E30 Zone

so ive bought a m20b23 engine with and 5 speed manual behind it from a 1985 323i and i want to swap it into a 1990 318i that had a m40b18 with an auto behind it. The engine is in the car and now all i need to figure out is how to wire the engine harness up to the body wiring. any help would be much appreciated

Welcome to the Zone!

You are probably best off converting the (L-Jetronic) M20B23 to Motronic, so it can hook up to the later type wiring loom. See this link for details:

http://www.e30zone.net/e30zonewiki/inde ... tronic_1.3

You will probably have to use a 325i chip in a six-pot ECU (your 318i one won't work), and possibly exhaust system.

ok, if i go down that road will there be any problems with timing or the tune being that the engine might have different specs?

In an ideal world, you should use a chip programmed with a map specific to your engine, however, a standard 325i (M20B25) map will probably run well enough to get you up and running.

Another Zoner, mattyb converted his M20B23 to Motronic a few years back, wth good results; enter "M20B23 + Motronic 1.3" into the search field to get a few relevant threads.

http://www.e30zone.net/modules.php?name ... 78&start=0

That seems a lot of work to end up with a 323i Many of the late ones (and from the date yours is) were not happy engines. As one member on here once put it "they were a bitch for piston-slap".

How do I know? I have had one since the late 80s and still have it. While it was on the road I took the engine down a few times and eventually swapped the pistons to a later type that was supposed to cure the problem. It improved matters but did not get rid of it to my satisfaction.

When it eventually goes back on the road it will be bored out to 84mm and have 325 internals to go along with the motronic 1.3 unless I do anything more adventurous.

Unless you know the engine or have heard it running it may be a lot of work for a less than ideal end result.