M20b25 engine conversion

Post Sun Jul 10, 2005 7:26 pm

anyone have done 90' M20b25 motronic 1.3 engine conversion onto 90' E30 M40 chassis ??

i have m20b25 complete engine, engine wiring, engine control unit only....

basically what i need to do ???

Post Sun Jul 10, 2005 10:38 pm

Gearbox won't fit at the bottom, IIRC, diff ratio is a bit high, front springs aren't strong enough, brakes a bit iffy, air meter/filter mounts wrong, radiator small and no bracket for the resevoir for the correct one, wrong coding chip for the front of the instrument cluster.
You really need a cheap donor car to do this conversion. Can be very cheap with a duff engine, if you've already got a good engine.

Post Tue Jul 12, 2005 5:23 pm

updates: ok basically i have everything u mention above...

but can i just plug e30 325i instrument cluster onto my m40 wiring ???

how about the engine side ?? theres a 2 1/2 inches connector to the fuse box ... m20b325i engine have more pin than the m40b18 engine....

how if i just plug in ??? wat will happen ??? any experience ???

thanks

Post Tue Jul 12, 2005 8:27 pm

The 325 instrument cluster will fit the M40 wiring, and the M40 cluster will work fine with the 325 engine, if you change over the white coding plug, plugged into the front lower right of the cluster, behind the trim piece below the cluster.
The comnnector by the fusebox is known as the C101 connector.
All post facelift engine looms should plug straight in. The extra pins are for things like oil level sensor etc., which your M40 body loom probably doesn't support.