I can't tell the difference...can you tell the difference?

Post by **sakimano** » Mon Jun 11, 2012 4:32 am

Borrowed a friend's GoPro and strapped/suction cupped it on the exterior to see:

a) how loud the car is when I cruise around my neighbourhood (windows up in an Audi is very deceiving....the cars are great at suppressing noise)
b) what the difference, outside the car, is when sport mode is engaged and you're going WOT

So I did a few rips through the gears then edited the clips into a video. Honestly I can't really tell a difference. I do know that when I was idling, there's a huge difference which you can tell in the car, but while WOT, I can't really discern. Can you?

http://www.youtube.com/watch?v=iVMJs8c1e6w

(title is a reference to a lame old commercial we used to have over here back in the 80s in case Brits are wondering) http://www.youtube.com/watch?v=phEtATUR5Uk

Post by **RS04YOB** » Mon Jun 11, 2012 7:51 am

Nope

Post by **sonny** » Mon Jun 11, 2012 9:52 am

What backing did you use on the GoPro, the open or closed vent cover?

Post by **Spwong** » Mon Jun 11, 2012 1:11 pm

I just got my RS4, so have been reading up on this.
It seems even without the sport button engaged, the flap opens up at higher rpms. Sport button is only for a louder idle and a slightly more aggressive throttle mapping. I may be wrong but it might explain why you don't hear a difference at WOT.

See page 29 here:

http://www.s4-mtm.com/images/RS4V8-StudyGuide.pdf

Excerpted:
Audi RS4 Exhaust Flap Control
A further difference is the layout; one exhaust flap is located downstream of each of the rear silencers. The exhaust flaps are fitted to give the engine a sporty sound. Low-frequency droning noise at low engine RPM is prevented. At high engine RPM and high exhaust gas flow rates, flow noise and exhaust back pressure are reduced by opening the additional cross-section.
The exhaust gas flaps are closed at idle, low engine load and at low engine RPM.

Function
The exhaust flaps are switched by a vacuum actuator. Both vacuum units are switched by an electrically activated solenoid valve. The exhaust flaps are switched according to a characteristic map.
The factors of engine load, engine RPM, gear selected and the shift signal from the Sport button are used to plot the characteristic map.
For example, the exhaust flaps are opened at idle when the Sport button is pressed.

Post by **Timster** » Mon Jun 11, 2012 1:19 pm

Welcome.

FON.

Rule 1.

Post by **Spwong** » Mon Jun 11, 2012 1:25 pm

Also page 41 explains it further. In Sport mode, the flaps close up again after engine speed increases, and then open up again depending on speed and load.

Post by **Spwong** » Mon Jun 11, 2012 1:28 pm

Thanks Timster.

Post by **RS04YOB** » Mon Jun 11, 2012 1:31 pm

Rule 2 don't mention the "CBU"

Post by **Spwong** » Mon Jun 11, 2012 2:30 pm

I'm not translating too well from this (that) side of the pond - FON, CBU? (I'll stab - CBU is some repetitive,ad nauseum question related to the intake manifold that I won't ask?)

Post by **adsgreen** » Mon Jun 11, 2012 2:52 pm

Spwong wrote:Also page 41 explains it further. In Sport mode, the flaps close up again after engine speed increases, and then open up again depending on speed and load.

Also completely wrong

Flap position is based on sport button, revs and gears. thats it.
http://forum.rs246.com/viewtopic.php?t=93014

The thing is I don't think the stock exhaust will be louder par-ce... it's more of a tone difference.
Miltek no res is definately louder - by 10 dBA. mine was tested at 4500 rpm and was 88 with sport mode off and 98 with sport mode on.
Just over 8 times as much pressure waves interpreted by the human ear as approx twice as loud.

Post by **sakimano** » Mon Jun 11, 2012 6:42 pm

Spwong wrote:I'm not translating too well from this (that) side of the pond - FON, CBU? (I'll stab - CBU is some repetitive,ad nauseum question related to the intake manifold that I won't ask?)

FON = <beep> Off Noob
CBU = Carbon Build Up (favourite topic of most RS4 owners in the US who blame CBU when their bad driving results in poor 1/4 mile times, or they lose a highway pull vs. a tuned A3 2.0T)
Rule 1 = Pics or it didn't happen (that's a guess, but that's rule one on most forums)

As for the flaps, I was under the impression that the flaps are always closed, except when sport mode was engaged. When engaged, gears 1-2-3 flaps open from 0-1000 rpm, then close from 1000-4000, then re-open from 4000-redline. Gears 4-5-6 in sport mode have the flaps always open.

You can hear mine squeaking when they open/close a few times during the video, but I edited those sections out (just the normal driving about part).

Post by **sakimano** » Mon Jun 11, 2012 6:45 pm

sonny wrote:What backing did you use on the GoPro, the open or closed vent cover?

open...this one

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