Exhaust Questions - diameter? planning EJ22T build

[outbacktweaked95]

Im looking at bending a pipe for my BK and i know that different sized pipes are supposed to give more torque and such i know not that much maybe 4 or 5 hp or ft-lb torque.

My question is that im planning on later on rebuilding a EJ22T to run and cap out at around 250 hp would it be a good idea to go ahead with 3" piping like im planning or would it be better to do smaller like 2.5 or 2.25??

right now im only doing from the cat back but i have to wait to get the money to get a cat and make some headers. thanks for the help.

Edited by Huffer for correct title and paragraph spacing.

[decke48]

ive heard 2.75 is the perfect number to run on a turbo car. but to right now you have a n/a car but plan on turboing the car go with 2.5 and if your going to stick with the n/a 2.25 is a good size

[outbacktweaked95]

so going bigger isnt really a better idea? ive heard that you ahve to have a certain amount of backpressure to your exasust system for it to work is this at all true?

[decke48]

3in in a n/a you will have problems (mostlikely) 2.25, 2.5in is good insurance. on a turbo car, zerosports tested there exhaust with 2.75in catless turboback. and acheived a recovered 4hp and provides better spool, over compeditors 3in catless turboback. since its only a 4 cylinder it doesnt push out that much exhaust for 2.5in exhaust (N/A). yes you need a certain amount of backpress for you O2 to work correctly so it doesnt cause turbulance. on a turbo car it doesnt really madder because the turbo provides the back pressure for the O2

[outbacktweaked95]

alright got ya what kind of "problems" might i have?

[decke48]

inaccurate a/f ratios

[98BG5GT]

What kind of muffler where you considering? A straight thru design or baffled/chambered design? From my experience I have lost bottom end torque from larger diameter tubing, but achieved higher horsepower in the powerband. As I upgraded components, such as a larger turbo and intercooler the large diameter tubing paid off. Sounds like a fun project!

[rougeben83]

2.5" piping is good for around 300whp as a general consensus among the ej20/WRX guys on NASIOC...I'm pushing 280whp out of a 2.5" exhaust right now.

2.5" was also acceptable on an ej25 N/A when I had it; I'm not sure how much the displacement difference would matter affect that though.

[outbacktweaked95]

Im looking at using a Borla xs pro muffeler and i am looking to maybe hopefully rallycross this car in the next year or so. im not looking for preformance now cause i know its not going to happen due to the cars age on the motor but im trying to plan ahead b/c i got rear ended and bent my cat to pipe part and now it leaks and i wanted a excuse to put a larger exaust on it. Alos i work in a metal fab shop so the differance for me between a 3" pipe and 2.5" is like 10 bucks at the most casue im doing all my own bending custom hangers and flanges

also i know that i have to get some O2 sensor bungs for my sensors to set in but can i go with a universal O2 sensor when i do it casue I think there the stock ones from 1995

[Reason]

im not looking for preformance now cause i know its not going to happen due to the cars age on the motor

Hey man, I have a 98 L with 244k miles and putting down a whooping 95.7 WHP, the sky is the limit!

[Grafton]

the exhaust shop next to my place does great work and doesn't charge too much, if you go custom that is, once i order a high flow cat i've already got a quote of $180 for 2.25 all the way back with custom built headers

[Huffer]

3" ID is good for turbo applications... especially if you plan even a medium horsepower build.
3" on even a stock boosted car really livens it up.

Exhaust piping is cheap enough in the entire cost of a build, so you should be able to do it a few times differently before you break the bank. I'd be more concerned about EM, the block, turbo and injectors.

[outbacktweaked95]

so if i go with 3 inch right now it wont hurt anything and will work with my planned upgrades purfectly fine right??

[Huffer]

^^ a 3" won't hurt anything - you will notice reduce "pickup" because of the pipe diameter. But if you keep the stock axle-back or nothing bigger than 2" then you at least won't be one of the "loud yet slow" crowd.

[Airgne]

i have 3in id on mine, and i had more pickup with that than the 2.50in id exhaust that was on it.

[outbacktweaked95]

Well i picked up the streight pipe and took it to the shop awaiting to be bent I went with 3 in ill see how it works.

[outbacktweaked95]

I was also wondering what all do resonators do?? do they actually make any differance?

[Huffer]

Resonators cut the drone in the exhaust.

[outbacktweaked95]

not to be an idiot but can ya give me a better example of drone? my exaust is modeled off of Reasons which here is a soundclip that he supplied
http://s2.photobucket.com/albums/y16/EJ ... CF0112.flv (http://s2.photobucket.com/albums/y16/EJ25Legacy/?action=view&current=DSCF0112.flv)
what would it do to this kind of exaust ??

[impreza_GC8]

^ Drone is really only noticeable at certain speeds. Highway drone is something to be avoided. You really don't know if you will drone or not until you put the exhaust on and drive it for a while. I have owned both resonator'ed and non resonator'ed exhausts and I never had any issues with drone although it was present at 2800 rpm I didn't cruise at this rpm so it didn't matter. Build your exhaust the way you want it (I agree with your decision to use 3" piping) and if you have a drone at the exact rpm you like to cruise at on the highway, worst case scenario, then throw the car up on a rack and stuff a resonator in there. There is a company called "Vibrant" that makes some good resonators.

[outbacktweaked95]

alright thank you very much