Engine – Cayenne V8
Page 1.32
Oil Pump
The integration of VarioCam Plus, the mechanical vacuum pump and the
fact that the lower part of the crankcase is fully aluminum means that oil
throughput on the Cayenne S and Cayenne Turbo is very high. A rela-
tively large and efficient pump must be used to guarantee the required
oil supply. However, a lot of energy is required to drive such a pump and
this energy requirement in turn increases fuel consumption. To coun-
teract this, a variable oil pump is used for the first time in the Cayenne S
and Cayenne Turbo.
Function
Depending on the input values for engine rpm, engine load, engine oil
temperature and the expected change in engine rpm, a specific control
valve position (-4-) is defined using a map in the DME control unit. The
control valve position regulates the oil pressure for the spring piston on
the gear wheel, which can move in axial direction. The oil pressure on
the control piston is not regulated on the other side. The control valve is
open fully in the non-energized state and as a result, the oil pressure is
the same on both sides, which means that the gear wheel will not move.
In other words: the pressure difference between the spring piston and
the control piston can be used to control every position. When the gear
wheel moves, the teeth are still only partially engaged and as a result,
performance and friction as well as energy requirements are reduced.
1 - Oil pump chain drive gear
2 - Oil pump driven gear
3 - Movable oil pump gear
4 - Oil pump control valve (lowers pressure on
spring end of control piston)
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