Amp draw/efficiency question
 

Ok guys. A friend and I are in the process of setting up Ofna Hyper SC10's. We both have Neu 1509/1Y 3600kv motors that we run and they do a pretty good job.

My question is being that we are limited to 2s lipos, would I experience more efficiency and less amp draw by running a 1509/1.5D 4500kv?

Of course I know that efficiency increases as the Kv drops and the voltage rises. However we are limited to 2s voltage. So that leads me to my next understanding of Neu motors being most efficient under 30-35k rpms. So the 4500kv motor would but it right at 33,300rpms and at a higher rpm throughout the throttle range.

Both motors are plenty strong enough for these trucks on my track. We are trying to reduce amp draw to extend run time. I would love to step up to 3s on the 1Y but can't.

Help is appreciated.

If you geared lower with the higher kv motor to get the same overall speed vs the 3600kv motor, then I think you'd see better efficiency yeah- all other things being equal ( motor size and voltage etc ). I doubt it would be a massive difference, but a temp gun, stop watch and eagletree would be handy for sure...

Having to use a smaller pinion with the faster motor would (I think) reduce current draw during startup since the motor can spool-up easier. However, the faster motor has a higher no-load amp draw. If that translates into the loaded amp draw then it may cancel out, or even negate, the benefit at start-up.

This thread illustrate the "sweet spot" issue of a brushless motor.
Low Kv and low voltage isn't good, high Kv and high voltage isn't good either. You are comparing Low Kv at low voltage and mid Kv and at voltage. The low Kv motor has smaller thickness of its widings wires, that's why it does'nt like high amp draw and need more voltage at same power, but that's why low Kv keep the ESC cool and happy.
==> I would say that geared for the same speed and at the same voltage, the higher Kv would be best.
It's also for thoses reason that we speak about "sweet spot" for brushless motor and why a certain minimum and maximum RPM is advised. For the 15 neu series, the "sweet spot" (according to most users) would be between 35 and 40K, so IMO the 1,5D would be better and run cooler at the same power.
NuZ

I found the sweet spots of these motors to be around 25-30K rpm. I run a 1509 2.5Y (1450kv) on 6s in my 8ight build so I am just out of range. I am limited to 12/46 or 13/46 or temps start getting a little out of control. It's also a freakin monster - went up to a 17 tooth pinion gear for fun in the street and I was able to pull wheelies with a locked center. I've tried some pretty hot setups too: Tekin 1900 kv on 6s and Castle 2650 on 5s, with the power potential not being seen until you gear really really high. However, keeping the rpms less than 30,000 on either of these motors results in much cooler temps, with the potential to gear rediculously high and keep temps down at the same time. My thoughts are just to stick with the 3600 and gear up if more speed is needed.