It is true, RC motors can overheat. Many people may be caught off guard by how easy it is for an RC motor to overheat.
I, too, have experienced some of my RC cars overheating, and this has taught me the importance of really knowing how RC cars and their motors work.
RC motors will heat up as they are operated, but they can overheat if not tuned and step up properly. It is not safe to get electric RC motors over 150°F and nitro RC motors over 300°F. Overheating an RC motor should be avoided as this can damage and destroy the motor.
When it comes to RC motors and how to keep them within the best working temperatures, there are a lot of little caveats and details that you need to be aware of.
In this article, I share with you everything you need to know to better understand how, why, and when your RC motor may overheat and, most importantly, what you can do to prevent it.
Is Overheating Bad for the RC Motor?
Overheating is always going to be an issue and, in fact, one of the things that can and, most likely, will destroy any RC motor.
Overheating can cause the RC motor to fail, have poor performance, or even cause a short and damage or destroy the ESC and the batteries.
Some motors may send their temperatures back to the ESC, and if they are overheating, the ESC will shut the motor down, which could prevent damage due to overheating. However, other motors will not have any such means of thermal protection.
Brushless vs. Brushed vs. Nitro RC Motors
Brushless motors are more efficient than brushed motors.
In brushed motors, there is more friction and more electrical resistance between the brushes and the commutator interface. This leads to higher, on average, working temperatures in brushed motors compared to brushless motors.
With that being said, depending on the magnet, brushed motors can usually withstand a little more heat than brushless motors.
Nitro motors use nitro fuel (or glow fuel) and thus will have higher operating temperatures.
How Hot Should an RC Motor Get
The temperature RC motors can get to will vary a lot depending on various conditions.
Normally electric RC motors will operate in the 80°F to 130°F range. However, in particularly hot days and on closed tracks that are not temperature controlled RC motors can easily exceed 150°F. Some RC motors may even get up to 220°F.
Nitro RC motors are a little different and will run at higher temperatures—generally around 190°F to 260°F. Some nitro motors may go up to and above 300°F.
How Hot Is Too Hot for an RC Motor
How hot is too hot for your RC motor is going to vary by the motor.
Generally speaking, you want to keep your RC brushless motor below 150°F. Temperatures between 150°F and 160°F should also be safe for an RC motor in most cases. Temperatures above 170°F may cause permanent damage to the RC motor and should be avoided.
Many people would consider 110°F to 150°F to be the sweet spot and will try to avoid going above these temperatures.
Around 180°F, you will be risking damaging the magnets of the motor. The magnets will demagnetize, increasing the kV and heat output, which will fry the whole motor.
Temperatures above 200°F will most likely permanently damage the motor.
For a nitro RC motor going above 300°F, is usually considered too much. Temperatures around 350°F will most certainly destroy the glow plug as well.
What Causes RC Motors to Overheat?
Now that you know which temperatures are a no-no, it is time to take a look at what actually will make your RC motor overheat.
In most cases, even one of these reasons may be enough to make your RC motor overheat, however, often it may be a combination of at least two.
The Operating Conditions
The weather is the number one reason why an RC motor may overheat even if correctly set up and tuned. During the summer, when the temperatures are generally higher, depending on where you live, you are most likely to have the RC motor overheating.
RC car steers but won’t move? Read my related article here
However, it is also possible for an RC motor to overheat during the winter. Just because the temperatures are low doesn’t mean the motor cannot overheat.
It may sound strange and counter-intuitive, but it can happen. People are often driving their RC cars for extended periods of time during the winter, and if the cars are not properly set up, don’t have good airflow, and ventilation they can overheat.
With that being said, one day, you may be running your RC car just fine, while a few days later, it will overheat because the temperature or the humidity has changed.
This is why it is important to keep track of the temperature of the RC motor all the time in order to prevent overheating—this applies to both electric and nitro motors.
The type of track you are racing your RC car on will affect how hot your RC motor can get. The different types of terrain will cause different amounts of strain on the motor and the drivetrain.
Asphalt and paved roads will usually cause the least amount of strain on the RC motor.
Dirt and grass (especially tall grass), however, can create more strain on the engine, causing it to overheat.
The Setup / Tune-Up
Several different things can lead to higher RC electric motor temperatures.
- Higher kV motors will generate more heat.
- Stickers wrapped around the motor.
- Over-gearing or under-gearing.
- The body and airflow.
Nitro motors are a little different, and there can be a few more things that will affect their operating temperatures like:
- Poorly tuned low-speed and high-speed needles.
- Fouled glow plug.
- Clogged up air filter.
We will get into more detail about all of these in a moment.
The mechanic behind this is very straightforward—the longer you use your RC car, the hotter it will get. Even if the motor at first is remaining relatively cool, the temperatures can suddenly spike with prolonged use.
This brings us nicely to the next topic, which is about the best way to track the motor’s temperatures.
How to Monitor the Temperatures of the RC Motor
The first step in preventing your RC motor from overheating is to have a means of measuring how hot it gets. This is why an infrared temperature gauge will be an excellent addition to your existing toolkit.
A temp gun or gauge can be used to measure the temperature of not only your RC’s motor but the ESC and other electronics. It will give you the much-needed feedback, which you can use to adjust accordingly and prevent overheating.
When you get a new RC car, run it for about two to three minutes at a more conservative pace and check the temperatures. If the temps are okay, drive it again for two to three more minutes at higher speed and feel free to push it a little bit harder—recheck the temperatures. Do that until you reach normal racing and running speeds.
It is important to continue to monitor those temperatures even after these first initial test runs.
