Engine – Cayenne V8
Page 1.34
Oil Spray Jets
The temperature of the pistons in the Cayenne S and Cayenne Turbo
engine is reduced by means of spray cooling. The spray jets are fitted
on the upper part of the crankcase. The spray oil is also used for
improved lubrication of the cylinder lining. To ensure the necessary
engine oil pressure at low rpms and high engine oil temperatures, the
spray jets have an opening pressure of approx. 1.8 bar.
Positive Crankcase Ventilation
During combustion, every engine blows some of the combustion gases
past the piston towards the crankcase – these gases are called blow-by
gases. If these gases are not drawn off, the pressure in the crankcase
would increase considerably. A vent connection is installed in the
crankcase for this reason. For environmental protection reasons, these
gases are not released into the atmosphere, but are sent back to the
engine for combustion via the intake system. Of course, these positive
crankcase ventilation gases contain a high proportion of engine oil and
other combustion residues as well as fuel residues in some cases. If
these gases get into the intake duct, they will contaminate the intake air
and can then impair running smoothness, exhaust emissions and reduce
knock resistance. For these reasons effective oil separation is important
for the engine.
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