Hello, i currently have stage 1 Gm tune with k&n SRI. Im wondering if its worth it or make any difference installing a hahn downpipe? Catless vs catted? I dont want to tune or get a CEL.

 

Don't need a tune. Can also core out the cats if you are bored. My rear cat is a 3" hole in it. Nice added sound and a few free HP. Otherwise just get a carless DP

 

GMS1 will perk up with a downpipe.

Catted vs catless is all up to you. Zzp has a 200cell and 400cell cat options. And angled bung's to help not get a CEL.

If you're never going to aftermarket tune it grab a catted dp with the angled bung and call it a day.

 

Okay, my local performance shops recommends hahn parts and has had good success with them. Would i get a CEL with hahn catless or catted downpipe?

 

Zzp parts hands down. Getting a cel when changing anything on these cars is a risk taker. You never know what will happen.

 

Hahn sucks. Go ZZP with angled bung. I have a catless with the angled bung and have never thrown a code.

 

You will get a cel with catless and quite possibly catted. How many cells does the Hahn cat have? Is there an angled bung option? Why do you want catless if you're staying gms1? If you want least hassle go 400cell with an angled bung or stay stock.

 

Not true.

 

I got a code with a 400 cell cat and no angled bung. You sure it's not tuned out by your trifecta? I shouldve got the angled bung but too late now.

 

I bought a used catted CIA downpipe when I had the Cobalt and it never threw a code. It picked up 3-4 mph in 1/4 mile trap speed compared to a buddy of mine who had only GMS1 and ran on the same day.

 

Should've got the bung man, makes all the difference. It's not tuned out, I asked Vince to and he refused to do it.

 

I too have this one. Worked great for 4 years now. Not sure if you can still get them.

ZZP or turbo XS would be the best options.

Frankly all 3" downpipes are the exact same design only difference might be the brand of cat should you choose to keep it and bung location.
Anyone with an angled bung shouldn't throw a cel.


Best bang for your buck mod as those dual cats are the biggest system restriction.

 

Hahn is overpriced and most of there parts have a tendency to rust through.

I believe ZZP and turbo XS only use stainless.

 

Hey, thanks everyone for your replies and everything. I wana do a downpipe and catback exhaust and leave it at that WITHOUT getting a CEL. What kind of gains if any will I get installing the parts?

 

Cat back will be 1-0 hp
3" dp will be 3-5 hp

K&n Sri could -5 to+5 hp depending on mNy variables highest being if the filter is adjusted so it isn't scewing your fuel trims.

Bone stock gms1 usually put down 265-275whp 290-305wtq

Most put down with those mods about 275-285whp 295-310wtq


Witt k&n and 3" hiflow cat (gms1)I put down 282/??? Tq wouldn't pick up due to a tac issue but most put down 305 ish at that hp level.

Obviously there are a million factors involved that will change those numbers.

 

How should I rotate the filter for the intake?

 

Here's a catless dp and modded intake on 19.5lbs.

 

It depends in allot of cases, the k&n intake thread should have the best info on that. I can't remember the best orientation (currently stock airbox and winter storage so I can't even check.)

But an interceptor is your best friend. You can monitor fuel trims with it and figure out the best spot to keep it close to 0.

Getting a custom tune is really your best bet to dial it in.

Since there really isn't any cobalts left on warranty at this point I don't see any reason not to just get hpt tuned by a reliable tuner and take advantage of the mods you have. Even stock there is hp to be had.

 

A dp should give you around 15 hp +/-. 3-5 hp is too little.

I do agree though about positioning the filter on a K&N SRI. The best way is to rotate while monitoring fuel trims.

 

It can get you that much IF it has been tuned for. Gms1 will allow for hp gains to some extent but you need to truly tune to get that kind of potential out of it.

 

My zzp catted downpipe has a regular bung and not angled. Hope I don't have a cell problem when I install it this summer. I was expecting the angled bung.

 

I have a catted TurboXS downpipe and angled 02 bung, but my ZZP tune deletes the CEL for that anyway I believe.

 

based on your best case estimates (1 hp for CB, 5 hp for DP and 5 hp for intake), you are going to get 11 hp with these mods and GMS1 vs only GMS1. 11 hp won't give you 3 mph at the end of a 1/4 mile, you need 20-30 hp for that. On a really good day, you might get 10 hp for CB and intake combined, and that may be a stretch, which means 10-20 hp for a DP.

 

I was stating low averages based on all the dynos I have seen. And also for hi flow catted down-pipe. un tuned for you hardly see the same gains as with a tune for the mods. There are a ton of variables no two cars in two locations at two different temps humidities and sea levels are going to get the same gains.
One fact seems clear from cat back dynos though. Stock turbo the cat back isn't restricting it hardly at all and there is no bang for buck value here. Unless you tune it to the max of the k04 or turbo swap you don't see the gains from it.


You could go to the track and pick up 3mph one day vs the next just from temperature differences hitting the sweet spot with your tune.

My best mph were on cool days 15°celcius or so but with shitty slow times due to not getting the traction to put it down.

 

Both runs were on the same day and same track, like I said in my first post. Both had GMS1 but my friend's was otherwise stock and ran 104 mph and mine had an intake, CB and catted DP and ran 107 mph.