Which motor would be more efficient for my E325

[rcnorth]

So I just put a scorpion 1880kv on my TT E325, only 2 flights so far. 150t MG, 14t pinion running @ 65% throttle. power & HS seemed about right, but I was hoping for a bit longer flight time, down to 33% after 4.5 min.

Just wondering if the 1360kv motor running at 75% with 15t pinion would be any more efficient.

Any thoughts?

[ahahn]

Assuming you keep the same pack, I think you will find the second option less efficient. Motors like to turn up around 80% of their no-load rpm (based upon a fixed voltage). In other words, as you bog a motor down, it gets less efficient, not more. In your case changing the Kv that much adds a big degree of uncertainty in my mind--I am not sure if you will even get enough power out with that low of a Kv and only going up a tooth, even if you up the throttle.

I also note, the ESC is more efficient at 100% throttle than at lower throttles.

So I would say I doubt you will get a lot more flying time than before, assuming you mean to try and keep the same head speed.

You can test out my opinion pretty easy. Just buy a 12 or 13 tooth pinion, keep the same motor, and up the throttle to get the same head speed. See how much longer (or shorter!) the flight is. My guess is that the lower tooth pinion with a higher motor rpm (but same head speed) will be somewhat more efficient. However, probably not a huge difference though.

[rcnorth]

Thanks for the reply. After a couple more flights, it seems that 63% throttle is about as much as this heli can comfortably handle. 65 & over I get the odd belt slip on the tail even though it's snug. So idle 1 is 60% & 2 is 63. It seems I can get around the same HS running the 1360 with 15 pinion at around 80-85%, so it may be a better way to go since like you say motors & esc like running @ 80%+.