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i was looking to go stg 2 over the spring/summer and i was wondering what down pipe i should be looking for. i have an 07 wrx. i plan on hooking this up to my sti cat back so i can keep the sound low only until i WOT. should i go catted or uncatted? can i use sti d/ps? are they the same? if i go catless, will i get boost creep still even though i have enough back pressure? what size should i get? i think i should go bell mouth.

wrxSIN wrote:i was looking to go stg 2 over the spring/summer and i was wondering what down pipe i should be looking for. i have an 07 wrx. i plan on hooking this up to my sti cat back so i can keep the sound low only until i WOT. should i go catted or uncatted? can i use sti d/ps? are they the same? if i go catless, will i get boost creep still even though i have enough back pressure? what size should i get? i think i should go bell mouth.

Well, if you want stg 2 that pretty much means your standard bell mouth 3" DP. Problem is though, some of them will not hook up to the cat back, but i dont know much about which ones will or will not.

As for catted vs catless, I'm bias to uncatted, as they will not restrict flow, and i never really liked cats anyway. However, running around catless has a few problems, 1) its illegal and you may/may not pass state inspection 2) its loud, at WOT you and everyone else in a 10 block radius knows you are cat less and 3) the smell. If you dont mind those three problems, then catless is for you, but i suggest that you spend some time around a catless car, just to get an idea of the sound and smell. Catless DP's are also cheaper than catted units.

As for boost creep, every car is different, but i dont "think" adding just a DP will make you creep that much. If you add an entire TBE, then yes you'll need tuning to compensate. I'll let the other guys chime in here since I'm a year or so removed from the suby world and could be spouting shit out of my ass.

From what I have seen, catted DP will help w/ the boost creep when going to a larger diameter exhaust.

^^^ True since you're reducing flow.

Spaz (Ross) has the reasons down pretty well to go with/without a catted DP. As far as fitament is concerned, the best thing to do is call up the person you are buying it from and ask. Most catbacks will hook up to most dp/mp's, but there are exceptions!

I would say if you want the silent but deadly stay catted. Im running an Invidia catless dp and a megan black catback. I never go past 15.4 psi. For some reasons the 07 wrx's are alittle more prone to the creep. But with a stock catback you probably will be fine. Just not reaping the full benifits of your new dp. Also I no that Mad Dad sells a midpipe that bolts to aftermarket dp's and tapers to the stock axle back size. So you could run the STI axleback with it. Just my .02 cents.

You have the wacky 07 WRX down-pipe which means you may not be able to use a "shorty" downpipe like the Oakos, Stromung, or bosal for around $145-$225.

If you can find a 02-05 WRX mid-catpipe. I think Allan (WRXWagon2112) still has his for sale. You could use it and pick-up one of the aforementioned down-pipes and you will not have to worry about it mating to your STi cat-back.

I'm using the Oakos on my FXT and it worked like a charm!

Otherwise you are forced into a catted down-pipe with a donut gasket, and if memeory serves me right there is only one, Cobb. And it's $595!

drwrx wrote:You have the wacky 07 WRX down-pipe which means you may not be able to use a "shorty" downpipe like the Oakos, Stromung, or bosal for around $145-$225.

If you can find a 02-05 WRX mid-catpipe. I think Allan (WRXWagon2112) still has his for sale. You could use it and pick-up one of the aforementioned down-pipes and you will not have to worry about it mating to your STi cat-back.

I'm using the Oakos on my FXT and it worked like a charm!

Otherwise you are forced into a catted down-pipe with a donut gasket, and if memeory serves me right there is only one, Cobb. And it's $595!

Prodrive makes one that is overpriced shorty catted DP for like $699 Turbometrics Thread LINKY

...I have a buddy selling his catless Full DP 2.5" one but I think it works w/ the stock midpipe (2nd cat pipe in the stock TBE).

