I was under the impression that a catback does little performance wise (5 hp?).
Could someone then explain this statement from Modern Performance on their catback?

Introducing the MPx 3 inch Catback exhaust for the 2008-2010 Chevrolet Cobalt SS Turbo.

If you want a 3 inch, stainless steel catback exhaust that will connect to your factory downpipe or the MPx downpipe you've found the best option! Furthermore, we have dyno tested and seen a 12 horsepower gain with this exhaust with a relatively stock Cobalt SS Turbo!


Now the only *fly in the ointment* is>>>was this dyno WITH the MPxdownpipe added as well?
It doesn't *sound like it*.

 

From what I know you wouldn't even get 5hp from a catback

 

i think its cus turbo cars love bigger exhaust systems. and i think the 3" is an upgrade over stock

 

The gain from an exhaust depends on other supporting mods and the tune.

 

My question is then...with *supporting mods*...is it still ANOTHER 12 HP with the catback added? Or are they trying to pull a fast one and throw the catback in with gains attributed to other mods?
They're saying the cobalt was *relatively stock*. I take that to mean mods would be maybe intake...but NOT a tune.

 

TRUE....
The TC catback is NOT 3" all the way.

 

Turbo cars love as little back pressure as possible. The stock exhaust is 2.5in and probably really restrictive so it is possible to see that much gain from just an exhaust because of the .5in increase in size. Evos, Sti, and pretty much any turbo car sees a huge improvement with just an upgraded exhaust.

 

Boy...that's not what most people here are saying.
Almost everything I've read here ....."Don't bother with catback if you're looking for performance gains, the TC catback flows very well..." In fact, I was of the opinion..now I'm not so sure. If you are pushing 300 WHP and 21 lbs...is the stock catback restrictive at that point?

 

Why don't you buy the cat back dyno before and after and let us know...

 

I might do that, but I'm only using my *ricer run* test for now..60-100 pull with a stop watch. I already have current results with the DP just added. I see Treadstone just came out with one that's around $499...Mpx is a bit less.

 

maybe with a tune they gained 12 more hp with the catback

 

Well I found someone else had the same question....it was never answered:

https://www.cobaltss.net/forums/4724699-post89.html

 

isnt the stock tc catback 2.75?? i worked on my buddys tc and his seemed a lot bigger then mine and i have the megan 2.5" catback

 

what about supercharged balts? what size exhaust do you guys recommend?

 

Catback ONLY!
Can somone tell me WHY you would get this with an SC, but not our TC?
Was the exhaust on the SC THAT restrictive? This catback is only 2 1/4"!!! So it can't be much bigger than the stocker.

https://www.cobaltss.net/forums/dyno...results-32554/

 

i have a 2.5 catback and well it lets air flow threw lol

 

Yes, stock TC is 2.75 in most places. The Mpx and Hahn are a full 3".

 

Agency claims verified 10 WHP (Mustang Dyno) with Catback alone:

Agency Power Catback Exhaust System Chevrolet Cobalt SS 08+

This exhaust system was tested on our Mustang Dyno and achieved approximately 10 horsepower gain. With horsepower also came improved throttle response, and low end torque gains. This exhaust is designed to work with the 2008 and up Chevy Cobalt SS sedan.

I see this is only a 2.5"....then again they say verified 10 HP. Could be 3" might not be needed with under 350WHP?

 

why doesnt anyone do the supra 4" exhaust ahahaha

 

On a completely stock cobalt SS, changing the exhaust is only good for about 15hp max with no other changes.
If you have a cat delete downpipe, intake kit, and running 30psi boost, changing the stock exhaust would probably be good for 35hp. So it all depends on the set up.

~jason

 

lol 4'' what ****** would do that?


:shifty eyes: <_< >_> <_< I haz 3.5 inch on my civic.

 

I thought my muffler delete was good for 35 hp :P

No way that a catback would get you 35hp on the stock turbo.

When you get around 350whp and up, you need a 3" full exhaust to get any performance gains.

 

The catback exhaust is only good for maybe 5 "peak" hp gain. However, Im betting that they are suggesting that you can see as much as 12 hp gains in other areas of the power curve.

 

This. Better get a catless downpipe and a tune if you want more than 5 hp. The two cats in the stock downpipe is the most restrictive piece in the exhaust. There is another piece that goes up over the driver side rear wheel that isn't mandrel bent and goes down to 2.3inch or so but thats the only other "bad" spot in the stock exhaust.

IMO. Go catless with muffler delete

 

Ronn, I had the MPx catted DP on for a while, and then added the Hahn exhaust. No noticeable change in power or spool. Just sound. 2.5" is what the stock system is, and it flows plenty for < 325 whp. You won't find any appreciable gains going to 3" with the stock turbo.