TheHoffmann Posted September 25, 2018 Share Posted September 25, 2018 Hi I'm new to the forum so please if I do something incorrect please tell me how it's done A few weeks ago I purchased what was left of a crashed 05 STI. After some inspection and disassembly I saw that the whole running gear (Engine, Gearbox, Differentials, Brakes...) was in perfect shape and that it was just the shell that was wrecked. My original plan was to swap everything over in my 06 Legacy wagon, redeeming the 121kW engine from it's job and powering the car what the factory should have done. Now most of the technical challenges are solved, and the electrical problems begin...What do I have to change/modify to make it work? The need of changing the wiring harness was what I know, but now I realized that the STI had no CANBus and no one can tell me what I need and what not. And now the major problem: I am from germany so everything I do has to be some sort of 'OEM'.. I hope that some of you can help me finish this project because the germans are to 'german' to help me... Link to comment Share on other sites More sharing options...
boxkita Posted September 27, 2018 Share Posted September 27, 2018 What if you swapped the entire harness over? Otherwise there are a couple us company that make custom harnesses for Subaru. Iwire.com is one I think. Build my car Boxkita Track days Link to comment Share on other sites More sharing options...
utc_pyro Posted September 27, 2018 Share Posted September 27, 2018 Now most of the technical challenges are solved, and the electrical problems begin...What do I have to change/modify to make it work? The need of changing the wiring harness was what I know, but now I realized that the STI had no CANBus and no one can tell me what I need and what not. Yes it does. People just tend to say it dosen't because the bus isn't exposed on the ODB-II port. Unfortunately we'll need a bit more info on your car, because it sounds like you're not in the USA. If your Legacy is a turbo it's easy, you can run off the same ECU. If not you'll be swapping over a lot more stuff electrically. Do both the Legacy and STI have an immobilizer/key transponder? How handy are you with soldering? Do you have access to the (EDM?) wiring diagrams? Any funny laws over there that would keep the dealer from touching the car to register the immobilizer between things that should be together? Link to comment Share on other sites More sharing options...
TheHoffmann Posted September 27, 2018 Author Share Posted September 27, 2018 Yes it does. People just tend to say it dosen't because the bus isn't exposed on the ODB-II port. Unfortunately we'll need a bit more info on your car, because it sounds like you're not in the USA. If your Legacy is a turbo it's easy, you can run off the same ECU. If not you'll be swapping over a lot more stuff electrically. Do both the Legacy and STI have an immobilizer/key transponder? How handy are you with soldering? Do you have access to the (EDM?) wiring diagrams? Any funny laws over there that would keep the dealer from touching the car to register the immobilizer between things that should be together? No, unfortunately it's a NA 2.0, I have the whole STI so if parts are needed I probably have them. The key of the STI looks like it yeah. I think that my dealer could give me access to the EDM wiring diagrams. No that I know of, it's a small family owned dealer I think they would do that. Link to comment Share on other sites More sharing options...
utc_pyro Posted September 27, 2018 Share Posted September 27, 2018 Ok, from a high level you'll be transplanting the STI engine and transmission harness into the legacy, along with the body side portion of it leading to the ECU. You'll then merge this harness with the one from the legacy for your power, canbus, and immobilizer bus connections. You'll likely need to modify the starter circuit wiring as well. You should be able to keep the Legacy body computer and gauge cluster with the STI ECU. The CAN messages should be close enough for everything to more or less work after you register the immobilizer. This will be a test and see thing though because it might throw codes even if it technically works. As a backup you can get USDM/JDM Legacy GT ECU (former is STI is single avcs, latter if dual avcs). On the DCCD in the STI transmission, you can try and retrofit the system from the STI (cheap) or add a 3rd party controller (easy). Gauge cluster obviously wont display this data, but it wont freak out from the extra messages ether. Not sure on the trim packages they offer over there, but if the Legacy does not have VDC you'd probably need to retrofit the steering angle sensor from one if using the OEM DCCD controller. An aftermarket controller would be more or less plug and play with no strange hackery. Link to comment Share on other sites More sharing options...
TheHoffmann Posted September 30, 2018 Author Share Posted September 30, 2018 Ok, from a high level you'll be transplanting the STI engine and transmission harness into the legacy, along with the body side portion of it leading to the ECU. You'll then merge this harness with the one from the legacy for your power, canbus, and immobilizer bus connections. You'll likely need to modify the starter circuit wiring as well. You should be able to keep the Legacy body computer and gauge cluster with the STI ECU. The CAN messages should be close enough for everything to more or less work after you register the immobilizer. This will be a test it and see thing though because it might throw codes even if it technically works. As a backup you can get USDM/JDM Legacy GT ECU (former is STI is single avcs, latter if dual avcs). On the DCCD in the STI transmission, you can try and retrofit the system from the STI (cheap) or add a 3rd party controller (easy). Gauge cluster obviously wont display this data, but it wont freak out from the extra messages ether. Not sure on the trim packages they offer over there, but if the Legacy does not have VDC you'd probably need to retrofit the steering angle sensor from one if using the OEM DCCD controller. An aftermarket controller would be more or less plug and play with no strange hackery. Ok perfect so both wiring harnesses and this could work. It's an UK model so there is no DCCD, which makes it a little easier. Right now I'm looking at all the different Subaru hubs because I thought of changing the PCD. I found that the 07+ STI uses the same front hub like the 06 legacy, so the wheel bearing assembly with PCD 114.3 could theoretically fit. But I can't find one that would fit the rear. The point in it is I would have to modify the axle or the PCD for the teeth on the axle because of STI and legacy. Link to comment Share on other sites More sharing options...
utc_pyro Posted September 30, 2018 Share Posted September 30, 2018 I don't think an easy solution as ever found for fitting 114.3 in the rear. Most people are using Spec.B rear axles to go form the STI R180 to the Legacy hubs. There is a lot of information on the mechanical aspects of the STI transmission swap here: https://legacygt.com/forums/showthread.php/6mt-master-swap-thread-107137.html Link to comment Share on other sites More sharing options...
boxkita Posted September 30, 2018 Share Posted September 30, 2018 Madrig has a solution for the rear trailing arm. It involves drilling the arm for the STI hub. Hkc-speed has the conversion that free range racing did. Last I heard, he was having his machine shop customize the rear axle bars to fit STI splines. I'm not sure if he fixed the trailing arm, too. Drilling was easy, getting the abs sensor to mount up was difficult because you have to rotate the hub which interferes with the mounting holes. Build my car Boxkita Track days Link to comment Share on other sites More sharing options...
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