Layout Drawing - BMW 745i Repair Instructions

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Layout Drawing
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2
3
4
5
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7
8
9
10
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air cleaner
air flow sensor
compressor
2
exhaust gas turbocharger
turbine
charge air coole r
air valve
bypass valve
exhaust manifold
intake manifold
control line
3
4 5
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The turbine is propelled by the velocity of exhaust gas flow. Since the turbine and compressor are con
nected with each other, the compressor takes in air. The intake air, which enters the compressor via the
air cleaner and air flow sensor, is passed on to the charge air cooler after supercharging. The charge air
temperature is reduced here and then the charge air continues via the charge air necks, the opened
throttle housing and the intake manifold to the separate cylinders.
The charge pressure must not exceed approx. 0.7 bar (10 psi), so that it must be controlled. This is ac·
complished with the help of an exhaust gas bypass valve. The compressor and bypass valve are connec -
ted with each other via a control line. The bypass valve wi1l open when charge pressure is excessive, so
that part of the exhaust gases will flow into the bypass pipe of the exhaust system. This reduces the
pressure on the turbine and therefore also the charge pressure.
Since the compressor wi U still be running when closing the throttle, there could be unwanted backpres·
sure in the charge air neck. This is avoided by applying an air valve. A vacuum hose connects the air
valve with the intake manifold. The air valve will be opened by the vacuum produced when the throttle
is closed and the charge air wil l flow through the bypass line to the Intake side of the compressor.
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