Positive Crankcase Ventilation: Description and Operation

Crankcase Ventilation System Description





A crankcase ventilation system is used to consume crankcase vapors created during the combustion process instead of venting them to the atmosphere.

Fresh air is supplied through a filter to the crankcase, the crankcase mixes the fresh air with the blow-by gases and then passed through a positive crankcase ventilation (PCV) orificed tube (5) into the intake manifold (3).

The PCV orificed tube (5) restricts the flow rate of the blow-by gases using a 2.5 mm (0.098 in) orifice located in the camshaft cover tube (5). If abnormal operating conditions arise, the system is designed to allow excessive amounts of blow-by gases to back flow through the crankcase ventilation fresh air tube (6) into the air cleaner resonator (1) in order to be consumed by normal combustion.