TR3A twin cam. And then there's the wiring...

The refurbished and re branded engine looks great tucked into the freshly painted inner fender structure. I spent hours in the garage just staring at it in that state. It's clean and unencumbered. At night, after brushing my teeth and shutting down the house, I'd often creep down to the end of the hall and quietly open up the door to the garage for one last look at it. I couldn't help myself. I always hoped the wife wouldn't notice the level of obsession.

Well it didn't get to remain unencumbered. The wiring had to be added. And there's a lot more to an EFI car than to the twin side-draft car. It is challenging trying to lay a harness into a different car. There were way too many important circuits to just willy-nilly start cutting and manipulating as I saw fit. No, I had to figure out how to mesh the existing Miata lengths harmoniously into the TR3. This took days. It doesn't look  like it by the pictures, but it was a looooong time to get there. The one main rework I made was for the Mass Air Flow sensor (MAF). On the Miata it's situated on the left of the engine. On the TR3, it's going to be on the right, directly in front of the throttle body. I had to restring the 6 or so wires. Not too big a deal.
                                           
 Trial fitting new harness to an original TR3 harness path way opening in the fire wall

As for the computer, well the Miata had it behind the passenger seat. Consequently, there was like 4 extra feet of harness to get it there. I can't mount it there, and there are way too many circuits to just cut, shorten and re solder. I strung it across the dash and mounted it above the drivers kick panel area. 4 feet. It's rubber mounted and oriented  so that it's accessible, yet protected from the elements. I also mounted the fuel pump relay and diagnostic link nearby but out of sight.

Further integrating the engine into the chassis required connecting the TR3 accelerator pedal to the Miata engine. Do you use TR3 linkage? Miata linkage? Custom? I reasoned that the best thing to do was to utilize the Miata accelerator cable and graft a bracket to the original TR3 pedal. If the cable ever needs replacement, it's easy as calling Moss or your local parts store. As a bonus, the orientation, shape and throw of the pedal remain basically stock!

 The un-loomed wire harness. I had to strip it to remove unnecessary circuit for lights and things like that. Having it naked allows more flexibility to bend and flow where you want it. Tape it all up after it fits right.

 Looks like it will work, and here's a convenient spot for the under hood fuse and relay center.

 Shazam! There's still some taping and final considerations, but it's coming along. The clean look has given way to a busy network of components and wires.

 Engine computer rubber mounted under the dash. Attached to the heater support bracket you can see the original Miata computer diagnostic port. (Also a sneak peek of the accelerator bracket).

 Getting high pressure fuel to the engine...this sweet package was salvaged from a late 80's BMW 535i. It comes complete with whisper-quiet Bosch pump, filter, bracketry and hoses. Score!!

 Here's the BMW parts mocked up within the frame rails on the passenger side.

And here's my accelerator connection solution. Drilled, of course for weight savings (ha ha). See the picture of the pedals above for it's installation. It is offset to clear the steering column.