BH Outback STi swap

[Romy]

Background:

I've wanted to do this for a long time. I've had 2baru (my 2nd green BH Outback) since 2012 and in the back of my mind I've always wanted to turbo swap it. I'm lazy and don't want to write 'Outback' so I'll go with BH, as that's the model code - I guess technically, with an STI swap it's a never-made BH7 :) When I was deployed to Iraq/Kuwait in 03-04, I read car mag after car mag about the STI and kept thinking it would be sweet to get one after deployment. Well, that just didn't happen; not so practical to spend most of what you saved on a car.

Fast forward to my post graduate school, decent paying engineering job self, with my daily driver cresting 300k. In 2baru, I had replaced the 5mt with a $140 junkyard 5mt which lasted a year. Luckily I fixed the old 5mt in the interim and swapped it back in. I replaced the EJ25 at 240k but it's now leaking oil from the rear main like a bitch. The trans mounts are shot, the engine mounts too. I've blown up two driveshafts in as many years (towing motorcycles does that). It overheats when towing sometimes. It's an old car. So on the last large roadtrip, my wife an I experience one of those blown drive shaft, leaking engine moments. We have aircooled VWs so breaking down is not a big deal, just a bit surprising on the reliable car. The question becames, do we get rid of 2baru for a new 'baru, or fix 2baru? My wife likes 2baru and it's well known that a happy wife equals a happy life, and so the swap plans formed

I picked up an 04 USDM STI engine out of Ohio. It came mostly complete but I had to add things like exhaust, intercooler, wiring...

Mechanically, this swap isn't hard. The Baja Turbo is basically a BE/BH chassis anyway, so I used parts from Baja Turbo's when I could (like the wiring) and just jammed away. The wiring is by far the most pain in the ass. I also added in the auto climate control off the H6 cars, which was just more wiring. I'll get to that stuff in later posts.

So here's where I started:

https://sl-i.net/FORUM/images/imported/2017/11/32622406572_0a99699e74_k-1.jpg

Ready to pull out:

https://sl-i.net/FORUM/images/imported/2017/11/32622407352_1f1f38d8da_k-1.jpg

And we're clear!

https://sl-i.net/FORUM/images/imported/2017/11/32622407902_a84b6a3455_k-1.jpg

And here's where I ended (or at least completed the swap):

https://sl-i.net/FORUM/images/imported/2017/11/24345361948_8567996b5f_c-1.jpg

[Romy]

Electrical Reserved

I'll attempt to upload what I had to do to make the wiring happen. I have a rather bulky excel spreadsheet...I'm not sure there's an easier way to confer all what needs to happen to make this swap work.

I used both 'bulkhead' harnesses (front and cabin) from an 05 Baja Turbo (BT) and merged in the wiring from my Outback as well as an H6 Outback. Beyond the turbo engine, I also wanted to retain the windshield heater (Baja's didn't have one), use the Baja 'sport lights' and 'cargo lights' for roof rack lights, add in the H6 Outback auto climate control, and add in the later year Outback 6x9 in the rear cargo area. This meant donor harnesses from the junkyard and a decent amount of time staring at wiring diagrams and figuring out how to merge things.

There are also some major harness connector differences between 02 and 04 (donor H6) that I found. If you do this swap and have an 02 or older and use 04+ BT stuff, be aware you'll need basically an 04 (maybe 03) donor Outback wiring harness.

When I refer to wires of two colors, the first color is the main wire insulation color, the second is the stripe color. When I refer to connectors/pins, I use the connector from the wiring diagram followed by a slash and the pin. I'll use the Integrated Module blue connector and pin 10 as an example - this would be B281/10.

