Red07SSNA

CED has a serious exhaust system available in addition to their GMPP exhausts. It is the Random Technology 2 3/4" cat back exhaust. It is at least twice as loud as the GMPP performance. Install is pretty much the same as the GMPP cat-back exhaust install. CED provides a 2 3/4" downpipe/cat assy too (I didn't go that far).

The basic parts with GMPP touring resonator pipe next to it to show the difference

https://www.cobaltss.net/gallery/fil.../1/Exhaust.JPG


Close-up of the pipe diameters, RT on left GMPP Touring on right:

https://www.cobaltss.net/gallery/fil...1/Exhaust3.JPG


Tailpipe/muffler installed:

https://www.cobaltss.net/gallery/fil...1/Exhaust4.JPG


Clean install (tailpipe looks too far to left in picture -- camera angle)

https://www.cobaltss.net/gallery/fil...1/Exhaust5.JPG


Clean look:

https://www.cobaltss.net/gallery/fil.../TailPipe2.JPG

D4u2s0t

looks good. but curious as to why you went with a 2 3/4" exhaust on a n/a ss

Red07SSNA

Like the awesome sound and "show-car" look!
After reasearching all the exhausts available this one was the largest and not-so-expensive (more then the GMPP touring but less then some of the other brands).

D4u2s0t

makes sense. as long as you don't care about performance, and like the sound it's a great exhaust. i'd love to hear some sound clips though.

Red07SSNA

I don't understand your comment on performance? The exhaust still has to go through the manifold and 2.25 downpipe/cat. This just frees up the exhaust after those two items. It still moves nicely...butt dyno says feels the same...ears say more power...lol!

D4u2s0t

what i meant was it's too big for your 2.4 engine. shouldn't go over 2.5". if anything you would want a bigger manifold/downpipe, not a bigger catback. the exhaust is losing a lot of velocity with the sizing of the pipe. that size probably wouldn't help performancewise unless you were putting out a LOT more power, with a super or turbo or something.

Red07SSNA

I'm sorry but I disagree with you on this. What you're saying is that you get more power with an exhaust then if you have an open exhaust. I still have the same back pressure because of the mani/downpipe/cat so the velocity through those doesn't change.
If you were correct then the drag racers that run open headers would make more power by installing smaller complete exhaust systems.

D4u2s0t

i see why you would think that, but your logic is flawed. what you're doing is creating turbulence, which is reducing your exhaust velocity. you can't compare running open pipes to running the wrong size pipes. it's not the same thing. the exhaust gasses are flowing through smoothly, and then starting to "swirl" around in the catback.

if just putting a bigger exhaust was better, we would all be running 4" exhausts.

if you want to test this, take a straw, and wad up a little piece of paper. blow it through the straw. it will shoot across the room. now, at the end of that straw, put a bigger straw. now that same spitball will piddle out the end, and barely go anywhere. now, take the original straw and cut it down a little bit. once again, it will shoot across the room.

Red07SSNA

LOL! LOL! With flawed logic like that I can see how you come up with incorrect ideas. Increase the size of the spitball and physics -- not me -- would tell you that you can shoot the spitball just as far since the PSI would end up the same. If I want to shoot spitballs out my exhaust you'd be correct! LOL! LOL! Where do you get turbulence out of increasing the size of an exhaust? I can assure you at 2-6K RPM the exhaust is flowing too fast out the downpipe to get any turbulence from a freer exhaust. If I ran an open exhaust after the downpipe/cat then the turbulence would be really excessive -- I guess the car wouldn't be able to move at all then?

D4u2s0t

i'm not going to argue this point. do some research. a 2.75" is way too big on a lightly modded 2.4. it's even too big for a stock 2.0.

Red07SSNA

You were argueing..lol? If I want to make more power I should put on a smaller exhaust! With your spitball logic research I'd bet a 1" pipe woud really increase my exhaust flow velocity and I'd be able to do a 10 second quarter mile....lol

D4u2s0t

yes, you SHOULD put on a smaller exhaust and i guarantee that you would make more power. 1" is a little extreme, but bet a milloin dollars if you switched to a 2.5" exhaust, did a before and after, you WOULD gain with the 2.5" here's a great article i found on exhaust velicity. you are obviously too set on your thinking, so will probably call it bs or something, but here it is:

When contemplating a modified exhaust system there are those who want the biggest diameter pipe that can be had. Their idea must be that fatter pipes are more effective at venting than narrower pipes. This sounds reasonable but it is not quite correct. Sure wider pipes have greater volume and higher flow capacity, but that is just half of the story. Capacity is one consideration but gas velocity is the other factor.
An experienced exhaust designer knows that the best exhaust is one that balances flow capacity with velocity. A given volume/time of gasses will travel faster through a 2" pipe than the same volume of gas passing through a 3" pipe. So when taken to its extremes we can see that a too narrow pipe will create backpressure (restrictions to positive flow) problems and a too wide pipe will cause a very slow flow with no backpressure.
The optimum is where the fastest velocity is achieved with the least constriction possible.

