I installed a STI catback on my '02 wagon (thanks for the deal KA05STI). It went very well. I like the little deeper rumble but it definately isn't too loud. I confirmed that the midpipe diameter was the same that was on the car stock (2-1/4" ID). My questions are: 1. Will a downpipe (helix, invidia) bolt straight to the donut type flange on the stock 2-1/4 midpipe or will you need some type of adaptor? 2. If I install a downpipe with the STI cat back is it safe to run the Cobb stage 2 map or should you have 2.5+ ID all the way back? Any feedback is appreciated.
You can find a downpipe that will mate with it, or you can get an adapter. Or a 3" to 2.5" mid pipe. You"ll need an up-pipe before you can go to Stage 2.
I'm fairly certain that this is not the case. Granted, it's highly recommended so that there is no chance that your uppipe cat grenades your turbo, but I don't believe it's one of the necessary mods to run the Cobb stage 2.
Im sure you can run the stage 2 map with just a downpipe. The uppipe would do wonders on your car(from what I've heard) so I would buy it and install it. Might as well. But im sure the guys above me know more about this than I do, lol I don't drive a bugeye.
Turbo xs makes a shorter downpipe so you would have to get turboxs dp, race pipe or cat, and mid pipe.
You need to do an uppipe.. too much risk with higher EGT chunks of cat breaking off in to ur turbo...
Since up-pipes are somewhat pricey, you could probably get a stock one from an 05+? I believe they are catless after 04, am I right? Anyway that would be a less expensive way of ensuring that your turbo doesn't receive an unwelcome visit from happy little pieces of substrate.
catless up pipe is REQUIRED for "stage 2." Either gut the stock one (NOT easy or fun), trade your stock catted one w/someone who is going back to stock, buy a gutted one, buy an 06+ WRX one, buy an 04~07 stock STi one, or get on ebay and get one. As for the downpipe, there are a few companies that make downpipes that will fit with the stock centerpipe/catback. The STi muffler supports stage 2. Cobb Stromung (catted or catless) Lachute Those 3 make awesome downpipes that work with the stock catback. I dont know if Lachute makes one for the WRX, but if they make one for the 5MT Legacy, it will fit the WRX. I know they make one for the D5AT Legacy, and were the first to do so. Otherwise, everyone else makes downpipes that DO NOT FIT with the stock catback. DO NOT FIT meaning you'll have to MAKE it work. The center pipe and any 3" downpipe will physically bolt together, but the flange is so thin on the center pipe that making the 3" 2 bolt gasket not leak will be a chore. It works, I've done it before...but then again, most of them leak either the next day or 6 months later. Very few have lasted longer. The heat cycle and lack of thickness in the flange makes for the flange flexing and allowing it to leak. Plus there is no more flex built into the system, that will put more stress on the entire system...sometimes resulting in a broken up pipe, even if it has a flex joint. I would, once you get the UP/DP installed, drive to a known good exhaust shop and have them cut off the donut flange off the center pipe and replace it with a standard 3" 2 bolt flange, then a flex joint and then a 3" to 2.5" coupler. FTW.
Thanks all for the replies - esp. WJM. I guess I will be looking for a Cobb or Stromund - I really want to keep some sort of cat in the system. I was planning to try to find an uppipe to gut at the same time. Hopefully sometime this summer.
Taken from Cobb's map notes for stage 2 on 93 octane: Of course you'd be foolish not to have one if you were running stage 2, but I'm sticking with not required. But yeah definitely get one if you are planning on doing a stage 2.
What's the rep on cobb's uppipes w/EGT Bung? $235 is a lot but if it'll keep me from ever having CEL & UP leak problems I'll step up for it.
go for a gutted uppipe. OEM filament and put put a bolt in the egt. ( do the resistor mod or get tuned)
The invidia dp says that it will bolt to stock. Will - does this fall into your category of making it work or it bolts but is less than ideal. The Cobb and Lachute are pretty expensive ($600+). I actually could not find good info on the Stromung though. Anyone have info? If the invidia works that keeps my options on the used market a bit more open. Again, I want a clean solution to bolt to the stock STI midpipe.
The invidia requires 'massaging' to work. Check out boxer4racing.com for the Stromung. They have awesome fitment and work with the stock center pipe/donut gasket stuff.
Thanks again Will. So it looks like the Cobb and Stromung are similarly priced new, but the Stromung is 2 piece. Is there any thinking on if one is better than the other? My logic says the 1 piece is less likely for leaks, but with the 2 piece I could always remove the cat down the road.
My Invidia DP fits up to my STI catback with no leaks. It might require 'massaging' as you say, since Batlground had to reweld the flange to fit the cat-back due to having to reflange the turbo-side of the DP. On my setup it works, I dont know about how it'll fit on a stock-ish setup.
What are peoples thoughts on this? GTscoob - you are running a 2.25 STI catback with I am guessing something close to stage 2. With just a downpipe and 2.25 catback is it OK with the cobb stage 2 map? I know I could get a tune, but I am trying to keep this as cheap as possible.
The stock WRX/STi center pipe is like 2.4" ID and 2.5" OD. The WRX muffler (all years) is 2.25" OD right after it bolts to the center pipe. The STi muffler is 2.5" OD all the way into the muffler and the outlet is larger than 2.5" OD and under the chrome tip its 3". The stock center pipe and STi muffler is more than enough for stage 2 and 3. Its the upipe and downpipe that need to be changed for Stage 2 and beyond.