which is better for the car an 3in exhaust or 2 1/2 becuase the back pressure

which is better for the car an 3in exhaust or 2 1/2 becuase the back pressure


Bigger is always better. It is possible to tune an exhaust (notably 180* headers on V-engines, but you will never fit a set on a passenger car), but it is not feasable to tune an exhaust on a street vehicle.

Backpressure = pumping losses on the engine. Gross output-losses=net output.

Less backpressure means more net power to the ground. The whole engine needing backpressure to make torque is a myth. Please let it die here.

I think rev it up already tested it and said they lost power with a full 3" vs 2.5".

in the beginning you may lose a little power, but it will open the door for more power in the long run with more mods.
I wish I would have gone ahead and got a 3" instead of 2.5" at first, now I am trying to sell my current and buy a new exhaust.

I can see 3 inch exhaust working out well for a turbo'd car, but for a supercharged? I don't see how there could be an advantage to having 3 inch on a system where the exhaust has nothing to do with the forced induction.

I can see 3 inch exhaust working out well for a turbo'd car, but for a supercharged? I don't see how there could be an advantage to having 3 inch on a system where the exhaust has nothing to do with the forced induction.
I can see your point there but I do believe with some more power mods with someone getting in upwards of 300hp a 3" exhaust could help a bit.
If the whole twin-charged thing goes through then we can see if a larger exhaust makes a difference on the dyno.

To each their own. Numbers don't lie.

-2.5" = good all around power

-3.0" = less at the bottom, but better top end than a 2.5'

Like ommega said, in the long run when you wanna reach 300hp or more, 3" is the obvious choice.

three inch is the better choice

Im gonna end u pgoin w/ three inch I believe, Im just worried about how my exhaust will end up sounding...

What do the cars come with stock??? If you are not planning on going with plenty of mods like say 300+hp then i would stay with 2.5 maybe 2.75, but 300+ def go with 3"

the only cars that you see with 220-230 hp running 3" exhaust are turbo'd ones and that is to let the turbo spool faster

I am going to go w/ 2" exhaust stock.....that is what I ahve been told and my srt came with that also...it went bye bye less than a month after i got the car....my first was intake, exhaust then go up from there later.

I think rev it up already tested it and said they lost power with a full 3" vs 2.5".

I would very much like to see the dyno plots of both configurations. I assume they have them and weren't going by how the car 'felt'

I doubt you will loose any power with a 3'' exhaust over a 2.5''. I would definetly go 3''. It will be better all around.

the cobalt 272 had a 3.5" exhaust, another guy posted a dyno gain of 10 whp with a 3" cat-back on another forum.