The low end "torque" of the 3 w may be nothing more than a well setup carburetor.
Torque curves on these are really tough to guess and for the most part - useless.
Throttle response however is VERY important.
aircraft engine loads increase in a non linear fashion-- which means that the off the line torque -such as a passenger car or street bike needs - is not required .
what is needed is simply max power output -on prop used .
swapping carbs around on engines changes response -in a large fashion.
both Tillotson and Walbro have more little redrilled permutations of basic designs -- thanyou can imagine.
This is not a put down on 3W - I like em.