my goal is for someday reach 400 horsepower, and i was talking to a lead guy at flowmaster exhaust and he said 2.5" exhaust will suport up to 400 h/p, and i went to the local import shop here and they said they are doing 2.5" on there 89 civic hatch w/ b18b and wrx turbo and that will be pushing around 18 lbs. so would 2.5" be good. I had a friend with a turbo eclipse that did 3" everything and it seemed to bog a lot.

 

well of course people are going to say 3" will produce more power, which it will...but if you plan on keeping a/c and that junk then, 2.5 is for you! it shouldnt be a problem to hit 400whp with a 2.5", it will be alot easier and spool slightly quicker with the 3" though...its really personal preference!

~K

 

2.5" is so quiet

 

It has nothing to do with personal preference. If you put too big of an exhaust on, you slow down the exit speed of the gases and loose the scavanging effect. I think 2.5 would be fine.

 

Except on a turbo you want the biggest you can get. Hell, some people with rx-7's and supras run full 4" exhausts.

 

i have a 3" thermal w/no cat or resonator. no turbo on it yet. its sooo loud. drove 1500 miles with it and my ears were cloudy for a few days. it will be greatr when i get the snail on though(im running a 2.5" dp too)

 

I have a 3" thermal on my LS, and i wish i went with a 2.5. It's very loud, even with the VS resonator. If you care anything about how loud your cabin will be, or plan on taking any road trips, don't get 3".

 

No.

 

what do you mean no. the bigger the better with a turbo. thats why running open dp is the best.

 

No, what?

 

After reading this I cant wait to throw on my 3" exhaust.

This will be along summer since Im not going FI til fall

 

3" will help spoolup quite a bit, I think that's a pretty commonly known fact. The less restriction in the exhaust system the better, for a turbo car. Ask anyone that has actually driven a turbo car with open dp, then put the exhaust on. They will tell you it spools noticeably quicker with the open dp. When I put my 2.5" exhaut on my car after running open dp for a couple days, the spoolup was a *lot* slower, almost creeping up to full boost. Where as when I was running open dp I could floor it and have full boost very quckly. 3" inch exhaust is actually the next mod on my list, personally.

Justin

 

3" is the only way to go on a turbo car if you have the money.

And you can keep A/C and that junk as you say with a 3" exhaust all you need is a 2.5" downpipe.

 

Sorry buddy, but you've obviously got a little to learn about turbos. Bigger is better, end of story.

 

its not like a turbo creates any back pressure.

 

Smaller exhausts scavenge the gasses better, and LS trannies let you stay in boost longer.

Stock exhaust+LS tranny+B16 (most powerful motor ever made by Honda, since it has a little more HP but a lot less torque (and since torque doesn't mean anything)) would be the BEST setup to get.

All this plus a 14B or maybe even T25 turbo would kick ***! Instant spool up!

 

LOL...oldie but a goodie

Justin

 

If the phrase bigger is better is true with absolutley no exceptions, why aren't people running seven inch down pipes on their race cars? I would think that if it helped all that much, figuring out how to get that big of a dp in the engine bay would be worth the effort. I know I don't know everything, but it seems to me that once you get to a certain pipe size, it just doesn't help anymore.

P.S. I plan on using a three inch dp by the way.

 

Um never mind, I'm going to go read some more turbo books. Learning is good.

 

My theory is that if you have a 500 whp car and it's good to run a 3" downpipe with no cat and a moofler. Then it's cool to run a 300whp car with a 2.5" downpipe and 2.5" exhaust with a moofler. There's no need to have to listen to all that noize especially if your a daily driver. Get a 2.5" If you are worried about noise. It's probably a difference of about 10hp and maybe 500 RPM sooner spool time. Not worth it in my opinion. That equates to about .12 of your 1/4 mile time.

Right now, I'm running my old 2.25" exhaust. this is with a rev hard turbo and 6psi and the lag is about 1 second. I'm gonna upgrade to a 2.5" soon.

 

turboing a honda is about making sacrifices, 3" isnt that much louder than 2.5", just live with it!

 

i made 565 whp on a 2.5 exhaust. I just never got around to changing it out but i bet i would have made more hp with the 3".

 

Not necessarily, how about this



Or here is the link... http://www.hughlett.net/Mario'sPage.html
Its a square 3" which has an area of 9 sq" vs a 3" round that has 7", so actually its like running a downpipe that starts out at nearly 3.5" directly between the turbo and the A/C compressor!!!

Tell me what else can't be done, and I will do it!!!
Randy


[Modified by Mochanic, 2:22 AM 2/15/2003]

 

Forget what everybody has told you about 2.5" exhaust!!!
I just drove the car with the 3" square downpipe I made, and it made huge power everywhere! Spools very quick, is not any louder than a 2.5", FITS WITH A/C, comes off in under 30 secs. Goes on in under 1 minute, has no clearance problems, looks and sounds good, and did I say makes huge power?!?!

Randy

 

hook me up with a straight DP Randy

-Justin