RacingSolution

I think 3" would work well.. what is everyone else running?

OuterHeaven

Everyone is going 2.5". Unless you are trying to get over 300 WHP then I would stick to 2.5" otherwise go for 3".

trdtcpr

OEM

RacingSolution

I should have clarified.... This question is mainly for the turbo owners...

Backpressure is no friend to a turbo and the 2.5" catbacks are popular with the N/A cars.. Thats the main reason why I think a 3" would be suitable

peteyd

3" is a nono on the tCs. 2.5" is more then sufficant for our tCs. with 3" too much pressure is lost and you end up losing hp. the biggest i would go would be 2.75" thats max 2.5" is rather nice.

zer0

3" is the way to go. Not on the S/C though it seems.

Munch

Stock exhaust with an electric dump is even better

zer0

^^ True

ZPIracing

2.5" will support up to 400whp 3" will be needed after that. The main concern when running a 3" exhaust system is that it has to ran under the crossmember making it the lowest point on the vehicle.

zer0

Makes no sense... ZPI has run some of the fastest times with no exhaust at all(open downpipe).. Explain that...

ZPIracing

all of our times are on a 2.5" downpie typically running open at the s-pipe

zer0

of course its 2.5", most companies only have 2.5" downpipes to offer... ive yet to see a 3" turboback, besides Rasta.

Munch

It's still an open exhaust

RacingSolution

How low are we talking about?

JtunedTC

2.5" is what im running on my custom setup .. seems pretty i deal .. for a n/a car thats already running 2.25" stock

zx12guy

3" turboback is the way to go, hence the reason why it's one of the first mods on any oem turbo car (dsm,evo,subbies, etc..)

peteyd

those cars are also running 1 bar/14.psi as well. double the boost of the average modified n/a car. i gurantee just about any honda/scion/acura/toyota thats boosted from n/a will be running 2.5" unless they are boosting 1 bar or more.

Souljah347

because with bigger piping the exhaust gases cool faster and take longer to push out. people think that some backpressure is needed which isn't the case. you use 2.5 because the gases stay hotter and travel faster (i'm not entirely sure the reason but i'v read a article by magnaflow on it). it's all about volicity, so yeah, running an open downpipe the exhaust gases escape faster, but it you have 3 pipe the gases expand and cool making it harder to be pushed out.

i know i could have worded that alot better but i hope you get the general idea

peteyd

works for me

RacingSolution

Going with a 1/4 " larger piping makes sense when you are adding bolt-ons.. but when you are doubling the horsepower/torque with a turbo setup, that 1/4" larger piping doesn't seem efficient enough.. You're dumping in a lot more air into the motor and need to get it out as efficient as possible with as little restriction as possible.

N/A cars want backpressure.. but on turbo's... backpressure in the exhaust will bog the turbo down ... the turbo itself will provide the backpressure..