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  1. #1
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    What kV motor do you run?

    Looks Iíve fried the ESC in my truck. Looking at replacements and am curious about which kV motors people are running. From my understanding lower kV is basically more torque and less top speed and the opposite goes for higher kV. I think for me a slightly lower than stock kV motor would be beneficial since top speed isnít really what Iím after. That usually results in mass destruction if you get a little carried away. I think with different gears and more battery the same top speed could still be achieved pretty easily. Anyone have any extra info on motors and their capabilities before I pull the trigger on my theory? Any info is good info, Iíd like to hear it all. Thanks!
    If it's not broke, don't fix it! Just upgrade it..

  2. #2
    RC Champion olds97_lss's Avatar
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    I'm running a 3665 3100kv in mine currently on 3S with a max10 sct esc. Had some issues the last time out and I'm not sure if it was my older packs dipping and tripping LVC or not. I need to get more wheel time on it to see how it does.

    I know with the max10 sct/3660 3200kv combo, I was overheating the motor (has a sensor wire) even with a fan on the motor just running at the skate park on 3S. Which is why I tried a longer motor with a bit less kv.

    If I end up having heat issues this spring with the esc, I'll replace it with a spare blx185 I have on hand.
    https://www.youtube.com/c/olds97lss

  3. #3
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    I use a Hobbywing SC Max 10 Ezrun combo with the 3660 3200kv motor (5mm shaft).
    I drive it on 2S, with a 15t pinion 54t spur, ProLine Badlands MX28 tires.

    No issues with overheating, unlike olds97_lss, but he drives on 3S (don(t know what gearing he has).

    I like this combo (have the same in my Slash 4x4).

  4. #4
    RC Champion olds97_lss's Avatar
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    Quote Originally Posted by StijnH View Post
    I use a Hobbywing SC Max 10 Ezrun combo with the 3660 3200kv motor (5mm shaft).
    I drive it on 2S, with a 15t pinion 54t spur, ProLine Badlands MX28 tires.

    No issues with overheating, unlike olds97_lss, but he drives on 3S (don(t know what gearing he has).

    I like this combo (have the same in my Slash 4x4).
    I was running 3S, 13/54 with trencher 2.8's, MIP X-Duty axles.

    Video from then:
    https://www.youtube.com/watch?v=_1EBwvChhI4

    This was later with the hobbystar 3665 3100kv and 14/54 gearing:
    https://www.youtube.com/watch?v=5kinemQjeO0
    https://www.youtube.com/c/olds97lss

  5. #5
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    Quote Originally Posted by olds97_lss View Post
    I'm running a 3665 3100kv in mine currently on 3S with a max10 sct esc. Had some issues the last time out and I'm not sure if it was my older packs dipping and tripping LVC or not. I need to get more wheel time on it to see how it does.
    Did you have any issues fitting that 3665 in a stock chassis?

  6. #6
    RC Turnbuckle Jr.
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    Quote Originally Posted by BrokenPede View Post
    Did you have any issues fitting that 3665 in a stock chassis?
    3660(550 size can) is the biggest drop in motor.


    Sent from my iPhone using Tapatalk

  7. #7
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    Quote Originally Posted by Gripdog7205 View Post
    3660(550 size can) is the biggest drop in motor.


    Sent from my iPhone using Tapatalk
    Thanks, thatís what I was thinking but wasnít 100% on that.


    Sent from my iPhone using Tapatalk
    If it's not broke, don't fix it! Just upgrade it..

  8. #8
    RC Champion olds97_lss's Avatar
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    Quote Originally Posted by BrokenPede View Post
    Did you have any issues fitting that 3665 in a stock chassis?
    I had to cut a bit of the esc mount off and I ground out a bit of the chassis under the motor.


    https://www.youtube.com/c/olds97lss

  9. #9
    RC Qualifier czlynx's Avatar
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    I put a castle 2650kv in and had to grind out a bit as well.

