911 CARRERA Models
System components include a connecting vent hose between crankcase and oil tank, a main vent hose with orifice between the oil filler tube neck and air intake duct above throttle, an auxiliary vent between oil tank and intake port below throttle, vacuum control, air switching valve, and temperature switch.
Crankcase vapors and blow-by gases flow into oil tank, where excess oil is separated from gases. At temperatures above 50°F (10°C), gases are drawn into intake manifold through main vent system. At temperatures below 50°F (10°C), temperature switch opens allowing vacuum to open auxiliary vent passage in air switching valve. Gases are then drawn into engine through auxiliary vent to prevent throttle icing.