Integrated Module:

The integrated module is used on the BT is the same as the BH one. The BT doesn't have a rear hatch, or a front wiper deicer, which are the only real differences in wiring going to it. There are two connectors on the integrated module; a blue one (B281 - 16 pins) and a gray one (B280 - 20 pins). On the blue connector, pin 10 is missing (B281/10) as is pin 1 on the gray connector (B280/1) on the BT harness. For the wiper deicer to work, pins B281/10, B281/13, B281/4, and B280/1 all need to be connected. Two of these (B281/4 & B281/13) are grounds, however, they directly connect to the wiper deicer plug (B177/1 specifically) which has to be swapped over.

Also, if using a JDM black face gauge, two (well three) wires need to be tapped into from the integrated module / headlight switch (which has a 17 pin connector: B71). The connections are: B280/18-B71/11 (blue), B280/16-B71/12 (Green/Yellow), and B71/10 (black) which is a ground. I don't know if the ground is necessary to tap into, but I'm going to break it from ground and route to the black face gauge so that the black face gauge is reading the same reference voltage as the headlight switch. On cars with a black face gauge stock, these wires run to the SMJ, ports O6 (blue), P6 (Green/Yellow), and N6 (Black). If you look at a EDM or JDM wiring diagram, note that the colors are different than USDM cars. On an EDM/JDM car two of the three wires are different colors - the Green/Yellow wire is Green, the Black wire is Blue/Green (and the Blue is Blue).

[Romy]

The parts list.

I'll edit this later and upload an excel file (or similar) with all the part numbers, but here's some general commentary. Sometime between 2002 and 2004 (I believe it it was 2003 models) Subaru decided to change their electrical connectors. They also eliminated the super multiple junction (SMJ) as the connector for the engine room harness to passenger compartment around this time, as well as swapped to something called the 'Integrated Module' to combine functionality of several independent modules into one (such as wiper, illumination, etc.). What this meant for me with an 02 Outback but 04+ Baja Turbo (BT) and STI parts was that simply merging harnesses was going to be hugely difficult. What made more sense was just getting BT bulkhead harnesses (engine and compartment - see the factory service manual for terminology). But due to the intervening year connector change, this also meant the BT harness wouldn't plug up nicely to my 02 rear harness. So basically, I needed at least a rear harness from a more modern BH and front harnesses from a BT, and some merging skills. But it's not quite that simple either - 04 was the only year that any BH had a fuel pump controller, and it was only for H6 cars. Which meant I needed a 04 H6 donor car. Luckily the junkyard has/had one. Slightly annoyingly, there are two wiring harness pass through ports on the firewall for the BH while the BT only uses one. Some body plug (which I have yet to locate a P/N for) goes in the other hole.

Now remember that connector change I mentioned? Well, turns out the rear doors and rear hatch all had different connectors (front doors are the same, but the driver's side has an extra connector on later cars for a buzzer). Also the G-switch under the center console, the charcoal canister vents/solenoids/harness, the fuel pump, the A/C pressure switch that goes on the liquid tank on the passenger strut tower (4 pin is needed, not 2 pin as the 02 had), the radiator fans, and the windshield wiper motor. So generally, if you plan to do a swap like this, it would be best to start with an 04 H6...and a BT donor...and an STI donor (I can't afford three donor cars, hence my junkyard/ebay route).

There are a few other parts that the BT uses while the BH does not. BT's are drive by wire (like the STI) and so the drive by wire pedal is needed, as is the mounting bracket; the former is not hard to find and can be bought new, the latter is NLA from the dealer so I had to find a used one. Because it's drive by wire, the cruise control module and mechanism goes away (it sits about where the turbo does). And of course the pedal cable hole needs to get plugged.

The air cleaner box is the same as the WRX; the baffle box (or whatever) that goes behind the fender is the same as any H6 car, as is the cold air scoop.

BT fans are the same connector as STI fans - you can't easily reuse 2.5 NA Outback fans. I'm not sure (but I'd guess) that 03/04 BH fans are the same as BT.

Impreza GC lower control arms (LCAs) are the same as BH arms (and B4 arms for that matter). B4 rear upper control arms were aluminum. And BP Spec B trailing arms will also fit with some splicing of ABS connectors (covered on some forum somewhere, I think the legacy GT one). This doesn't relate to the motor swap, but I'm doing it anyhow.

