hey i have some questions about which exhaust i should get to give me the most performance with out losing too much back pressure? Also which exhaust company to go with and how they compare?

 

I think the Cobalt Cup car is running 2.5". That's what GM Performance put on it. Personally I would follow there lead if you don't plan on doing too much beyond stage 2.

 

but wat are the differences between the 2.5 and 3 inch performance wise?? and which company is good to go for and why?

 

I'm starting to feel like a broken record.

Corsa, company that fabricated the 3" system for the current Grand Am car told me that the 3" system is not required and that next years competition system will be 2.5".

Therefore, Corsa's newly released cat back systems (touring and sport) for the Cobalt 2.X liter applications are all 2.5" systems.

For more details see my epic Corsa thread somewhere on this page

 

When I talked to a lot of the different companies making exhaust for the cobalt they said it would be more efficient in combination w/ other mods to get 3inch but a lot of them were going w/ 2.5 inch b/c of the noise db levels were harder to control. WOT 3inch is going to be better as long as you have some back pressure somewhere like a CAT, or a good muffler design.

 

3" would only be better for all out drag racing , where you are only concerned about peak power

on the street with ocasional drag , or racing duty 2 1/2" is best


ive seen lots of camaro's run 600 whp on a single 3" system , so 200-250 whp makes the 3" seam like over kill

 

a 2.5 is more then enough for a 4 banger, hell i have a 3" custom exhaust in my IROC. i think a 3 inch is just to much go with the 2.5

 

The fact that an engine needs backpressure from the exhaust is a MYTH; every backpressure will cause some HP loss because that is restriction. An for the SS exhaust, 2,5" is OK to cause no loss up to 300 BHP.

 

im going with a 3.0 inch.

 

Needing back pressure a Myth = BS

The backpressure of a exhuast system directly affects where HP and Torque is added or lost.

An exhaust that is wide open will produce more peak HP in the high rpm's but some low end will be lost.

 

I was thinking that same thing but then I was told the difference between 2.5 and 3 is just weight there isn't significant gains.

 

To add to the backpressure opinions -----
It is the the first X# of inches out the head that effect it , not 5 ft down stream
Just cant remember what X is
But if you put on a 1" exhaust --- well this is lets say, obvious ---- slam a potatoe in a cops exhaust , they love it!

 

im goin with the gm lead and getting a 2.5 inch

 

I love my 3"

 

Let me get what's been said straight...
Nevermind....

 

I got a 3 inch exhaust. I am happy with it. It looks and sounds better than the stock system.

 

Dangit.....The 3" diameter exhaust on my 2004 Redline....Specific enough for you now lol

 

kewl...I thought there was a mess with the back pressure thingy...decided to stay out of it...

which is better..has there been any kind of numbers established...?? they should be real close..

 

I wonder what makes people think that? I mean...top fuel dragsters run open headers to elimate almost all back pressure. If they needed to run back pressure don't you think they would have some kind of longer exhaust on there?

 

I would think they need some back pressure to keep the exhaust gases moving at a certain speed. Although reducing back pressure will result in gains of HP, reduce too much and you might start to lose torque. If the exhaust tubes are small (within reason), they keep exhaust gases moving at a higher velocity...Make the tubes larger in diameter and then the gases spread out more hence the velocity drops off resulting in a loss of torque.

As for running open headers- you can run a decent amount of back pressure through the exhaust manifold only (or even through the head if it's designed for that application) however, if the temperature drops to fast...you will run the risk of burning the valve.

 

you dont want backpressure, back pressure is always bad, but bigger is not always better. you need velocity and if the exhaust is too big you wont have it at low rpm. on a stock sc/ss a 3" exhaust would run like butt at low rpm and still not have very significant gains up top. if your car is never going to be over 300 hp dont even think about a full 3 inch

 

back pressure is back pressure, its needed...in moderation
Too much/little can effect performance dramatically.
Not real sure it'd make much of a difference whether you have 200 or 400 hp.....who knows..n4ggs makes sense..
What size is the exhaust offered by GM.? If it's 3" then by all means go for it. If it's not, find out why.

 

i'm going with a 2.5", every engine needs some back pressue. I think with my 2.0 4 cylinder 2.5" is the best choice for me. plus if the GM cup car is made to specifically to be faster than other cars, if a 3" had much of a benifit, they would probably put a 3" on it.

 

Do u have a sc ss? I have a stage 2 ss typhoon short ram, I'm looking into exhausts and am also debating 2.5" or 3"

 

old thread. highest activity from a member is 2.3%, followed by .3 % and a bunch of 0.0

just go 2.5 or stay stock. ive been on a megan 2.5" and corsa touring 2.5" and i just want to go back to stock.