This situation will arise when the pipe is wide enough so that there is the least level of positive backpressure possible whilst achieving the highest exhaust gas velocity.
The faster the exhaust gas pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The scavenge effect can be visualised by imagining the high-pressure pulse with a trailing low-pressure area behind. The faster the high-pressure pulse moves the stronger the draw on the low-pressure gasses and the gasses behind that. The scavenge action is like (but not exactly) suction on the gasses behind.

The greater the clearance burned fuel from the combustion chamber the less diluted the incoming air/fuel mix is. Scavenging can also aid intake on overlapping valves (where the exhaust and inlet valves are open at the same time) by drawing in the intake. These are good things to happen.

So instead of going for the widest pipe possible we should be looking for the combination of the narrowest pipe that produces the least backpressure possible. In this scenario we achieve the least restriction on positive flow and the highest gas travel speed.

redlineblueline

good read but thats what the exhaust manufactors employee there engineers for...thats why i think its better to buy a prebuilt than custom though it costs more its also engineered more

Sharkey

iTrader: (1)

to add to that, generally with an exaust manifold and shorty headers, most of your scavenging is done through the exaust system. a long tube header is very effective at scavenging, however it must be very well designed for the motor its going onto. a 1.8l engine and a 2.4l engine would have very different primary lengths, pipe diameter and collector design. but with scavenging done with headers, exaust becomes a restriction behind the collector and thats why race vehicles run open headers. however just because exuast isnt needed on a high performance vehicle with headers doesnt mean that bigger exaust is better. again, if you go too big the exaust velocity slows down and creates turbulance.

that being said, only aplies to n/a motors. headers and exaust scavenging is very differenty on a forced induction motor. on a supercharged motor a header is still very important. something with long primary tubes favores low end and thats were you need the scavenging to get the torque. once in boost, scavenging plays no effect and the header does become a restriction.

exaust, contrary to what many beleive exaust isnt just a pipe, its highly engeneered. header design is what allows a pro stock engine to be more than 100% volumetric efficient, and surpassing 120%.

Sharkey

iTrader: (1)

double post

07 SS/SC

How much did the catback cost you?

HunterKiller89

iTrader: (1)

you know..this is pretty much corrent....but the thing is, you dont HAVE a larger spitball...you have a 171hp spitball...so you dont want to be increasing pipe diameter to 2.75in

please trust us...we know what we're talking about

anyway, it sounds like an ideal system for +stgII cobalts...the +250HP range...maybe a little too big for them even actually...my only complaint is if its as loud as you say, i think it would probably get annoying on the freeway

Red07SSNA

After reading all your posts I went out and did something novel....I drove my Cobalt around instead of reading theories. My Cobalt runs nice and doesn't appear to have any "loss" in power, in-fact, it feels and sounds great. There is also a black VW GTI owner that is probably incorrectly thinking I have an SS SC Cobalt after a little acceleration fun run :-)

D4u2s0t

ok, bad example. don't use a spitball. blow through the straw. and see which stream of air feels stronger.

basically, you're flowing the same amount of air slower. you're not flowing any more air than you were before. the velocity is just much lower.

new example. blow through a straw, then blow through a paper towel roll. yes, that's an extreme example but it's the same principle. in order for the velocity of the air to be the same, you will have to flow much more air through the larger "pipe"

Rippin07

Sweet on the exhuast man, looks good. Good idea going for a drive instead because all these guys would rather share logic and inexperience (with the exception of a few) and their negativity.
If you get the chance to get some sound clips I would love to hear the exhaust.
PS> 3" cat back on a stock 2.0L has been dyno proven several times to make more power than stock. Must have just been a screwed up dyno operator or two or three right? LMAO

redlineblueline

it might make more peak HP but where does it hit in the powerband, and how peaky is it?

Red07SSNA

$599 plus shipping.

All I know is when I put my foot into it the car moves just as quick as before. TC is the limiting factor, I have to ease off the line and then floor it or the TC kills power -- even in "L" when the TC is supposed to be off.

D4u2s0t

i didn't expect this thing to turn into what it turned into my bad bro. as long as you love it, who cares about what everyone else says. best of luck with your new mod

Red07SSNA

Thanks for the positive feedback. The sound is real deep and "throaty" and when I have the auto in "I" and the tranny downshifts as I slow down the exhaust makes it sound like a manual tranny with the small "afterfires" with the engine braking. I've had both the GMPP touring and the GMPP performance and this exhaust is nothing like those two (I replaced a GMPP touring cat-back exhaust with this one).
Sorry, I don't have anything to record with.

I agree with you there! Funny how we get "engrossed" with our personal ideas...The worst part of the web is that we are not physically in place together. I assure you if you were able to drive my SSNA with this exhaust you'd like it.

cobalt_driver

wow...idk...it sounds nicer, but U NEED BACKPRESSURE! people that say "Oh U don't want back pressure" well u need a certain amount, or else, lol...well, go ahead and throw a 3" exhaust on. You'll get beat by hover rounds but i guess the sound is whats important... And ur beating GTI's? nice kill, but they probably don't know how to drive, bc I've seen Stock GTI's smoke stock SS's. Also, dust knows what he's talking about, and not all of us who offer knowledge are arrogant n rude. Accusations like that are probably the reasons for them being rude to u.