Much better

[alex_123_fra]

OK thanks. It would seem then "Bottom end/ slow " running is better with improved breathing, this is pure guess work.

Yes, precisely. It just feels like the engine has been 'released' and is now able to operate as intended, whereas it was really uneven and stifled before. The S5 I had also felt free to breath (at the bottom end), which is why I started exploring ways of achieving similar with the RS4.

I will give this a try later today, run it for a week and see what happens,

John, could you post up how you disconnect the flaps...maybe with a pic? I want to do this but not really sure how to go about it.

[audijohn]

Yes, precisely. It just feels like the engine has been 'released' and is now able to operate as intended, whereas it was really uneven and stifled before. The S5 I had also felt free to breath (at the bottom end), which is why I started exploring ways of achieving similar with the RS4.

I will give this a try later today, run it for a week and see what happens,

John, could you post up how you disconnect the flaps...maybe with a pic? I want to do this but not really sure how to go about it.

Alex, job done took 5 mins each side.
Lay under rear you will see the pipes (one each side black rubber) using longnose pliers carefully ease off the pipes, find two 4mm threaded bolts, remove the heads, cut them to 1 1/2" long , taper the ends with a file or grinder if you cant get them into the rubber pipes, I had a peace of 1/4 OD 1/8 ID tubing, you will need to buy/find some.
cut this in two pieces 1 1/2" long (2).
Push one end of the bolt into the existing rubber tube and the other into the new piece and then connect into the diaphragm, when you've had enough or need servicing, remove and re connect.
Photo attached it's the pipe at the bottom, bit blurred sorry.

[Jezzer]

I will give this a try later today, run it for a week and see what happens,

John, could you post up how you disconnect the flaps...maybe with a pic? I want to do this but not really sure how to go about it.

Alex, job done took 5 mins each side.
Lay under rear you will see the pipes (one each side black rubber) using longnose pliers carefully ease off the pipes, find two 4mm threaded bolts, remove the heads, cut them to 1 1/2" long , taper the ends with a file or grinder if you cant get them into the rubber pipes, I had a peace of 1/4 OD 1/8 ID tubing, you will need to buy/find some.
cut this in two pieces 1 1/2" long (2).
Push one end of the bolt into the existing rubber tube and the other into the new piece and then connect into the diaphragm, when you've had enough or need servicing, remove and re connect.
Photo attached it's the pipe at the bottom, bit blurred sorry.

So what you are saying John is with the bolt you are blocking the vacuum to the diaphragm.

[audijohn]

John, could you post up how you disconnect the flaps...maybe with a pic? I want to do this but not really sure how to go about it.

Alex, job done took 5 mins each side.
Lay under rear you will see the pipes (one each side black rubber) using longnose pliers carefully ease off the pipes, find two 4mm threaded bolts, remove the heads, cut them to 1 1/2" long , taper the ends with a file or grinder if you cant get them into the rubber pipes, I had a peace of 1/4 OD 1/8 ID tubing, you will need to buy/find some.
cut this in two pieces 1 1/2" long (2).
Push one end of the bolt into the existing rubber tube and the other into the new piece and then connect into the diaphragm, when you've had enough or need servicing, remove and re connect.
Photo attached it's the pipe at the bottom, bit blurred sorry.

So what you are saying John is with the bolt you are blocking the vacuum to the diaphragm.

Yep the bolt minus the head is what stops the vacuum, and it goes back to normal in one min flat this way, so easy.

[ChrisRS4]

I just went and took a couple of pics of mine, might help..

I used a bolt and a mini clamp on the vacuum hose




And then tucked it up into the bumper. I had some silicone vacuum hose laying around, so I cut a short length and used a woodscrew in the end, and slipped onto the valve inlet.

[audijohn]

Well I can't believe this, I have done this mod, and no real drama with noise at all, in fact sound is nice, anyway just done a 20 mile cross counrty jaunt, 60/70 MPH B roads, 28 MPG!!!!!!!!!!!!!!!!!!!!!!!
Feck me. I have a theory on this one. I think doing this stops the exaust gas recycle and that's whats giving smooth lowdown power and increased MPG, anyone.
I have never seen that MPG on B roads and not hanging around particularly.

[DoctorD]

I tidied up my installation tonight and noticed that the valved pipe is unsilenced and goes straight through the rear silencer box (albeit with some resonating liners around its circumference). No wonder it sounds different now. Quite a clever design too.

[Jezzer]

This question was unanswered earlier on on the first page. Are the valves on the exhaust left open when the engine is not running. I would have thought they were shut however they would have to stay open to enable you to carry out this mod once the vacuum pipe is disconnected. If you didn't block or clamp the pipe once it's taken off the diaphragm would the vacuum draw in dirt up the pipe?

[DoctorD]

This question was unanswered earlier on on the first page. Are the valves on the exhaust left open when the engine is not running. I would have thought they were shut however they would have to stay open to enable you to carry out this mod once the vacuum pipe is disconnected. If you didn't block or clamp the pipe once it's taken off the diaphragm would the vacuum draw in dirt up the pipe?

Yes, the valves remain open when the engine is not running. The Vaccum actuator functions to 'close' the valves. When disconnected the valves just stay open at all times.

You need to block the pipe once disconnected. Most of us seem to settle on the idea of fitting a screw into the end of the pipe then clamping it out of the way. The rubber pipe which fits the actuator attaches further back to a green plastic pipe that is already clamped (via a bracket). If you remove this green pipe and clamp the rubber pipe in its place then that will keep it out of the way.

[S4INT]

I did this to mine a couple of days ago, and have to agree with everything written before. Car now feels more torquey and responsive at low revs, mpg marginally better, and no issues with extra noise, except on cold start where it now makes the house vibrate....

[alex_123_fra]

John and Chris, thanks a lot for the pics...very useful. Will now have a think about how to do mine.

It is impressive that fuel economy increases so drastically with the valves simply staying open. If this is indeed a safe mod, it would seem that everyone with the standard exhaust should do it as there isn't a downside!

[mobility&lifestyle]

After taking a look under my car just out of interest what would happen if i just disconnected the black hose from the green pipe? Would this have the same effect? (not that i'm going to do it of course )

[DoctorD]

After taking a look under my car just out of interest what would happen if i just disconnected the black hose from the green pipe? Would this have the same effect? (not that i'm going to do it of course )

Nearly. You still need to block the green pipe to retain the closed-loop vaccum within the system.

[Attranac]

You need to block the pipe once disconnected. Most of us seem to settle on the idea of fitting a screw into the end of the pipe then clamping it out of the way. The rubber pipe which fits the actuator attaches further back to a green plastic pipe that is already clamped (via a bracket). If you remove this green pipe and clamp the rubber pipe in its place then that will keep it out of the way.

Shouldn't you block the actuators end aswell?

Nearly. You still need to block the green pipe to retain the closed-loop vaccum within the system.

What would happen if you lost the 'closed-loop vacuum' ?

[hugy]

After doing this mod,what happens when the S button is pressed?Does the sport mode still work?