uh well the title is pretty straightforward, Ive always wondered what size the stock pipes were on the exhaust.... 2.5? i was looking into mandrelexhaustsystems.com and they had various sizes and i didnt want to get the same size as my stock lol

 

2.25"

 

isn't it 2.5 till the axle , then its dropped to 2.25?

 

Correct .... Same as the SS/SC minus the downpipe.

This has been discussed a million times .... USE SEARCH BUTTON

 

does the forums have a search button? ive searched for it, but i couldnt find it. lol.

dont answer that. i just found it... im ghey. sorry

 

Haha, it's all good man.

 

Yes the stock exhaust is 2.5 inch until it reaches the rear axel portion and drops down to 2.25 inch. You should get the cti over the axel kit for 95 bucks like I did then buy a muffler like magnaflow or borla, etc and get it all welded up and then you'll have a custom 2.5 inch exhaust for a cheap price. But mandrelexhaustsystems is a good deal though.

 

Well, yes & no. The inlet of the production resonator is only 2 1/16" I.D. So you would need to replace the resonator as well to have a "true" 2.50" system.

 

For a na 2.4 a 2.25" exhaust flows plenty good enough.. because you need some back presure.. the size pipe is not the big restriction..Its the stock cat and the big ass muffler on the back... If you dont mind it being loud get a DP with a Hi-flo Cat and a after market muffler..

I read a review that the GMPP Catback only made 1.2 whp on the dyno over the stock catback..

 

yeah true but if you wanna go cheap and still have a decent catback exhaust that is the way to go. I'm gunna throw a dynomax superturbo muffler on mine next month to give me some good sound.

 

Look closer to that article. They said they made almost 10 (or so) hp in some places of the rpm band.

Agreed !

 

You must be looking at a different review...


http://www.gmhightechperformance.com.../photo_15.html

1.2WHP 1.3LB-FT...

 

1.2 PEAK horsepower. If you could read those postage-stamp-sized dyno charts, I'm sure you would see that in the lower RPM range there could easily have been 10 whp gains.

 

Thanks for explaing that for me man ....

I knew when I read that article I saw it gained 10 hp over a portion of the RPM band.

 

i just wanted to know the size of the stock guys. so that i know to go big or go home. lol

 

I know for fact, because I've measured it. The SS/SC LSJ downpipe has 2.0" outlet, which is all that matters. The size of your exhaust only matters at its weakest link.

 

That's a little off. The LSJ's downpipes outlet is just under 2 1/4" i.d. I measured my downpipe when I had it off my car a month ago.

 

Then ours are different because mine was ~2.05" inside diameter, using a digital measure. I.D. of the inlet was 2.25". On mine.

 

My I.D. at the inlet was 2.25" as well, but that is only for a short portion. It then opens up to about 2.667" I.D. .... Most of the downpipe is 2.785" O.D. The places it is smaller are at the dimple for the rear 02 sensor which narrows to 2.25" and the small neck down portion right before the 2-bolt outlet flange which is 2.345" O.D. (which is where you claim only 2.05" I.D.) I measured mine carefully, because I was sick and tired of everyone on this site claiming the production LSJ downpipe is 2.50". I stand by my measurements 100%. I can't say your measurements are 100% wrong, because there could be slight differences as you mentioned.