Operation

The primary control is through the PCV valve which meters the flow at a rate dependent upon intake manifold vacuum.

When intake manifold vacuum is high - during deceleration, low speed driving or idle, the PCV valve controls flow to a low flow rate since blow-by levels are low under these conditions.

When intake manifold vacuum is low - during acceleration or high load operation, the PCV valve controls flow to higher flowrates to accommodate increased engine blow-by.

Under full throttle operation or abnormal conditions, such as a worn or damaged engine, or high speed/light load operation, the system allows excess blow-by gases to flow through the fresh air tube into the inlet duct to be combined with incoming air from the air cleaner.