What are the butterfly valves controlling one of two outlets on each muffler for?....
12-23-2004, 03:26 PM
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What are the butterfly valves controlling one of two outlets on each muffler for?....
The tail pipes actually have two outlets that "Y" into a single tail pipe. Is this for a more quiet drive until you tip into it which i9s when the vac opens up the butterfly from the second pipe? Why don't we have quad tips on our mufflers and call it good?
12-23-2004, 05:08 PM
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no, but many of us have blocked the vacuum line
1/ pull off black hose that connects to muffler from plastic elbow connector on rear bumper 2/ screw small screw into plastic elbow. 3/ reconnect black hose. vacuum activation now dissabled. some think it makes the car sound louder. i have not noticed a significant change in noise or performance
12-23-2004, 05:14 PM
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I guess that you already have. Suprises me that Audi does this on a S-4.....
as this is their performance oriented model. I kind of laughed at the fact that they have two pipes that meld into one and close one off with a butterfly. The noise can't be that bad...
I would like you to answer if in your opinion it would be worth making the mod for the butterfly to stay open all of the time, performance wise.
I would like you to answer if in your opinion it would be worth making the mod for the butterfly to stay open all of the time, performance wise.
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12-23-2004, 05:18 PM
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Suprising, I would have thought it to be the other way around....
valves oppen as RPM increases and close as rpm drops. Typically a bit of back pressure might improve extremely low end grunt.
12-23-2004, 05:34 PM
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Re: What are the butterfly valves controlling one of two outlets on each muffler for?....
I noticed your S4 is a 2005 model... I thought the 2005 S4's dont have the flaps in the exhaust??