Exhaust Flap
12-02-2004, 05:25 PM
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Exhaust Flap
It is my understanding that the muffler flap stays closed while the car is at low RPM so it sounds more subtle. When you get on it, the flap opens and it sounds like a muscle car. At least my 2005 does. I want to figure out how to keep it open all the time so it actually sounds like a V8 at idle. Any suggestions?
12-02-2004, 05:44 PM
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Re: unhook the vacuum line attached to the muffler, plug it with a screw, and
did it make much different sound or performancewise. I really just want it to be louder at idle without changing the exhaust
12-02-2004, 06:50 PM
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No. Flap is open at low RPM for more noise and closes over 1,700 RPM to reduce noise.
<center><img src="https://www.audiworld.com/features/tests/2004_s4_002.jpg"></center><p>
12-02-2004, 06:54 PM
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Actually it's the other way around - the flap is open at idle to make a more open sound and closes
under conditions of acceleration. Removing the vacuum link and corking off the vacuum lead allows the flap to stay open during wide open throttle acceleration.
The early 2004 B6 S4 exhaust systems with this (mis)feature sounded pretty ghetto with the flap valve bypassed and most of us who tried it and really heard how our cars sounded from outside simply bailed and bought an aftermarket system.
Someone tried to dyno this mod early on and determined that the gain was in the 1-2HP range if you could believe the 1-2% margin of error.
The early 2004 B6 S4 exhaust systems with this (mis)feature sounded pretty ghetto with the flap valve bypassed and most of us who tried it and really heard how our cars sounded from outside simply bailed and bought an aftermarket system.
Someone tried to dyno this mod early on and determined that the gain was in the 1-2HP range if you could believe the 1-2% margin of error.
