im planning to add a CA stage 3-4 (2.6 pulleys/60lbs injectors n mor) kit plus a whole exhaust system so at the end im probably goin 2 b makin anywhere fro 260 to 300 hp...dont really kno whether to go wit a 3" or a 2.5" exhaust?

any suggestions?

 

3" Of Course!!!

 

3 inch wont make any more of a difference than a 2.5 trust me

 

I Have A 2 7.5" On My Car, Screams! Lol

 

thnks guys... so far i got 3 diff. opinions all goin fo diff sizez...wha kind of 2.75 exhaust u got aroon02?

any mor suggestions?

 

I think Dezod (Random Technologies) is the only 2.75" exhaust available.

3" will kill some of your low end torque, but it makes up for it in the top end. (actually lack of low end torque will help launches slightly on street tires)

2.5" is should be good.

Here is thread I made about Supercharger exhaust sizing.
https://www.cobaltss.net/forums/2-0l-lsj-performance-tech-47/recommended-exhaust-sizing-46796/

 

i vouch for the 3" in first gear taking off (i have a CTI 3"), mine allows for easier acceleration control off of the line. I'm sure that'll actually help a lot when you're running tiny pulley's and you can't get traction whatsoever when launching, i've only got GM stg 2.

 

get 2.5

 

gm 2.25 is good for 300, but i would def go with corsa if you plan on makin g more

 

hello no torque with a 3 inch =]

 

go for a 2.5 inch exhaust man cause you will see alot more low end power and torque!! 3 inch is just too big and will cause loss of power in the low end

 

muwhahah....i'll show you how my car hows "no torque"

go 3in man....the exhaust cross section is much larger leading to a much better flow...

you do loose a tiny BIT down low, how ever the cars ability to breath on High RPMS is much improved....

for the best overall results you must ditch the cat...not even a high flow unit will do.....

 

You could go catless like ^ said and go with a 2.5"; that would give you alot better flow but would maintain torque well enough. The 2.75" would also probably be a good choice (probably a bit too big).

 

yah i agree i got the cti header and DP catless with a corsa sport, sounds mean a hell, cant wait to get a dyno now i dont know what id be pushing

 

I have a 2.6, 60's, meth and soon a heat exchagner. I opted to go with a 2.5 no cat. Car feels fast to me.

 

2.5" Corsa Touring

 

Stock exhaust FTW!

 

3" with hi flow cat - might I suggest hahn

 

3 inch

 

dont get 3" get 2.5". your gonna lose alot of lowend with the 3"

 

This thread needs a poll.

Either way go with 2.5" It's all you need. That's my 2 pennies.

I have the 2.25" GM exhaust because it's all I need.

 

yeaa good idea^^didnt kno i could do that...have gotten different responses from everybody..alot between 2.5" and 3" so inserted a poll to see everyones opinions on this...hope you guys vote because im still undecided with almost an equal amount of votes between the two sizes...

ps thnx for the advices, learning alot from this site

 

i'd go with one inch pipes, custom made header pipes with one inch pipe, then take it all back to a lawnmower muffler.. 3" is the way to go in my book..

 

less torque = less wheel spin? isnt that a good thing for the cobalt?

 

Torque is power, so yes, less torque = less ability to spin out. If you want to run drag slicks you won't care about that. If you want an everyday driver and use stock tires, it could affect your driving, but power is power.

Either way, the exhuast will gain torque, 2.5" or 3". They will just gain more torque at different rpms causing more peak torque (using less than or equal to 2.5" and/or long tube headers) because low and mid is where our torque curves peak, or higher hp because there is less torque already at later rpms (hp is proportional rpm*torque) but first gear is gonna spin either way with that kind of horsepower.

What are you looking for in your car? do you like low and midrange pulls in second and 3rd? or do you want to autocross keeping in peak rpms or do you just want a seat of the pants at high rpms?

Either way, both exhausts won't change more than a couple ft*lbs of torque in different areas, so the gains won't be seen on the extreems and still won't be that great of a difference when full exhausts are used at those diameters combined with headers of the same tuned rpm.

(i still say both 2.5" and 3", i like to step up the size instead of use one straight huge pipe, Full 3" from collector back i think is a little overkill)