ECM

Wow, it sounds like you will be able to do what the highest level of Rotax Dongle is capable of doing. (changing the engine settings)

I would be interested in your final findings (ignition timing and fuel injector settings) for leaned operations.  I suspect you probably can get a lower fuel flow than the factory has set.

Will your computers allow different ignition timing between the front and back cylinders?  As I recall there is a difference in the Rotax programing.  

Good Luck.

Please keep us advised. 

James Porter

This may be a good way to trash your engine. Rotax has specific reasons for certain ECU setting. Changing them without knowledge of the system and why it was done that way may spell disaster. 

Roger, your comment of “a good way to trash your engine” is open ended. Are you referring to a failure from detonation from fuel and timing settings? I already stated that initial full throttle runs will be static, while monitoring fuel, timing, and EGT via a laptop looking at a wide band O2 sensor signal. Knock sensor signals are also monitored. RPM and MAP are a function of the propeller pitch setting. So enlighten me further as how I might “trash my engine”. My previous 45 years as a mechanic, and a recent turbocharged auto project using MegaSquirt yielding  400 hp from 2.5 liters leaves me somewhat  familiar with tuning. 
I would use the Rotax electronics if I HAD them. On second thought, I would rather be able to make my own fuel and spark tables.

James, I’m guessing the different timing setting from front to rear is related to the Rotax ‘soft start’ feature. 
The MicroSquirt uses ‘waste spark’ so the answer is no, I can’t mimic that feature. My cranking timing setting will compensate for the soft start. I operate a 912 ULS now without the ‘soft start box’ and seldom have a harsh start. Experience with a 582 taught me to get the RPM out of the ‘rattle’ zone immediately on start up. Thanks for your interest, and I will update as I move ahead with this project. My spare time is limited as the owner of a GA aircraft repair shop.

Just going by memory, the two degree difference was noted at higher power settings and not during start.  I don't know where I read this but I recall an article or opinion that changing the timing between front and back cylinders helped with the engine vibrations caused by having the engine mounted in rear mounts and the front two cylinders being further away from the mounting.

I just don't recall where I read that or even if it related specifically to the Rotax.

I was under the general impression and opinion that it was done more for unwanted vibration control.

Again, good luck and please keep us posted regarding your findings.

James Porter