S4 Exhaust Valve tweak

yyuksel

Registered User
I wonder if this is something that can be changed on the car programmatically?
 

SMI77

Australia
Hi. I'm somewhat confused. If I understand correctly, because the flaps are before the 'Y' & the muffler on the left side and the right side flap is after the muffler on the right outlet, unless one says 'open sesame', the exhaust will always exit thru only 1 tip (second from the right looking at the rear of the vehicle).
Also, exhaust gases that choose to go thru the left muffler can't, because of the flap cutting off both left hand tips. So they must do a 'U-turn' against oncoming gases, fight their way back to the junction, and flow into the single exit thru the right muffler. WOW! This is Audi's technologically advance free-flowing efficient exhaust system.
Thinking on...... some aftermarket exhaust manufacturers charge 'an arm & a leg' for a system that still requires the owner to donate their own exhaust valve assemblies. But in doing so, this replicates the exact problem with the OEM system???
Disclaimer: I am old and failed physics/chemistry at school. Obviously I am missing something v-e-r-y basic here.
 

Thundercliffe81

Registered User
Hi. I'm somewhat confused. If I understand correctly, because the flaps are before the 'Y' & the muffler on the left side and the right side flap is after the muffler on the right outlet, unless one says 'open sesame', the exhaust will always exit thru only 1 tip (second from the right looking at the rear of the vehicle).
Also, exhaust gases that choose to go thru the left muffler can't, because of the flap cutting off both left hand tips. So they must do a 'U-turn' against oncoming gases, fight their way back to the junction, and flow into the single exit thru the right muffler. WOW! This is Audi's technologically advance free-flowing efficient exhaust system.
Thinking on...... some aftermarket exhaust manufacturers charge 'an arm & a leg' for a system that still requires the owner to donate their own exhaust valve assemblies. But in doing so, this replicates the exact problem with the OEM system???
Disclaimer: I am old and failed physics/chemistry at school. Obviously I am missing something v-e-r-y basic here.

You can't be the only one. You just baffled the hell out of me and I started this thread! I just followed someone's instructions and tried it myself. Exhaust is now louder at lower rpm. Valves opened. HOWEVER! And I'm noticing this more just lately...by putting it into comfort, it 'still' makes the exhaust a little quieter.


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CharlieP

Registered User
You can't be the only one. You just baffled the hell out of me and I started this thread! I just followed someone's instructions and tried it myself. Exhaust is now louder at lower rpm. Valves opened. HOWEVER! And I'm noticing this more just lately...by putting it into comfort, it 'still' makes the exhaust a little quieter.


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The reason I believe it seems quieter is that in economy mode the rpm is dropped slightly on idle hence the noise is lower same result as the cold start option the ecu is programmed to hold a higher rpm so it sounds louder. I still have the valves open all the time on my s5 and don't intend on closing them


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Daggerit

Registered User
Hi. I'm somewhat confused. If I understand correctly, because the flaps are before the 'Y' & the muffler on the left side and the right side flap is after the muffler on the right outlet, unless one says 'open sesame', the exhaust will always exit thru only 1 tip (second from the right looking at the rear of the vehicle).
Also, exhaust gases that choose to go thru the left muffler can't, because of the flap cutting off both left hand tips. So they must do a 'U-turn' against oncoming gases, fight their way back to the junction, and flow into the single exit thru the right muffler. WOW! This is Audi's technologically advance free-flowing efficient exhaust system.
Thinking on...... some aftermarket exhaust manufacturers charge 'an arm & a leg' for a system that still requires the owner to donate their own exhaust valve assemblies. But in doing so, this replicates the exact problem with the OEM system???
Disclaimer: I am old and failed physics/chemistry at school. Obviously I am missing something v-e-r-y basic here.

I think that in terms of the 'U-turn' idea what will happen is that there will be a build up of pressure in that branch of the exhaust and then the exhaust will take the path of least resistance and exit through the other side that's open, basically just flowing straight past it.

