custom questions

[ctownhawk]

there is a local shop that two of my friends have went to for their custom exhaust setup. I was wondering if there are any popular setups. i tried checking out e30tech, but it seems all they talk about are 3 inch pipes for turbo'd motors.

i plan on getting longtube headers later on, so i guess i have to get the exhaust put on along with the headers, otherwise they wont fit; correct?

do i have this right? headers> dual 2.5inch pipes to a dual 2.5in to 3.0out Y pipe to the cat. then a 3.0 to 2.5 y pipe out to dual 2.5in pipes until it hits the muffler. finishing up with dual 2.5 tips?

i dont remember who had them, but someone on this forum had dual 2.25 curved chrome tips on his and i liked the way they look; although i'de probably want them a little bigger. anyone know which im talking about?

[MR 325]

Dual 2.5" is WAY too big. Single 2.5 is perfect for a N/A M20.

[AndrewBird]

I'd go dual 2.25". You can't really have to big of an exhaust (until you get get REALLY big anyway), but there is a point where larger isn't any better.

A stock i is what, dual 2.25" all the way back? Or smaller?

[matt]

I'd go dual 2.25". You can't really have to big of an exhaust (until you get get REALLY big anyway), but there is a point where larger isn't any better.

A stock i is what, dual 2.25" all the way back? Or smaller?

MUCH smaller. 1.75ish. And yes, you CAN have too big. Single 2.5 is pushing too big for a stock M20. Big enough that you'll lose more torque than you gain HP.

The irony is that this will make the car feel faster, because it will make the HP and torque curves steeper.

Dual 2.5" is WAY too big. Single 2.5 is perfect for a N/A M20.

Single 2.5 is perfect (a little too big) for any motor up to 300hp. Seriously.


/rant

[ctownhawk]

okay so i make the pipes the same size, if not .25? bigger than the stock ones? how about the size of the tips?

[matt]

I would do one pipe. 2.25 all the way back with a highflow cat, resonator, and muffler. Then put whatever tips you want on that. Most magnaflow tips are 2.25 inlet anyway.

[drifty340i]

Yip a 2.25 will be heaps, 2.5 will support 350hp without restriction. my 4.0l v8 e30 runs a single 2.5

[MR 325]

Single 2.5 is perfect (a little too big) for any motor up to 300hp. Seriously.

Unless you're boosting, then 3" it is. :)

[MR 325]

Yip a 2.25 will be heaps, 2.5 will support 350hp without restriction. my 4.0l v8 e30 runs a single 2.5

I would never run tiny single 2.5 exhaust on a V8.

[matt]

Unless you're boosting, then 3" it is. :)

Well, with a turbo motor the only downside to the larger pipe is weight and routing problems. An NA motor will actually lose torque if you use too big a pipe. But yes, with a turbo bigger is always better. Of course there's still a point of diminishing returns.

[ctownhawk]

whats the benefit of a single 2.25 vs dual pipes of a smaller diameter?

[matt]

Dual has better ground clearance and better sound control.

Single is lighter.

[drifty340i]

I would never run tiny single 2.5 exhaust on a V8.

Trust me its heaps on a 300hp ish small 4.0l v8 mate, we have done ALOT of research and talked to all the experts. We have done tests on the 4l v8 in question and all of them lose tq, low and middle range hp with the 3inch pipe. only making it up in the high range, with no advanages over a good mandrel bent 2.5 inch zorst. It sounded crazy to me at the start to, i though a 3inch would be the go, was actually quite worried the 2.5 would cause restriction. how wrong was i lol

[silversleeper]

i would think that the ideal N/A setup for our cars would be either SINGLE 2.25" or DUAL 2".

As for best sound, I have not the slightest clue. I really am interested in running a custom dual exhaust with an x-pipe.