Need Some Exhaust Advice

[paul_psi]

let me start with sorry if this is in the wrong section still getting used to the site. okay I have a gt3582 turbo sitting on a new Etm manifold Etm has also made me up a dump pipe witch is 4inch coming off the turbo now here's my problem should I continue with the 4inch drop it down to 3.5inch or even 3.25. my plan at the moment is 3.5inch straight through to the dif have a flang at the dif to dump it then have a muffler with just a straight pipe out the back I don't want it to load I'm trying to make the car look stock with hidden power. any ideas would be great I'm chasing 400kw

[GTSBoy]

The bigger the pipe, the noisier it will be and the more muffling you will need to try to keep it quiet enough.

That's a big turbo and will benefit from a big exhaust. I would think 3.5" will be acceptable from the cat back. Of course you're going to want either a nice big 4" 100 cell cat or a suitably disguised decat. And with all that bigness, you are going to need a decent centre muffler under the car and a decent big muffler at the rear. With just one muffler at the rear it will bellow like wounded buffalo.

[KiwiRS4T]

3.5in will be good. One muffler will be loud.

[paul_psi]

would it be spastic loud? would 2 be to restrictive?

[simpletool]

A 3.5" is a good size for a 3582. The bee's d!ck in power jump to 4" won't be worth it at 300-350rwkw. You also won't notice the power drop from a 2nd muffler. Just make sure it is a quality large capacity straight through type (oval body).

[paul_psi]

thanks for the quick reply's im goint to have just a fake cat on there it will be straight through ill use 2 mufflers to try and keep the noise down ill make sure that they are the oval type

[R31Nismoid]

would it be spastic loud? would 2 be to restrictive?

If you get the biggest possible rear muffler under there, it won't be "too" bad, but make no mistake it will be loud and potentially drone heavily on the FWY

2nd Muffler - If you are external gating then don't bother reading the rest below as you'll be totally fine

So the 2nd muffler might pose minor restriction if you are plumbing the gate. By minor i mean it might hurt you 3-5rwkw on a dyno which you'll never notice in a street car, but you will be noticeably quieter (as long as the muffler is again, big as you can get). So if you are in an area where defects/Police are a problem, I'd err on the side of caution with a high-mount etc

[paul_psi]

I'm running hight mount external gate pumb back to try and make it a bit quieter ill put 2 mufflers in it won't be hard to make a straight pipe to throw in before I race and dump at dif for a straight through system