[maxxdude1234]

Thats to do with what Serum was talking about; the sweetspot. All motors (and engines) have a certain RPM range when they are most efficient, known as the 'sweet spot' (I'm sure it hs many other names). The sweet spot varies for all different motors, but for motors of the size we are using it is just under 40krpm. At 22volts the motor is only doing 19000rpm, but at 33volts it is doing near 30000rpm, nearer to the sweetspot, hence higher efficiency.