2.5 vs 3.0 exhaust

[Doug Sugar]

hey guys, i did a search on this but need some advice

i currently have a 91awdtsi
mods are k&n turboback 2.5 exhaust boost gauge and controller

my buddys is parting out his car
and I am taking his evo3(manifold, turbo,02housing)
uic pipe, fmic, 550cc, fuel pump and s-afc.

he also has a turboback 3in exhaust, would it be worth it to replace
the 2.5 for this level of mods, i will not ever be going with a turbo larger
than the evo3 16g.  So i dont want to spend the extra cash for a larger exhaust unless its really worth it

[Nathan Tralenberg]

personally I would take the exhaust, the more flow the better!,

[Neil Fowlie]

i dont think it would be worth it to go out and buy a brand new 3 inch $1300 or whatever.
but if you can get a good deal , and then sell your 2.5 why not

from what I understand to use the evo3 o2 housing you have to mod
the downpipe, so it may be easier to replace the works

as far as extra power, maybe a few extra hp as you approach redline

[mike griffin]

if you buy his and wanna sell yours, lemme know.
or if he wants to sell his, let me know too.

[Artem Goloubov]

with 3" you get more flow at top end, but low end will suffer. Personally I think 3" is overkill for anything below 400HP on this cars.

My next exhasut will be 2.5" all the way from the turbo outlet

[Mike Meron]

3" makes your car sound like it has an external dump when its internally gated.

PS i dont have an external dump yet.
PPS but i do have in excess of 400 CHP and WHP

[Matthew Giene]

If you can get the exhaust off you buddy for a good price, go for it.  It will be better than the 2.5" you have, but if the price is near what it would cost is high.  Stick with what you got.

Also, just cause you think you want to stay with the 16G now does not mean you will not want to change later.  Many people on this board said the same thing and now run bigger.  :wink:

Personally I think 3" is overkill for anything below 400HP on this cars.

Most of the moded cars here are running 3" and I am sure they are not pushing 400 HP.

[Fraser Cassells]

3" Exhaust on a 4G63T is a no brainer, no personal feelings will change the fact it helps rather than hinders.

I personally feel personal feelings based on ignorance should be called uneducated biased opinions rather than personal feelings.. But thats just me. I am having a flashback to 1996 when people didnt have a clue as to how to make these cars fast for cheap.

[Robin Toor]

If you want to save money and will not get a turbo bigger than a 16G, stick with the 2.5" exaust. The 2.5" exaust is nice as it doesn't scape as much on bumps when your car is lowered.

If you have money to spare, and you have future plans for a turbo bigger than a 16G, get the 3" exaust.

I'm making an excess of 400whp on a 2.5" cat back with a 3" downpipe. I'm sure I could make a lot more with a full 3" exaust, but a 2.5" will not hold you back too much. Then again if I remember correctly I think I was running open downpipe on the dyno...

[Artem Goloubov]

In my case 3" exhaust gave me an awful power band of 4700 to Redline. With anything below 4600-4700 just too slow. However that 's running a 14b @ 15PSI.

As people mentioned above if you planning to go bigger that 16G invest the $ into a 3".

BTW personal opinion is not taken from thin air, and is based on experience of making my own exhaust systems and tuning the car, take it for what it is.


Art

[Mike Schmid]

Evo3 16g will flow 40+ lb/min, I don't think it's too small to utilize a 3" turbo back.

Like someone else pointed out too, the evo3 02 housing is different than the standard one and the exhaust won't match up very well at all.  Get the 3" that's matched to the o2 housing and big ebough to really make use of that turbo.

[Eric McIntyre]

id say get the 3" and keep the old one around just incase you dont like it... if you dont like it, swap it out and stick with your 25, if you do like it keep it and sell off the 3" for what you close to what you pai, or about the same

[Andrew Steele]

As Fraser said, no brainer.

Go for the 3" ...

I went from stock o2 and stock dp to evo O2 & 3" turbo-back, much happier. (this is with the EVO 16G)

[John Hartman]

the only considerations here should be cost and sound.

If you have the money and its a good deal, then its up to you if you like the sound.

I personally would never go back, but it DOES drone a bit on the freeway and its a bit loud for some peoples taste.

also have a look at the quality and fitment of the whole thing.  Is it any good and will it last?

[Jess Atendido]

well since we're talking about exhaust now i have a question...what happens if i have a full 3" turbo-back pipings...but my muffler inlet is 2.5"...how would this affect me?