Best motor upgrade for 1/0th scale short course truck

[Bri26]

I guess we will have to agree to disagree. In my opinion, a good handling and well balanced RC vehicle is not only good for racing but is also good for bashing. Sure you can throw a less suitable brushless motor in a particular RC vehicle and it will work but it doesn't mean it will still be as enjoyable to drive. The EZRUN 3660 specifically states that its recommended for a 1/10 4wd short course truck. The longer can is not only heavier but gives more torque than a 540 brushless motor which isn't needed on a 2wd. The thing is if you are jumping a 1/10 2wd short course truck, do you really want the rear end sagging due to too much weight and it parachuting like crazy because the front end is flying too high?

Bottom line, you should think of KV as the maximum power potential of the motor in regards to a specific number of LiPo cells. If all KV was the measure of the balance between speed and torque, then all the motors with a similar KV would run exactly the same if you adjusted the gearing to match each motor to the same top speed. This isn't the case, a higher KV at 2S will outperform a lower KV both in speed and torque when geared for maximum performance. Another way to say it is that if you increase the pinion gear on a lower KV to match the top speed of a higher KV, it will have less torque than the higher KV. This is why it's important to think of KV as the absolute maximum power potential of the motor.

Brushless motors that are used in RC racing are designated in turns such as 25.5T or 21.5T. A 25.5T motor will never be faster on the track in the same vehicle than a 21.5T motor. If the 25.5T does have a so called torque advantage over a 21.5T motor, you lose that advantage when you increase the pinion gear to get the top speed to anywhere close to that of the top speed of the 21.5T motor.

Here is a link to some more information in regards to different KV ratings and torque - https://www.radiocontrolinfo.com/three-misconceptions-in-rc-brushless-motors-more/

Anyway, it's been a good discussion and hopefully it has brought some good insights into selecting a brushless motor.

 

[Greywolf74]

I guess we will have to agree to disagree. In my opinion, a good handling and well balanced RC vehicle is not only good for racing but is also good for bashing. Sure you can throw a less suitable brushless motor in a particular RC vehicle and it will work but it doesn't mean it will still be as enjoyable to drive. The EZRUN 3660 specifically states that its recommended for a 1/10 4wd short course truck. The longer can is not only heavier but gives more torque than a 540 brushless motor which isn't needed on a 2wd. The thing is if you are jumping a 1/10 2wd short course truck, do you really want the rear end sagging due to too much weight and it parachuting like crazy because the front end is flying too high?

We can agree to disagree. For bashing I couldnt really tell much of a difference in my stadium truck with an extra 70-80g in the back. Sure if you want to talk racing then we can nitpick.

Bottom line, you should think of KV as the maximum power potential of the motor in regards to a specific number of LiPo cells. If all KV was the measure of the balance between speed and torque, then all the motors with a similar KV would run exactly the same if you adjusted the gearing to match each motor to the same top speed. This isn't the case, a higher KV at 2S will outperform a lower KV both in speed and torque when geared for maximum performance. Another way to say it is that if you increase the pinion gear on a lower KV to match the top speed of a higher KV, it will have less torque than the higher KV. This is why it's important to think of KV as the absolute maximum power potential of the motor.

Again you're talking about racing when no one else is.

Brushless motors that are used in RC racing are designated in turns such as 25.5T or 21.5T. A 25.5T motor will never be faster on the track in the same vehicle than a 21.5T motor. If the 25.5T does have a so called torque advantage over a 21.5T motor, you lose that advantage when you increase the pinion gear to get the top speed to anywhere close to that of the top speed of the 21.5T motor.

Here is a link to some more information in regards to different KV ratings and torque - https://www.radiocontrolinfo.com/three-misconceptions-in-rc-brushless-motors-more/

Anyway, it's been a good discussion and hopefully it has brought some good insights into selecting a brushless motor.

So I looked at that link and its interesting but I have a couple of problems with it. Firstly, they dont explain where they are getting the numbers they are using. As far as I can tell they are arbitrary numbers. Additionally, They dont show how they did the math as to how they came up with the nMn/A numbers they got but lets hypothetically say that the math is correct. What they dont talk about is how much hotter the higher KV motor will get and how much faster it will get hotter. So again, only important if your racing becasue if you're not racing then you arent gonna wanna bake your motor with an extra 23A of current for an extra 3nMn/A (basically nothing) or torque. That being said, I will say thanks! You taught me something about brushless motors however its really only applicable in racing where you care more about winning than burning up your motor. Still though, I enjoy learning something new.