I imagine this would be the case up to a set RPM when the back pressure begins to get to a higher level and then there will be some combination of valves that open to release the gasses and reduce the exhaust pressure overall. I don't know if it would be the one before the 'Y' or on the other side, but I would imagine that one is RPM based and the other is activated under Dynamic mode. I'm just guessing about this but it's what would make sense from an engineering perspective. :)
 

Daggerit

Registered User
Hope the above makes sense the one thing I do notice is that if you use the car properly the mpg is very low


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Makes sense to me! :)
 

Thundercliffe81

Registered User
The reason I believe it seems quieter is that in economy mode the rpm is dropped slightly on idle hence the noise is lower same result as the cold start option the ecu is programmed to hold a higher rpm so it sounds louder. I still have the valves open all the time on my s5 and don't intend on closing them


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Just checked. You are right, Sir!


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SMI77

Australia
Thank you, gentlemen.
Would appreciate a comment on "unless one says 'open sesame', the exhaust will always exit thru only 1 tip"?
I ask this, because whilst we have owned ours for only 2 weeks and driven 2200kms (approx. 1400 miles) I have only cleaned 'soot' off of only 1 tip.
Pretty disappointing that one purchases a not-so-cheap performance orientated vehicle with quad tips, but only 1 works, unless directed.

CharlieP, depends on one's definition of 'properly'. It is not an entry level A4. Our last vehicle was a modded Subaru Liberty(Legacy) turbo wagon 'Tuned by STi", dynoed @ 212kw (288bhp) 'atw'. Had many fond memories driving it with enthusiasm, & a grin 'ear-to-ear'. However, keeping both eyes open, when coming up to a red traffic light, I cruise up to it, not roar up to it using unnecessary fuel requiring heavy braking, as I see many a driver do.
I will be 'driving' it, but not all the time. Our last tank, with highway driving was 800kms, close to 40mpg if my maths are correct.

Trivia, it is currently 10.30 pm here.
 

Daggerit

Registered User
It's a bit disappointing... It always annoys me driving behind an S3/Golf R (seem to be the most noticeable culprits) which have the inner most of the four black and the outer two still super shiny. Just bugs my OCD...


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TripleD

Audi S4 Avant Owner
It's a bit disappointing... It always annoys me driving behind an S3/Golf R (seem to be the most noticeable culprits) which have the inner most of the four black and the outer two still super shiny. Just bugs my OCD...


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I remember a friend welding a metal tube onto the side of his exhaust to make it look like a twin exhaust, then getting some charcoal and rubbing it on the metal to make it look 'in use' :D
 

Daggerit

Registered User
I remember a friend welding a metal tube onto the side of his exhaust to make it look like a twin exhaust, then getting some charcoal and rubbing it on the metal to make it look 'in use' :D

That's hilarious...
 

gone

Registered User
We used to sit round a candle years ago, people passing by thought we had a telly from the flicker on our faces ...

The black tip is annoying but sometimes, just sometimes the quieter approach is appreciated so I'll be leaving the flaps as are, unless I try them and like it :whistle2:
 

R.A.G

Registered User
Thank you, gentlemen.
Would appreciate a comment on "unless one says 'open sesame', the exhaust will always exit thru only 1 tip"?
I ask this, because whilst we have owned ours for only 2 weeks and driven 2200kms (approx. 1400 miles) I have only cleaned 'soot' off of only 1 tip.
Pretty disappointing that one purchases a not-so-cheap performance orientated vehicle with quad tips, but only 1 works, unless directed.

It very much depends how you drive and which drive mode you predomantly use.

If you drive around in efficiency (or auto/comfort at low revs) the car will spend most of its time gassing through the single exhaust tip, if you drive in Dynamic (or individual set as so) the exhaust valves will spend much more time in the open position and you'll see more even spread of soot across all four tips.

