Exhaust size Whats better? 2.5 inch or 3 inch?

[Inane]

can anyone provide me with some info about what would be the ideal best size for the exhaust (performance wise) for my caldina gtt??

had a couple of quotes recently, where guys behind the counter have said "nah ya don't need a 3 inch!, a 2.5 will do the job fine"

but I don't really trust that opinion as they follow up with comments like
"ya haven't had anything done to it have you? its not a turbo or anything"
(3 seconds after I said that I needed a high flow exhaust and there was no issue about backpressure as the car was a turbo)

I've had several such...

(on the recomendations of heading into total performance, I will do that, but its a bit difficult to do seeing as I work in town )

[[HITONU]]

a 3" will be better for high up power and will sacrafice some low down torque, the 2.5" will still free up the turbo and save the torque but wont have the same up high power...

[Al]

How much power do you want?

[Tranquil]

How much power do you want?

And how much noise can you put up with?

[Malcolm]

I have a 2.5" exhaust and a high flowed ct26 and I don't feel that the car is choked at all by the exhaust, and I have 1/4 mile times to prove it.
I think as long as you have a good 2.5", that is from the turbo and with straight through mufflers and as few bends as possible, it should be fine for atleast 300hp @ engine.

[gt4mike]

Like allfours says, you can make pretty good power on a 2.5". Depending on how far you want to take your mods basically will tell you what size you need. Whats probably more important than the exhaust is making sure the cat is gone - thats where most of the power can be made in the exhaust system and is probably first on the list before doing the rest of the exhaust.

Some others said that you will get less low end with a 3" exhaust, but I'd have to disagree with that. The amount of backpressure the turbo creates is a lot more than an exhaust will ever create, and if anything having less pressure in the exhaust is going to improve the spool-up time of the turbo because its going to have less pressure to battle with on the exhaust side. Obviously its much harder to make a 3" exhaust quiet.

[TRDmod]

i have to agree, the 3inch is pretty good, i have driven a 205 with out any exhaust and compared to mine, its abit different, it tends to holds the push harder for a little bit longer, and more responsive somehow, top end not quite sure as i ddint take it to puke on a test drive:) but mine i have. i like the sound of a 3 inch, it sounds wholesome, sounds very complete:)

[Mr Revhead]

have a think about the power levels your talking about.... now what do ppl racing 500hp cars have compared to 300hp. one of the most common mistakes made in exhausts is fitting a pipe thats too big.

for a caldina id say the 2.5 is fine untill your pumping out 300ish, remember you want to keep the gas velocity up, the less back pressure the better. making sure your cat and mufflers are flowing enough would be the first worry.

[diss7]

Get a 2.5, 3 is too big. I'd even have a 2.5 if I was pumping out 300hp. 3sgte isn't a revving motor anyway, its a mid range tourqe'r, so get the exhaust to suit.