 

[Bri26]

Here is a video that explains the math -

 

[Greywolf74]

Here is a video that explains the math -

Thanks for the video. Its nice to see the math more in detail but all of this still leaves me with 2 unanswered questions.
1) How does the extra heat generated by higher current come in to play with all of this?
2) If all motors of the same can size have the same potential for maximum torque and RPMs then whats the point of lower KV motors?
the first thing that pops in to my mind is that they make lower KV motors so you can get the same performance with less heat but again if thats true then why have higher KV motors at all? Looks like i gotta keep digging in to this. i really want to understand these other parameters and how they relate to KV/KT

 

[Bri26]

I think a lower KV motor is suited for those who want a slower motor or to run more cells. You also will get a lower amp draw on a lower KV motor which should lead to a longer run time.

 

[Greywolf74]

I think a lower KV motor is suited for those who want a slower motor or to run more cells. You also will get a lower amp draw on a lower KV motor which should lead to a longer run time.

Good point about longer run times. It will be lower temps too which i suppose is favorable for bashers since we tend to care more about longevity of parts rather than maximum performance. Unfortunately for me This means that instead of buying the 4.5T motor I bought for a no prep build I should have bought a 2.5T and a bigger ESC lol.

 

[More_Power]

I don’t know squat about all this techno stuff. That being said, let me weigh in on this.

if I was to do it all over again, I would have done one of these 2 things for my 2wd slash (mostly a street basher);

VXL 3S 4 pole motor on the 4SVXL ESC with an off the shelf traxxas 4S battery (or 2 2S traxxas batteries)

or

Traxxas 540XL motor (2,400Kv) on the 4S esc.

with traxxas warranty and having a traxxas location 40-45 mins away, if I burn up the 3S motor, I’ll just get another one.

 

[Greywolf74]

I don’t know squat about all this techno stuff. That being said, let me weigh in on this.

if I was to do it all over again, I would have done one of these 2 things for my 2wd slash (mostly a street basher);

VXL 3S 4 pole motor on the 4SVXL ESC with an off the shelf traxxas 4S battery (or 2 2S traxxas batteries)

or

Traxxas 540XL motor (2,400Kv) on the 4S esc.

with traxxas warranty and having a traxxas location 40-45 mins away, if I burn up the 3S motor, I’ll just get another one.

IDK squat about working on 1:1s so were even!

 

[RC MAN]

A 3100kv motor on 2S will have less RPMs than a 3800kv. Were on the same page there but, the 3100kv doesn't have more torque because it spins slower. "Torque is determined by the number of winds on the armature and the strength of the magnets. A low Kv motor has more winds of thinner wire—it will carry more volts at fewer amps, produce higher torque, and turn a bigger pinion"

I agree with you there a 3800kv motor will have the same torque as a 3100kv motor at the same voltage but usually you can run lower kv motors at a higher voltage. The 3800kv motor will also spin faster making more top speed.

 

[RC MAN]

I wouldn't put the EZRUN 3660 motor in a 2wd short course. It has too much torque and it weighs a lot. My opinion, you would do a lot better with a lighter weight 540 2 pole or 4 pole brushless motor.

I very certain even if i was racing, 80 grams or so at the back isn't going to do anything especially because the Truck i have has a much lower center of gravity than the Traxxas slash and i am running it on a 325 gram battery.

 

[RC MAN]

Also would any of you guys Know what gearing i should run on the Ezrun 3660sl 4000kv on a 1/10th scale SCT 2wd. I've seen reviews of the motor saying it did 65+ mph easy on a stock Traxxas Slayer with a 14T pinion and 36T spur. Then i've seen this video

that said they got 70mph on a 35T pinion 55T spur with that motor in it. any help would be much appreciated.

​

 

[Greywolf74]

Also would any of you guys Know what gearing i should run on the Ezrun 3660sl 4000kv on a 1/10th scale SCT 2wd. I've seen reviews of the motor saying it did 65+ mph easy on a stock Traxxas Slayer with a 14T pinion and 36T spur. Then i've seen this video

that said they got 70mph on a 35T pinion 55T spur with that motor in it. any help would be much appreciated.

​

Is your goal to do speed runs with the 2wd slash? Id start with maybe a 2:1 gear ratio and tweak it from there.

 

[WickedFog]

My head hurts now. Thanks a lot guys!

 

[Greywolf74]

My head hurts now. Thanks a lot guys!

LOL, So did mine but were getting smarter every day!

 

[RC MAN]

2) If all motors of the same can size have the same potential for maximum torque and RPMs then whats the point of lower KV motors?
the first thing that pops in to my mind is that they make lower KV motors so you can get the same performance with less heat but again if thats true then why have higher KV motors at all? Looks like i gotta keep digging in to this. i really want to understand these other parameters and how they relate to KV/KT

Isn't it if all motors were the same size the lower kv ones you could run at a higher voltage making more torque and the higher kv ones you have to run at a lower voltage.