THREAD LINKY

Also, I had a pretty sweet setup on my last FXT: Helix 3" Catted DP => Daddy's Maddad 3"to2.5" intermediate pipe w/ flex joint => STi OEM axleback. Good flow and very low volume.

This time around I have to go on: Cobb 3" catted DP => stromung 2.5" intermediate pipe => Prodrive 2.5" axleback

The Prodrive Shorty down-pipe will have the same problems on the 07 as all the other shorty down-pipes. The 06-07 WRXs have a different down-pipe/cat-midpipe sections than the 02-05 WRXs and 04-7 STIs. I believe they are actually from the LGT.

The problem in a nutshell is if you want to keep your STi cat-back (or axle-back) you will either need to get a full length downpipe that either has a 2.5" donut gasket that will allow you to bolt-up the stock cat back, or you buy any bellmouth down-pipe (catted or uncatted) and then by a 3" flat flange intermediate pipe that will allow you to boly on your STi axle-back.

Daddy's sells such an item for $195
http://www.daddysscp.com/dcart4/product ... =17&page=1

But that's a lot of coin for what can be solved easily by just getting a used stock 02-05 WRX (or 04-07 STi) mid-cat pipe for $50 and getting an oakos shorty for $144 or a stromung for $195 or bosal for $225.

Or, hunt for a deal on a TurboXS stealth-back. You can find them for about $500 on ebay.

might go stg 2 sooner than later.
http://forums.nasioc.com/forums/showthr ... ?t=1393758

Turbo XS Stealthback (catless) -->$300 plus a stock exhaust, and maybe some help doing the swap.

good deal?

it is catless though, so i might be worried a bit about boost creep even though i think i am able to hook it up to a stock sti axle back (calling turboxs to confirm)

The TXS stealth-back can use any 2.5" flanged axle-back that will fit the WRX/STi, so you won't have any fitment issues. You can always pick-up a TXS Catted section for around $200 later on.

You may have issues with boost creep even with a catted pipe as it is in the mid-pipe and not the down-pipe. If you have a boost gage, at least you will be able to monitor if indeed it is happening.

Another idea to consider regarding the cat is to purchase a metal substrate aftermarket cat and have it welded into your race pipe. You can typically pick one up from jegs, jc whitney, etc for under $200.00.

My experience with the TXS exhausts - if you have an earlier downpipe casting, it can hang low under the car. If you plan on lowering your car it could be low enough to scrape. Getting a smaller (read: NOT TXS) cat welded into your race pipe might save you some precious ground clearance.

Either way, at $300, that's a decent price.

drwrx wrote:The 06-07 WRXs have a different down-pipe/cat-midpipe sections than the 02-05 WRXs and 04-7 STIs. I believe they are actually from the LGT.

Gotcha!

complacent wrote: My experience with the TXS exhausts - if you have an earlier downpipe casting, it can hang low under the car. If you plan on lowering your car it could be low enough to scrape.

Yes, I know many people that the fitment was WAY too low and that the TXS downpipes have a little issue w/ all their same DP coming into production exactly the same. My friend Chris had to get his DP cut/rewelded by a guy at TXS to get his forester specific DP to fit properly...even after being raised it still was low.

sirwilliam wrote: Yes, I know many people that the fitment was WAY too low and that the TXS downpipes have a little issue w/ all their same DP coming into production exactly the same. My friend Chris had to get his DP cut/rewelded by a guy at TXS to get his forester specific DP to fit properly...even after being raised it still was low.

Keep in mind, not all TXS downpipes are affected. That's why I had mentioned to look out for an "earlier" downpipe casting and a lowered car. I have a TXS TBE on my Forester and it actually hugs the subframe really tight. Not at all hanging low.

complacent wrote:I have a TXS TBE on my Forester and it actually hugs the subframe really tight. Not at all hanging low.

Wait...huh? You got a forester? How do I not know this? You must have posted somthing. Man, my memory is REALY shot. No, you must not have mentioned...I would have remembered this....hmmm? Are you messing w/ my mind, Colin?

