Scavenging Concept; Check Valve - Porsche Cayenne V6 2008 Service Information

Engine – Cayenne V8
1 - Adjustment direction retarded
2 - Adjustment direction advanced
3 - Camshaft controller
4 - Solenoid hydraulic valve

5 - Check valve

6 - Oil pump
7 - Oil pan
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Scavenging Concept

A scavenging restrictor is installed on the end of the control pressure
line to keep the switching time to a minimum during valve lift control.
This scavenging restrictor is used to bleed the line and reduce switching
time.
Check Valve
The camshaft requires a high drive torque at times due to the valve
actuation, but the camshaft continues rotating unaided at other times
(alternating torques). If a check valve is inserted into the P-line and the
solenoid hydraulic valve is energized, for example (adjustment in
direction of advanced valve timing), the controller automatically intakes
oil via the feed line, the solenoid hydraulic valve and the check valve for