Crankcase Ventilation System

Crankcase Ventilation System

General

During combustion, every engine blows some of the combustion gases past the pistons towards the crankcase - these gases are called blow-by gases. If these gases are not removed, the pressure in the crankcase would increase considerably. A vent connection is fitted in the crankcase for this reason. For environmental protection reasons, these gases are not released into the atmosphere but are returned to the engine for combustion via the intake system.

These crankcase ventilation gases naturally contain a high proportion of engine oil and other combustion residues as well as a high level of fuel residues in some cases. If these gases enter the intake duct, they will contaminate the intake air and can then impair running smoothness and exhaust emissions and also reduce knock resistance. These reasons show why effective oil separation is important for the engine.

Crankcase ventilation system for turbo engine

The diagram shows that the crankcase ventilation system in the Cayenne Turbo engine essentially functions in the same way as in the naturally aspirated engine. However, there is not always a vacuum in the intake system of the turbo engine as there is a corresponding pressure in the turbocharging area. Additional check valves (I) are therefore installed here. As a result, separation can be performed in the intake area just like on the naturally aspirated engine, and the air is supplied between the air cleaner and turbocharger in the turbocharging area.

Crankcase ventilation in the Cayenne Turbo is performed by a positive crankcase ventilation (PCV) system. This system ventilates the crankcase with a stream of fresh air, which evaporates fuel that has been carried in.

For this purpose, fresh air is removed between the charge-air cooler and throttle valve and is delivered via an air pipe to the crank chamber. The pressure gradient that exists at any time between the removal point and the crankcase causes a steady flow of fresh air through the crankcase.