1986 325e 1.3 motronic conversion?

[savagesaint21]

I have a complete m20b25 engine from a 1990 325i. It’s still in good running condition from what I heard from the owner and I was going to swap it in to my 325e but someone said it’s not a direct swap? Because I have the smaller fuel tank? I’m so confused. Should I just convert my car to 1.3 motronic? How would the wiring work if is have the smaller fuel tank? Please help I really want to start my build but I need some guidance. And which is worthwhile? Converting my eta engine to 1.3 motronic or should I just swap in the i engine? Which is going to be more fun/ easier? Lol please help sorry I’m not a mechanic at all this is my first build and my engine is almost 260k miles I’m gonna need a refresh or new engine soon.

[THE DUDE ABIDES]

Get yourself a 173 ECU to go with the i motor. Motronic 1.1

[ScottSneed]

Get yourself a 173 ECU to go with the i motor. Motronic 1.1

Incorrect, a 173 is motronic 1.3. Any 'i' ecu will do (524,173,525..) if you decide to swap it. Research a stroker conversion which involves putting the i head and associated top end parts onto the eta block

[THE DUDE ABIDES]

Incorrect, a 173 is motronic 1.3. Any 'i' ecu will do (524,173,525..) if you decide to swap it. Research a stroker conversion which involves putting the i head and associated top end parts onto the eta block

Indeed. That's my mistake. For some reason I was thinking it was 1.1.

[TobyB]

As to fuel pumps, the eta external pump system will work for an i car. IF it's in good shape.
You can also put the high pressure pump in- tank (what I did) but you'll have
to do some replumbing and find a '91 318 fuel sender, as you'll need an additional return
line. Or just add one to your sender. Carefully. I brazed one in.

It's not too hard. If you have a round C101, you just need to check/cut pin 20,
and maybe move a few pins.

hth

t

[ForcedFirebird]

173 variant ECU's are Motronic 1.3, 153 variants (2 circuit boards inside) also are a direct plug and play, but are Motronic 1.1.

Don't go mix and matching parts, unless you are braking them. If you just want an easy swap, take the whole 2.5 with the harness/ECU and put it directly in the car (or rebuild and install). The stock b25 makes more power than an eta with an 885 head.

Just make sure to look at pin #20 on the c101 round connector at the firewall. Some late harnesses will fry your wires. Peel the boot back and if one side is empty, you are good.