Why 4.5?

[SpEEdyBL]

I'm actually going to exchange my HV4.5 with an HV7.5, and have my fast motor be the castle neu 2650. Both motors will be run on 4s and 5s packs. Your right that the HV4.5 revs pretty high, but the real issue is gearing it properly. 45mph is the slowest you can go with this motor in a buggy.

Ideally, higher rpms are better up to a certain point i.e the sweet spot, and novak motors have their sweet spots at a higher rpm than other motors. Also, smaller motors that need more rpm to make the same power have lower idle currents, which makes them more efficient. For example, a neu a 2700kv 1512 1y on 4s will probably be more efficient than a 2200 1515 1y on 4s if you gear for the same speed. Both motors are equivalent powerwise, so no matter what speed you gear for, you will get the same results. The only reason why the 1515 would be better is because it can handle more voltage for more power without dropping off in efficiency.