[SpEEdyBL]

To get the same power from 4600 (with the same voltage), it needs to draw at least some amount more current than the 5700. You can do that just by gearing higher, as I see you did, but it will heat up more (due to higher resistance) and it will take longer to get to top speed. Basically, you may never be able to get the amperage required to match the 5700 taking off from a standstill, but you will be able to maintain a higher current throughout the powerband. Although, depending on the motor, this could be the better way to get power, because resistance is not the only contributer to power loss. There is also iron loss which is the voltage times amps the motor pulls at no load. So a motor running at 7 volts that draws 5 amps will always waste at least 35 watts of energy no matter what. Lower kv motors have lower iron losses which makes them more efficient, not because they draw less amps. Even though heat = I^2*r, a 2000kv motor has four times the resistance as a 4000kv motor of the same model, so drawing half the current doesn't really do much in that perspective. Now you can see why the feigaos seem to heat up at all gearing levels and why lower kv motors are needed to achieve more power. Of course, iron loss varies from motor to motor, so a 4000kv neu motor could have less iron loss than a 2000kv feigao motor at equal voltage on each.