow is increased during high load operation to improve the ventilation performance.