Also i only want to run my rc car on 3s so wouldn't i want the biggest motor i could fit in there for 3s and the highest kv motor rated for 3s?

I guess we will have to agree to disagree. In my opinion, a good handling and well balanced RC vehicle is not only good for racing but is also good for bashing. Sure you can throw a less suitable brushless motor in a particular RC vehicle and it will work but it doesn't mean it will still be as enjoyable to drive. The EZRUN 3660 specifically states that its recommended for a 1/10 4wd short course truck. The longer can is not only heavier but gives more torque than a 540 brushless motor which isn't needed on a 2wd. The thing is if you are jumping a 1/10 2wd short course truck, do you really want the rear end sagging due to too much weight and it parachuting like crazy because the front end is flying too high?

Whats wrong with a lot of torque it just means you can run a higher gearing and go faster?
and can't i just counter weight 80 grams at the front of the car?

 

[Greywolf74]

Isn't it if all motors were the same size the lower kv ones you could run at a higher voltage making more torque and the higher kv ones you have to run at a lower voltage.

That's true but I was talking in the context of two motors with the same max cell rating. For example a 3800kv and 5700kv are both 3s max motors

Also i only want to run my rc car on 3s so wouldn't i want the biggest motor i could fit in there for 3s and the highest kv motor rated for 3s?

When you said biggest motor are you talking about putting a 1/8 scale motor in a 1/10 scale kit or are you talking about highest kv rating? Highest kv rating up to a point. Higher the kv, the hotter that motor will run. Biggest physical size? Not necessarily.

Whats wrong with a lot of torque it just means you can run a higher gearing and go faster?
and can't i just counter weight 80 grams at the front of the car?

For the sake of balancing yes you could use counter weights but the less weight, the higher your lipo voltage stays, the higher your voltage the faster you'll be. That's why racers might care but for bashing it doesn't matter imo

 

[RC MAN]

When you said biggest motor are you talking about putting a 1/8 scale motor in a 1/10 scale kit or are you talking about highest kv rating? Highest kv rating up to a point. Higher the kv, the hotter that motor will run. Biggest physical size? Not necessarily.




what i meant is putting the biggest can size motor that i can fit in it which at the moment seems to be the hobbywing 4 pole 4000kv 3660. i have to stick with the width 36mm but i can change the length and so the longest length of a motor with the 36mm width is that motor. and as for the kv i wanted the highest kv for that motor size and voltage so the hobbywing 4000kv 4pole 3660 has also won in kv as well. and also science it’s longer and is a 4pole and i am going to run it in a 2wd it will have more torque than other motors there for i can gear it higher. it also has a very good kv for the size so i see it as a win win for the kv and the torque.

also would 80 grams really make a difference? it really doesn’t seem like it will do squat to the voltage or balance.

 

[Greywolf74]

also would 80 grams really make a difference? it really doesn’t seem like it will do squat to the voltage or balance.

I've seen racers who hollow out or grind down parts of their chassis in order to shave 10/15 grams. Every little bit helps. I guess its just how competative you want to be.

 

[Bri26]

Whats wrong with a lot of torque it just means you can run a higher gearing and go faster?
and can't i just counter weight 80 grams at the front of the car?

Too much torque is bad that it can make it really hard to get the power down. A 1/10 4wd drive short course truck has more parts in the drivetrain and is a heavier vehicle overall so it can handle more torque than a 1/10 2wd short course truck.

You can add more weight to the front for better balance but with that being said a lighter RC vehicle will always outperform a heavier RC vehicle as long as both vehicles have a good weight balance. By using a lighter weight motor in the rear of the vehicle, you are essentially moving the weight more forward and lowering the overall weight of the vehicle.

 

[RC MAN]

Too much torque is bad that it can make it really hard to get the power down. A 1/10 4wd drive short course truck has more parts in the drivetrain and is a heavier vehicle overall so it can handle more torque than a 1/10 2wd short course truck.

You can add more weight to the front for better balance but with that being said a lighter RC vehicle will always outperform a heavier RC vehicle as long as both vehicles have a good weight balance. By using a lighter weight motor in the rear of the vehicle, you are essentially moving the weight more forward and lowering the overall weight of the vehicle.

how does a lot of torque make it hard to get the power down. i know the wheels might spin but since it has a lot of torque i can just gear it up and make it go faster. i just need someone to explain it because my tiny brain can’t get around it

and also do you mean a lighter vehicle with the same motor and same gearing as the heavier vehicle. not all the time because i have a friend who has a 1/18 scale rc monster truck which has a massive motor in it which makes it capable of 70kph. now as you can probably tell that is way to fast for a super LIGHT 1/18 and when it gets up to like 50kph it’s just uncontrollable. so sometimes things just need a little more weight.