franky996

The stock exhaust is way to quiet, so I decided to build my own exhaust. Went with a 2 into 1 merger piece, then 3 inch tubing all the way. Muffler is 3 inch in, dual 2 1/2 inch out. The inside of the muffler is just a simple y shape, you can see through it. The sides have perforated metal with sound deadening material. The tips are just 2 1/2 inch tubes, slightly polished up. The whole system is stainless steel and was welded with stainless wire.
Stock exhaust weight in at 68 lbs, the new one weighs 38 lbs.
Sounds really great, absolutely love it.
Material cost was about $200.- and time to build was 4 hours.

2001 S8

With no middle muffler, how is the cabin noise at interstate cruising speed?

franky996

Cabin noise is fine at cruising speed. I'm actually surprised how quiet it is inside the car. I installed a cat back exhaust on my friends '05 Mustang GT , back in '05, and it was horrible at certain rpm's , very noisy cabin drone. I was worried about that in the Audi, but don't get any of that

twentysevenlitres

Start a production line then, as a few of us will want one!

mAgnum8

That system although it's lighter, seems to me like it would be a lot more restrictive. I installed an X-pipe and removed the resonator, leaving the stock rear muffler. I lost some weight and have a freer flowing system

franky996

The system is much more free flowing than your setup. Both , the OEM double pipes and the 3 inch single pipe easily outflow the engines cfm rating. The restrictions come from the resonator and the muffler. The muffler I use doesn't have any restriction inside.

mAgnum8

OK, if you say so.

silverd2

You can argue with math, but math will win every time.

1st, a 3" (ID) pipe has a cross section area of approx 7.06 sq inches.

a 2 1/8" (ID) pipe (stock D2 A8/S8 after cats to rear muffler) has an area of approx 3.53 sq inches...x 2 pipes = 7.06 sq inches, netting the SAME capacity.

As for center resonators, they are mainly "tone changers"...not that restrictive really. Most people remove these for sound "quality" (tone), not hp gain.

A less restrictive rear muffler simply moves torque/hp to high rpms (with maybe a VERY slight hp gain) at the great expense of low/mid rpms (freer flow = killed low end) where 99% of all driving is done. I have to assume you may feel a gain in your low/mid rpms due to the "confused" set up I see in this "custom" exhaust....but, arguable, a likely loss at redline...all for the following reason:

That absurd fitting placed behind the cats (photo) would never have been put there by ANY decent pro exhaust guy, unless it was an emergency to get a car back on the road when the correct parts were not available. Exhaust flow exiting through each of the 2 pipes (exiting the cats) is forced to make TWO near 90 degree turns AGAINST the other pipe's flow, before entering the 3" pipe! ...direction change = restriction ...resulting internal turbulence from this set-up = more restriction!! Even though the 3" pipe may have the same "capacity" as the 2 stock pipes, that doesn't mean that just ANY fitting can continue the flow without a HUGE impact in the form of restriction.

Changing exhaust direction (forced to go around corners) is precisely how some of the most restrictive mufflers dampen sound.

I would have to assume that this BADLY designed fitting more than robs the system of any gains netted by a full flow rear muffler.

You can argue all you want with math & physics, but without proof in the form of a dyno test, against a stock system, it's just words.

If you achieved the "sound" you were looking for, good for you...not to mention the possible bonus of a "slightly"(?) more responsive feel off the line.

Cheers

franky996

Awww, well look at that. A forum troll feels he has to enlighten us with his wisdom. I always get a kick out of losers like you, who do nothing but post on forums all day ( 5year member, 2200 posts! And I'm sure you post on other forums also).

As far as the exhaust goes, the merger piece doesn't make a 90 degree turn like you state it does. But maybe I need to get back under the car and check, since you know for a fact that it does.

I was going to post the dyno results, but why bother, you know everything and I'm sure you can tell us how it went.

I won't read this thread anymore, so no need for you to reply, but you're going to anyway. Probably more than once, since you feel you have to show your other forum buddies that you're the fountain of wisdom and knowledge

silverd2

Ohhhh, did I hurt your feelings princess?

...and that's 2283 posts, thank you very much.

"I was going to post the dyno results, but why bother, you know everything and I'm sure you can tell us how it went."

That's hilarious...you've never even seen a dyno...it didn't "went" all, now did it?