2005 XT Swap - Out with the EJ25/5EAT, in with the 2008 JDM Spec-B

In December my Outback developed a misfire in cyl #2 and was diagnosed with 20% low compression, another EJ bites the dust. At the same time I love the car and want to keep it, so instead of taking the advice of many I'm instead going to attempt an EJ20Y swap from a 2008 Spec-B. Yep, I went in the exact opposite direction, difficult. Still, I did get the diff, driveshaft, and half-shafts, so that's all essentially bolt-in

Since I bought a front clip I get everything aside from the downpipe; since its twin-scroll finding a proper downpipe is a pain. Let me try to break down my approach, I have a decent idea from my research about what's involved but would love some advice. I know it is dual AVCS, I know a manual swap is a pain, I know the wiring could be a killer, and finding a downpipe has been almost impossible (aside from paying like $1400 for an imported one, ha no thanks). So, some thoughts so far:

Trans swap

Basically, swap as much over from front clip, unless someone has a solution to do it more easily with a few auto harness splices; I know cruise control is always a problem, but since I have the stalks and everything would that cover it?

Also, can I just swap the RHD pedals and slave cyl to my LHD Outback, or should I just get the USDM 2008 STi setup and be done with it?

From what I've read I need to modify the crossmember for the 6spd, but I'm not clear if I can or cannot use a 2008+ STi crossmember instead; its hard to find Legacy info, so I'm worried I'm mixing up Impreza stuff.

I plan on a new clutch, mounts, and 1-2 other things since it'll all be apart.

Swap Idea #1

Do a complete swap - engine, trans, harnesses, and figure out the auto-to-manual wiring. This is the most straightforward and I know everything will work together. However, a few possible issues:

- I don't know if I get the body ECU, so I might need to get one since the 2005 is K-Line instead of full Can-Bus (which means dealing with more harnesses)

- Basically, use as much JDM as needed to make it work

Swap Idea #2

Use as little as possible from the front clip (only what's necessary, essentially long block and 6spd stuff). How much would my 2005 wiring jive with the newer stuff, aside from the AVCS?

Random thoughts

Are the twin-scroll headers the same between the Impreza and Legacy?

Since I don't have a downpipe and the TD04HLA is a bitch to find parts for, what about swapping Impreza stuff? If the headers are the same I could swap to a vf36/37 uppipe, turbo, and 2008+ Impreza TS downpipe - its easier to find parts, and the 6spd/chassis are basically compatible.

Also, since the 2008 parts are full Can-Bus, could I use a 2008 USDM STi ECU to run the dual AVCS and be covered on OBDII emission testing?

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I have the clip ordered and an air pump delete kit in hand, but I'm waiting to buy anything else until I have a full plan of action. Thanks for all the help, in about a month the real fun will begin

So after more research and talking to Dewey at THMotorsports for way too long, I think I'm going to take this approach regarding the dual AVCS and how to get this thing running:

1. Install new clutch, GV/GR STi master cylinder and steering rack, mounts and bushings, maybe a Fluidampr, it also will need a manual-trans radiator. I've also debated an STi front differential install since the Spec-B is open diff. This stuff will all happen when the car is in pieces.

2a. I bought a 2008 USDM Spec-B engine harness, (just in case). So, I swap in untouched EJ20Y, swap USDM intake stuff, swap to LHD Can-Bus engine harness, and run a dual AVCS USDM 2008+ STi ECU with recoded immo to make it plug-and-play. This is the easiest and most USDM-friendly. It will communicate with OBDII for emissions and have all kinds of 93 octane USDH support. Will this work? I have no idea, but the logic is sound

OR

2b. If that electrical trickery won't work this is the back-up plan. Swap USDM single AVCS exhaust cams and seals into U20 heads (Z20s with air pump), install oil feed plugs, leave ex. cam solenoid installed/unplugged since it aids in oil circulation but doesn't matter to the USDM harness and ECU. Button it up with new valve cover gaskets and timing belt setup. It has a 12mm oil pump stock so I'm fine there

3. Swap in frankenstein Y engine and Spec-B trans. I haven't found a good source for whether or not the Legacy-specific 6spd crossmember simply bolts in, it seems like its not that simple. I'll need a downpipe, I'm going with an AVO VF38/44/TD04HLA S1303G3LA001T, its a cast divided outlet which bolts to a 3" catted pipe (and should bolt to my stock-for-now catback). Change/fill all fluids.

4. Double-check everything. Do whatever I can to prep it for startup - tune is of major importance, if I go with step 2a I want to make sure the car keys on and I can read the USDM ECU. Time to call iWire again. Start car and prey is doesn't blow up.

List of to-do:

Figure out if the Spec-B harness would talk to the STi ECU - if that works, then the AVCS issue might not be one at all. It will need to have the JDM exhaust pigtails installed, no big deal. The only other Can-Bus issue would be the BIU, but I should get that in the clip and be able to figure out the harness. I'll also need to deal with the auto-to-manual wiring, ugh.

Figure out crossmember issue, it sucks this won't happen until I have it in-hand. Get manual console trim (assuming JDM doesn't work/is trashed), and anything else for the manual swap.

Am I crazy? I want 2a to work so bad since its so simple, but we'll see. I'll post some pics soon.

Well, you got a lot of work ahead of you, that's for damn sure. You're going to have to pour over the JDM wire documentation as well as the USDM documentation. That's going to be a bag of ass. I'd check the bulkhead diagrams because that should leave everything behind the engine alone.

If I were in your shoes though, I would look into an aftermarket ECU, just to alleviate the engine wiring wonkyness. You will most likely have to repin the spare harness to fit the USDM engine as well ANYWAY so going aftermarket would be 90% of the work completed. I don't know if 2a will work with the OBD2 sensor as you're intending.

It's doable, but I think it's really going to suck either way.

Front clip is apart and ready for the engine swap, tomorrow I start work on the Outback

http://www.subaruoutback.org/forums/109-gen-3-2005-2009/416186-2005-xt-jdm-spec-b-swap-imported-front-clip-auto-manual-conversion-bolt-ons.html