Has anyone tried a 2 into 1 exhaust on a 3.0T

[Burkeomatic]

Ok, hear me out. This is theoretical, and I may not do it. I also searched, and found nothing.

I know this seems counterintuitive and maybe a little bit stupid, but I am asking just out of curiosity. I know the real answer is "try it and see what happens" but stick with me. I am hoping to hear from someone who knows more about exhaust theory than I do, it has been over a decade since I have taken physics and while I do vaguely remember the harmonics lab, it has been a long time.

Now that my car is decatted, I knew it would sound bad in the absence of the suit case resonator, but I wasn't prepared for just how bad it would be. I do have a set of the JHM baffled/catted downpipes on the way in, which I think may help considerably. It is a good thing I decatted my car though, my cats were on the way out, and crumbling/melting.

Anyways, I have been bouncing this idea in my head around for more than a year, I'm just not sure how I should go about it. I have been studying 370zs which are also cars that sound like butthole when they are uncorked and especially decatted.

I have noticed that the single exit exhausts for that car sound considerably better than the duals, and gives you more of the "I6" sound as opposed to the lumpy V6 sound. I would assume that is because more pulses are combined there is greater opportunity for the wavelengths to cancel out and result in a smoother sound.

This is a comparison between 2 370z single exits - for the record, I like the cheaper one better.

https://youtu.be/k-c0bop7Fvs?t=305

So if I were to go with this, I would assume I would want to dump both exhausts into a 3 inch pipe, correct? The ID of the OE exhaust is 2.25 inches from what I found giving me an area of about 4 inches, and the 3 inch pipe has an area of about 7 inches, technically 87 percent of the original size. That should be okish right?

Then in theory, if I were to continue, where would I want to put the y pipe? Would it be advantageous to put it after my already installed x pipe? Or would it be better to delete/sell the x pipe and put it coming straight off the down pipes? I feel like the latter, but the lazy/cheap in me wants the former.

What do you all think? Is it completely idiotic? I know the idea is still half baked, but I have been considering it, but I really just now started thinking about it. If anyone that knows about building and constructing exhausts could chime in, that would be great. If you just googled some crap to try to answer my question and seem like a know it all, I have already googled it. However, I would not turn down a good read on exhaust design theory.

[ActiveMonkey]

A few guys have done versions of what you are talking about.

https://youtu.be/SsFQN4nmgko

https://youtu.be/n5_ACFD3rRI

https://youtu.be/qqEehLrxP4c

https://youtu.be/IYRUIvFolfo

https://youtu.be/7TPiFxR8NvU

I think it would be best to join into a single 3.5" where the downpipes normally end then run the single pipe back just past the differential where it would then Y off into dual 2.5". This should produce a nice deep tone however i think the drone would be awful. I've recently gone there 6 or 7 different iterations of my exhaust and it takes a lot to quiet down a catless car. You only have so much pipe to fit resonators and mufflers.

[Burkeomatic]

A few guys have done versions of what you are talking about.

https://youtu.be/SsFQN4nmgko

https://youtu.be/n5_ACFD3rRI

https://youtu.be/qqEehLrxP4c

https://youtu.be/IYRUIvFolfo

https://youtu.be/7TPiFxR8NvU

I think it would be best to join into a single 3.5" where the downpipes normally end then run the single pipe back just past the differential where it would then Y off into dual 2.5". This should produce a nice deep tone however i think the drone would be awful. I've recently gone there 6 or 7 different iterations of my exhaust and it takes a lot to quiet down a catless car. You only have so much pipe to fit resonators and mufflers.

Thanks, my mistake for searching for C7s instead of B8s. Gotta break out of the bubble. I actually liked the way all of those sounded. Sound level isn't really my concern, I'm not upset with the loudness of my car now. It is a little boomy between 2-3k, but I can deal with that, because I never cruise there. It is the God forsaken tinny rasp that is killing me, and none of those cars had it. I need to check into their set ups and get an idea. Thanks!

Maybe it is time to start practicing on my welds again.

Edit, now I am having really bad ideas, I wonder how much different the exhaust routing is on a B8 quattro vs a C7. Because you see I could buy a 3 inch exhaust for one of those and a y pipe and save myself a ton of work. The main thing I am worried about is getting it through the rear suspension/axle area.

