3" To 3.5"/4" Exhaust

[usmair]

Hey guys

I think there are a few other guys in the same situation as me.

My car came with a 3" HKS cat back system from Japan (it's really really quiet, I kinda want something louder). I have also had a hi flow cat and 2.75" front pipes fitted to the car.

I'm now planning ahead to future mods. I currently have -9s and am planning to put 20psi through them with e85. This obviously means over 300rwkw...

From what I've read, people highly recommend getting a bigger exhaust for anything over 300kw.

But since I've already got a full 3", I wanted to know what kind of gains I would expect to see if i upgrade my whole exhaust to a 3.5 or 4 inch system.

If its something like 20rwkw then I suppose its worth the expense.

But then again I have no idea how much a 4" system costs and where I would find one. I'm expecting them to be around $2000 (dont need a titanium or anything too fancy).

So can people please shed some light on this based on prior experiences.

- Did you upgrade from a 3" to something bigger? If so, what kind of gains did you see?

- Do I need a 3.5 or 4 inch system for -9s with e85?

- Where can I get such an exhaust (online, Just Jap, custom???)

Cheers

Umair

[usmair]

errr why isnt this coming up under new topics

[DCIEVE]

Purely from a cost point of view, the 3.5" stainless is expensive, from memory the cost per bend was roughly double what I had previously paid for 3" and took a while to find. 4" is more common (i.e. cheaper) but in my case there wasn't room.

There are plenty of threads discussing the merits of big exhausts.

[TiTAN]

you can get off the shelf 3.5" exhausts.

if you can weld you can make your own, i priced it up from an exhaust shop (this was for a cat back)

This is for a 3.5"

$95 for a donut (get 2 if you want to make front pipes as well)

$39 per M for straight pipe

$350 per custom dimension muffler, in my case 18*12*8 & 17*8*5. obviously an off the shelf size will be cheaper (eg 16*11*8)

$18 per flange (includes gasket)

[usmair]

can u pls send me a link to the off the shelf items

Edited January 9, 2011 by usmair

[NYTSKY]

I have a 3.5inch-3.75inch HKS exhaust for sale if you are interested $400 and it yours. I made 15rwkw gain over my 3inch.

I have replaced it with a custom 4inch turbo to tip and it wasnt cheap! Material alone has gone past the 2k mark.