Well, its more on a range basis. 3" exhaust is prolly good for up to 600 hp, but the AMS Evos with 900+ hp use 4" exhaust. I'm just saying, 2.25" is way to small for people running smaller that a 2.8" pulley. I would be worried about blowing my head gasket. Why do you think drag racing cars use either large exhaust, or no exhaust at all. Hell my dad and I had a low 10 second '63 Nova and it had open headers. Then we had a mid 11 second '71 nova with dual 3" side exit, and that only had 450 hp.

 

but again this is a small blown engine vs classic muscle so the same rules cant neccisarilly apply.

edit: thats what i mean by people 'thinking' one way because for along time that is what has worked vs tested info proving the other argument

 

Well on one had we have a 383 cid v8 that is NA, on the other hand we have a 122 cid I4 BUT it has 18.5 psi of fuel air mixture going into the cylenders.

 

not true with all drag cars look at pro stock cars

 

and im fairly certain that 2.5 inch, especially mandrel bent with no cat and a very effective muffler is good well past 260 hp, the mentioned ams evo is a prime example, its only running 4 inch in a turbo car with 900hp, that should show you that you dont have to. turbo cars are going to need more room than s/c more than likely. so it doesnt make sense that you would need a 3 inch for anything above 275. side note- blown- your car does sound sick as **** though

 

Why thank you One of the many benefits of having 3" exhaust.

 

What about them? They run open headers with 4" collectors...

 

I think the concern with the exhaust size and losing bottom end is because of physicalities of exhaust velocity.

Now, when I typically hear the word "tune", I'm thinking of concerns of either computer related situations, fuel adjustments or management or ignition timing adjustment. With that said, I don't understand how "tuning" would cure the loss of low end power with going with say an 3" exhaust system.

Do you mean something else as far as tuning?

Not trying to question you, just trying to understand your statement.

 

that could be but i could have sworn they did not run that, and after about half an hour of searching the internet i cant find any good pics of under the hood of one. pretty sure they run an intricate number of neckdowns and what not

 

Well I got both during the group buy. Plus I got an even better deal on the header from Cobalt Addiction for setting up the downpipe group buy. So I payed about $390.00 total.
The Cobalt Addiction header/2.5" downpipe combo is the best bang for your buck.

 

I under stand what you mean and don't understand. But like i said speaking from experience, when i took off my cat and put on my 3" downpipe and exhaust i lost a lot of my bottem end power. But when we tuned for my no cat and 3" downpipe to compensate for it we gaind back all the bottem end power and made alot more topend.

 

Ok, my question is how and what did you use to "tune"?

 

TuneTimePerformance does all of my tunning. Ive been working with them for a wile now. We decided to do a basic tune first then get it on a wide band and see what its doing. After we got all the data they retuned it to make up for the loss. Now i have great bottem end power. I don't wan't to give away what they did but if you give them a call they can help you. They are very knowledgeable and help full. So all im saing is that if you tune properly you won't lose any power!

 

No they just run straight headers, with no exhaust system of any kind. I go to the national event in phoenix every year, and one of our family firends is on the crew of one of the pro stock teams.

 

Ok, the tune helped with power return from the loss of putting a bigger exhaust system on then. Well I guess my question is, if you were losing power w/a 3", why not just go with a smaller exhaust system. You were losing power for a reason...

Just curious.

 

Because you gain top end with a bigger system, but if you know how to tune properly for the big system you can get the best of both worlds.

 

Ehh, theres a limit to that. I personally like the absense of low end, that means less chance of spinning the tires at the hit of the throttle.

 

True but you could be gaining more power with a better exhaust velocity on a 2.5" exhaust system. It might feel like you gained alot of power on the top end cause w/a 3" exhaust, it's taking so long for the velocity to build up.

 

exactly what i was thinking, bigger is not always better...

 

found the information, i knew they didnt run straight headers...

http://www.carcraft.com/techarticles.../photo_01.html

http://www.carcraft.com/techarticles...tem/index.html

 

Thats not what she said.lol......Any ways your right bigger isn't always better. But a 3" isn't too big, on a stock car yes it is but a car with some good mods no it isn't. Im running a 3" exhaust because i have a 2.7 pulley (18psi). Thats alot of psi regardless of what car or how much power is being put down. Like blown-4-banger said on a forced induction car you don't wan't any left over gasses. The air is being forced in so let it out as fast as you can,(not saying put on a 4" exhaust), and when tuned properly you get best of both worlds.

 

i agree but i think 3 would be too big on mine, and turbo and s/c are different as well

 

My header somewhat has that venturi effect. The collector is 3" but it comes in two parts, the first part is at the end of the header where there is a cone at the end of the collector 2.5" in diameter then there is a tube the mounts against the cone that is 3" in diameter. So the header goes from 3" down to 2.5" then back up to 3".

 

i second that

 

Here is a question for u guys, I have a GMPP stage 2 and CAI and 2.9" pulley, would you go for a magnaflow catback 2.5", or a GMPP catback and GMPP manifold. I canada here anyways they are about the same price.