M20b23 info

[zqeexz]

Right, my m20b20 will probably be due a rebuild in the next year or so (200,000 miles just rolled up, and it's my daily driver) and I was thinking about turning it into an m20b23. From what I understand everything but the crankshaft, rods and pistons are the same as an m20b20. Firstly am I right in thinking that?

Another issue is the ECU, my 320i is a 1990 model which means it has a Motronic set up and all original 323s had the older L-Jetronic set up, can I get a Motronic 323 chip? and is there anything else I am missing?

I don't want to go down the road of an m20b25 swap or an m50 conversion; as I would like to keep the original engine number (for road Tax & Insurance reasons), if the m20b23 conversion is not possible I will just rebuild the m20b20 as normal when the time comes.

Lastly if what I have written is correct, how much should I expect to pay for 323 crankshaft, rods and pistons?

Thanks for any help

[jimmyspeed]

hi zqeexz - am thinking of doing the exactly the same thing myself in the future but luckily i have my first e30 a 323i as spares which blew up!!!!!!! , dont really know exactly whats involved but if you use the search option you should find some answers did some research for you so try - this link

http://www.e30zone.net/modules.php?name ... same+parts

[Coyote_ar]

zqeexz, i was planning on doing this mod on my 1984 320i too. mine has the old L-Jet. AFAIK, the ecu for the L-Jet on the 320i and 323i is the same. so i guess that the motronic for the 320i should be able to cope with the 323i.

BTW, the rods on the 320i and 323i are the same, 130mm. so you wont need to change those. just pistons and crank.

In in a similar situation as you are, i wont be changing my block, but for different reasons. In my case i decided i will go for a 2.55 liter conversion. i will bore out the 320i to 84mm, use the 323i crankshaft, 320i rods and custom made forged pistons.
I really dont know how well the L-Jet will do with such a setup, but im planning on switching to MS-II for fuel and maybe ignition.

Good luck with your project.

[Speedtouch]

According to these lists, a 323i sometimes has a different (308) ECU from a 320i (301 & 309):
http://www.carclinicmagazine.com/bmw_ecu_list.html
http://www.atpelectronics.co.uk/Catalogue/bmw.htm

[Coyote_ar]

i guess 320i and 323i with LE-Jetronic, share the same ECU, while the 320i and 323i with motronic do not. that would make sense, since LE-Jetronic is a pretty primitive ECU, while the motronic is quite more advanced.

301 is for both 320i and 323i, but thats LE-Jetronic. 308 and 309 are motronic.

[Speedtouch]

Are you sure? I was under the impression that all 323i's used L-Jet and Motronic was only used on 325i and '88-on 320i's in the six-pot range.

[Coyote_ar]

my bad, you are right. 308 and 309 are the later LE-Jetronic units. from 84 to 87. while 301 is the older 82-84.