Exhaust system diameter choices

[chappers]

Been reading lots of cool project threads, mind blowing!
I'm just curious about the decision to go single 3" exhaust route?
What is the reasons for single routing?
Complexity, cost, flow, sound?

I know on the 200 20v I have, it's a single down pipe then splits to twin 2.25", then two cats, 2 resonators and both go through a single muffler shell then twin tailpipe.
But mine's a Stebro system, so not sure if standard system is 2.25"?

If you do a 3" down pipe, it could be divided into 2x2.25" and have more CSA.

I'm not doubting the decisions people have made, I just wanted to know the reasons as I'm thinking of modifying mine and not sure the route I want to take.

I still have k24, I want to remove the cats and the resonators, but undecided if I'll chop up the existing stebro or start afresh.....
Can I bolt up 3" down pipe to the k24? Any benefit of doing so?

I appreciate your advice guys.

Cheers
Chris

[loxxrider]

I think the reason people go with a single 3" is to save on weight and complexity. Also cost. The only thing you gain by having two pipes is ground clearance, and that is sometimes an important consideration. 3" downpipe won't really help the k24 over what you've already got. Getting rid of any cats, resonators, or mufflers will help a lot more.

[chappers]

Hey thanks for the explanation Chris
I really like the insanity of your t44 sedan!

I'm wondering what the 3" single (no cat/resonator) sound like compared to a 2x2.25" (no cats/resonators)? Assuming everything is the same with the engine.

But first step is to remove stuff hehe

[123quattro]

FWIW, a single 3" will support 600whp. That's the reason most people do it. It's easy and good enough for nearly everyone. Tons of cheap (good) mufflers available as well.

[loxxrider]

Hey thanks for the explanation Chris
I really like the insanity of your t44 sedan!

I'm wondering what the 3" single (no cat/resonator) sound like compared to a 2x2.25" (no cats/resonators)? Assuming everything is the same with the engine.

But first step is to remove stuff hehe

Thanks! It is a little crazy.

All else being equal (including the muffler) it really shouldn't sound much if any different.

[123quattro]

two smaller pipes will have a raspier sound than a single 3"

[ChrisAudi80]

It think one good reason to ditch the stock UrS exhaust system is the weight, 110lbs. A single 3" system with cat can be as little as 35lbs IIRC.

[amd is the best]

FWIW, a single 3" will support 800whp+. That's the reason most people do it. It's easy and good enough for nearly everyone. Tons of cheap (good) mufflers available as well.

Fixed it for you.

[lorge1989]

"support" is a funny word. Sure it will work, is it optimal? Far from.

Read this:

http://www.superstreetonline.com/how-to ... test-tech/

I'll be doing 3.25 or 3.5 on my car this summer.

[loxxrider]

From a fluid mechanics standpoint, there is certainly something to gain, but it isn't much. Possibly 10 percent which the article above supports. Interesting that they didn't use the same muffler though... That makes the tests validity questionable to me.

Anyway, the only thing you're doing by not going to a bigger size is increasing the boost needed to make the same power and hurting spool a little. So thermal efficiency may drop off a bit, but for the most part you aren't losing much.

Unless you're making over 600 whp, I think more than 3" is pointless.

[audifreakjim]

Hmm. There is an evo test out there like the superstreet test that showed no gains at similar power levels from what I recall. Can't seem to find it at the moment.

[lorge1989]

I searched around and found it lol.

http://highboostforum.com/forum/showthr ... -from-2007

I'd like to see pictures of that evo exhaust. I like the supra test because although we don't know much about the mufflers, it is obvious that there are minimal bends to change the results.

[dana]

"support" is a funny word. Sure it will work, is it optimal? Far from.

Read this:

http://www.superstreetonline.com/how-to ... test-tech/

I'll be doing 3.25 or 3.5 on my car this summer.

Given the PITA it is to run even a 3" on a small chassis audi, I would take the .5% loss in horsepower to save my sanity.

