[BrianG]

I can see how it can be confusing for a person newly into brushless.

It comes down to this: it takes X amount of power to launch your vehicle with the acceleration and top speed you want. But you have to take gearing, weight, etc into consideration.

Power is volts X current. Looking at this formula, it's probably easy to see that for a given power, increasing the voltage decreases the current and vice versa. However high power is easier and more efficient to obtain with higher voltage and lower current. Lower currents are drawn when using higher turn motors (higher resistance).

Torque is dependant on motor kv and current. Torque (in ft-lbs) is 1352 / kv X amps / 192. So, decreasing kv or increasing current creates more torque. For the same kv, larger motors will generate more torque compared to a smaller motor. This is because they will draw more current (lower resistance).

For example, lets say you think you need 1500w to make the vehicle perform like you want. Let's say you have a 6s and 4s battery. 6s (22.2v) requires 67A. 4s (14.8v) requires 101A. The 6s option is better to use 6s than 4s because of the lower current. You generally pick the highest voltage your ESC and wallet will support. Then, you pick your motor kv based on that voltage. Some motors have a higher max rpm than others. Cheaper motors lose efficiency at higher rpms. Feigao/Wanderer motors typically operate best at around 35k max rpm. Better motors operate better at higher rpms (like up to around 58k for Neu).

You also have to pick the proper size motor (for torque) based on the size and weight of vehicle. Larger vehicles like buggies, truggies, MTs, etc work better with larger motors like XL series, or Neu 1512 or 1515 series, or an equivalent size motor.

So really, when designing a system, you start by picking the size motor you'll need (for the torque). Then, decide the voltage (higher is always better). Then, pick the motor kv based on that voltage by dividing the max rpm by the voltage you decided on.