Can a 320i engine harness be used on a B25?

[Danni540]

Hello everyone!

The reason I ask is because I'm about to swap an M50B25 Vanos into my 318i, but the engine I have comes out of an E34. I have all the parts needed to convert it to an E36 engine from a donor B20, which is also Vanos, and logic tells me that on the outside, these motors are identical and therefor the wiring harnesses can be swapped between without problems. But experience has taught me that BMW doesn't always follow logic and what sometimes seems to be the most straight forward task, can become one of the more challenging ones.

I have read the sticky swap thread and I will use it a lot, since I'm putting a 6cyl OBDI engine into a 4cyl OBDII car, that thread is great help!

But it doesn't address this question. Probably because there was no 320i in the US (which leads me to believe I will get very limited answers from here hehe)

I'm still getting my hopes up that some one who reads this knows this.

So, can I use an M50B20 Vanos engine harness on an M50B25 Vanos engine? And if I can, will the B25 engine computer work with it or will I have to use the B20 computer as well?

Thank you in advance!

[granlund]

The two harnesses are different in the way that the have different part numbers. This can mean total incompatibility, or that one cable is 2cm longer or have a sligthly different color. I would also check the wiring diagrams in the back of the Bentley manual wether you can see any differences.
http://www.realoem.com/bmw/partxref.do?part=12511748889&showus=on&showeur=on
http://www.realoem.com/bmw/partxref.do?part=12511703279&showus=on&showeur=on

[Danni540]

The two harnesses are different in the way that the have different part numbers. This can mean total incompatibility, or that one cable is 2cm longer or have a sligthly different color. I would also check the wiring diagrams in the back of the Bentley manual wether you can see any differences.
http://www.realoem.com/bmw/partxref.do?part=12511748889&showus=on&showeur=on
http://www.realoem.com/bmw/partxref.do?part=12511703279&showus=on&showeur=on

Thanks for the reply. I did some research and found that a 320i has a different MAF sensor and different knock sensors. I think that the knock sensors will be a problem if I will use the 2.0 electrical system. To work properly, they have to send the computer precisely the right signal so that it lets the engine run right. My theory is that with with 2.0 sensors connected to a 2.5, which has different internals, the signal will be different from what the computer expects which will cause it to adjust the ignition timing to the worse.

This is only a theory though, I am by far an expert at this. The 320i donor car is still in running condition so I'm going to do some experiments on it before I try to put the harness on a 2.5.

I'm starting to think that I will have to source an engine harness from an E36 325i vanos to be able to get this working properly....

[nikvlahovic]

Did you find anything?