I'm working on my exhaust for my turbo sunfire project. Planning to try and reach 275-300hp. I need some advice or opinions on exhaust.

Currently working on:

3" down pipe
3" flex tube
3" all the way to the cat position (not likely running the cat).

I have the megan racing 2 3/8" cat back from there....but this is my question - this system is supposed to be for N/A. Any thoughts about the muffler being too much back pressure? I think the pipe is decent size. Wishing it was 2.5", but I think it will work.

Anyone have an experience with this system on their turbo set-up?

Why start the system off with 3" then neck it down to 2.5? I'd finish off the system with 3" or change the 3" stuff to 2.5".



Tinkles

2003 Cavalier 1SV
Bagged and Blown

Unfortunately I bought the exhaust way early in the project.

I preferred to run 3" down for the lowest back-pressure and that's already started so no turning back there. It's just matter of what I do from the cat back position.

I was thinking that as the exhaust travels and cools it likely will not need 3" all the way back on a 2.2 and the smaller pipe could help keep the velocity up. 3" all the way back is a bit overkill IMO. I'm not an expert here so that's why I"m posting. Open to any thoughts or experience.

Edited 1 time(s). Last edited Thursday, November 05, 2009 6:10 PM

Necking it down will create back pressure. Either make the 3" into 2.5" or sell the Megan and get a 3" system.



Tinkles

2003 Cavalier 1SV
Bagged and Blown

3 inch = WAY too large for 275-300. You should not be talking 3" until your ready to flow the numbers on the hot side for 450-500 at the least.

2.5" should be better for what your looking to do. If your running a cat the 2 3/8" (thats a weird size btw, I'd check that) behind the cat should be fine as long as its a TWC.



Buildin' n' Boostin for 08' - Alex Richards

The megan cat-back is tig welded stainless - I measure about 2 3/8" not quite 2 1/2". I supposed they advertise it to be 2 1/2".

So I guess that's what I'm getting at here, I started a little large on the pipe with 3", anyone really see an issue necking down to the 2 1/2" other than Tinkles? I appreciate your guys input (thanks tinkles).

Edited 1 time(s). Last edited Friday, November 06, 2009 6:48 AM

you should be able to get the custom tubes inc 3" cat back pipe for about 200. Add the muffler of your choice and your good to go.

sure you dont "NEED" 3" pipe at 300 hp, and you may loose a ft-lb or two below 3krpm, but it can help reduce boost threshold and increase top end significantly. this begs the question to the OP, what turbo will you be running and what powerband are you expecting.

I'd have NO reservations running 3" pipe on ANY turbo build...

If I were you I would sell the megan catback, and buy 3" piping from CTI and a muffler of your choice. Prolly be around the same money all together.

Think of it as turbo's dont like restrictions, like bottlenecking the exhaust. Im running a 2.5" dp and 2.5" dynomax short bullet res, then 3" piping from the catback location and eventualy will be going to a full 3" back. Unless your not running a properly sized turbo for your displacement then 3" all the way.

I think you guys talked me into just finishing out the exhaust 3" all the way.

I'll sell the Megan Racing Cat-back.

I'm running the GT2860RS -quick spool - decent overall power capability - check the other specs and pics in the profile. I keep it updated.

I cannot vouch for fitment yet, but i recommend Atomic Fabrications for a 3" system. I have one of his 304SS 3" systems in my garage(going to be installed next weekend) and the craftsmanship and quality of the work is top notch. Not to mention Adam(owner, fabricator, mechanic) is a very nice person to do business with.



Tinkles

2003 Cavalier 1SV
Bagged and Blown

Interesting link...Do you mind sending me a PM or posting back here when you get the system on? I would be interested in your feedback on the fitment. A pic or two of the tight spot near the gas tank would be interesting.

Something like this? I would put our quality/fitment up against anything on the market right now. This is one of our 3" stainless
systems with the rear end just about slammed.

I would also keep in mind any future plans for upgrades. If any at all. A 2.5 system would be a good size for your current setup. A GT30 upgrade and your back in the same position as you are now. Just something to keep in mind









Atomic Fabrications
Full race and street car fabrication shop.
www.AtomicFabrications.com

Thanks for the post. I have been checking out your site the past couple evenings.

Fantastic looking fit and great welds!

I have a 1.6" drop, so that's good to know that it will work with the drop. I'm sold on the 3" in case I upgrade turbos. I figured 2.5 would be fine, but what the heck - might as well prepare for the future.

I have the sunfire so I have a different rear bracket position, but I can build one to suit, or shoot you some measurements. Get it in the ballpark and I could handle it from there. I also need to put my rear bumper on. I may need a few inch offset on the muffler/tip section.

So I thought I would keep you updated on the progress. Went ahead and fabbed up the rest. I just have some minor stuff to do like checking the final fit - welding on the muffler, and adding the tail-pipe, some ceramic coating and header wrap.

From the pictures you can see i'm no migwelding expert, but it should be functional.

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downpipe.jpg (22k)
downpipe2.jpg (23k)
mainsection.jpg (38k)

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tailsection.jpg (24k)

the welds look a bit better today after removing the slag - I'll hit them with some cold galvenizing spray. Sorry Atomic for not splurging on the stainless system. If I were to go stainless - I would definitelly buy from you. Your tig welds are awesome and the finish look is unparalleled. If the system I built doesn't suit or last me, you'll be getting a call. I don't dare attempt this again. My body hurts from the time under the car and I learned enough for now.

LOL yeah you get spoiled with a lift real quick. Some how i still manage to feel sore at the end of each day though!

Good luck with the final fitment.



Atomic Fabrications
Full race and street car fabrication shop.
www.AtomicFabrications.com

Trust me all the soreness pays off in the end. 3" is always the way to go on turbo set-ups, the whole exhaust to horsepower comparison is mute imo. I run 2.5" n/a and I know countless k-series hondas with n/a builds that run 3" because 2.5" is a restriction for them. Just my .2 cents.

Thanks for the input guys. i appreciate the support. I'm glad I went with the 3" all the way. The resonator and muffler combo should produce a decent tone without the raspiness.

Atomic, you're right a lift is nice, but you still get sore anyway. All the detailed work, welding and holding the exhaust to align the brackets etc etc will get you sore anway :-)