B20 to B23 stroke

[cebriete]

Hello everyone!

My name is Brice, come from France and sharknose enthousiastic since how far I can remember!

A while back I had the chance to get a 320i from 1988, which was my daily driver for few years. Then I had to move house and unfortunatly the car stayed outside unused for few years 900km from my new place.

This year in April I decided to collect the car, check in which condition it was and start to rebuilt it completely. I will make a dedicated topic with all the picture of the work.

When I will be done with suspension, brake, drivetrain and cosmetic I plan to refurbish the engine. Of course as all of you guys I'm not against a few extra hp so I was thinking to swap a b25. But here the price are going crazy and you cannot find any engine below 1.5k for something you need to rebuilt. So you need to add on top all the part and a bit of labor for what I cannot do myself.

So then I had this idea to refurbish my engine, that will cost me barely more than a tired b25 in unknowed condition, but take advantage to stroke it into a 2.3L. As bore is the same I just need crank and piston from b23 and that can be found very cheap and done quite easily.

Here come my question: As I have a post face-lift, I didn't check yet my ECU but I guess I'm motronic, will the mapping be able to handle the new displacement ? What about injectors should I go for bigger ?
Basicaly I'm wondering if it's just about throwing the crank and piston in my b20 or if I need further mods to be able to use 100% of the increased displacement ?
If you have any feedback about this b20 to b23 stroke I'm really interested.

Thanks in advance.

[82eye]

the 323i never had a motronic ecu. all the 323i's were l-jet. l-jet and motronic don't mix. you'd have to choose a path and convert completely. the 320i ecu probably won't run it. there are aftermarket solutions for an ecu that might run the car, but i have no idea what is available to you.

[cebriete]

Thanks for your input. I was expecting that if my plan was to drop in a full b23 l-jet engine but not just by swaping crank in my motronic.

So to you what will be the problem ? Is it that the larger displacement will cause greater air volume and that the AFM will not be able to catch up ending in inappropriate fuel timing ?

In this case is it possible to tune my ECU or stand alone one is needed ? Because if it's the case a b25 might be cheaper in the end.

[82eye]

Thanks for your input. I was expecting that if my plan was to drop in a full b23 l-jet engine but not just by swaping crank in my motronic.

So to you what will be the problem ? Is it that the larger displacement will cause greater air volume and that the AFM will not be able to catch up ending in inappropriate fuel timing ?

In this case is it possible to tune my ECU or stand alone one is needed ? Because if it's the case a b25 might be cheaper in the end.

the fueling maps in the ecu's are all tied to the displacement of the engine. you'd probably need a standalone ecu tuned for the specific car. the 320i wouldn't be enough and the 325i ecu would fuel too much.

[cebriete]

Make sens indeed... If stand alone is needed I will forget this idea, not interesting cost wise.

BMW E30 M20B20 upgrade to m20B23 comparison (youtube.com)

Just found this guy that made the conversion. In the comment he seems to say that he run with Motronic ECU but with EPROM ship tuned for ignition and fuel.
I will try to reach him and get more input on the ship.

[digger]

doesnt the m20b20 from 88 have the same motronic as the B25? obviously different fuel maps, maybe different sensor calibration etc but the architecture, o2 sensors, system etc fundamentally the same. if thas the case then a proportional increase in injectors would probably be all to get it running pretty close. i would assume if the same motronic then there are also chips but i dont know for sure

[82eye]

doesnt the m20b20 from 88 have the same motronic as the B25? obviously different fuel maps, maybe different sensor calibration etc but the architecture, o2 sensors, system etc fundamentally the same. if thas the case then a proportional increase in injectors would probably be all to get it running pretty close. i would assume if the same motronic then there are also chips but i dont know for sure

it runs a different ecu with presumably different mapping. i'm sure the only difference is the chip. the early b20 motronic 1.1 ecu was a 152. from late 87 up they look to be 1.3, and list 381,172, and 087 as the ecus. there are both 35 and 55 pin ecus being used, i have no clue which are which.

i'm sure he could run it if he got the right chip matched to an ecu he could use.

edit - found this : ECU - E30 Zone Wiki they look to all be the same 55 pin. as long as it isn't a 152 you should be able to get a chip.

[cebriete]

Thanks a lot for the inputs guys, I will dig into that !