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Quick KV/Turns question

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Old 04-25-2016, 04:45 AM
  #1
TampaRC
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Default Quick KV/Turns question

As I try to educate myself on brushless, can anyone give me a brief bit of knowledge on kv and turns.

I have a sensorless 3650 motor that I want to replace with a sensored.

It has 12.5 turns and 3000kv. (came with a 1/10th buggy)

I am trying to find a replacement with specs that are close, BUT how far can I vary? What if I go with higher or lower turns?

What if I go with higher or lower kv?
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Old 04-25-2016, 05:19 AM
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I am looking into these things as well. Here's what I found. I have not run 15 different motors in the same vehicle to compare performance, so consider this post atechnical background, not user testimony.

Generally speaking: if you go higher KV the motor will spin faster on the same voltage. It does not necessarily have lower torque (you will sometimes hear this as if it is a law of physics, it is not). However, you may have to gear down the vehicle to keep temperatures in the acceptable range, which negates part of the theoretical speed advantage of the higher KV motor. Also, it's not because a motor is rated at twice the KV that your car goes twice as fast of course. Diminishing returns (or more accurately: rapidly increasing losses).

So in general, a higher KV motor is just a faster motor.

As for turns, it's hard to draw any conclusion about brushless motor performance from its turn rating. Turn ratings are mostly used for technically regulated race classes. KV is the spec you should be looking at. One brand's 4000KV may be a 10.5t and another brand's 4000KV may be a 8.5t.

Also, try to get specs on current draw. Make sure your ESC is up to it.

If you're happy with the speed it does now and you think your ESC has some headroom, get a slightly higher rated one? If it's too fast, you can gear it down. And if the motor you buy is a bit lower quality than the one you are replacing, it should reclaim the lost torque when you do gear it down to the original motor's speed.

Experienced posters correct me if I'm wrong but I'm pretty well read on the subject if I say so myself, heh.
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Old 04-25-2016, 12:06 PM
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agree with xlDoom

Just note you can go with a lower Amp draw motor on an ESC like you can use a 60Amp motor on an 80 Amp ESC, but can not do the opposite if you use say a 80 amp motor on a 60 amp ESC it will blow the ESC.

Kv on a motor means RPM's per volt so if you use a 2s pack on a 3500kv motor the motor will spin at 25,900 RPM

Side note turns has always been a poor determination for a motors specs(outside what an ESC can handle) as one 12t motor can spin 1-2000 rpm faster then the other it is even worst in brushless.

Last edited by SyCo_VeNoM; 04-25-2016 at 12:08 PM.
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Old 04-25-2016, 03:33 PM
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Great info guys !
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Old 04-30-2016, 12:39 PM
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Also the less turns the motor is the faster it will go but you'll use more battery power
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