okay, here is the deal. i'm trying to figure out what combination of an up pipe and a down pipe to install on my '03 WRX, but i'm concerned about emissions and CATs because i live in california, home of the strictest emmissions laws in the US. just installing an up-pipe automatically gets rid of one cat, i haven't seen a single aftermarket up pipe with a cat. there are downpipes with CATs though. is there anyone in CA running an up-pipe/down-pipe setup who has tested the emissions? i'm thinking about going with one of the following combinations:

Perrin Up-pipe + Perrin Downpipe (with optional CAT) = 2 cats in car

Scooby Sport up-pipe + Perrin Downpipe (with CAT) = 2 cats in the car

Scooby Sport up-pupe + Scooby Sport Downpipe (no cat) = 1 cat left in car

any of the three is going to make more power than stock, but can i pass a smog test with 2 cats? if not, i might as well go without cats in both the up and down pipes. i'm not worried about visuals, since nobody from the DMV is ever going to crawl under the car and be able to tell the differance between the stock pipes and aftermarket. the goal here is to get the turbo spooled quickly, get the car making better torque (i'm not super concerned about peak HP) and to keep it super stealthy.
anyone out there running a similar setup, or have any suggestions? other than a duffguard radiator shroud and air splitter, everything under the hood is stock. oh yeah, i'll probably be installing a ScoobySport muffler as the next mod to keep things flowing freely, but quietly. thanks.

 

I am running catless right now with a helix sp and pde up-pipe. I used to have an hks hiper, but it was way too loud. The up-pipe cat was used for cold start emmisions. The car will pass the sniffer with the stock downpipe and no up-pipe cat. As far as the visual, I doubt they can see the up-pipe. I can't stand the smell of running catless and maybe a cop might smell it and pull me over so I am going to have a dp made with high flow cat.

I would chose that setup. You will only have one cat total as the perrin dp replaces the stock dp with 1 high flow.

When its time for a smog test, just swap the stock downpipe back in.
Jay

 

hmmm. i thought that the Perrin downpipe would only replace the front catalytic converter as shown in the diagram here (scroll down, it's like four posts down):

https://www.i-club.com/forums/showth...threadid=14107

and not the rear cat. if the car will pass emissions with the pre-turbo cat gone, and the stock downpipe and rear cats in place, i can't imagine that it would fare much worse with the Perrin high flow cat and the stock rear cat, if in fact the Perrin downpipe allows you to keep that unit.
like i mentioned earlier, i don't think that the DMV here would catch a non-stock up/down pipe, so i'm really not the least bit concerned with the visual inspections.
anyone make a better down pipe with a high flow cat than Perrin? i've heard that MRT and Stromung make them....thanks.

 

The perrin dp replaces both the dp and midpipe.



I am want to do a APS discharge pipe and custom the rest with a highflow.

jay

 

do most downpipes replace the mid pipe as well? if that's the case, it looks like i'm going to have to go with the Perrin, because anything else would leave the car completely catless, which is a big fat $2,500 no-no in California.
i'm guessing that running the Perrin downpipe and uppipe combination would give me two issues to deal with at the ECU level: the removal of the EGT in the perrin up-pipe, and a cat inefficiency CEL from removing the rear cat. Perrin sells a resistor fix for the EGT, any reccomendations on a ECU fix for the CEL? ScoobySport's active fix maybe?

 

Stromung makes downpipes (catless & highflow catted) and 3rd cat eliminator pipes that both bolt on to each other as well as stock exhaust pieces. If you just want to remove cats, that is the easiest way to go. You could remove either one or both. The downside is that the opening on the turbo side of the downpipe is just like stock, flat (not bellmouth or twin-dump) and the piping is the same diameter as stock (2.5 inches). If you're interested, I have a Stromung catless downpipe that I used for a few months that I could give you a decent price on. And yes, the midpipe is quite a bit easier to remove than the downpipe, although many people here (not me) would say the downpipe is very easy also. If you want to go with a single cat after the turbo I'd look into the TurboXS stealthback. It bolts to the stock exhaust and wouldn't be any harder to remove than the Perrin downpipe for smog testing.

 

I'm selling my Stromung CATLESS downpipe because I upgraded to a Vishnu turboback. Stromung doesn't have a website, but some vendors that sell them could probably answer your questions about them. I'm pretty sure you can have an exhaust shop weld a high flow cat in just about any pipe you want if it's that important to you. I figure one cat is good enough. I guess I'll just have to roll the dice on the visual inspection. If it can't pass with just one highflow cat, I'll try with the stock turboback. If that doesn't work due to the catless uppipe, I'll change everything back to stock and sell the car to buy an EVO. It's not worth the headache every year to swap out the exhaust. Honestly, if you're so worried about emissions that you want to replace every cat with a highflow cat, you're just wasting money. I really doubt that you're going to gain much that way. It's my understanding that emissions testing isn't required until the car is over 5 years old anyway. That gives us a few years to figure it out.

 

i just can't imagine that anyone smog station attendant would be able to find the up-pipe, let alone know what it is or that it's supposed to have a cat. heck, i don't even think a cop would if you were pulled over. i seem to recal reading the instructions for the perrin up-pipe install including the line "remove intercooloer," so unless the smog techs do that i doubt they'd see it.
i'll have to call the kind folks at xcceleration.com and see if they have dyno graphs for their fully cat'd systems. if they make power, that might be a good way to go, either that, or mix in one of their high flow cats to get a system with two cats.