Can I run Stg2 with catted UP and catless DP?

I was under the impression that getting a catless DP and leaving my stock catted UP in would be sufficient for Stage II but a buddy of mine told me it's a bad idea to run Stage II with a catted UP.

 

I don't want to run totally catless, so if he's right then I'll have to get a catless UP as well as a catted DP making Stage II quite a bit more expensive than if I could just go with a catless DP...

You can but, most don't recommend it. It can hinder your spool and cause lag and others worry about the up catt coming apart and killing your turbo. It's rare but, it has happend. On my stage 2 TBE after I added my FMIC I was able to get my stock turbo to hit target boost of 18.5 @ only 2800rpms.

I see, so really the best setup, considering I'd still like to pass inspection, and definitely don't want lag, is to go with a catless UP and a highflow catted DP.

 

Thanks for the info! Guess I'll need to keep saving my dollars then.

I ran my stage 2 with the stock up for about 8 months with no problems..but there is always that very small chance that the cat may break apart and destroy your turbo.

You can get a '07+ LGT or WRX up they are both cattless and look stock. You can also buy a used shorty DP pretty cheap. I run shorties DP then a hi flow catt. With my old setup I was hitting 277whp with stock turbo and with my new 20g setup I'm hitting about 340whp with a shorty.

Good idea, I'll look for a used catless stock UP. There are probably a bunch of them on NASIOC.

 

Where can I get a used shorty DP and does it have to be LGT specific or could it be a WRX/STI one?

 

Also where can I get a hi flow cat and does it need to be welded in or is it just bolt on?

 

Thanks again for the education. I'm still trying to wrap my head around how all of this stuff works.

Need LGT specific one, or you could just find a gutted stock one or gut yours.

^ Yep for that total stock look. Guy I work with is running a 20G in his outback with gutted stock pipes. You should be able to get a used OEM catless UP for pretty cheap..@$75-100. Be sure you install all your pipes at once. Don't do the DP then go back and do the UP...cause you'll have to remove the DP again. Plus...be sure to get all new gaskets and zip tie your vaucum hoses.

What about this, would this work? Could I get JUST the front section from the Perrin DP set:

 

http://www.5-starperformance.com/servlet/the-935/Perrin-Subaru-Legacy-GT/Detail

 

It says that you can buy only one section and it will fit the stock setup if you buy only one piece. Then I could gut my midpipe (this is where the final cat is located I believe?). And that way I'll have replaced both of those cats with one high flo cat for only $300. That leaves only the uppipe!

 

Genius or retarded?

Yes you can use just the one section.

 

You have three cats ('05-06)

Up, Front section of DP, back section of DP. You only "need" to replace the front section of the DP with a high flow cat or catless to run a stage 2 map. However removing the one in the Up is a safe option and will improve spool up of the turbo 200-400RPM. The rear section is not a must, but is recommended to optimize your results and help the system flow as is a full upgraded cat back.

 

Other "shorty" options include Crucial Racing (which has heat coating..been running mine for a long time now), Flow and Stromung. Flow is, I believe, the cheapest option....other than gutting your stock pipe.

 

http://www.pltek.net/newlegacy-exhaust-dp.htm

Diagram for you.....

I believe the Crucial shorty DP is over $300 and is also backordered. The Flow shorty DP looks like it doesn't have a high flo cat in it so I'd need to replace my rear DP section with a high flo cat. How much are those and where can I get one?

 

I feel like the Perrin catted front DP section with gutted rear DP section would be the cheapest. Does that sound right or am I missing something?

I believe the Crucial shorty DP is over $300 and is also backordered. The Flow shorty DP looks like it doesn't have a high flo cat in it so I'd need to replace my rear DP section with a high flo cat. How much are those and where can I get one?

 

I feel like the Perrin catted front DP section with gutted rear DP section would be the cheapest. Does that sound right or am I missing something?

 

You could call up Jeremy at Crucial or send him a PM. He may have some DP's laying around.

 

Yes the Flow is a catless front section. I ran the crucial catless shorty with my stock mid pipe with cat for over a year. You can do that too, no need to replace the cat in the mid pipe or "have to have" a high flow in the front section.

 

I'm not sure how strict emissions are in your state, but for MD they simply plug the car in and look for CEL's. As long as you don't through a CEL you should be fine. As for visual inspection, nobody took a look....and I was rumbling with a full turbo back including a magnaflow catback.

