I did a search, didn't find much opinion... I've been out of the game, reluctant to mod due to emissions testing, but my '03 is now exempt so I'm modding the car more.... I want to know which will give best gains and where in the powerband the gains will be with 2.5" or 2.25" custom bent up compression bent exhaust. I have HEARD that 2.5" NA shows not a huge loss of low end. The most this car will be modded NA (unless I get the GM ecotec SC kit) will be WAI, 4-1 pacesetter header, LZM tri-flow cams, Throttle body, Hp tuners, possibly headwork and maby lightweight crank pulley and few other bolt-ons, so not sure if 2.5" is overkill for those mods.
I don't want to lose a big amount of low end, regarding the cat, I want to retain a cat, but till probably get a aftermarket cat with the same diameter as the pip size I choose. Also I don't want a loud exhaust so any suggestions for a good low key muffler that's not too restrictive.
Thanks
Don't buy from MANTAPART!!
Well, if you think its possible you may go the for the S/C someday, then go with 2.5", and really, I'd look into buying some mandrel-bent elbows and welding those in to assemble the exhaust rather than compression bent tubing. Not only does compression bent look like ass, but its more restrictive too. I know mandrel bends are more expensive, but trust me, take the time and spend the money to do your mods right, or my advice is to not do them at all. Anyone here can tell you how much more money you end up spending going back to fix something you cheaped out on at the beginning.
Arrival Blue 04 LS Sport
Eco
Turbo
Megasquirt
'Nuff said
Doesn't the eco come stock with 2.25" exhaust?
I plan on a turbo someday... would 2.5" be best for that too, or larger?
Buddy Club Ecotec Cavalier
* More to come *
This is a common debate. 2.25 has too high of a pitch for my taste. so I went with 2.5, it's mostly personal taste. your talking a 1/4 of an inch
eco's have i think 1 7/8 O.D. piping from at least that cat back. and its crush bent. check out ebay for mandrel tubing bends. i just ordered a 45/180 combo pipe. for $30 shipped. im also using aluminized steel for welding ease and price. I'm personaly going with 2.5 piping.
theres an article on the net i read recently, its about how backpressure is not what helps low end torque. back pressure is a side effect of the exhuast velocity because the same amount of gas is going through a smaller tube. velocity helps scavanging. that being said a muffler that causes back pressure will not improve low end torque. i thought this was an interesting article and just wanted to share its points.
Listen F***ers. FASTERTHANAHONDA is a joke because I WORK FOR HONDA. I'll talk @!#$ about Fords to, that doesn't mean I can beat a 12 second mustang.
2.5 is the way to go Dom.
This way if you get that bug to further the power requirements of the car, you won't have to redo the exhaust.
And of course do the mandrel bent setup.
Good luck with it.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO! 
I actually forgot why I've been delaying the exhaust system, I plan on doing the IRS swap and will need a different exhaust setup there, so there's no point in doing the exhaust until after I do that swap, doh!
Don't buy from MANTAPART!!
I have the gm sc and I have actually had both sizes, I had the 2.25 first then my bf bent me new pipes that are 2.5 and honestly didn't notice too much of a difference, its louder but better sounding, I can bearly hear my supercharger now though
haha
the 2.25 is recommended for NA applications while a 2.5 or 3 is reccomended for boosted applications. many shops can custom bend a 2.5 or 3 for you. hopes this helps
Shado
The reason for this thread is because I have heard from people with 2.2 eco NA cars that they didn't lose a lot of lowend with 2.5" exhaust, I wanted to confirm on JBO but it seems like noone that's NA has any opinion on this or done this. Of course 2.5" would be perfect for a supercharged car... I think I'm going to go for 2.5" but I'll have to wait until I do the IRS swap since the catback will need to be custom made.
Don't buy from MANTAPART!!
Quote:
many shops can custom bend a 2.5 or 3 for you. hopes this helps
Most of these shops crush bend the exhaust.
In doing so, especially at any bends, creates a sort of stretching which narrows the actual diameter of the piping.
I had a shop do this for my car with 2.25 piping. Upon close inspection, realized that there are sections of bends that are 2 inches or smaller at those bends, completely restricting my exhaust.
So this is why I'll never, ever have an exhaust system done by an exhaust shop unless they'll do mandrel bends.
Good luck Dom with your plans and you do know to post up your IRS when you do it.
Misnblu.com
Newbie member since 1999
Thank you Dave and JBO!
