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N55 Engine
Crankcase Ventilation
The blow-by gasses flow into the settling chamber of the cylinder head cover through an
opening located in the rear of the cover. Here, the blow-by gasses are directed through
holes on to an impact plate, against which the oil impacts at high speed, and drains off.
The blow-by gasses, cleaned of oil, flow via the pressure control valve (depending on the
operating mode) through the non-return valves into the inlet pipe upstream of the
turbocharger, or via passages in the cylinder head ahead of the intake valves. The sepa-
rated oil is drained via a return flow duct into the oil pan.
Naturally Aspirated Mode
The standard function can only be used as long as a vacuum prevails in the intake air
manifold, i.e. in naturally-aspirated engine mode.
With the engine operating in naturally-aspirated mode, the vacuum in the intake air mani-
fold opens the non-return valve (15) in the blow-by duct within the cylinder head cover.
This draws off blow-by gasses via the pressure control valve. At the same time, the vacu-
um also closes the second non-return valve (12) in the duct to the charge air intake pipe.
The blow-by gasses flow via a distribution rail integrated in the cylinder head cover,
through the intake passages (16) in the cylinder head, which lead directly into the intake
ports, ahead of the valves.
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