PCV System: Description
The positive crankcase ventilation system prevents unburned gases (hydrocarbons) from entering the atmosphere by recycling them back into the combustion chamber. This is accomplished by drawing vapors from the crankcase through a Positive Crankcase Ventilation (PCV) valve and routing them into the intake manifold.
From the intake manifold they are drawn into the combustion chamber as the intake valve opens and the intake stroke of the piston occurs. The unburned gases are then burned during the combustion process. See Fig 1 .