AutoPi as a piggyback automatic transmission controller

Hey guys.

I have been looking for a solution to allow me to manually control the operation of the torque converter lockup clutch on my Subaru Legacy. As standard the TCU unlocks the TCC the lightest touch of the throttle, which results in the revs bouncing around all over the place under normal driving. It’s bad for fuel consumption and performance, and as the car has an aftermarket exhaust, it also sounds a bit weird.

I know that a switch can be wired in to the TCC solenoid to give manual control and keep the TCC locked, however it would need to be switched on and off every time you wanted to change gear or come to a standstill, so this isn’t really ideal. I am interested in developing a more integrated solution using a Raspberry Pi with a CANBUS interface, my search led me to AutoPi and this board, it sounds like exactly what I am looking for!

The idea would be to have the AutoPi monitor parameters such as MPH, RPM, Throttle Position and whether the car was in manual shifting mode, in sport mode or had cruise control switched on. Based on these parameters I could then write some custom code to control the TCC activation independently of the TCU by varying the voltage on one of the GPIO pins.

For example, the control might look like this

IF mph>20 AND gear > 2 AND shiftMode = Manual AND SIDrive = S# THEN activate TCC solenoid. (By sending 12v to a specified GPIO pin)

The end goal would be to allowing me to keep it locked up under a wider range of driving conditions, but still unlocking automatically where needed to prevent stalling and enable shifting.

Does this sound like a feasible AutoPi project?

TIA for any advice.

1 Like

Hi Kozy,

I’d say it sounds feasible…as long as you manage to meander your way through the CAN system to that solenoid… i guess it depends on how hard Subaru wanted to secure that node and whether then you’ll need to checksum the change.
In my case the limiting factors are research time and sufficient programming skills(just recently started with Python and RPY world)…but from what i’ve seen out there anything seems possible with sufficient skills & research time investments.
As yourself here, i’ve chose AutoPi as well for pretty much the same reasons, final goal is to try to connect to drive train(engine, transmission) to fine tune stuff for my liking; my “poison” is an Audi A6 '10 plate so i have the feeling it’s gonna be even more of a challenge…

George M.