What are some of the better brands out there...and will they fit the brand new SS/SC...or will we have to wait awhile for companys to make one for the new Cobalt?

 

if your gonna get an exhaust do it right and get a full catback other wise leave it alone.

 

full catback??

 

I agree, and I think that will be one of my first mods.

 

I dont see any reason why you can't get a muffler you like and go to an exhaust shop and have them either replace the existing muffler or fab up a whole new exhaust.

If you doing to do a high flow cat or new exhaust manafold thats a different story, if you just looking for a nice sounds, why spend hunders of extra dollars.

 

it comes with a 2.5" exhaust, so unless ur pumping the HP towards 300, it should be fine... changing the muffler for a better sound would be something to think about...

 

look at magnaflow, borla, and hks make nice sounding mufflers. but like i stated if your gonna do an exhaust do full cat-back makes since and will cost 65-120 more to do full cat-back.

as far as changing the cat, unless you can get a direct bolt on replacement leave it alone cuz i'm sure that will void warranty. and i believe its illegal to replace a cat before 60k miles. atleast here in california it is. but i read on the redline forums that a company made or someone had a custom 3" catback and showed some damn good gains.

 

bolt on's wont void the warranty only if you open the motor like cams/porting/heads/intake manifolds/etc. you can put lots of things pulleys/exhaust/headers/air intakes/throttle bodys all will not void your warranty

 

ask your your dealer because 02 sensors will be effected by the cats. and then talk to a smog shop to see if its legal to swap out the cats under 60k miles even with a 50 state legal cat.

 

yeah and to pass the visual inspection part of emissions testing, you have to have a cat (but that doesnt mean it cant be gutted...lol)

 

cats can only be changed if it is damaged of has more than 60k miles on it, you can gut it but there's a chance you wont pass the sniffer but with a new car it should be ok

 

the cat that will come on the s/c version will be the largest truck cat in GM's lineup... so replacing it will do no good, getting a good header, and matching to a 2.5 inch exhaust (2.25 stock) or even a 3" to a free flowing turbo muffler will be a good idea

 

No emissions testing where I'm from, so if I want I can prolly just go straight through... just gotta make sure the right sensors are still sensing the right things.

 

which they won't, unless you buy an O2 simulator... one o2 sensor before the cat, one after... if they both read the same thing, the computer's gonna get upset.


and gutting the cat will make you lose power. the exhaust will travel from the small pipe into the much wider cat body and expand to fill it; this will drastically slow the exhaust flow. then the now slower flow has to enter the small pipe again; it just isn't going to work.

 

Straight through on a turbo=good

Straight through on a S/C=bad

The turbo provides the necessary backpressure, so it makes since to provide as little restriction as possible after the turbo. On an S/C, the exhaust has nothing to provide backpresure besides the usual parts, so straight back takes away the backpressure, and your performance decreases.

 

I see. Bad for low end anyways right? I'm not sure about top end, you see a lot of S/C drag cars with open headers, but thats purely for performance.

 

backpressure is a myth; on a four stroke engine, the most power will be produced with zero backpressure.

the reason too larg a diameter exhaust costs performance is not backpressure, it is velocity.

I'm trying to find an article by borla, magnaflow or flowmaster(can't remember which) which proves this ang goes into good detail; when I find it I'll post.

 

Yeah thats kind of what I thought... I know you have better low end power w/ more back pressure, but who cares. I'd rather have higher peak in a sports car and just shift more. And I think some people think backpressure is needed as it is a little bit of overrev protection.

 

to be honest, i'd rather have less low end power to keep traction, and gain up top where it belongs...

 

http://www.miata.net/garage/KnowYourCar/S4_Back.html

cliff notes at bottom

"Is Bigger Better or is Faster Best?



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.



Exhaust pipe diameters are best suited to a particular RPM range. If we used a constant RPM engine this would be easy to specify. But a variable RPM engine will mean that not one size suits all. It is possible to vary the size of exhaust volumes according to rpm but it is very expensive (Ferrari has done it). The optimum gas flows (volume and speed) are required at the RPM range that you want your power band to be located. For a given engine configuration a small pipe diameter will produce higher exhaust velocities at a low RPM (good) but create unacceptably high amounts (bad) of backpressure at high rpm. If you had a car with a low RPM power band (2,000-3,000 RPM) you would want a narrower pipe than if your power band is located at 5,000-7,000 RPM."



CN- too much of a good thing is a bad thing. also, the less backpressure had typically makes the car sound like an old honda 1.6L.

not good at all.