Up, Down and Catback (Perrin, Cobb, Borla)?

I currently own a pretty much stock LGT 5MT wagon and I'm interested in making some more power. After reading on here for a while, I think I've narrowed down my choices, but I have some concerns that I'd be interested in hearing some comments about.

 

I'm looking at getting a solid catless uppipe and I have no real problems with doing the EGT resistor and/or CEL fix via a reflash with the associated tune (conceptually anyway, we'll see how much trouble I have in actually doing it). I think the Perrin uppipe seems pretty good.

 

In addition, after spending some time in the exhaust sound thread, I like the Cobb down with the Borla cat-back combination (I understand that recordings won't do any of them justice, but since I'm not going to spend a long time traveling around and finding exhaust notes to listen to in person, this will have to do in a pinch). I'm interested in making more power, but I don't see any real need to get carried away with that. (Note, I think the Cobb catted pipe is the better choice since I would still like to pass emissions in MA.)

 

As I understand it, the Borla catback is a 2" exhaust and the Cobb downpipe is basically a 3" at the turbo end, tapered down to 2" at the cat end. Therefore, I *think* it should fit to the stock turbo and the Borla catback without any adapters.

 

That's what I think I know, though feel free to correct any misconceptions I might have about this plan.

 

Here's my questions though. I read somewhere (I'm pretty sure it was Bren from Bren tuning on another Subie site) say that these cars really should have a 3" exhaust. Bren seems like a pretty reliable source, but I guess I'd like to hear some arguments either for or against.

 

My other question has to do with adding a wideband O2 to the downpipe. I believe the Cobb downpipe is designed with a bung in it already for a wideband O2 sensor, but I think it seems awfully close to the turbo (like 2-3"). I've read a number of other posts that have said that the ideal position for the wideband O2 is much further down the pipe, like 8-10 inches away from the turbo. Seems like Cobb would know what they're doing with the placement of the O2 sensor. How important is it to get further away? Is this critical enough to eschew the Cobb?

 

Comments? Note, I freely admit my completely noob status, so again, please feel free to correct any of my misconceptions.

I am looking at a similar setup for next year. I've acquired an STi uppipe, and would like to get the Borla CBE based on the sound samples I've heard on Youtube. Not sure what downpipe should be going in between to get a good match in terms of power/emissions (I want mine catted) and also what gaskets are required.

Bump for opinions on 2" vs 3" exhaust and for wideband O2 sensor location, specifically as they relate to Cobb and Borla.

 

Thx!

Cobb DP tapers to 2.5" at the flange, not 2". Similarly borla is 2.5" at the flange and tapers down to 2" in the "y" pipe (which is more like a T-pipe on the borla).

^^ I didn't realize that. So, the question basically remains: is that significantly more restrictive than a full three inch turboback all the way? And the important corollary: is it bad enough to make the Cobb/Borla combo a bad c hoice?

 

Keep in mind that I am looking unleash some fun in my daily driver rather than looking to build a dedicated track car. I'm not looking for 400whp here, but nor do I want to make a choice that I'll end up being unhappy with or that significantly restricts my future options.

I don't think that the 2.5" neck down is any thing close to a significant restriction on the stock turbo.

 

Plenty of power for a DD with a Cobb DP and whatever catback you want (even stock). Main power gains come from opening up the downpipe and having a bellmouth instead of a plate blocking the wastegate.

What you want to do is really listen to different setups and go from there, especially with a wagon as you'll be dealing with drone more. I've got the same car as you and have a perrin up/catted down mated to an autospeed cbe. The other thing to look out for is how far/inset the tips of you're cbe will be. I agree the wb should be further back but that'd be the least of my concerns with you're setup especially if you are having a protune done by Bren.

Scoobydoobie is correct in terms of power. Most of it will come from the DP and UP changes. The mid and y pipe combo will certainly free up some WHP but the big bang is from the DP. And I agree with Firepuma as well, drone on some of these setups for a DD is something to consider more than 3" or 2.5". I have a full Perrin Turboback and I can tell you it definitely drones on a sedan. I'm willing to live with because I love the sound but definitely something to consider.