I have an 07 Tc and im waiting for the 07 zpi kits to come out so i can get one, but my question is that i am doing a dual exhaust setup on my tc and i have the turbo canisters and i already have my bumper cut i don't know if i should go with a 3" pipe or 2.5" pipe? Any suggestions?

 

A single 2.5" pipe is more than enough. So going dual, you shouldnt go any larger. The dual exhaust is just getting you looks anyway, so dont go huge on the piping.

 

A search would tell you that the pundits say 2.5" is plenty. Go bigger, and you lose exhaust temp & velocity.

 

...and that's for a single exhaust. Strictly speaking, a 2.5in exhaust has a cross-sectional area of about 4.91in^2. So even 2" pipe after the split would be effective (having a cross-section of about 6.3in^2).

 

I'd say 3in and 2.5 after the split if you go dual. I would put 2.5in in an N/A of course it wasn't dual and yes I have seen it work I/H/2.5 Exhaust and feels great so there's my opinion. :D

 

Turbos work better with less or no backpressure.

I did a dyno test on my N/A 240sx before..

2.4 liter KA24DE

A 3" headerback exhaust showed a gain of at least 15whp

With stock exhaust it only pulled 157whp

With 3" exhaust it pulled 173whp

The mods were:
ASP crank pulley
OBX header
Custom intake
Fully advanced timing

 

So generally speaking, am i better off doing a straight 2.5" cat-back or 3" cat-back or 3" from cat to axel and then 2.5" from axel to mufflers?

The mufflers i bought have a 3" inlet so i thought that i should go with 3" pipe. I was told that turbo cars work best with bigger exhaust pipes since it helps the car somewhat breath better. I know for now its going to run crappy since my car is N/A but i plan on putting in a turbo so i really wasn't worried about that though, but then again it depends on how crappy the car will run.

 

TC's have the highest stock displacement for a 4 cylinder motor, so a 3" exhaust would actually benefit the car. Some people just can't stand the noise because the bigger the piping, the louder your car gets! It'll sound like a cross between a 4 banger and a muscle car. But bottom line, if you're gonna go turbo you might as well go 3"

 

your best bet is...after your turbo is installed, to get a 2.5"downpipe and 2.5" piping the whole way UNLESS you are pushing close to or over 300whp, then you can go 3" on both. You are not gonna have that much back pressure unless you're pushing a larger amount of hp

 

That's exactly what i want to go for once i get the turbo. I'm hoping for at least 300whp or very near to that. I plan on keeping my cat and getting rid of the resonator to sort of help tone the noise down a bit. Do you think that'll help? I was thinking of a high flow cat for now and then going cat-less once i get the turbo, but im trying to avoid getting CELs because this and my R32 will be my everyday car (mainly the Tc though).

 

And you base this on... ?

Based upon most setups, and the word of the better tuners that have put time into the tC, 2.5" is all you will really see any benefit from. 3" on this sized motor is pretty much overkill unless you are doing huge numbers for the car.

 

I agree with 2.5" all the way.. unless you will be and are making over 315whp or up then you would want 3"...

 

BTW any idea how much hp a stock block can hold before having to do internals?

 

I dont think anybody really knows exactly.. it has been debated many times... A few people were pushing 10psi and blew there engines... I would guess if your gonna push between 275 whp -300whp on a DD you would really want to look into beefing up the internals for longevity reasons.. better safe then sorry.

 

I'm with engifineer on this one...wtf are you talkin about ....thats like sayin the mustang has the biggest v6 of any v6 so it must need huge exhaust...

as far as stock displacement goes, ever heard of a 2.5 litre...*ahem* subaru impreza hmmmm or bmw 325...



no it will sound like doo-doo. please dont ever compare the sound of a vette, a Mustang GT, a Viper, any V8 from the 60's, to a 4 cylinder with duals. I'm officially offended.

 

sorry dont wanna be the bad guy...i might have been a little harsh. sorry

 

so you guys recommend that i go with 2.5" duals instead of the 3" duals on a turbo set up?

 

I think 2.5 will be plenty. I am running this set up on my NA and the "duals cause loss of back pressure" talk is BS. I can post my track times to prove it.

 

Since you're going with dual exhaust...2.5" will be your best option. Dual 3" exhaust would probably actually rob you of some hp. If you're over 300whp, then a single 3" would do good, but with a dual setup...2.5" all the way!!

 

Thanks