This is kinda basic question and I didn't know where it belonged so go ahead and move it if needed mods.

Anyway, I would assume the stock is about 2" or something close to that on the Cobalts. If you went to a 3" pipe with new header, cat and muffler, would it actually lose performance as you would have less back pressure? I eventually want to throw a turbo in the car (as I have made like 50 threads about sorry for being annoying) but I would get 3" exaust first as it would be cheaper to do and I could do it without voiding my engine warrenty. However would it loose performance as being to big of a pipe without a powerful enough engine to push it through?

I didn't put this in the 2.2L section as I wanted to know on all the models like the SS SC, 2.2L Coupe and cars in general.

 

I'm not sure on the 2.2L Eco, but the 2.0L SC has 2.5" exhaust piping from the header back. There have been guys with ION Redlines that have installed 3" exhaust and reported noticeable performance gains. I'd say that you won't have to worry about not enough having enough backpressure, with electronically controlled engines I don't think the PCM would allow the car to lean out like older carbuerated engines could.

 

on the 2.2 eco model i would go a full 2.5" catback nothing more. on cavaliers with that engine its shown a good gain more than a 2.25" cat-back did.

on a 2.0 s/c i'd probably go with a 2.75" or keep stock 2.5" but go full stainless for lighter weight and add a header. cuz if your not pushing 300hp its not worth getting the 3" and lose a bunch of tq. so i'd keep 2.5" but go stainless mandrell bends so its lighter and flows better keet a new header higher flow muffler. and you should be good to go.

 

2.5 sounds about right then. Thanks for the responses! I'm new to 4 bangers and I'm not sure what works and what doesnt on them. I guess I'll just have to see what kind of header to get and pipe and cat and muffler. Does anyone have an exaust set up out there for the cobalts (coupes) yet? On my current car I just went with hooker headers, flowmaster mufflers and magna flow cat, however there are sooo many different companies when it comes to newer cars its a bit confusing.

 

Show me concrete evidence that says you will "lose a bunch of tq" by upsizing your exhaust to 3" and I will believe it. Otherwise I will believe the numbers that I have seen in various forums, magazines and real life on other cars (FI and N/A) that show an increase in both hp and torque by opening up further exhaust flow.

Go to ************** and check out the gains that guys have gotten by going to full 3" exhaust if you don't believe me.

 

On the 03 cobra, you will lose about 20hp/tq by going to electric cutouts, which are just basically open headers. On that engine, the eaton needs some backpressure to make power. Not sure if that applies to the cobalt engine at all. I think you should be fine going to 3" all the way back.

 

How much is gained from opening the exhaust depends on the car, no matter what. Say an SRT could have considerable gains, but I wouldnt rush to conclusions on speculating how much power putting a 3" on the SS S/C or even just the 2.2. Basically guys we will wait and see, companies will find out what sizes are best, and you can also try your own hand. But man the cars not out yet! MY freinds WRX lost about 10 horsepower from putting a custom mandrel bent pipe under his car, my other freind who put a 3" cat back on his Firebird gained about 15 at the wheels, so it depends on the car, how much air its sucking up, how much its letting out etc. I think we can't make assumptions, just decisions when we actually get the car, I say just take it from there.

 

Well the problem is I want to upgrade the exaust to 3" so when I get a turbo and all that goodie stuff it wont be a problem (exaust I mean) However I dont want to be driving around with no backpressure so it takes like 5 minutes to get out of first gear.

I wouldnt run straight header as thats illegal and running a straight header doesnt seem worth the loud level.

 

i'm pretty positive you will lose some amount of tq through out the power band, the car only produces 200tq thats not that much for a fi car especially pumpin 12psi, thats why i'd keep it less than 3" to get a good gain all throughout the power band where imo i think going 3" the tq will die out sooner. and you wont get as good gain through out it.

i'm sure you look at peak power as gain i look throughout the rpm band. sure the 3" catback on a car can peak at a 12hp gain but the rest of the power band it shows a loss, where as a 2.5" catback will show a moderate 7hp gain peak, but the rest of the rpm shows about 5, definatly the 2.5" is more worth it in my opinion. these are just estimates. who knows if it will actually be like that. its just my personal prefference, i'd much have a good gain all throughout the rpm band then just peaky gains. broad power band wins races not peak bands.

 

^ ^ ^ doesn't the SS come with a 2.5 inch exhaust

 

yeah but upgrading to a stainless mandrell bend 2.5" will probably produce more, saves weight also. we really have to wait to see what aftermarket companies like borla and magnaflow develop.

 

Ummm just to let everyone know, SRT's are turbo, so of course opening the exhaust does nothing but good. Your turbo is downstream from your exhaust, and creates alot of backpressure by itself, you want to eliminate flow restriction after the turbo so that you spin up faster and have less flow resistance.

S/C'ed cars have nothing downstream of the engine besides headers/pipes/cat/exhaust. If you open these up too much you will see losses.

 

What about titanium. I know they make titanium mufflers etc for other cars, although they are pretty expensive.

 

yeah titanium would be even lighter but costs will be out there. lol