 

Your cheapest option is to gut your stock pipes.

I was under the impression that having any of the stock cats was going to prevent me from going to stage 2. Can you clarify what exactly is necessary for running the stage 2 map that's on my Cobb AP?

 

The only other thing that I was thinking is, I have a Perrin catback right now, which is 3" I believe. If I get a 3" shorty DP but keep the 2.5" stock midsection, am I negating any gains I would have gotten with a full 3" setup?

 

Thanks again for all the answers, it's really helpful!!

To go cobb stage 2, the only cat that needs to be removed (or replaced with a hiflow) is the first one post turbo...so that would be the shorty section of the DP. You should remove the one in the up as a safety measure.

 

To get the most out of stage 2 you should go with no cats an aftermarket DP and catback exaust.

Thanks for clearing that up. I think I might get a shorty DP and a used catless UP and stick with the stock catted rear DP section for now. I don't want to run completely catless. Then later I can replace that one with a high flo cat if I think I need one.

 

As far as choosing a shorty DP. Anyone have any pros/cons or just general comments on Crucial vs Flow vs Stromung?

Not to mention getting a catless up will give you literally more HP gains than the DP change. I can vouch for the Crucial UP .

The only reservation I have about a shorty DP is that I'll be going 3" from the turbo then into a stock 2.5" rear DP section and then back into a 3" catback.... Seems kinda frankenstein exhaust =\ Anyone else forsee any issues doing this kinda thing? I know I can replace the 2.5" stock section with a 3" pipe w/ high flo cat later, but it still seems a little o.O

Crucial is 2.5". I have the crucial shorty + crucial mid pipe (2.5") with HFC and 3" magnaflow CBE. It's not ideal to go 3", then 2.5", then 3", but it's not going to matter all that much unless your pushing major HP. You'll be fine...although that mid pipe will be a bottle neck...you may get some back pressure. Why not just pick up a used OEM Downpipe and gut the first section? It will give 90% of the gains from an aftermarket pipe. Only downside is it has a blank plate over the wastegate

What if I picked up a Stromung divorced 2.5" shorty? Only $200 and that should mate up to my stock rear DP section just fine. Then I could grab a Grimmspeed uppipe for $165:

 

http://www.importimageracing.com/mm5/merchant.mvc?Screen=PROD&Store_Code=ii&Product_Code=3467up_pipe_225_2&Category_Code=933

 

Thoughts?

I'd get an Invidia up....only about $135-150 shipped and great fit and quality. I know JSCspeed carries them.

 

Do search in the exhaust forum. The stromung wll work but for some reason I'm thinking some people had slight problems with the fit...I can't remember.

Good call. The Invidia does seem pretty solid. The only reason I liked the Grimmspeed is I've heard that its alot easier to get proper fitment if you buy an uppipe with a flexpipe. (Though flexpipe on an uppipe does make me a little nervous about how it would hold up in the long run) Any thoughts on that?

 

I think this is the thread you were referring to:

 

http://www.legacygt.com/forums/showthread.php?t=44024

 

Doesn't sound like the Stromung is a bad choice. Especially because I'm not planning on going past stage 2 or getting a bigger turbo.

 

EDIT: Also found this however with some talk of rusting on Stromung catbacks:

 

http://forums.nasioc.com/forums/archive/index.php/t-90727.html

Diagram for you.....

 

That diagram and this thread make me want to donate to the site

 

I'm actually having problems finding the donation link, could someone find it for me?

 

(you guys just clarified a bunch of questions that I've had in the back of my head, the diagram was extremely helpful)

So I've been thinking, in the interest of saving money, I think I'm going to go with this plan. Gut my first DP cat. Leave the final DP cat. I'll replace the uppipe with an after market one, either the Grimmspeed or Invidia (I'm still not sure whether a flexpipe would be better or not).

 

Thoughts about this setup? I think it will be a very reasonable cost, and should be quite effective. I realize that the stock downpipe is going to be slightly more restrictive than an aftermarket one, but I should still be able to run at stage 2 I believe.

 

Anyway, does anyone have any knowledge on flex vs non-flex Up Pipes?

I have installed both. I guess the flex was alittle easier t install.