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377_060
Exhaust flap control Audi RS4
A further difference is the layout; one exhaust flap is
located downstream of each of the rear silencers.
The exhaust flaps are fitted to give the engine a
sporty sound. The exhaust flaps are switched in
such a way as to meet the statutory limits for
vehicle exterior noise.
Low-frequency droning noise at low engine RPM is
prevented. At high engine RPM and high exhaust-
gas flow rates, flow noise and exhaust backpressure
are reduced by opening the additional cross-
section.
The exhaust gas flaps are closed at idle, low engine
load and at low engine RPM.
Function
The exhaust flaps are switched by a vacuum
actuator. Both vacuum units are switched by an
electrically activated solenoid valve. The exhaust
flaps are switched according to a characteristic
map.
The factors of engine load, engine RPM, gear
selected and the shift signal from the Sport button
are used to plot the characteristic map.
For example, the exhaust flaps are opened at idle
when the Sport button is pressed.
Vacuum control
actuator
Exhaust actuator flap
Exhaust system in the RS4
Primary catalytic converter
Decoupling element
Main catalytic converter
Front silencer
Rear silencer
Fan-type manifold, 4 in 2 in 1
Lambda probes
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