[lorge1989]

yeah I checked out the clearance about the subframe last night, (before I had just shot it out the side). Needless to say I'm reconsidering 3".

[AngryTaco]

I had to beat the exhaust guy to do the 3" on my car. It fits but it's not fun. He claimed it wouldnt fit. I claimed he was full of shit. He did it and it came out well (but very tight)

[chappers]

Good discussions going on, but what I'd really like is to hear the different exhaust notes from everyone's different setups. Maybe at 3 operating conditions, idle, cruise and under load (WOT). If it's outside vs inside at those conditions even better.

The ideal setup would sound great at idle and WOT, but no resonance or boom at cruise @65-70mph.

[loxxrider]

I have some videos of my car with a straight 3" setup with a rear muffler only. Search loxxrider on youtube and you can find them.

I will have 3" with a cat and muffler on my new avant that I can take videos of. They both drone though. It's really hard to get these engines not to drone, especially in this chassis.

I forget what nick had, but I feel like it was a dual system? Or maybe that was just the rear muffler. Either way, his always sounded totally different than mine for some reason. Even when mine still had 3b cams.

[ringbearer]

I am going to install the OE rear muffler on my 3" turbo back. Thuppu did it with good results and still made good power, way more than I make or made when my car ran, lol.

I will sacrifice some spool and power for quiet.

[AngryTaco]

[youtube]http://www.youtube.com/watch?v=ARMX3Y7IBGM[/youtube]

[youtube]http://www.youtube.com/watch?v=N8d6NahdtkI[/youtube]

[chappers]

Sounds mean. Maybe a little too much for a daily?

What's the exhaust spec?

[AngryTaco]

The 5ktq downpipe ( I believe 2.5") opened up to a 3" system. No cat, spintech 6000 muffler with dual 2.25" tail pipes/no tips. The drone isn't too bad but I wouldnt mind it being toned down a bit. For a daily it was nice

[DE80q]

The 5ktq downpipe ( I believe 2.5") opened up to a 3" system. No cat, spintech 6000 muffler with dual 2.25" tail pipes/no tips. The drone isn't too bad but I wouldnt mind it being toned down a bit. For a daily it was nice

The 5k downpipe is more like 2.25". That's why I went with the UrQ downpipe, it is 2.5".

Here is my 20vt with said UrQ downpipe, catless midpipe, and stebro cat back. Basically complete 2.5" with resonator and suitcase muffler.
[youtube]http://www.youtube.com/watch?v=3p5_WGmg2I4[/youtube]

[40v4kq]

When derracuda and I built my 3" SS exhaust he used an idea he had never used before. He built a relief into the rear sub-frame where the exhaust passed above it. He also added a way-bigger-than-needed support to the lower side of the frame to add back any rigidity that was lost by adding the relief. A 4" exhaust would easily fit if needed/wanted.

[amd is the best]

I forget what nick had, but I feel like it was a dual system? Or maybe that was just the rear muffler. Either way, his always sounded totally different than mine for some reason. Even when mine still had 3b cams.

3" downpipe, no cat, 3" all da way, Vibrant stainless muffler at the tail.

It's all in the muffler. My brothers full exhaust is basically identical in design aside from a single tail mounted Magnaflow and it it MUCH more loud and the tone is completly different. His is more of a raspy scream where mine is like a deeper growl. The sound has remained somewhat similar between stock, GT3076 and ridiculous level.

Stock turbo:

[youtube]http://www.youtube.com/watch?v=aHSy-j2Wkq0[/youtube]

GT3076:

[youtube]http://www.youtube.com/watch?v=tdXhvTwUa8U[/youtube]

Stoopid:

[youtube]http://www.youtube.com/watch?v=ghyCwfiUA3c[/youtube]

[youtube]http://www.youtube.com/watch?v=I-70lO6eWWU[/youtube]

[chappers]

Holy Moly, I think Nick won the internet!

Now, how to make ours sound like that.....