ORIGINAL: mattnin
Here is my novak 13.5 motor, measured at 0 deg boost and 30 deg boost. You can compare my motor to my friends Novak 13.5 that I posted earlier. Notice his revs to almost 1k rpms higher but mine has more torque. I believe the only difference is that he has used his more, but they were purchased at around the same time.
Does the ESC you are using have an adjustment for 'boost'? 'fixed boost' isn't really an optimal thing to do for brushless motors, I know the castle ESCs I use let you set it via a 'forward advance' parameter and this way you can get the best of both worlds. ie. they are not going to use '30 degrees boost' at the lower RPM range where it actually hurts you. 90% efficiency and 75% efficiency is a pretty big difference, that's roughly 2.5x the motor heat which is mainly what restricts gearing over a 5-minute race. I know in stock 17.5 class where LiPo is now allowed, racers are gearing 'through the roof', ie. 35/67.
I also did see a post in the other board that brought up a useful notion that you should account for the rotational inertia of the motor shaft itself in addition to the flywheel. Is it significant relative to the flywheel?