The 2015 Subaru WRX electric steering rack conversion
This was originally posted on NASIOC at https://forums.nasioc.com/forums/showthread.php?t=2733605
This post will outline my project of replacing the hydraulic power steering in my 2010 STI with the electric power steering from a 2015 WRX. I'll try my best to cover everything, but it was a long journey (a little over a month,) so I might forget a few little things. First thing's first: Why? I couldn't get the air bubbles out of my hydraulic system. Eventually I replaced the whole system (rack under warranty from Subaru, lines with teflon -AN lines, custom reservoir, new pump, etc...) and it still leaked. I'm not terribly great with fluids, but I'm a bit better with electrons so I found an electric rack on eBay and decided to give it a try. Electric steering is the future anyway
2015 Subaru Impreza WRX electric steering rack
The top rack is from my 2010 STI, the bottom is obviously from the WRX. The length from endlink to endlink is exactly the same, but you can see that the mounting points are totally different.
2015 Subaru Impreza WRX crossmember (engine cradle)
Again the top is 2010 STI, bottom is 2015 WRX. The bolt holes for the frame are a direct fit, as are the control arm mounting points. Make sure that you get the extra bracing and the bottom plate from the donor car as well.
2015 Subaru Impreza WRX crossmember vs 2010 STI crossmember)
The major difference between the two crossmembers is the relief for the exhaust. On the 2015 WRX, the exhaust is run underneath the crossmember. The swaybar mounting points are the same, but as you'll soon see the 2010 swaybar won't work.
2015 Subaru Impreza WRX sway bar
The 2015 sway bar is a different shape, but you can re-use the original 2010 end-links (with one modification, outlined below). Since the 2015 bar is 2 mm thicker than the 2010 bar, you'll need bushings and mounts. I ended up using some Energy Suspension parts.
2015 Subaru Impreza WRX electric steering control unit (34710VA010 E2710-58020)
There are way more control units on eBay than electric racks for some reason. Make sure you get the plugs that go into the unit! I found some information on the smaller plugs (outlined below), but the larger 80 amp plugs were never found.
Electric steering computer connectors
2015 Subaru Impreza WRX steering linkage (sorta optional) -- The distance from the steering wheel splines to the electric rack splines turned out to be further than the hydraulic rack. I ended up modifying mine instead of buying another.
An Arduino Uno with the Seeed CANBus shield -- This turned out to be the most important part because without it, none of the rest of the system will work.