M10 to M20 Swap

[stanhayward]

By the by, here's the car in question.





Her name's Goodrin, 1985 318i with manual everything. Best $650 I ever spent! She idles at 250 rpm currently and one of the POs backed into something hard so the rear is a little mangled. Plans are to get a nice interior in it, fix her up and then M20 goodness to follow!

[stanhayward]

Hey guys have all the C101s and such now and just need to find the time to do the swap. It's cold as shit up here and I'm going to get the M10 running first, meaning I won't be making an adapter any time soon. To keep both harnesses intact - 318 body and 325 engine - I decided to make a short adapter with the opposite sides of the harness. Here's a quick diagram of what I mean:


And I found some good C101 wiring breakdowns e30kawi!

Square:


And round (and others):

[e30kawi]

oh ok thank you

[stanhayward]

agk wiring break down?

Sorry that wasn't very specific: on the agk motorsport website they have diagrams of the c101 plugs for 24v swaps, good info there.

[e30kawi]

I had a lot of luck just googling and also the agk wiring breakdown. Check that out

agk wiring break down?

[stanhayward]

Is there an issue with some of the wires? There are a few wires that I don't entirely know what they do and if they would be the same, like the fuel rate wire (would it be different if there is a different style fuel pump) and the load reductor relays etc ( i don't know what those are or do)

I had a lot of luck just googling and also the agk wiring breakdown. Check that out

[e30kawi]

Is there an issue with some of the wires? There are a few wires that I don't entirely know what they do and if they would be the same, like the fuel rate wire (would it be different if there is a different style fuel pump) and the load reductor relays etc ( i don't know what those are or do)

[stanhayward]

Okay thanks for that! Unfortunately I don't have an late round connector. I'll keep scouring the pick n pulls.

[packratbimmer]

I did the conversion a while back and had some trouble with the connecter (corrosion/bad connection). If you are good at splicing, just eliminate the rectangular connector and splice in the round one. Most of the wires are the same colors, but there are a couple of goofy colors that will need researching. If memory serves, the tach and economy gauges have their wires routed differently on the early cars.

[stanhayward]

I do have a radiator and hoses and all that jazz. And the battery can chill up front this is going to be a daily not a track rat so doesn't matter to me. From what I know you need to make an adapter from the M10 square C101 to the late M20 round connector. I think I'll go ahead and buy the car and see what happens.

[Jaxx_]

got a radiator?

edit: also, if you care, the battery will still be up front, and the rear battery area is different for the M20s, which means your battery won't fit back there. You can either relocate it with a smaller battery or deal with the battery being up front.

[Holland]

Subscribed, lol. Going to be doing this swap in the future.

[stanhayward]

Hey guys, stumbled upon a pretty sweet 1985 318i while looking for something to swap an M20 into. I have a complete M20 with wiring harness and mounts, ECU, trans, driveshaft and diff. Is there anything else I'll need to swap it over? I'll be going over to megasquirt as well

Thanks guys!