The official specifications for this fan unit are:-
The motor is a special version of Towerpro's 2409-7T with half the magnets removed (6 instead of 12) and an extended front end to fit into a 20mm motor tube. The output shaft is necked down from 3.175mm to 2.3mm. The actual Kv is 6657 rpm/V, 26% higher than spec! No-load current is also quite high, probably due to the use of poor quality 0.35mm thick laminations. Copper fill is good, but unfortunately not enough to counter the bad magnetics. Peak efficiency on 7V is a miserable 67% at 18A.
Fan design is no better. The impeller has a diameter of 53mm, but the shroud is 56mm, introducing 1.5mm of blade tip clearance. While this lets you get away with using an unbalanced impeller with less risk of blade strike, it adversly affects aerodynamic efficiency (a gap this large may reduce thrust by 5% or more).The spinner's diameter is 3mm larger than the motor tube's outside diameter, so I wonder if perhaps the impeller was originally designed for a different fan?
The shape and size of the impeller is virtually identical to a GWS EDF55, the only notable differences being no dimples or hole in the front of the spinner. Other features - such as the blades, spinner, even the two cutouts which allow access to the shaft adapter grub-screw - are identical. Therefore I conclude that Towerpro have 'cloned' the GWS impeller. The only possible improvement is that it is moulded from what appears to be carbon or fibreglass impregnated plastic, making it a bit stiffer than the GWS original.
I only ran the unit at 7V (equivalent to 2S Lipo) because I couldn't see any point in trying higher voltage. On 3S I estimate that it would draw about 45A and generate around 570g static thrust, but with only 64% efficiency and an alarming 170W of power loss. With such a large amount of heat to get rid of, I doubt that the motor would survive for long. 4S? Forget it!