S4 Exhaust Valve

[IceHanger]

Any S4 owners removed the vac pipe and tied it open?
Is it worth it and does it sound any better? it's certainty a larger pipe on the flap

 

[cobraBLACK]

It makes a slight difference but perhaps it's psychosomatic.

Stop messing about and get a Milltek non-res on there.

 

[GeoffDunk]

Both mine where stuck open when I got mine and I drove it for about 5000 miles like that.

When I took it to my mechanic for a service etc. I asked him to check the exhaust as it was def loader than I expected and what I had heard from others. Both valves were stuck open, some work and plenty of WD40 later they were sorted and the car never felt any slower but sounded quieter around town etc.

So I believe now power or performance difference.

I will end up with a Miltek or possible a blue-flame on it if I keep it long enough before the it's replaced for an RS4.

 

[dualmono21]

the exhaust flap is tied in with two vaccuum pipes which go to a non-return valve inside the passenger side rear quarter on the avant
when the engine creates enough vaccuum from the intake manifold the valves actuate and it becomes a little louder

if your running a milltek exhaust ( id reccomend the resonanted ..not the non resonated as it drones way too much on long journeys for me ) you need to blank the pipes off or the intake manifold doesnt work correctly and you will end up with a flat spot
also might be an idea to check the intake manifold is working correctly ... above 5000rpm it should open up the second stage of the intake
but the actuator on the front of the engine sometimes breaks ... again leaving you roughly 80bhp down

 

[RyanJonS4]

where are the pipes that need blanking?

and how do i check my actuator?

ryan

 

[stu_m]

These are called exup valves they have been used on bikes for years they serve two purposes

1 is to quieten the exhaust a little for noise emissions and 2 is to change the power curve at low rpm

They provide back pressure which gives you more torque but it's hardly noticeable

 

[cobraBLACK]

 

[dualmono21]

the pipes that need blanking off will be underneath your rear bumper
should be two rubber pipes about 5 or 6mm in diameter , you can blank them off here

some cars i have seen also have some valve and actuators inside the interior rear left panel in the floorspace at the bottom
some other cars have either never had this in place or have had it removed

the actuator for the second stage of the intake works at 5000rpm and is not easy to spot
you need two people to check this , one to rev the engine above 5000rpm and the other to look down on the front edge of the engine , the actuator itself is near the top of the front of the engine

if its moving fine , thats how it should be , if it isnt you could be in for a very very expensive repair , to repair the intake you have to buy the entire intake manifold as a little plastic and brass bush has worn and stopped working
audi in there wisdom dont sell this part on its own so you have to buy the entire manifold

anybody whom finds it isnt working please give me a shout as it is possible to repair it , but you have to be very very carefull

 

[p1tse]

How do I check this on my 04 cabriolet tiptronic
I feel mine is rather quiet

 

[dualmono21]

which bit do you want to check the ex up on the rear silencer or the actuator which is on the second stage of the intake manifold

ideally you need two people to do both

have a look at the actuator on the ex ups and see if you can see a small pin moving in and out at just over and under 1700rpm
for the intake manifold you need to go above 5000rpm and look down in between the front slam panel and front of the engine
you should see a small actuator move 90 degrees if you dont then it could well be seized or not working at all
end result roughly 80bhp down on stock

 

[p1tse]

Thanks

I had a look at my exhaust and no such pipes

 

[JimGreen]

Remember that the last of the B6 S4's didn't have this valve (My late B6 S4 doesn't), so check if you have it to start off with.

If it does have the valve, simply remove the vacuum pipe off the actuator on the rear exhaust box, put a "Golfing Tee" or something similar in the end of the vacuum hose to block it off and secure it with a mini tie wrap to keep it in there, otherwise it will draw air into the vacuum hose and cause your engine to run weak. And that's the job done.

Simples