resipsa

I'm getting ready to purchase a Corsa exhaust for my stock 95 LT1 6sp. I have a choice between the 2.5 inch system and the 3 inch system. Does anyone have anyone have experience with both. Which one did you purchase?

88BlackZ-51

going to go out on a limb, and say 3.0 inch piping isnt necessary for stock LT-1 that dyno's around 265rwhp in stock trim. i would think 2.5" is plenty.

Zix

Well, fist off Corsa doesn't make a 3" inch system for C4's, only 2.5"...unless the 3" is brand new, and I would really like to get it! But on a stock LT motor you really don't need it. Do you plan on doing any major engine upgrades like heads/cam or stroker later?

Mr. Peabody

I do believe that this is what I have read to be the case over and over on this forum. Unless you are making a significant change to the volume going through the motor the 2.5" will be best and might even add 10+ RWHP.

93 ragtop

2.5 may well be enough, but I gotta ask. Why did the factory use 2.75 pipes?

mseven

I would like to see a 2.75 available, but I would think the corsa 2.5 might flow almost as good compared to stock (lt), based on the quality of the bending. Numbers on comparisons would be better

LT4BUD

Don't know the answer to your question specifically, but several years ago one of the car mags did a comparison test......best was B&B which was the only 3" tested.....but there was very little difference ranged between about 8 -11 hp as I recall......and the difference between systems is really insignicant...only couple hp

Exhaust wise the limits are the factory headers and cats....not the cat back portion....so very little (10hp) can be gained with cat back only...

I would pick based on looks and sound and of course cost...all else being equal bigger .....so I am running 3"...but not Corsa...so don't really know answer to your question...

Casethecorvetteman

Do you spend alot of time ubove 5,000 RPM? If not i cant see the advantage to a 3 inch on a stock standard car,(you may notice the bigger diameter made more power but at higher RPM) and in my opinion, 2.5 inch system would better suit the stock config unless youre planning to supercharge or internally modify in terms of displacement/cam/porting etc (as stated by Mr. Peabody) Without changing the stock manifolds and cats for free flowing type ones, 3 inch is almost a total waste of time anyway. Going too large may even result in a slight fuel economy loss.

Strick

If you go too big with the exhaust , you'll really slow down the flow of exhaust throught the system which is not beneficial. One benefit of the 2 1/2" is the fit, better clearances, easier to install. Yeah, listen to me with a 3" B&B catback on my mostly stock LT1, but I love the look.

resipsa

Thanks for the replies. I am thinking about long tube headers and free flow cats. Probably do them in the near future. If finances allow, I will eventually upgrade the cam and heads. I would like about 350-400RWHP. I dont think the 2.5 inch system would prevent this, but I just wanted to hear what others had to say.

Casethecorvetteman

wouldnt we all hey???

93 ragtop

When I orig. modded my motor, I did the cam, heads, and LT headers, but kept the stock exhaust. It actually sounded pretty good. Its deeper in the tone area, and its louder. I believe it was Nathan who had a friend who did the same and liked it.
Anyways, I have tried the above combo, removed the stock resonator and installed 2 bullet cats in their place, and tried the Magnaflow mufflers as well.
To the best of my ability, checking drag racing slips, there is no difference in the systems as far as performance goes. Orig. I thought the cats slowed me down 1 tenth but it turned out to be bad plugs.
The bottom line I am getting at, is if you plan to do headers, Id do them now instead of the cat back. With these you will see a power increase and better sound, IMO the catback will only help sound and looks.

MYCoupe

Yea, but remember that it necked down to 2.5" just before entering the mufflers. I also suspect that it necked down inside the resonator, but I've never seen the inside of one. The exhaust will only flow as much as the smallest openning.

93 ragtop

Thats not true with air flow. The length of the reduced dia. has an effect on the overall flow. An extream example would be, take a 50ft length of 1/4 copper pipe and pressurize it with 50lbs of air. Measure volume output and you will find it is less then a 50 ft. 1/2 in pipe with a 1/4 in opening on one end. I personally suspect that GM engineered the systems on the LT1 that way to keep good flow, yet for some reason reduced to the 2.5 going in and out of the resonator and muffler to help with resonance. But as said, that is just a guess. But you can bet they didnt spend the extra money on a 2&3/4 system for nothing.

rocco16

How do you figure?
You may slow down the velocity, but you won't decrease the volume of flow(CFM).

Larry
code5coupe

95PoloVert

Take a look about halfway down this page at the last entry for GS #340.

FWIW, he claims he picked up 14rwhp going from 2.5" to 3" around the 400rwhp level.

Casethecorvetteman

You lose on the scavenging effect.

the blur

I don't like the idea of reducing from factory 2.75" to corsa 2.5"
that just does not make sense... and doesn't leave room for HP gain with future mods.

I had the same issue with my F-body. I have an all stock 3rd gen 5.0L Fbody. The muffler rusted out.
The factory was 2.75", and some aftermarket were 2.5".
but I searched until I found a 3" cat back. and going to 3" did not reduce power. MPG went up, low end torque went up, etc. Bigger is better, especially with the restriction of the CATS.

AORoads

RadPolo96

Well I have Headers and High flow cats.I also have 3" all the way back. You realy only feel a difference up top around 4500-5000 rpm. I also have heads and cam and am putting down around 330rwhp. So you have good potential to get 350 as my car has always dynoed low.