Yea, I got a toaster. Needed the space. Just didn't make a fuss about it.

Back to teh OP:

I also had various versions of the TXS stealthback or turboback on my 04 WRX (Tein springs, sways, etc) and my 05 STi (Tanabe springs, various other susp goodies) and both times the cat pipe would drag over things like garage entrances. So keep the price of the SB and your suspension goals in mind when purchasing.

so scratch the stelath back. im gonna pick up a divored catless perrin d/p frm 96 accord. i have confirmed with the seller and perrin that even though its 3" it will be able to hook up to my sti cat back. but my main concern now is about the d/p bieng divorced. i read from nasioc on unabombers faq that it might cause irratic boost or boost spike. can any one confirm this?

I saw that 96accord got rid of it for the invidia. Did you ask him why?

I run a divorced wastegate and haven't had any issues.

hes getting rid of his dp because he wanted to go make a whole invidia system with an invidia g200 cat back. and he likes his bell mouth better, nothing is wrong or bad with the perrin

BUMP BUMP. took us like 2-3 hours for a down pipe install. 1 broken bolt. 1 missing gasket from the down pipe to the intermediate pipe, and the stock turbo heat shield doesnt fit over the divorced watse gate...anyone wanna gimme some input on how long i could run this like this for? i plan on going to andrewtech on monday and seeing what they can do. which bolt # do i need? gasket? heat shield? let me know!!

also, if anyone knows what size bolt it is, that would be awesome. its one of the upper bolts from the turbo to the down pipe.

wrxSIN wrote:BUMP BUMP. took us like 2-3 hours for a down pipe install. 1 broken bolt. 1 missing gasket from the down pipe to the intermediate pipe, and the stock turbo heat shield doesnt fit over the divorced watse gate...anyone wanna gimme some input on how long i could run this like this for? i plan on going to andrewtech on monday and seeing what they can do. which bolt # do i need? gasket? heat shield? let me know!!

also, if anyone knows what size bolt it is, that would be awesome. its one of the upper bolts from the turbo to the down pipe.

lol, as long as the police don't catch you! You're not going to do any harm running like that, so no worries. You'll probably just be a lot louder than you want to be. You can cut the stock heat shield to fit or you can just leave it off, it's up to you. Did you break a bolt or a stud? You can buy replacements for both at Autozone, just take the broken piece in to compare it. Depending on the DP that you went on is how easy it will be to find a gasket. You could also get gasket maker from Autozone (get the kind you cut, NOT the gooey crap) and make one yourself

2/3 are done! swapped a heat shield with someone that needed a stock heat shield, so now im running a heat shield. bought a bolt/nut from the dealership for like 14 bucks cause it was more convient, and now all i need is the downpipe to intermediate pipe gasket, i might just run it with out a gasket, anyone object to that? or is it not a good idea etc. im gonna call perrin on monday and see what kinda gasket they have with the d/p.

There could be two problems. Your AFR's might be a little screwed up since you have either a leak, but I doubt it would be big enough to cause any troubles. You might get some popping when you let off the gas is all The other bigger issue is if you are loud enough that you attract the attention of the police. Exhaust tickets start to add up :/

Sabre wrote:There could be two problems. Your AFR's might be a little screwed up since you have either a leak, but I doubt it would be big enough to cause any troubles. You might get some popping when you let off the gas is all The other bigger issue is if you are loud enough that you attract the attention of the police. Exhaust tickets start to add up :/

well, ill doubt ill have problems with cops, although im running a catless dowpipe, its hooked up to a stock STi cat back. not loud at all and i do hear popping when i let off the gas after WOT. ill still try the gasket thing on monday.

wrxSIN wrote:and i do hear popping when i let off the gas after WOT.

That is unburned gas spontaneously combusting. It usually occurs at the tailpipe on catless cars, but it can occur in other parts of the exhaust if your running really rich or if your plugs are fouled.