Positive Crankcase Ventilation: Description and Operation

Fig. 1 Gasoline engine positive crankcase ventilation system.:

The closed positive crankcase ventilation system, Fig. 1, consists of a baffle in the rocker arm cover to separate oil particles from blow-by gasses, an orifice in the intake manifold to draw blow-by gasses and route them to the combustion chamber and a hose connection to air cleaner to supply fresh air to the crankcase through the rocker arm cover. Under normal operating conditions, blow-by gasses are mixed with the fresh air drawn from the air cleaner and are routed through a hose from the rocker arm cover to the regulating orifice in the intake manifold, and directed to the combustion chamber. Under full throttle conditions, blow-by gasses are routed to the intake manifold through both the orifice in the intake manifold and the fresh air supply hose to the air cleaner.