Positive Crankcase Ventilation

Positive Crankcase Ventilation

General

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 fitted 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 a lot of 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. It is obvious for these reasons why effective oil separation is important for the engine.

Positive crankcase ventilation - naturally aspirated engine







Positive crankcase ventilation - turbo engine

The positive crankcase ventilation system in the Cayenne Turbo can reduce the amount of fuel that goes into the engine oil during combustion. The aeration and ventilation system (Positive Crankcase Ventilation - PCV) ventilates the crankcase with a steady stream of fresh air, which accelerates the evaporation of fuel that is carried in.







For this purpose, fresh air is removed between the charge air cooler and throttle valve and is delivered to the crank chamber via a line. The pressure that exists at any time between the removal position and the crankcase causes a steady flow of fresh air through the crankcase. To ensure the legally required vacuum in the crankcase in all operating states, the vacuum in the intake manifold is used in the part-load ranges. A pressure-regulating valve regulates this vacuum until the required value is reached. The vacuum from the compressor is used in the boost range (no vacuum present). This system thus ensures a constant disposal of the fresh air delivered by the PCV system and the blow-by gases, which are supplied to the combustion process in this way.