exhaust sizing

[SR24DET]

what is the right size exhaust size to use. I heard with an all motor car the best is 2.5" and with a turbo you should have 3" or higher. A buddy of mine has a modded MK4 and he went to an exhaust shop and they told him he shouldnt go over 2.25" and his is turbo. WTF is the right sizes?

[Pirate_Freder]

my understanding is that from the headers(exhaust manifold) on back you want to go as big as possible. the headers determine how the pressure works out and from then on just get it out as quick as possible.

me personaly, i am waiting to get some DC Sports headers and an HKS Hi-Power 85mm(3.4in) piping cat-back exhaust. and yes the 85mm model is meant for the sr20det but it bolts right up.

[LayNLow240]

it depends on displacement also.2.4L na ka shows nothing but gains with a 3 inch exhaust, and anything turboed should have at least a 3 inch or bigger exhaust.lower displacement cars(most hondas, some toyotas, etc) should stick to 2.5inch for na and 3 or larger for turbo.stay away from whatever shop told you that.

[somedude]

people have tried to tell me that if you go to big you wont have any backpressure and the car wont even run. bullshika-ka. the only thing you can possibly lose with a bigger exhaust is a little bottom end because at low rpm/low volume of exhaust flow, you lose some scavaging effect

[centralcoaster33]

Hmmm, I recently had a custom 2.5" stainless steel exhaust welded together for me. I mean ALL of it is new except the manifold. Even the cats are have 2.5" piping. I did't get a resonator and it's super loud. I get blub blub race car type sounds when I shift and when I deccell at low speeds, and some almost backfiring sounds. I think all this gurgling might be pretty bad for my engine. Worst of all, my butt dyno says there are no power gains with my new exhaust! Maybe worse gas mileage and super loud, but now power. Before I start to blame zero backpressure, I plan to see a mechanic about my TPS and timing. Other than the exhaust I have a lightweight flywheel and underdrive pulley, so with no momentum and no backpressure, maybe I need a timing adjustment and then I'll get my desired power back.

[somedude]

gurgling, crackling, and small backfires are most off the time(again, in my experiences) are exhause leaks. when you let off and you engine brake instead of the exhaust leaking out, it will suck air into the exhaust. what muffler are you runnin

[teddy]

2.25" or 2.5" for all motor KA. 3"+ for turbo. Please have a resonator welded in while you're at it. It helps improve the sound, and doesn't make your car retardedly loud.