Exhaust system diameter choices

[amd is the best]

Holy Moly, I think Nick won the internet!

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

Simple, 3" piping, no cat and this muffler: http://vibrantperformance.com/catalog/p ... ts_id=1162 (or similar Vibrant).

[audifreakjim]

Sounds so good

[AngryTaco]

[chappers]

Like I previously mentioned above, I wanted to do some baseline recording of the tailpipe sound, interior and drive-by and maybe some from standstill acceleration away from the camera.

This is my first try ever at using a GoPro to record video, and also my first ever Youtube clip, so please bear with me...

http://youtu.be/ksafMVSq9BE

I thought it would be good to have a few shots a different positions and at different operating points to record for posterity what it sounded like stock(ish) so that if and when I ever upgrade the darn thing I can track the changes.

If anyone has any pointers I'm all ears, because I noticed the sound was a little muffled on this one and there is an annoying rattle in the video which I think I can fix with some strategically placed rags/foam...

Cheers
Chris

[chappers]

Hmm such a noob I cant even get the youtube link to embed properly!!

[paradox11235]

I'll be going from stock exhaust with gutted cats and deleted center muffler to a catback setup i found for cheap that merges back into one 3" pipe with a resonator and muffler, don't know the brand. I'll try to take some sound clips.

[chappers]

I'll be going from stock exhaust with gutted cats and deleted center muffler to a catback setup i found for cheap that merges back into one 3" pipe with a resonator and muffler, don't know the brand. I'll try to take some sound clips.

Great I'm keen to hear it, are you planning to record it while it's stock and then again once you change it?

[paradox11235]

Yeah, I'll do before and after. The gutted cats and deleted muffler has a tiny bit of growl to it, and you can hear the motor revving unlike the stock exhaust. But it's still pretty quiet, can't even hear it on the highway

[chappers]

Cool, I was thinking of removing the cats and the resonator, keeping the twin pipes as an intermediate step before doing single 3". Plus as people have already said maybe 3" is a bit overkill unless you change turbos etc....
BTW, Do you have any tips for recording the sound?

I'm borrowing a Gopro from work so only get weekends/evenings to try it.
I'm going to try record the inside sometime this week, set it up as if it's a front passenger, sort of head height.

[paradox11235]

I just recorded a clip of my exhaust before putting the new one on, which merged to 3" with a huge resonator and a flow master muffler. It's lower but not really any louder. I might remove the resonator...

[chappers]

Cool, are you posting the video up anywhere?

I've not recorded the inside yet, but when I do I'm then removing the cats and resonators. That will probably be a week or two away.....

[chappers]

I removed the cats and resonator this weekend, took me forever on jack stands, cutting and welding everything!

It's got a nice burble now, but when I took it for a test drive under load it knocks or chaffes on something, very irritating.
I had a quick look when I got back and it looks like it's very low in the middle, and I think it's now knocking on that exhaust tunnel cross brace. Is this brace even needed?
I had to remove the brace to get the exhaust off and someone had sheared 1/2 the bolts before me.
So i'm not sure what's it's actually there to do?

Either way I need to get back under and work out why it's sat so low.

[loxxrider]

I took that brace out on my 200 20v sedan about 7 years ago and never noticed a difference. I'm sure it serves some purpose, but I never cared to figure it out and it hasn't caused a problem since.

[chappers]

Ha thanks Chris, it didn't look like it did much.

Catalyst had seen better days!

[lorge1989]

Going to bump this up with some more data. Most of the these findings were done by my friend in conjunction with Breakout Motorsports in NY so I cannot take credit.

They are working on a BT 1.8T TT. He had a 3 inch exhaust and downpipe. They remade the downpipe and the exhaust system to be more free flowing. The downpipe is still 3" but the exhaust is straight through 3.5 inch.

Pre turbine pressure was 45 psi at 23 psi at 7750 with the old exhaust.

New exhaust (same turbine housing) its 28 psi. Thats a 17 psi pressure drop preturbine, it only took a 5 psi pressure change post turbine to make this happen. The airflow is 15-20g/s higher on the street at the same pressure with the changes. Now its 28psi pre turbine at 26psi inlet, the expansion ratio makes the post turbine pressure very sensitive.

One of the reasons this change was so dramatic was because of the high overlap cams they are running, so the engine needs as close to 1:1 as possible.

These dynos are on pretty much same pressure setting, the first one is the old exhaust, the second the new one.

[dalspaugh]

Interesting!

What exactly did they do to make it more "Free flowing?" seems like an ambiguous solution with big gains!

[dana]

i recognize that dude, I think he came up to me at an Autozone in the Rochester NY area when I had my big turbo 90.

[lorge1989]

Interesting!

What exactly did they do to make it more "Free flowing?" seems like an ambiguous solution with big gains!

I didn't mean to be so vague. The old exhaust was a 3" with your typical performance muffler, just one I believe and the down pipe was 3" as well, but with some not-so optimal bends, if you have ever seen what a TT downpipe looks like you know what I mean. The new exhaust still has a 3" downpipe just better designed and a straight through 3.5" exhaust with a cutout with a cat in it for emissions haha.

i recognize that dude, I think he came up to me at an Autozone in the Rochester NY area when I had my big turbo 90.

Yep thats Brandon. Hes in the finger lakes area.

[dana]

Yep thats Brandon. Hes in the finger lakes area.

Yep, that was him for sure. They were in a b5 1.8t with an hx35.

[loxxrider]

Nice. When I put a t3/t4 turbo on my 1.8t jetta I took the aftermarket crap muffler off and put a 3" straight through on it and gained 60 whp. It can make a big difference!

But that difference is absolutely not in the pipe diameter in this case. 3" straight through is plenty for 600whp.