Well first off you will not pass emissions without cats. All you need to do is put back in your stock pipes when you go get your emissions tested. Almost not if all upipe and downpipes will mate with any system. I have a HKS carbon Ti catback I love it, it does show the most gains out of any other cat back exhausts, I would go with that or just the regular HKS Hiper exhaust, and yes get your helix pipes, I've heard good things about those.

www.gruppe-s.com

Great site, great prices.

 

I have the Nur-spec R and it is very loud without the silencer. So if you dont want the loudest cat back out there you should go with something else or buy the silencer if it doesnt come with it. Also, Cobb and some other companies make turbo back exhausts with high flow cats.

 

Like stated, no cats mean no passing the smog test. Helix is an excellent company and it's what I would've recommended for up- and downpipe. The Blitz Nur-Spec is ungodly loud, especially without cats, but it makes awesome power. The Apex N1 is not so great for the WRX: its 2.5 inch piping is too small. However, it's very quiet. If you want an Apex, get the GT-Spec: its 3 inch piping is much better for power.
Other catbacks to consider are the HKS Hi-Power (good power, deep but not TOO loud sound), Greddy Evo (decent power, quiet), and (though I wouldn't get one myself) the Borla Hush (looks and sounds almost stock, good power)

 

i have the hks non ti. it's pretty sweet. nice sound to it. Only prob is that it's loud on the highway. i hate droning. eww.
It also protrudes at a slanted angle. I personally hate that. It's cool guess. I'd rather have a smaller exhaust. The sound is worth it though. Not like i ever see my exhaust anyways.

 

i have a helix downpipe and HKS upipe used for about 5k miles for sell please PM me if you are interested thanks

 

Apexi GT Spec is loud, you will definitely need the silencer if you go catless. It mates right up so you won't have to worry about leaks. It doesn't sit flush with the bumper and with the silencer in, you won't have to worry about melting your bumper or it turning black from the exhaust fumes.



:banana:

 

half my bumper turned black after i put the gt-spec. the gt-spec's exhaust tip sits about 10mm below the bumper. but it has a really low sound that turns into droning on the highways.

i have switched to a hks hipower and i must say that it is very nice. (besides its big & attracts too much attention)
the hks has a higher pitch. even though i have no cats, it isnt too loud.

 

Hey Ryan did ya sell your GT-Spec? If not, what're you asking for it?

 

IIRC, the cat in the uppipe and the cat in the first part of the downpipe directly behind the turbo are there to pass the EPA's cold start emissions test.
So... I'm thinking that removing those and leaving just the last cat should allow you to easily pass sniffer based emissions. Our cars run pretty clean when they are tuned well.

Of course this wont give you quite as large of a performance jump as running completely catless...

 

A lot of aftermarket downpipes get rid of two cats, so if you put the stock downpipe back on, you should be able to pass emissions. It's not terribly hard to do either. I’d say for value, the helix downpipe is one of the best. You can find them at gruppe-s or mpj performance.

From what I’ve heard, the only difference between the carbon ti and the hipower is that the ti has carbon fiber wrapped around it.


Ryan, are you going to pick up that Apexi from high school?



:banana:

 

Berry -- depends on what Lil' Ryan asks for it
chrisej20 -- the HKS Carbon Ti is not so great per se; it's the HKS Hi Power that's a great exhaust, whether in CF Ti finish or stainless steel. The Hi-Power is a great overall exhaust in regards to sound and performance, and it's one of the highest torque making exhausts for the WRX. Some people don't like the gigantor tip though, but I like it

 

I'd recommend losing the cats in the uppipe and downpipe, but keeping the 3rd cat/mid pipe section. This will keep your car from stinking and emmissions blatantly dumping out your tail pipe. Your options for a downpipe would be.. bosal, stromung, vishnu.. possibly some more out there... and then find a catback that suits your taste as far as noise and apperance is concerned, the difference in one to the other isn't really that significant.