[serg72]

Thanks, my mistake for searching for C7s instead of B8s. Gotta break out of the bubble. I actually liked the way all of those sounded. Sound level isn't really my concern, I'm not upset with the loudness of my car now. It is a little boomy between 2-3k, but I can deal with that, because I never cruise there. It is the God forsaken tinny rasp that is killing me, and none of those cars had it. I need to check into their set ups and get an idea. Thanks!

Maybe it is time to start practicing on my welds again.

Edit, now I am having really bad ideas, I wonder how much different the exhaust routing is on a B8 quattro vs a C7. Because you see I could buy a 3 inch exhaust for one of those and a y pipe and save myself a ton of work. The main thing I am worried about is getting it through the rear suspension/axle area.

All 3.0 B.8 ; B 8.5 and C7 have the same exhaust system, differing only in length. They are quite problematic in tuning the exhaust sound. I passed this test not long ago, I am satisfied with the result. In the Q5 section, 8R talked about his experience.

[Burkeomatic]

All 3.0 B.8 ; B 8.5 and C7 have the same exhaust system, differing only in length. They are quite problematic in tuning the exhaust sound. I passed this test not long ago, I am satisfied with the result. In the Q5 section, 8R talked about his experience.

Thanks man, I'll go over there and look for it. I went in on my lunch break to find it and got sidetracked about a radar detector recommendations. I couldn't find the user "8R".

On that note, I got my JHM pipes today, and I accidentally ordered the 2.5" exit.

Oops.

On the bright side, reducers are $30, and if I want to do a 3.5 inch exhaust, dual 2.5 inch to 3.5 inch is way easier to find than 3.5 to dual 2.25, so there is that I guess.

[serg72]

Thanks man, I'll go over there and look for it. I went in on my lunch break to find it and got sidetracked about a radar detector recommendations. I couldn't find the user "8R"

It doesn't use the 8R, it's the branch of the Q5 8R.
I was describing my experience building the exhaust.
https://www.audizine.com/forum/showt...xhaust-Q5-2014

[Burkeomatic]

It doesn't use the 8R, it's the branch of the Q5 8R.
I was describing my experience building the exhaust.
https://www.audizine.com/forum/showt...xhaust-Q5-2014

Oh, ok thanks that z pipe looks nice.

[Burkeomatic]

Ok, I'm back to this. The AWE exhaust is damn near insufferable. It's probably fine with stock cats, or even the downpipes that go with it, but it just isn't working out on my cat delete/JHM catted downpipe set up. Maybe I'm getting old, but that resonance that rattles everything in my car and drones me to death is annoying. Everything in the AWE exhaust and my JHM pipes seems strategically placed to keep me from adding another muffler/resonator. I also don't want to hack it up, because if I do, and I still don't like it, I've killed the resale value of that exhaust and I have a bunch of really expensive pipes to throw away.

I've ordered a merge collector thingy that will go from both 2.5 downpipes to 3 inch.

Now I have been doing some research on installing s4 exhausts on to a6/7. The positive of this is that it would save me a decent bit of fabrication. I found this for $400.

https://shop.redline360.com/products...BoCzfwQAvD_BwE



It looks like it should fit, and from what I gather is that all I should have to do is extend it about 6 inches.

Judging my that little resonator, I may have to end up replacing that. I would just end up hacking it off somewhere upsteam and joining it, and extending it a little in the back. I don't want to pay more than say $500 for this option, as I would be taking a perfectly good exhaust and hacking it up.

Of course, I have a ECS resonator delete pipe I was never able to sell (I did have some dipshit offer me $20 when I was only asking $100 for a $300 part, and at that point I decided I would rather throw it away). That would make a pretty good jig to start the midpipe of the exhaust, and I think fabbing the rear part would be a little easier. I would rather go the more prefabbed route, because my fabrication skills aren't that great, but I'm not sure and could go either way. The benefit to the entirely custom route is that I could go ahead and use whatever parts/mufflers I wanted.

Thoughts? Ideas?

[BuickTypeR]

has anybody done dyno before and after curious of what gains or loss in hp and tq.