Isn't that cause turbos use exhaust pressure to create boost? (therefore, eliminating back-pressure after the turbo allows for more efficient compression) Since the SC doesn't use exhaust pressure to create boost, I don't think bigger is always better......

 

i agree with you on that, Im not saying that you HAVE to go by that but I would rather go by actual information that ppl have researched than a bunch of teenagers that list decals and painted calipers as mods. it's not my chart supercool it's just a reference.

that was in the context of a turbo car..... 2.5 is best for S/C but 3" while hurtin low end will help high end and espically if you making more than 300hp

 

Okay so bigger for turbos huh? Then why at over 1000 hp he can still run just a little 3 incher. According to your chart a 700+hp car would need at least 4".

Since he's at 1200hp might as well bolt on one of those diesel turbo exhausts right. You know the ones I'm talking about the 5" or 6" pipes.

Sorry but that reference is flawed. Where'd you get that chart from anyways?

And this guy I'm talking about is actually in his 40's. Hence the money to build an 8 sec car and a 7 sec car. And I really don't talk to guys who think they have fast cars, like your friend with the stealth and talon. I listen to the older guys who have been racing cars for decades not a 24 year old.

 

once again it was a reference *******, ur dad's bum buddy and you can run whatever you want I couldn't care less. HERE I found the latest and greatest exhaust reccomended by all ppl with 400 years of racing experience.



hi/flow cat included.

 

That's funny, but seriously where is the reference from I would like to complain to the person who made it, if you insist it isn't you.

 

I think its off a stang forum, I saved it a while back just a reference for what other cars use for exhaust at whatever HP, it's difficult to find exhaust info for supercharged cars but anyways...I didnt make it

 

Okay thanks. No offense meant.

 

that chart doesn't say much but predict using numbers that seem to match.

what about exhaust velocity/flow for the pipe and overall pipe design. if a 2.25" can flow just as well as a 3" due to flow characteristics and design then the only difference in either would be size and sound

that chart basically says anyone that reaches over 200 hp on a 2.25" exhaust is lying but there are plenty of people reaching over 250 with the 2.25" exhaust from gm. plus we also need to have a 4.1 liter engine to even think about it according to the chart. it seemed like a nice try but appears to have been made by someone that thinks that is how it works.

 

 

HI
IT hard to see what is better.
Me I am looking to reach 300hp when I have all the money for all my mod.
I have stage 2 right now runing at 18psi and intake and exhaust is on my list for this summer, but first what is the stock size exhause, it not the same 2.25?
Me I was thinking to get the 3'' corsa exhause but I am not sure any more.
what is the best exause type and size for 280 to 310hp?

 

I love charts - Corky Bell.

Archie - looks like ur 2.5 dual is to big, you should be running a 1.5-2.0 And I need around 500 more hp to match that 3" of mine

 

and this is a perfect example that shows why most of the road race cobalt teams have went back to a 2.5" exhaust, from a 3" even at 300whp a 2.25 isn't going to be that restrictive

 

I love charts too!

I would say that one is much closer to reality. It says bhp which would be crank hp, I guess? My 458 whp would be somewhere like 500-525 crank so 2.5" is about right.

Cool, thanks for finding a nice chart. That one looks more professional with an explanation too.

 

With a 2.8 I was making 18.5 PSI, which is more than I should be making. I felt the stock exhaust was restrictive so I started replacing it. Switched to a 3" DP w/cat and the boost went up to 19.1 when I was expecting to go down. Was confused at the time. Thinking about it I realized that with the 3" DP I was creating more back pressure then even before. All that air rushing through the 3" and then get really slowed down with 2.25 stock exhaust. So I bought a 3" exhaust, havent put it on yet but Im betting that my boost will drop to 17PSI right where I want it. If this turns out to be a bad choice I'll swap to TAG 2.5 header back and buy you guys a E-beer or keep it because ill be turbo next summer

np, but I think ur looking at the single tube numbers the dual numbers are to the right of the other numbers and says that a 1.5-2.0 would be good for ur 500+ rank hp

 

A Guinness e-beer and I'm in.

Oh, you're right. Damn now I hate all charts!!

 

@ the moment im not liking them either, anyways Im done, good arguing with ya, peace

 

see that chart makes much more sense. so it looks like the 2.25 would be good for over 300 hp before it starts to become a restrictive component looks like roughly 310 hp with no restriction. since I am not making big power right now the 2.25 is perfect until I get ready to jump into a sc'er swap at which time a 2.5" would be a good idea yay!

 

at the dealer do you know is that where they place the lift arm just b4 the back wheels right at the edge. i have neons right close to there and dont know if theres clearance for that. and dont want them to cruse them so i have to ask them about it.

ryan.

 

i just ordered the cat back exhaust (preformace) for my cobalt which is on order too...... any advice if i should get the flat or the cut piece

 

IMO either one looks good. I went with the straight tip because I didn't know how radical the angle cut would look. When I saw the angled tip on another member's car, I liked that as well.

 

Both tips are winners in my opionion. I like the angled a little better though....all personal preference. Congrats and Enjoy!

 

Each cars power curves and exhaust requirements are different and what size pipe they require, but 11-12 hp gain from just a cat back changeover on a 4 cyl is pretty damn good.. Our 600 hp Pontiac dyno charts showed it choking with 3" dual exhaust yet our 850 hp Z06 is fine with 3" dual exhaust and actually dropped hp with larger. Our Datsun race car picked up hp with 3" single and choked with 2.5" and 3.5" hp dropped off even with retuning. Dyno results vary alot depending on different sizes of pipe and whether its mandrel bent or crushed pipe turns, sizes of cats whether single or dual, muffler types and sizes/restriction, header tube sizes and collector sizes and so on.... Ive been racing for 35 years and have seen so many different variations of what works and what doesnt on exhausts its mind boggling. Gotta have those dyno numbers to compare with no other changes to car other than exhaust each time to compare. If you change pipe sizes/muffler types or cats you gotta tune for the size/flow differences otherwise its not a fair comparison other than a baseline difference.

 

wow i just read 10 pages of exhaust banter... i know a thing or two from owning many cars and playing with the exhaust on most of them. here goes. too much exhaust no matter what N/A sc turbo nitrous whatever is no good. too little exhaust is no good either. flow is very important. what you want to do compared to what youll actually do is the most important. if you want 900 hp sure the smaller exhaust wont be good. if youll actually only make 260 and then be done the smaller exhaust is fine. honestly just think for a minute how far your gonna take the vehicle and then get what works for that situation. my trans am it was a big decision to go with 1 5/8 primarys or 1 3/4 primaries one gave better low end the other gave better top end. i drove my car at 1k rpm more than i drove it at 5k rpms so it was a no brainer. hopefully you all can figure out what your gonna do compared to what you wanna do and get what you need.

 

fantastic sound, nice work posting not only the dyno results but some vids to go along with it

 

Very well said!