  10. #10
    RC Champion olds97_lss's Avatar
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    Quote Originally Posted by czlynx View Post
    I put a castle 2650kv in and had to grind out a bit as well.
    What motor is that specifically? Got a link? What size pinion do you run? 3S or 4S? Sorry, just wondering for future reference.
    https://www.youtube.com/c/olds97lss

  11. #11
    RC Qualifier czlynx's Avatar
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    Quote Originally Posted by olds97_lss View Post
    What motor is that specifically? Got a link? What size pinion do you run? 3S or 4S? Sorry, just wondering for future reference.
    I got it back before they made all their motors sensored, but I think this would be about the same.

    http://www.castlecreations.com/en/1-...or-060-0061-00

    I'm running an 18 t pinion on 3 and 4s. 4s is a bit on the crazy side honestly, but fun sometimes if I feel like fixing something.

  12. #12
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    I run a ET3S and 5000kv motor and it’s too fast on 3S and never overheats.
    Xmaxx 8S, Arrma Infraction, Nitro Rustler

  13. #13
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    is it true that running a lower KV motor helps with efficiency and run time.

  14. #14
    RC Qualifier GotNoRice's Avatar
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    Quote Originally Posted by Maxx. D View Post
    is it true that running a lower KV motor helps with efficiency and run time.
    There are a lot of variables at play that make this a fairly complicated question.

    Let's say, for the sake of keeping things simple, that we are talking about two motors that are the exact same size, and you are using the exact same gearing (pinion+spur) on both motors, but the two motors simply have different KV. If you had the choice of running, for example, a 3500kv motor with a 2s LiPo or a 2400kv motor with a 3s LiPo, the second configuration would be more efficient. The KV of the motor itself does not have a huge impact on efficiency, but the lower KV makes it more practical to use a higher voltage battery without exceeding max motor RPM, and that higher voltage is where the efficiency is going to come from.

    Some people are limited to only using 2s LiPo due to racing rules. That is the main reason why high KV (>4000kv) motors exist. When you are limited to 2s LiPo, your only options for extra speed are getting a higher KV motor or gearing up. In any situation where you actually have a choice, you are better off using a higher voltage battery with a lower KV motor and/or lower gearing.

    You have some flexibility when it comes to gearing, but in general the same rules should apply. Even without changing motor KV, you would be better off gearing down and using 3s rather than gearing up and using 2s. Higher voltage is almost always more efficient.

    One thing that complicates this is that in many cases, lower KV motors are also larger motors. A larger motor is not usually going to be more efficient than a smaller motor, but larger motors are usually more powerful and might allow you to run your truck in ways that you couldn't with the smaller motor.

  15. #15
    RC Champion olds97_lss's Avatar
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    Quote Originally Posted by GotNoRice View Post
    Some people are limited to only using 2s LiPo due to racing rules. That is the main reason why high KV (>4000kv) motors exist. When you are limited to 2s LiPo, your only options for extra speed are getting a higher KV motor or gearing up. In any situation where you actually have a choice, you are better off using a higher voltage battery with a lower KV motor and/or lower gearing.
    I wondered why there were so may 4k+ motors available. Didn't make any sense to me. Especially since I seem to cook anything that is 3200kv or more in any of my trucks without trying too hard on 3S. I always thought "who buys these 5000kv motors and what do they do with them in the 3 minutes they last?!?!" lol!

    I've since changed mine to run a 150A 1/8th esc and currently have my old ERBEv1 2200kv 4074 motor in it. I got the slash chassis to give me room for larger electronics.

