RE: Another brushless 'myth', lower KV = more torque
Once you're able to measure current, then you can do efficiency calculations also.
How much inherent error do you think there is in the process? Once you get the process down, run the same test twice or even several times and see what the standard deviation is. It looks like, especially in the 21000+ RPM range, there could be some significant error. But the general shape of the curves is a good sign. Need to get down into the lower RPMs, though.