A BT engine cradle (also called K-member) is needed to allow for the uppipe (or a cut/reweld on the BH one). An STI cradle will fit but will require STI arms, sway bar, etc. I already had aluminum LCAs so went with a BT cradle. Although a faster ratio steering box might be interesting, the car is meant more for camping/commuting/trips so I don't care all that much.

The STI (and BT) power steering pump is in a different location than the EJ25 one, so BT power steering lines are needed.

The intercooler sits right about where one of the A/C lines goes, so a BT A/C line is needed.

The boost control solenoid is the same as the WRX/STI, however the mounting bracket is BT specific and NLA. Like the accelerator pedal mount, junkyarding is needed.

The BT swaybar is different than the BH (or BE) swaybar.

The BT dash wiring allows 'Sport Activity Lights'; the switch harness is prewired into the harness. I'm adding a three switch panel and reducing the under-radio cubby size to do so. The p/n is 66208AE310; it's a RHD thing but supposedly there's a LHD version too (66208AE330). I got a cubby off of ebay with several switches in it. I'm adding roof lights to the rack I have as well as side rack lights (helpful at night when setting up camp) and will have a third spot for something else; intercooler spray perhaps, or just more lights.

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I also decided to swap in the auto climate control module. I snagged just about every harness I could from the junkyard so I'll post up how to wire that junk as well as the parts list later.

[Romy]

Auto Climate Control Reserved + other junk

In retrospect, the swap would go much faster without trying to merge in Auto A/C. The fun part about the Auto A/C is that there is no real wiring diagram for a manual car with Auto A/C for the USDM; I did find an EUDM manual which helped. Essentially, and not just limited to Auto A/C but in the whole swap, if you see the wiring diagram showing a wire goes to the 'Trans control module' it instead means you need to wire it to the vehicle speed sensor on a manual car.

There are several sets of wires that are shared between the manual A/C and the Auto A/C; however, there are also many wires are unique to each system. You really need a wiring diagram to do this swap as you need to merge both instrument panel harnesses and bulkhead harnesses. I can't see doing this without having the harnesses out of the car, but if you're slick, you could probably do the bulkhead one with it in the car. And perhaps just swap to an Auto A/C dash harness and ignore the unused transmission connections (this would need to be verified; not sure if it'd work). I chose to retain the capability to swap back to manual A/C so I merged harnesses.

Several parts are needed to do the swap; the junkyard is a good source of parts. On the whole, you'll need:

Auto A/C Module w/ the in vehicle temp sensor (get the screws too)
Sunload Sensor & Defog Vent (on the passenger side dash - for the love of god don't cut the dash harness; you'll need it also)
Blower motor resistor (auto A/C is 3 pin, manual is 4 pin - get the felt washer too)
Evap Thermo Switch (wedged into the A/C heat exchanger - Auto A/C is 2 pin; manual is 3 pin)
Air Mix Actuator and lever arm (on the bottom of the heater core housing - the manual A/C version has a cable attached between it and the mode panel on the dash)
Dash harness
Bulkhead harness

Merging the dash harness is pretty straight forward. Look at the wiring diagram, and the wiring pinout I upload later, and get soldering. The bulkhead harness isn't too bad either, but the annoying part is the 'Mode Actuator' - it's near the gas pedal (I'll upload a pic). The wires which go to it differ in order between the Auto and Manual A/C. Which means you need to swap pins. Or in my case, have two connectors so that I can always swap back to manual A/C if I don't care for Auto.

More to come...

[Somac]

Holy cow, great thread! I just read through it all and man am I overwhelmed with everything I'll need to do a swap OEM-style. I never knew how much had changed between 00-02 and 03-04s. I guess I'm really glad I have an '04 now! I might have to harass you over PMs for some help with mine.

[Romy]

Sure, not a problem, ask away :)

[duncanm]

noice!