Boost Mode - BMW N55 Manual

Index
A
B
C
D
E
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

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.
36
N55 Engine
Explanation
Ambient pressure
Vacuum
Exhaust gas
Oil
Blow-by gas
Air cleaner
Intake manifold
Impact plates
Oil return channel
Crankcase
Oil sump
Oil return channel
Exhaust turbocharger
Oil drain valve
Charge air intake line
Hose to charge air intake line
Non-return valve
Pressure regulating valve
Throttle valve
Non-return valve
Passages in cylinder head and cylinder head cover