This was one of the main reasons I did the mod, I'm a bit sad and like keeping the tips nice and shiny (they're a big feature of car for me), by having a continual even distribution of soot across all four tips they are far easier to clean using my WD40 routine! :sm4:
 

SMI77

Australia
It very much depends how you drive and which drive mode you predomantly use.

If you drive around in efficiency (or auto/comfort at low revs) the car will spend most of its time gassing through the single exhaust tip, if you drive in Dynamic (or individual set as so) the exhaust valves will spend much more time in the open position and you'll see more even spread of soot across all four tips.

This was one of the main reasons I did the mod, I'm a bit sad and like keeping the tips nice and shiny (they're a big feature of car for me), by having a continual even distribution of soot across all four tips they are far easier to clean using my WD40 routine! :sm4:
 

SMI77

Australia
SMI77 is now flaps open. Settings on Individual with suspension on comfort & the rest Dynamic. Louder, with the sunroof ajar at the back, but not obtrusive. Actually a little excited, thinking the sound will improve with some mileage. This happened with the gorgeous Japanese HKS 3" system on our last Subaru Liberty/Legacy turbo wagon.
Incidentally, the quality & workmanship of the HKS is light years better than most of the current systems around for the S4, and for less $$'s.

Was seriously contemplating cerakoting the tips, but when under back with the screwdriver, torch & mirror, I noticed the the tips are spot welded on the bottom and top of each tip. ******!!

R.A.G. - try Amway Metal Cleaner for the tips.
 

Daggerit

Registered User

pierreluigi88

Registered User

Daggerit

Registered User
This might be it - £430 fitted, but not for sports diff models.

https://www.mgautos.uk.com/product/audi-s4-milltek-active-valve-control/

@Thundercliffe81 have you got sports diff? Think I might try what you did, but wondering if the diff uses the valves somehow and unplugging the controllers might screw it up.

I'd imagine if it required them then it would flag up an EML, which it doesn't, so I'd assume that it everything else will continue to operate as normal. That said, it does apparently flag something up in the background.
 

RichardMMM

Registered User
I've actually plugged mine back in as I didn't notice a difference between having the car in dynamic (or individual) compared to having them unplugged. Having them plugged back in means I have the option of a quieter motorway journey as it was quite boomy at 80mph even in economy. There doesn't seem to be any benefit of unplugging other than if you want it noisier in comfort/economy.
 

Daggerit

Registered User
I've actually plugged mine back in as I didn't notice a difference between having the car in dynamic (or individual) compared to having them unplugged. Having them plugged back in means I have the option of a quieter motorway journey as it was quite boomy at 80mph even in economy. There doesn't seem to be any benefit of unplugging other than if you want it noisier in comfort/economy.

I found it louder at lower revs than just being in dynamic as the passenger side doesn't open at those revs I don't believe. I left the other side plugged in so it still allowed a small change in noise when cruising to stop drone.
 

Thundercliffe81

Registered User

Thundercliffe81

Registered User
Bit of FYI and some advice needed reference this mod. Took the old girl in for service today and these fault logs came up:

22c0f79a0098655489ab51f405ea926d.jpg


Obviously the back box came up and it has before so was expecting that but...faults in brake electronics?? Wouldn't this be under 'Immediate attention' and not advisory?


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SRB93

S5 B9 Coupe - Glacier White
Bit of FYI and some advice needed reference this mod. Took the old girl in for service today and these fault logs came up:

22c0f79a0098655489ab51f405ea926d.jpg


Obviously the back box came up and it has before so was expecting that but...faults in brake electronics?? Wouldn't this be under 'Immediate attention' and not advisory?


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Did you not re-connect and clear the codes before taking it back?
 

Thundercliffe81

Registered User
Did you not re-connect and clear the codes before taking it back?

Didn't have the means and due to my fly already being unzipped a couple of months ago when it was in for an aero refit (they done a health check), they already knew about it. They didn't even mention it this time. Just seen it on the report.