    Still, the motor runs hot on 3S, which surprised me. I installed a motor fan on it since my last run. Today, I ran 2 6200mah 3S packs through it today, about 20 minutes each. Saw 113 at the esc and 121 on the motor. It's 70F out today and I ran it pretty hard the entire time. I think the 2200kv I have in it is getting tired. There isn't a ton of resistance when I rotate the shaft by hand. May have gotten a tad warm when I had it in my ERBEv2 on 6S...
    Last edited by olds97_lss; 05-31-2020 at 02:21 PM.
    https://www.youtube.com/c/olds97lss

  16. #16
    RC Qualifier GotNoRice's Avatar
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    Quote Originally Posted by olds97_lss View Post
    I've since changed mine to run a 150A 1/8th esc and currently have my old ERBEv1 2200kv 4074 motor in it. I got the slash chassis to give me room for larger electronics.

    Still, the motor runs hot on 3S, which surprised me. I installed a motor fan on it since my last run. Today, I ran 2 6200mah 3S packs through it today, about 20 minutes each. Saw 113 at the esc and 121 on the motor. It's 70F out today and I ran it pretty hard the entire time.
    What gearing? I'm using a Castle 2200kv 4074 motor with a Mamba Monster X, geared 18/54, which is basically the lowest gearing I could get away with that still allows the gears to mesh. I also extended the truck using the Slash 4x4 chassis. I run mostly using 4S. When it comes to the ESC, there is a reason why it's limits are measured in Amps. Amps, or current, is mainly what is going to create heat in the ESC. Higher battery voltage means less amps are required for a given amount of watts (power) going to the motor. You could potentially hit the limits of your ESC even just using 2s if you geared high enough and your 2s pack could actually supply that many amps.

    121F is not bad at all. You shouldn't cause damage to your motor until you hit 80C or so, which is about 175F.

  17. #17
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    thanks for the info! but how about motor timing, i know the more timing equals more power and heat but would your run time be shortened? was driving my losi DP Pro at the track and by the time i was done i was able to hold my hand on the motor (stock motor) but i only lasted 40m with two 4500 mAh 75c 3s lipos. i was thinking about increasing my timing what do you think? through my firma esc the next step up is from 15-18.75 degrees is that to much?

  18. #18
    RC Champion olds97_lss's Avatar
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    Quote Originally Posted by GotNoRice View Post
    What gearing? I'm using a Castle 2200kv 4074 motor with a Mamba Monster X, geared 18/54, which is basically the lowest gearing I could get away with that still allows the gears to mesh. I also extended the truck using the Slash 4x4 chassis. I run mostly using 4S. When it comes to the ESC, there is a reason why it's limits are measured in Amps. Amps, or current, is mainly what is going to create heat in the ESC. Higher battery voltage means less amps are required for a given amount of watts (power) going to the motor. You could potentially hit the limits of your ESC even just using 2s if you geared high enough and your 2s pack could actually supply that many amps.

    121F is not bad at all. You shouldn't cause damage to your motor until you hit 80C or so, which is about 175F.
    Running 19/54 with trencher 2.8's. I ran into similar heat issues when I was running 4S in my outcast (same esc). Without the fan, the motor got up to 160F. I was running it in grass quite a bit at the time and it was 84F outside.

    I was thinking about running 4S in this, but since I can't lower the gearing much (if at all) beyond 18/54, I wasn't sure if it was worth trying 4S. Since I run 2x3S in all my big trucks, I kind of wanted to stick with 3S so I could use the same packs in everything. However, once I use packs in a single pack truck, I label them so I don't use them in my 6S paired sets for my big trucks.

    Running 19T today cut my run time down quite a bit. Guessing it's pulling more amps for the gearing. So I may drop it back down to 18T before I run it again.
    https://www.youtube.com/c/olds97lss

  19. #19
    RC Qualifier GotNoRice's Avatar
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    You might check for any drive-line resistance, particularly things like old bearings that are wearing out. Most bearings won't simply fail, they will just get less and less smooth over time. You probably won't even notice much of a difference in the way the truck drives, but that extra resistance will cause the motor to heat up more quickly. I usually get brand new bearings once every 1-2 years. AVID usually sells a complete kit of upgraded bearings for about ~$25

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