BMW N55 User Manual

36
N55 Engine
Boost Mode
As the pressure in the intake air manifold increases in boost mode, blow-by gasses can
no longer be introduced via the passages in the cylinder head, otherwise, the boost pres-
sure could enter the crankcase. A non-return valve (15) in the blow-by channel within the
cylinder head cover closes the connection (16) to the intake air manifold. This protects
the crankcase from excess pressure.
The increased demand for fresh air creates a vacuum in the clean air pipe between the
turbocharger and intake silencer. This vacuum is sufficient to open the non-return valve
(12) and draw the blow-by gasses via the pressure control valve.
Index Explanation
A
Ambient pressure
B
Vacuum
C
Exhaust gas
D
Oil
E
Blow-by gas
1
Air cleaner
2
Intake manifold
3
Impact plates
4
Oil return channel
5
Crankcase
6
Oil sump
7
Oil return channel
8
Exhaust turbocharger
9
Oil drain valve
10
Charge air intake line
11
Hose to charge air intake line
12
Non-return valve
13
Pressure regulating valve
14
Throttle valve
15
Non-return valve
16
Passages in cylinder head and cylinder head cover

BMW N55 Specifications

General

Brand	BMW
Model	N55
Category	Engine
Language	English