Alan, I am somehow confused from that test. What it says? He measured several motors at the same rpm and he got some efficiency, but it does not say how good are those motors, it just says how well he used proper or improper prop for them ... for exmaple factory data for that worst AXI says the best efficiency is at ~20A and he runs it at 30A, so it is clear the result leads to too much copper loses. He got efficiency only 74%, while best therotical efficiency of that motor is 86%. I am also surprised he says that the motor is old and probably has reduced magnet strength, but his kv is 1336 instead of factory value 1390 - so I would say magnets are in very good condition.

BTW if I do my calculation, then I see the bes way to get those 191W on shaft is to load motor at 8,5V to only 26A at 10600RPM ... the efficiency will be 86% and input power only 221 - best in result.  (btw it also does not mean that the axi is best of them, because those others will be measured the same way over/underloaded - it only means the conditions are best)

The only relevant thing are propably iron loses. And here I see strange thing - those two dualsky motors. He says it will be difference in number of turns, but it does not answer so big difference in iron loses - I would say that the difference will be in magnets ... you can see that the resistance is almost identical, while rpm and iron loses difference are rorresponding (approx. 1:1.2)

Hmmm ... but ... I would like to see such table for our motors in governor mode (exactly like I always wanted to see torque/power curve for 2C IC engines and never got it) :-) ... but I have no idea how to measure it well ... I wold like to know what parameters will give better efficiency in PWM mode ... may be in winter ... (2025? )

But Alan, this could be good question for you - we have good and simple equations for efficiency, for rpm and so from Ri, I0, Kv ... do not you know something like that in PWM mode? I tried to measure inductance of winding and to make some calculation but I did not get very good results yet.

Igor,
I assume (if I understand your question) is that the prop just represents a load at 8000 rpm. So what he does (if I understand his test), is adjust the voltage from his power supply until each motor turns that prop at 8000 rpm. At that point he simply measures the power input (the throttle input on the ESC is at 100% every measurement is at full throttle).

I am not sure I understand exactly how he calculates absolute efficiency. I think he uses some theoretical calculation of the power the prop is actually putting out, not a dyno measurement. But if I ignore the absoluteness of the measurement, I would think the relative ratings make sense---at least if you are using those motors in the power range (~225-250 watts input and rpm (8000) that his measurements. And of course that is near where I operate (actually more in the 275-300 watt range for my Nobler).

I agree that this may be out of the sweet spot for some motors, but I do believe it isn't that far off where a lot of people are running them.

I  also agree that his comments about the magnets of the AXI doesn't make a lot of sense. Like I commented in that thread, that for a fixed condition (same prop at same rpm), the kV doesn't matter at all for motors using the same stator and magnet design, but with different number of winds--assuming the amount of copper used is the same (fewer winds but thicker gauge wire). And his data shows that.

I would expect that if he changed the conditions, like running a smaller prop at a higher rpm, that the efficiencies might indeed vary. It depends if you are in the resistive losses dominated rpm range (lower rpm -more loaded I think) or in the magnetic losses range (higher less loaded rpm range).

Yes you could think of some nice tests to make if you had a big power supply capable of a lot of amps.