5 Series E60 525xd (M57T2) SAL
The M57TU2 TOP complies with the EURO 4 exhaust emissions standard. The engine is equipped with a diesel
particulate filter for this purpose.
Brief description of components
The most important components for the 2-stage turbocharging are:
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1 small turbocharger
The size of the turbocharger used has a decisive influence on the operation of the engine (power and response
characteristics).
Because of its small mass, which are accelerated by the exhaust gas, a small turbocharger is extremely
responsive. Boost pressure is built up very quickly when the throttle is opened. This means that the engine
responds with much less delay.
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1 large turbocharger
A large turbocharger has different characteristics.
When the throttle is opened, the exhaust gas has to accelerate a large mass.
The turbocharger, and thus also the engine, therefore react more sluggishly.
However, if more final output is needed, i.e. high boost pressure and air flow rate, the larger cross-sectional area
of the turbocharger makes it more efficient.
For the 2-stage turbocharging, the two turbochargers are arranged in series. The exhaust gas first drives the
small turbine, then the large one. On the fresh-air side, the large compressor compresses the fresh air first, then
the small compressor.
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Turbine control valve
The turbine control valve controls the distribution of the exhaust flow between the small and large turbines. The
turbine control valve is pneumatically adjusted by a diaphragm can. The turbine control valve is variable in its
range of adjustment. An electropneumatic pressure converter charges the diaphragm can with a partial vacuum.
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Compressor bypass plate
The compressor bypass plate allows the small compressor to be bypassed on the air side. The compressor
bypass plate is pneumatically adjusted by a diaphragm can. The compressor bypass plate is either fully open or
fully closed. An electric valve charges the diaphragm can with a partial vacuum.
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Wastegate valve
Once nominal rating has been achieved, the wastegate valve opens to prevent excessively high boost pressure.
Part of the exhaust gas is fed through the wastegate valve past the large turbine. The wastegate valve is
pneumatically adjusted by a diaphragm can. The wastegate valve is variable in its range of settings. An
electropneumatic pressure converter charges the diaphragm can with a partial vacuum.
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DDE control unit
The DDE has been further developed for activation.
The DDE control unit also activates the above actuators for 2-stage charging.
The M57TU2 TOP has like the M57TU TOP no electrical air flap control.
In addition, the M57TU2 TOP has injectors with piezo-elements.
System function
When designing a turbocharger, a compromise must always be found between good response characteristics and a
final output.
The turbochargers used by BMW have variable turbine geometry to reduce this drawback of single-stage
turbocharging, although they are unable to eliminate it completely.
SBT 2-stage turbocharging E60, E61, E83, E90, E91, E92 M57TU TOP, M57TU2 TOP
BMW AG - TIS
21.02.2013 10:26
Issue status (12/2007) Valid only until next DVD is issued
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