Posted by Mike W. on February 15, 2006 at 17:45:01 from 207.200.116.196
In Reply to: E12+M50? posted by Siam E12 on February 15, 2006 at 16:18:14:
I haven't done it, nor even heard of it being done. But since I believe the M50 is just a fancy M20 I don't see why it couldn't be done. Several things do come to mind after recently helping someone do a M30B35 transplant into an E12.
You need the complete engine, everything from belts to hoses, oil pan to valve cover, all the sensors and the wiring harness complete. If you don't it will be a nightmare.
I strongly suspect the Motronic wiring harness will be realtively self contained. That's good, very good, keep it that way. It will probably be too short, but you should be able to mount the ECU in the intake cowling as long as you waterproof it REALLY, REALLY WELL.
The tranny will probably be on the weak side, but you need to keep it to keep your speedometer drive. Later BMW's used an electronic speedo. But it's my understanding it should bolt up to your tranny. Actually, if it's a ZF auto tranny, a ZF3HP22, they hold up pretty well, but flywheel might (or might not) be an issue.
You need to keep the E12 wiring that goes with the body, all the way back to the fuse box. That has things like the alternator connections, oil pressure, water temp and all. I can help you with what color does what on that part. There will be a few wires you have to connect from the body to the engine and motronic, not many, but a couple. I've never looked for a M50 wiring diagram, but it may well be out there on the Russian site that I found the E34 one on that was in English. Humor us, I know English isn't the only language, but it's the only one most of us here know how to speak or read or write, myself included.
Wiring will be the biggest problem, but keep the thought in mind that it is two different harnesses, body, the one on the E12, and engine/motronic, the part that runs the engine. There are a few things that go from the body to the engine, but only a few. Don't cut anything at first, until you're absolutely sure.
One more simple but important thing, make sure the oil pan will clear the crossmemember, if it doesn't you're in troule.
Mike