BMW E38 Engine upgrade 3.5L to 4.4L M62

[RichieE38]

Hi all,
After a bit of advice. Long story short, I took the 735iL for a swim and broke the 3.5L (electric are fine though). I then bought a 740iL with a good motor and trans, but rooted interior. I want to swap the motor into the 735iL.


So - a 4.4L M62 V8 into a 3.5L car. Both are pre-vanos

The swap itself shouldn't be an issue, but what I'm worried about is the ecu side of things.

Will the 3.5L ecu run the 4.4L motor, or will I need to swap the 4.4L ecu into the car.

If I have to swap the ecu, how do I get the computers to talk without triggering the immobiliser? Is that a simple job for a mechanic with a computer or is it not possible?

Would it be more worthwhile to swap the interior from the 735iL into the 740iL?

Any help and tips/tricks would be appreciated!

20220502_143854.jpg

[BimmerBreaker]

The 3.5 and 4.4 use the same engine computer/DME. The easiest and imo best route will be to retain the 3.5 DME (as it is already paired with your car's anti-theft system/EWS) and have it flashed to 4.4 software

The E38 looks like it made for a pretty good submarine. You look happy about it at least

[RichieE38]

That sounds a lot easier that I thought it would. How about the transmission computer? I've heard that they retain information re the individual transmission (something about how much pressure it puts on clutch plates) bit not really sure.

Cheers!