Motor anyone?

[BrianG]

The 8 or 9 is the number of turns.

Once you decide the voltage you want to run (the higher the better up to the limit of your ESC if possible and finances allow), you figure out the motor kv by taking 35000 and dividing by your desired voltage. The answer is the kv of the motor you need. Pick something as close as possible. The 35000 number is the maximum rpm you want to run your motor at for best efficiency.

So, for 4s, you'd need a motor with a kv of around 2400. A 1940/7 or 1940/8would work well.