Can someone explain me???

Hello my holly teachers, :005:
You have to explain me something your motor choices and gearings...
Is there an affordable way to go fast with the Robinson Racing slipper and its large range of spur gears' teeth number ??? Why do you all run 44 to 51T spur gears???

My feigao 540C 9l is rated at 2730 rpm, therefore it goes hot pretty quickly with 14cells+ 16 to 18/66 ratio... (i use lightning diffs)
I love my actual crazy top speed and torque, but it runs too hot, you always say that when i tell you that i run it about 90°C... but what i want is speed and torque!!! The thing that i'm sure is that i will go soon to lipos, and i will not have 500$ to spend in a high end motor + controler.

At least, do u think that it can be better with a specific cooling system? I thought to work on a homemade cage where to fix some fans...

Sorry but I NEED TO KNOW !!! :035:

Thanks to all for sharing your precious knowledge, and sorry if i'm not clear when i post here... :( poor alone french guy...
Fab.