Every time you are racing on a new track, the ambient conditions have changed, or you have changed something on your RC car, it is recommended to measure the temperature of the motor and the other electronics.
If you don’t have a temperature gauge, then you can put your finger on the motor. Be careful in doing so because the motor will be very hot; you can burn yourself. If the motor is so hot that you cannot keep your finger on it for more than one or two seconds, then the motor may be overheating.
Normally you want to be able to keep your finger on the motor for at least five seconds.
Another giveaway that your motor is overheating is that distinct burning smell.
How Do You Cool Down an Electric RC Motor?
An RC motor overheats because of poor setup and because we have let it overheat. Luckily, there are some things that we can do to prevent the RC motor from overheating.
Do Not Exceed the Rated Voltage of the Motor
RC motors have their limitations too. All you have to do is check your RC motor’s specs and see the maximum voltage or battery cells you can use to power it.
On the specs chart, there should be information about the maximum voltage the RC motor can run on.
You want the battery, ESC, and the motor to be all appropriately matched.
There is no hard limitation when it comes to how much voltage you can run through an RC motor, and this is where we can run into some problems—especially if we exceed the safe voltage ranges and RPMs.
All you have to do is take the kV rating of the motor and multiply it by the battery voltage. For example, a 3,300kV motor powered by a 3-cell battery can reach 35,640 RMP under no load. This (fictional) motor is rated for 50,000 RPM, which puts us comfortably below its maximum RPMs. This means that there is little to no risk of overheating or damaging the motor by using a 3-cell battery.
But, if we run the same RC motor with a 6-cell battery, the motor will reach 71,280 RPM, which is significantly above its capabilities—the motor will run for a short period of time, but it will quickly overheat and break down.
The closer you get to what the RC motor can handle, the more important it is to monitor the temperatures.
The ESC needs to be appropriately matched to the current demands of the RC motor and the battery’s voltage. Unlike RC motors, ESC’s have a hard limit on the voltage—in other words, if the ESC is rated for a 3-cell battery, then you cannot use a battery with more than 3 cells (or higher voltage).
Adjust Your Gearing
The gearing is vital in keeping the running temperatures of your RC motor in healthy ranges. In fact, in most cases, this is the first course of action most owners would take.
So how do you know if you are over-geared or under-geared?
There is a good rule of thumb that is easy to follow and gives a good general idea of what may be happening with your RC car:
- A hot motor and a cool ESC means you are under-geared.
- A cool motor and a hot ESC means you are over-geared.
In other words, you want everything to be warm but not too hot.
The gear ratios will determine the Final Drive Ratio (FDR), which represents how many times the motor turns relative to the wheel turning. An FDR of 6 or 6:1 means that the motor will make 6 turns for every single turn of the wheel.
If the FDR and the RC motor are not well-matched, this can lead to overheating. An RC motor with a lower number of turns (T) will take a higher FDR, while a motor with more turns will do better with a lower FDR.
Usually, opting for a smaller pinion gear is the best route to go as it produces the best results. However, a bigger tooth spur can also be useful in lowering the running temperatures of the RC car’s motor.
This also applies to your drivetrain and tire size. For example, changing the tires to a bigger size can make your RC motor overheat. In this case, you may want to go with a smaller pinion.
If there is too much resistance in the drivetrain and it does not spin freely, this can also cause higher running temperatures.
Add a Motor Cooling Fan
Adding one or several cooling fans can be a neat way to lower your RC motor temperatures. Usually, they are pretty cheap; some people even make their own cooling fans.
Those fans are usually attached to a heat sink that is directly attached or wrapped around the RC’s motor.
Motor cooling fans can lower the temperature of the motor by 10 to 20 °F.
You may also want to add more fans that will keep the air under the hood moving.
For more on motor fans, check out this post.
Drill Holes in the RC Car’s Body
Drilling a few well-placed holes in the RC car’s body is a very simple and old-school method to lower the temperatures of your RC motor.
The holes will improve the airflow around the electrical components and the motor; however, you have to be mindful that this can lead to more dust, dirt, and water entering the body.
Also, be careful; in doing so, you may end up damaging or destroying your RC car’s body.
How Do You Cool Down a Nitro RC Motor?
Nitro RC cars have high-speed and low-speed needles. If they are not tuned properly, they can cause the nitro motor to overheat.
As the names suggest, these needless affect the speed of the RC car. The high-speed needle is responsible for the mid to top speed of the RC car, and the low-speed needle is responsible for the zero to mid-speed performance.
If the nitro motor is overheating, this means that it is running too lean. So you want to enrich the fuel mixture, which will make the motor run a lot cooler.
Usually, the needles are turned counterclockwise to make the fuel mixture richer and clockwise to lean it out.
In most cases, the top-speed needle is going to be the one that needs to be tuned up but do not forget to adjust the low-speed needle if necessary, too.
After a tune-up give the RC car a five-minute test run and measure the temperature—rinse and repeat until you are happy with the temperatures of your nitro motor.
When it comes to managing the temperatures of nitro RC motors, it all boils down to the proper needle tune-up. However, other secondary things may affect the temperatures of the motor like:
- A dirty and clogged up air filter.
- A bad glow plug.
- Leaving your RC car to sit and idle—especially after high-speed runs.
What to Do If Your RC Motor Has Overheated?
If your RC motor is overheating, stop the RC vehicle, get it to a cooler place or at least out of the sun, remove the body and leave it to cool down on its own.
After the RC vehicle has completely cooled down, give it a test run. In certain cases, there will be no damage done to the RC motor, and the car will run as usual.
However, if the RC motor has been damaged, the RC car will either not start, or not have a lot of power—in which case you may need to replace the RC motor.
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