I wish I had started documenting this before I was 3/4 of the way through the process, but I didn't. The title is self explanatory; it's not what I WANT to do. It's exactly what I'm doing. To add, everything I'm posting here is strictly from memory. I will forget to add something, so ask me questions and It'll probably jog my memory enough to answer it if I can. So lets begin.
Driveline: What I'm using
Engine: EZ30"R"
Trans: TY856WVCAA (2006 Legacy 6MT Transmission)
Driveshaft: No change. 6MT uses the same prop shaft
Rear Diff: 3.54 "FM" Classification R160 (cheaper and easier to find, and a viscous LSD for what it's worth)
Mounts: 5MT sourced Transmission crossmember, EZ30 specific engine subframe.
Other Things:
Engine Mounts
A boatload of connectors from iWire
Pedal box (any 5MT pedal box will work)
Clutch master cylinder
Master cylinder hard line and mounting bracket
Slave cylinder flexible line
Radiator
Fan assemblies
Heater core hoses
Radiator hoses
A/C High/Low pressure lines
Intake
Haltech Elite 2500 & WB2
Front axles (The axles are the same but mine were roached)
Rear axles (AT uses 22 spline input, MT uses 25 spline)
STi 6MT short shift assembly (which you can buy here)
USDM Spec B shifter surround
Shifter boot
Shifter mounting plate
Shifter Stay bushing
Headers
Various Fasteners
So what fits and what doesn't?
Well, since this is a 4EAT shell, everything fits without modification. All of the mounting points for the manual transmission cross member, pedal box, and master cylinder are present. 5EAT cars will need some work but that's a discussion for someone that isn't me. Otherwise, the process is as simple as dropping the old engine/transmission out and swapping the new one in. Highly recommend mounting the shifter before mounting the rear of the transmission. There's not a lot of room in the tunnel once everything is in place.
Where it gets complicated is when you start wiring everything up. There are some commonalities between a 4 cylinder and 6 cylinder harness but they are few and far between. There are further differences between AT and MT harnesses. Most of them can be worked around if you're savvy enough but I'd wager for most people, it would be easier to just find a H6 Outback or Legacy donor and swap the bulkhead harnesses completely. I didn't do that because they're rare as hen's teeth in the southeast and I don't have the space to keep them both if I could find one. This, combined with the ease of tuning, is why I opted to run an Elite 2500. The way I've opted to approach this is by using a flying lead harness from Haltech, building an engine harness to run from the ECU to the engine receptacles, and merging other functions where needed.
So far the only major difference I've found electrically is the fan circuit. Fans on the H6 cars are controlled directly by the ECU through the PWM mounted to the sub fan shroud. I thought I could work around this by retaining the H4 fan assemblies in some capacity but it isn't physically possible. The solution, then, was to adapt the H6 fans to the H4 harness by cutting the pigtails off of the H4 fans and soldering them to the H6 fans. Since the Elite has multiple Stepper/DPOs, I was able to assign two DPOs to control the main and sub fan relays. It uses coolant temp values to trigger those outputs, so to test them, I set the "on" temperature a couple of degrees higher than what the coolant temp sensor was reading and hit the key. Worked a treat!
There are differences between the injectors and ignition systems between the two cars (obviously) but they receive power at the same points on the main engine harness, so the simple solution was to de-pin the ignition and injector power wires and place them in the new engine connector. Just run a ground wire for the ignition coils, since they are normally grounded to the ECU. The rest is controlled by the Elite. EZPZ.
The starter circuit is identical outside of the way it's controlled. The manual uses a clutch pedal switch where the automatic has an interrupt switch on the shifter assembly that breaks the ignition relay circuit when not in P or N. The latter is not used since the starter relay is controlled by the Elite using a switched ground DPO. The relay runs power through the clutch pedal switch and out to the Elite by setting the DPO to switch to ground when activated. Activation is controlled by a generic sensor ("GenSens") that is looking for 12V. This is wired to the start position on the key. As a secondary condition, the Elite also looks for engine RPM to be below 350. If those two conditions are met, then the elite switches the DPO to ground and the starter relay closes.
More to come. Here are some pictures from along the way.
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