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SRB93

S5 B9 Coupe - Glacier White
Didn't have the means and due to my fly already being unzipped a couple of months ago when it was in for an aero refit (they done a health check), they already knew about it. They didn't even mention it this time. Just seen it on the report.


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Fair enough, must be quite common for them to see anyway.
 

Thundercliffe81

Registered User
Fair enough, must be quite common for them to see anyway.

Well, that first time...the girl came out and sat me down to give me my keys back etc. She started smiling and said, "You do know there's an exhaust code showing right?" Grinning at me. So I just smiled back and said "yes, I'm aware of that".

It's just the 'Associated brake fault' that's thrown me.


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Craig Moorcroft

Registered User
I can only think of two things on the brakes that would be powered by 12v, the anti lock brake sensors and the brake pad wear sensors (unless it means handbrake). I'm sure if this was a problem with the ABS and warning light would show. Maybe its as simple as the brake pad wear sensor may not work anymore!
 

Thundercliffe81

Registered User
I can only think of two things on the brakes that would be powered by 12v, the anti lock brake sensors and the brake pad wear sensors (unless it means handbrake). I'm sure if this was a problem with the ABS and warning light would show. Maybe its as simple as the brake pad wear sensor may not work anymore!

Hmmmm. Cheers for that. Lends a bit of information at least. Certainly got me stumped! Good point, if there was a brake issue you'd expect to see a warning light as it's safety.


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SMI77

Australia
Problem solved……but the majority will not like it. If so, please click “<” now!!
Bought 2 x stainless steel 3” single inlet RS style tips, and installed by Beaudesert Exhaust, very well respected and also manufacture 4x4 systems, shipping Aust. wide.
Work entailed cutting both aft of the diff, removing OEM mufflers/valves/pipework/tips complete, and installing all stainless, flanges/8”x 2.5” round mufflers/pipework & adapters to tips. BE used their laser which was downloaded into their CAD and fed into their computerised mandrel bender to create the correct angle and length. The 3 x internal ends were flanged so the system can be returned to stock. The tips were originally to be cerakoted satin black. However, as BE were unsure if the inlet side of the tips had to be trimmed away, and by how much, they painted the entire section in satin black, with a gold fleck finish. Mindful that there is still a settling in period for the new sections, whilst it was not cheap, considering the work, the finished product incl. not loud and no dash lights, so far I’m rapt.
We have a pergola area off the end of an open-ended carport. When I sit in my favourite chair, sipping on a long 'Bundy' rum, I am looking straight at the rear of the wagon.

Initially the intent was to simply siamese the piping out of the OEM mufflers, cut the back of the new tips, attaching the pipes to the widened inlet tip.
On closer inspection BE were extremely reluctant to cut anywhere near the muffler outlet pipe, but before the valving (rhs), as they were most concerned they may damage the valving. I concurred, thinking many $$'s if I had to replace it.

Staff noted that the OEM mufflers' gasflow was an 'X' style, in that gases entered, say, via the left-hand inlet & exited into the right hand outlet pipe.

I mentioned about the poor chromework on the tips. Staff said it was not uncommon as the work of the cat was to liquefy the gases, which exited out the tailpipe but often was caught in the tip ‘metal roll’. It was suggested Audi could have simply had a hole drilled through near the tip.

I believe this idea was mentioned earlier on the forum. Whilst on the hoist, the owner looked under the new Audi/Porsche style V6 with the turbo in the ‘V’, and commented that for more power he would recommend new downpipes, with no problem with the exhaust as is.

Trivia, well not really!!! On preparing the job, I was asked where the battery was, to connect 'zappers'. Hmmmmmmmm???.....'nfi'!!!!.
Apparently it is located under the space saver wheel at the back, with a thick cable to the engine bay, ending with a junction connection.

Audi Exhaust Jan 18.jpeg
Audi Exhaust rear Jan 18.JPG
 
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