Inclined

The B7 S4's two inboard exhaust pipes have a vacuum solenoid controlled butterfly valve ( that is open when motor shut off ) . Does it work like the B6 S4 exhaust bypass valve where it stayed open until 1700 rpm for throatier sound at idle and drive off , then closed to pass drive-by noise regs . Or does it reopen at higher MPH speed with aggressive throttle ? Would plugging the solenoid vacuum line then keep all 4 pipes open all the time ? Or is there a fuse one could pull to disable it and keep the butterflys open ?

ub2slw

where are you looking? there's no butterfly valve on the b7 exhaust..unless it's above the pre-cats.

Reggie

I thought Audi did a way with that on the B6s

Inclined

There are two separate exhaust pipes emerging from each rear muffler can . The inner pipe has an internal butterfly valve about 3 inches aft of the can controlled by an external adjacent vacuum operated solenoid - like on Ferraris and the new C6 Z06 . The flap is open at rest and on some prev early B6 S4s ( though that was with one combined 2 into 1 rear pipe per can ) closed at 1700 rpm ( to give throaty idle and drive off only ) - which is different from the Ferrari and Chevy systems in that their valves OPEN at higher rpm for less backflow and louder tone .

Here's Viken B's orig August 2004 B6 S4 post on the bypass valve :<ul><li><a href="https://forums.audiworld.com/s4b6/msgs/118416.phtml">https://forums.audiworld.com/s4b6/msgs/118416.phtml</a</li></ul>

Pete @ Stratmosphere

I'm not aware of that on the B7. It's not on mine.

Inclined

Well that's odd - it's on mine ( early production 2005.5 ) ! Kinda like on the B6 S4 where some cars had it , then disappeared ? What's up with Audi with that ?
That begs the question - do the non -solenoided B7s have all 4 pipes open all the time then ?

SGC

Its not on the European B7's either.

ub2slw

mine is 02/05 and there are no valves like the ones on the b6 exhausts.....

do EACH of your mufflers have dual tips?

Inclined

yes, each muffler of my 01/05 build has two separate pipes coming from the muffler . Do you guys with later build cars without the exhaust flap only have " fake " dual pipes , i.e, one exit pipe that " y" s to two tips ?