Ignition timing issue and CAN bus ignition retardation by custom TCU in V12 M73

Hey everyone,

I have an issue that I can't resolve currently. The car is 2001 BMW E38 2001 750i with M73 V12. I've changed transmission on it from 5hp to 8hp using turbolamik TCU. Transmission side of the drivetrain works great. But due to some weird reasons my cars CAN bus is different from other e38s (I believe it's the facelift and M73 LEV combination).

Now to the issue. I've discocered that I have additional 7th and 8th bytes on the canbus. I don't know what 7th byte does but 8th definetly controls ignition. Using BMW's software DIS I've discovered ignition timing numbers. When I'm setting bytes to 00 car sets ignition to -15 KW (Kurbel Winkel which is crank angle so I believe it's a BTDC). On this value car idles very smoothly but I can smell fuel in the exhaust and lambdas are stuck at 0.8v (they are new).

I've managed to find in BMWs software that on idle ignition timing should be set between +7.5KW and +8.5KW which is other way that mine is set. After setting 8th byte to FF I managed to get into this ignition timing window briefly but car misfires violently and dies after 30sec. Sometimes it even achieves +18KW.

Is someone here who can help me understand if the numbers provided by BMW are correct? Should the car be idling at -15KW or between +7.5k and +8.5KW. Any help is hugely appreaciated as I really want to finish this car and start enjoying it.

I should add that I'm using stock ECUs from BMW and turbo lamik TCU which I have custom soft made to control 7th and 8th bytes

Hi Mateusz,

Cool project, let us know how you get on with the Turbolamik.

Every engine is different but i would expect the timing value to be BTDC not after.

Can you test it by swinging the value from say 20 degrees to 0 keeping an eye on idle rpm then adjusting the air bleed or throttle position to chase lambda?

Hey, thanks for the reply.

Took me 3 months but I figured it out. It was a broken power supply in radio tuner which was robbing power from sensor and causing ecus to freak out. I was going in completely wrong direction but in the process I've helped with turbolamiks can bus being spot on for e38s