Originally Posted by AirX
Well since everyone is putting their two cents I will too.
Heat dissipation is the prime reason not to run the lighter/shorter motors that have a kv that is rather ordinary in other fans that have a rotor design that has less loading. Even power from an efficient motor will produce heat from the current load at extremes but in the case of this Het 2w20 it suffers from the extreme in kv on the CS 70 that is normally used with 2800kv/90gr motor for 3s usage to 2150kv/167gr motor on 6s. Not only do you have to look at motor kv but length/weight/size.
The bigger the motor the better on any fan, but with the high load fans it`s even more important.
Just an example. I`ve switched the 3126 outrunner to a 2200kv on my CS-10 fan. On 6s it`s hitting 93a at about 2.1kw. But the intresting thing is that the motor is hitting 91% of it`s unloaded KV! 91% on a $20-$30 outrunner depending on where you buy it.
Those short inrunners will probably be lucky to hit 80% of their KV. The rest of the power is just turning into heat that will cause the motor tube to weaken and let the rotor hit the shroud.