Swapping My M42 For A M20b25....wiring Question

[a.chaaban]

what Needs To Be Done In This Swap Concerning The Wiring....do I Need To Rewire The Whole Car Or What?

[James Crivellone]

assuming its an 88+ M20B25 harness, it should just plug right in to C101

[gearheadE30]

Why the swap? If you're gonna do that, pull an M30 out of an e34 535i, it plugs in too. Unless, of course, you already have the M20.

[a.chaaban]

My Situation!!!

i currently live in australia.....bmw parts are as expensive as ferrari parts here...and rare to...just for a s50+ tranny is 15 grand......evryones telling me to do a m50 swap....for just the engine and box they want 4 grand plus!..... i have come across a m20b25 with the ecu, wiring harness and box...and diff for 1300 bucks...i was thinking in swaping the m20 in to my 90 model 318is...what do you guyd think and is it a huge task

[gjuu]

i currently live in australia.....bmw parts are as expensive as ferrari parts here...and rare to...just for a s50+ tranny is 15 grand......evryones telling me to do a m50 swap....for just the engine and box they want 4 grand plus!..... i have come across a m20b25 with the ecu, wiring harness and box...and diff for 1300 bucks...i was thinking in swaping the m20 in to my 90 model 318is...what do you guyd think and is it a huge task

I have done this recently - for the same reasons as you - I didn't want to put a M50 of unknown condition into my car - So I rebuilt an M20 (stroked with eta crank to 2.7 litres and 11:1 euro eta pistons).

So I have a 318is 2.7i

The engine bolted straight in and engine wiring plugged into existing body harnes no worries, used the m42 radiator - just had to change a couple of hoses.
It took a couple of hours to pull the M42 and box and clean up the enginebay, then another couple of hours to bolt in the M20 and box and hook everything up. Started first go but then it took a few days to get everything else sorted before I could drive it - driveshaft shortened (cheaper than buying a 6cyl one), exhaust hooked up, shifter etc.

result?? smooth and torquey and plenty of potential for more power once the engine has a few kms on it.....

got to love a freshly rebuilt engine