[mhiscott]

Over the past few months, I've been toying with the idea of transplanting an LS2/T56 from a 05/06 Pontiac GTO into my 2013 FRS. I am comfortable with the mechanical aspect of doing this swap, but I've been mulling over the best way to make it work from an electrical standpoint.

I'm no stranger to running aftermarket EMS systems, with a Megasquirt standalone and custom harness in my AE86, and reprogrammed ECUs in my Evo 3, DSM an Evo X.

The idea of running a reliable OEM ECU setup, however, has always intrigued me. I would like to use the OEM LS2 ECU, with an aftermarket painless wiring harness typically used for transplanting these drivetrains into classic muscle cars. The harness allows complete functionality with the GTO's ECU, minus emmissions controls. The original GTO drive by wire gas pedal would be retained, as well as the corresponding drive by wire throttle body. The only connections inputs required as a bare minimum to allow this sort of setup to "piggyback" off an existing chassis would be power, ground, ignition, and start wires.

What I was considering, was to remove the FRS's drivetrain, retain the FRS ecu and harness, which would be powered up as normal on key advance to the ignition position. The car in such a state would think the engine was not yet started, or stalled out. From what I can gather, all systems other than ABS/TCS/Gauges/PS/AC would work in such as state.

If I were to simply add in my new drivetrain's power harness and ECU, tied into the original harness for power/ground/ignition, I would have most of the functionality I would need to drive the car with the swapped engine.

Has anyone run a setup similar to what I'm suggesting (engine type does not matter), with essentially two harnesses working in parallel with one another independently?

To build on this, has anyone found a way to add in your own engine control solution while retaining operation of systems like the power steering?