How much of a difference do you guys think there is between the CA downpipe with and without the CAT.

I am asking this because I don't really want to have to go through the troubles of getting an O2 simulator or having the ECU flashed again to disable the sensor. If we are only talking about a difference of 2-3 hp then I am just going to get the one with the CAT.

 

no its a little more than that, im gonna say 5-15. its a big difference i know that. my buddy got his car dynoed yesterday and the only difference is that he has no cat and he dynoed 8more HP than me. He has the stock exhaust but ive come to the conclusion that an aftermarket exhaust does nothing, 2.5" or 3", until you get rid of the 2" bottle neck where the 02 sensor is in the downpipe.

 

so if your delete the cat you have to make computer changes?

 

They say the difference is like 5 HP

 

they say on their website about 7-10 hp for the whole thing... the cat will not make a 15hp difference... comparing your dyno to your friends car means nothing because these cars are all putting down different #'s and react to mods differently than another one...

 

This is from ZZP's website.
"Our downpipes are made from stainless steel. No worries about rusting or paint flaking off. It costs a little more but we feel it's worth it. All welding is done to the strictest of standards and bears a professional finish. Weld quality is higher than any other downpipe manufacture and a sample of one of our welds can be seen here: WELD We promise our welds to be 100% leak free. Even the flanges are stainless, which isn't something most companies can say. When shopping around, ask if the downpipe is 100% stainless, ask for a close up shop of their weld. You'll know right away, what true quality is and what it isn't.



Seen below, the stock pipe narrows down to a 2" hole before lowering into the cat. This is very restrictive, causes KR and a loss of HP.



Our 3" stainless, bolt in offroad pipes remove all of the stock downpipe restrictions. No more 2" inlet, no more O2 bung dimple, no more Cat. By doing so gains of over 15HP can be had along with a substantial drop in KR. Most users can drop a pulley size after adding our downpipe."

Also me and my buddy have the exact same tune. I know that no 2 cars are exactly the same, I was just stating the point, an aftermarket exhaust does nothing until you remove the 2" neckdown in the downpipe.

 

ok, you're not comparing apples to apples... your comparing a STOCK pipe and STOCK cat to an aftermarket pipe without a cat... it's not the same thing...

the question is will the 3" downpipe without the cat make that big of a difference... i doubt it. the quote that you just posted says that a 3" downpipe PLUS no cat will be around a 15 hp difference vs. stock

 

IMO i think 3" is way to big for a 2.0L...even with the supercharger you better be making some serious output to be useing a full 3" It's just unnecessary.

 

I dunno I have the 3" with cat and I could feel a bit of a difference in power, but in NY you have to have a cat for inspections and ****

 

Yeap! you are correct. The Downpipe should be the first thing to be upgraded on are stock exhaust that is the biggest bottleneck. Header second and Cat back exhaust third.

I would personally keep the cat in there. Their are nice High flow ones out there made by magnaflow.

 

Guy's with Intakes, 2.6" pulley's forcing over 17-20 PSI of air in the engine making over 250-275HP will benefits from a 3" exhaust. All that extra air needs to be released.

 

is it necessary to retune it after cat delete, header, 3' exhaust?

 

yeah im starting to question everyones knowledge on here if your pushing 17 pounds of boost you need BIG exhaust 3 inch i dont understand why there are people running gmpp its a 2.25 plus they run it with like a 2.8 pully and a ton of other **** first thing you need to do to your cobalt if it is stock is debadge that cobalt logo gm stickers and bowtie youll get some good looks if your bowtie is gone it will look like a dog when you play a high pitch in his ear haha , next you need to start with intake exhaust header and downpipe and THEN AFTER ALL THAT start messing with the boost and all the guages and all the bullshit but thats just my 2 cents what do i know lates

 

well I"m pushing 21 psi and I"m planning on going bigger (turbo swap once internals are done)... so a 3" exhaust is my way to go

 

With my set-up the 3inch coompliments it, i dont see why everytime a 3inch exhaust comes up people automatically think its to big, where is you logic and dyno for this?

 

I haven't seen any..... still waiting for someone to back up their claims....

 

I should have some dyno pulls in soon... to show the gains of the 3" over stock at least... I just cant take a day off for like a week or so

 

I'm getting a cat delete pipe, is there anything I can do to avoid the cel that comes with it? I'm getting tuned hopefully in the next 2 weeks, I'm hoping hp tuners can do something to get rid of the cel.

 

i have yet to see dyno numbers from a 3 inch exhaust company to out perform Corsa. Show me a dyno of a 3" being better than a 2.5" and i'll believe you, until then its to big.

 

no prob....

 

might lose some low end torque... but upper and midrange should be real good.... but I"m only gonna be dragracing no autocross or anything so it should make a difference

 

I just went to a local shop and had them do a cat delete. Cheap solution until a header I like comes out. Didn't want to spend the extra money on a downpipe when I will be replacing it with a long tube in the upcoming months. Plus for 40 dollars I thought what the hell. You will get a CEL unless you get an O2 simulator or have HP Tuners.

 

everyone has their opinions, personally i loved the sound of the corsa and wanted to get it. There might be some good 3" systems out there, like hahn for example. If you want a 3" exhaust then get one, i plan on pushing big horsepower and i only plan on running a 2.5" exhaust.

 

Thats exactly what I'm doing!!! Just want a cat delete for now until I get enough moola for the clear image auto header and a 3" downpipe. So hp tuners can stop the cel, like I said I'm getting tuned pretty soon here. I also want to get rid of the cat to save it, because I'm getting 60 lbs. injectors so I'll be running a little rich until I increase boost, and I don't want to **** up the cat. Plus it open the option to run 112+ octane leaded race fuels with no cat to clog, no worries.

 

No one has the dyno for it, but the Aam" 3inch exhaust made a 10hp gain on their dyno. Cant back that up because i dont have the dyno sheet.