Crankcase Ventilation System Description: Notes

A closed crankcase ventilation system is used in order to provide a more complete scavenging of crankcase vapours. Filtered air from the air induction system duct is supplied to the crankcase, mixed with blow-by vapours, and passes through a crankcase ventilation metering device before entering the intake manifold. The primary component in the positive crankcase ventilation (PCV) system is the PCV flow metering device (or orifice). Vacuum changes within the intake manifold result in flow variations of the blow-by vapours. If abnormal operating conditions occur, the design of the PCV system permits above acceptable amounts of blow-by vapours to back flow through the crankcase vent tube and into the engine induction system to be consumed during normal combustion. This engine ventilation system design minimizes oil consumption and significantly reduces the potential for oil ingestion during vehicle limit handling manoeuvres.