ummm gmpp is smaller then stock for the 2.4 or 2.2 up till the axle...

and the 12WHP was reported on a 2.2 which makes sense since it's only a what 1.5 or 2" exhaust.. so yea it'll help... sorry but realistically you're not getting 12 whp on a stockish size exhaust ... that would be equal to saying doing an axle back on the 2.4 or 2.0 would net 10whp or more

and thats why you SC lol same price and 3x or more HP lol

 

yeah the dyno's do show it..def not 1.2whp...and saying a intake gets more whp then catback..sounds a lil odd to me...a exhaust shud def get more whp gain..and cmon the gmpp intake=heat soak due to SRI...i dunno w/e ill have to dyno and def see what the outcome is...sounds weird though...whatever

 

click the link above.
the 12whp was a dyno test on a ss/sc
by jonnyb. you know....member #1....guy that owns the site?

 

hahaha. yeah and it dynoed 12whp on a 2.2 as well..why wud a ss/na get 1.2whp...sounds a lil odd to me.

 

as was said long ago when this was brought up....their dyno was fubar.
there is just to much proof showing gains around 8-12whp.

 

Then I got what........20whp from my 2.5" ARK....I doubt it.

 

dude.. why are you arguing with evidene.. its factual information proven.. stfu and stop the damn pointless bickering

 

b/c a renowned magazine stated otherwise bro. I doubt GM High Tech Performance is gonna blatently lie.

this guy agrees with me too.

 

I have a 2.4 with GMPP intake and catback and I noticed the difference in the cars performance especially when it's breathing I have a manual and drive it regularly 4000 - 6500 rpm . Seems to run best there . I have no dyno's , however , the difference as I said was noticeable and I am happy with the sound , quality and yes the performance of the exhaust . The intake was 1.3 - 1.5 hp area according to the dyno's I have seen . If you make a larger area for it to breath through , in the fender or put a ram air hood makes a large difference . In order to feel the the change in performance , I would think you would at least need a 10 hp gain in a car this size in order to really notice . My experiance anyway .

 

seriously though a 12 whp gain i can see possible on the 2.2 or even with the corsa 2.5 " exhaust but the issue with any dyno is... it wasn't on the same day with the same conditions... his stock pull was on 9-9 and his pull with the exhaust was 9-16 one was at 5 and one was at 12... without knowing relative humidity and temp for each day 12 whp means rather little.. the most restrictive part of the exhaust is the muffler and 2.25" axleback piping for the ss/sc and the 2.4 so and replacing that yields maybe 7 or so hp so replacing the whole exhaust with smaller tubing (albeit better flowing tubing, by the gas law shouldn't have yielded over 10 whp)

 

I would go for the Magnaflow. I am not a fan of the round coffee can mufflers cuz they usually sound like crap. Preference in sound depends on the person, but I think the magnaflow sounds a billion times better than any round mufflers. Just my two cents. I've heard a few Cobalts around town that sound like ASS and they all have those round mufflers.

 

believe it or not the largest piping isn't always the best piping. the reason for that is you need to keep the exhuast gases hot. and if the piping is to big then they have more room to cool down and thus slow down in flow. so the def. between 2.25 and 2.5 may not seem like much but smooth bends and the right size can do a lot. remember that extra .25 of a inch is over most of, if not all, of the piping so really you are getting an exhaust that is like 2-3 feet bigger (using 10 feet for example). that is a lot of air to heat up and move through.

 

you need to do some reading.
obviously you dont understand how exhaust works.
and your making yourself look a little silly.

 

Do a custom exhaust.... 2.5" mandrel bent piping ($100), magnaflow muffler ($75-100), so a full exhaust for $175-200.00 works for me, if you replace the resonator you are looking at maybe another $30-50.00

And there ya go!

 

got any vids?

 

Uh, no. Im personal friends with three highly accredited shops (Pro Motion Tuning.......(www.promotiontuning.com), PTuning (www.ptuning.com) and VIP Garage (www.vip-garage.com), all of which have in house dynos, and i've watched tons and tons of cars get dynoed. Just a cat-back typically nets under 10whp on a car w/o forced induction. Now to the crank, sure it might get more than 10, which is understandable. Turbo/supercharged cars on the other hand might gain more power b/c the factory exhaust is really restricting the turbo/superchargers full potential.

Go pick up an issue of like D-Sport, Modified, or Import Tuner or something and find one non-boosted car that gets more than 10whp from a cat-back alone. A full exhaust I can easily see 20whp or so. Like Modified recently put a Magnaflow cat-back on a new ('07) Civic Si, of which has larger piping than stock, and only got like 6whp out of it. And yes I understand piping size isn't everything. I know that too large is overkill, and that sometimes just a smoother bent pipe might be the key. But I just find it hard to believe that GM High Tech would be lieing on this matter considering they are a big name magazine and sold just about everywhere, and that an exhaust with factory size piping would make such a high hp gain to the wheels. Thats all. But w/e hate on me all you want. I've owned 4 cars (RX-7, V6 Accord 6-speed, E36 M3 and the SS) and i've done work on all of them, and had every car dynoed after mods besides the Cobalt, and I like to think I know what im talking about. But im gonna un-subscribe to this thread before I say something I shouldnt.

And for the record, I never doubted a 12whp gain on a SUPERCHARGED Cobalt, as cars w/ forced induction get larger gains from basic bolt ons. I just doubt it on a 2.4SS.

 

bro maybe its not doubtful...but even on that redline show..they dynoed a 2.2 cobalt with the gmpp exhaust and it got the same results..12whp..so i dont know wut to say.....

 

i guess the magazines know best.
and dyno proof from your own cobalt community must just be bullshit.

 

hahaha.^^

 

haha you just took the words RIGHT out of my mouth about this guy...

and just for the record, ALL magazines make mistakes. look for a 'your say' section in the next edition and look for a sent in letter that discredits what they say. happens all the time, one of my favorite parts of the magazines!

 

Would a Megan canister (only muffler) sound just about the same as the cat-back on an SS? Because my friend bought a Megan muffler a year or so ago for his turbo GSR Integra and never used it. He said he'd give it to me for like 1/3 the price of it new.

 

Sorry I don't...

 

go custom cat back in that case it's not expensive and you'll get some gain ie buy the muffler lol

 

My only problem with dropping the cash on an exhaust is that I usually make fun of auto 4 cylinders with exhausts around here because they sound GAY. lol. I actually like how my stock SS exhaust sounds after my intake, but deeper is always better!!