3" exhaust - Chevy Cobalt SS Forum : Chevrolet Cobalt SS Forums
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post #1 of 19 (permalink) Old 03-31-2010, 07:27 PM Thread Starter
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3" exhaust

So today I got the local shop to run my 3" exhaust (also got them to install my ZZPerformance 3" catless downpipe).

For some reason (maybe it's jsut in my head) I feel like I lost a good bit of power. But I don't get it. Everyone else LOVED their 3" exhaust. Is it in my head? Do I just need to get tuned for it? It's 3" exhaust with no mufflers or resonators - just 3" pipe. And I know someone is going to say "not enough back pressure" But I know that's BS. You don't want any back pressure for a turbo vehicle.

Anyone???
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post #2 of 19 (permalink) Old 03-31-2010, 08:54 PM
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Downsize sir. I suggest a 2.5" exhaust thats why yer losing power and yes a tune is involved in a sense. but to have an exhaust doesnt really require a tune. Some say you do but from a mechanical standpoint you dont need one.

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post #3 of 19 (permalink) Old 03-31-2010, 09:20 PM Thread Starter
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I really, really don't see any reason in down sizing.
3" exhaust is recommended by just about everyone I know that knows a LOT about cars - especially turbo'd. Almost every single exhaust available for ANY turbo car under the sun is a 3" system...no one would offer it if it was a bad idea/would hurt the vehicle in a horsepower sense. ANY place online worth mentioning would tell you The more flow the better fr a turbo application. It's not like a naturally aspirated engine where back pressure is required.

With that said, I'm not trying to argue with you or anything like that in any way. I jsut don't agree. And I've done my share of reading...and asking.
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post #4 of 19 (permalink) Old 04-01-2010, 08:29 AM
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why don't you try "siamesed" exhaust passages, it can reduced you three exhaust outlets.


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post #5 of 19 (permalink) Old 04-01-2010, 11:34 AM Thread Starter
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I don't know what that is. Reduce three exhaust outlets?
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post #6 of 19 (permalink) Old 04-05-2010, 03:35 PM
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If the only thing you change is put a bigger pipe on the exhaust it will totally change your low end torque curve and make it FEEL slower but on a dyno you could very well make more torque beyond 4500 RPM and lose some down low. It's a good sacrifice for 1/4 mile times, not so good for butt dynos. It almost always helps people get more traction in lower RPMs so you can grip and rip up top. IT'S ALL IN YOUR HEAD FOOO!

No doubt, you are making more power in the top end now regardless how it feels. Just don't expect it to add more than 15whp. The stock setup breathes pretty good so you can't take something that's efficient and expect it to gain crazy power when all you really did was make it breathe a tad better on one side of the motor. I don't know your mods but that's my .02.
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post #7 of 19 (permalink) Old 04-05-2010, 05:31 PM
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It also depends on how the exhaust is routed. Does it look like its straighter then stock or more curves? if you add size to the exhaust it doesnt make up for poor bends and bad welds that can cause restrictions. On the other hand it might just be in your head. and Im assuming you have a turbo cobalt? stock? no tune I mean?

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post #8 of 19 (permalink) Old 04-05-2010, 05:56 PM
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Quote:
Originally Posted by bruceg View Post
I really, really don't see any reason in down sizing.
3" exhaust is recommended by just about everyone I know that knows a LOT about cars - especially turbo'd. Almost every single exhaust available for ANY turbo car under the sun is a 3" system...no one would offer it if it was a bad idea/would hurt the vehicle in a horsepower sense. ANY place online worth mentioning would tell you The more flow the better fr a turbo application. It's not like a naturally aspirated engine where back pressure is required.

With that said, I'm not trying to argue with you or anything like that in any way. I jsut don't agree. And I've done my share of reading...and asking.
You are completely correct sir.... A turbo car with a 3" exhaust is the way to go. Like another member said, it may just be that the low end torque is not sufficient because you sacrificed but once you kick into boost, it should be a lot faster. Plus, your turbo would run cooler, and increase gas mileage
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post #9 of 19 (permalink) Old 04-05-2010, 07:56 PM Thread Starter
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Yeah, after having the exhaust for a few days, I may have lost a LITTLE power b***om end, but 3500+ RPM's it's definitely there plus some!

Mods so far: Dejon intake, Dejon intercooler piping, ZZP 3" catless donwpipe, 3" exhaust, and ZZP tune is on order....as soon as they get a freakin core in!!
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post #10 of 19 (permalink) Old 04-12-2010, 10:23 AM
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How does the GM Performance exhaust compare to anything else out there? I have the GM performance exhaust on my car(came with the car when i bought it) and im just wondering if i should change it out?
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