Limitless Speed Runners Motor KV selection

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Fallguy said:
I have been reading through this thread several times. Was able to get the castle 2028-1100KV motor. I downloaded that app and was going to figure out what size pinion etc. Please correct me if I'm wrong but doesn't the limitless roller come with a 2.8 ratio?
Click to expand...
Nope, Limitless has 3.3 (43/13)
 
Another example of how the big torque of the 1/5 scale motors are very capable on 6s or 8s.
I am estimating his FD ratio is near 1.4!!!?
He has been posting up a few videos of this 1/7 Arrma GT running on 6s and now is solidly running in the 160's on 6s.
Check out the amperage in the logs at the end!



1620654234422.png
 
LibertyMKiii said:
Another example of how the big torque of the 1/5 scale motors are very capable on 6s or 8s.
I am estimating his FD ratio is near 1.4!!!?
He has been posting up a few videos of this 1/7 Arrma GT running on 6s and now is solidly running in the 160's on 6s.
Check out the amperage in the logs at the end!



View attachment 144891
Click to expand...
Fake, I am certain that speed was put down by the lady on the scooter trying to steal his car ;)

Doing that speed with only 17k rpm must be an extreme FD indeed. His CH speed delay was like 11s btw
 
rotauq said:
Fake, I am certain that speed was put down by the lady on the scooter trying to steal his car ;)

Doing that speed with only 17k rpm must be an extreme FD indeed. His CH speed delay was like 11s btw
Click to expand...
That was kind of weird like he knew her? I would have been a lot more upset if someone was stealing my car. I cannot confirm nor deny that I would have bumped that scooter off the road to get my stuff back.

There has been lots of controversy about his runs under a bridge being accurate given the potential blocking of GPS signals. Being dark it is hard to tell, but didn't look as fast as other 160+ runs I have seen.

Imagine what that 641a would have been without 11 sec channel speed control!?
 
LibertyMKiii said:
That was kind of weird like he knew her? I would have been a lot more upset if someone was stealing my car. I cannot confirm nor deny that I would have bumped that scooter off the road to get my stuff back.

There has been lots of controversy about his runs under a bridge being accurate given the potential blocking of GPS signals. Being dark it is hard to tell, but didn't look as fast as other 160+ runs I have seen.

Imagine what that 641a would have been without 11 sec channel speed control!?
Click to expand...
It's not that difficult to change the datalog csv files either.

The speed is indeed hard to tell. It doesn't feel so fast, but video never does.
I was actually more triggered by the distance. It didn't felt like he covered a lot of distance. The GPS after the run showed 1625m / ~1 mile and that's including the scooter ride.(600-800m)
 
rotauq said:
It's not that difficult to change the datalog csv files either.

The speed is indeed hard to tell. It doesn't feel so fast, but video never does.
I was actually more triggered by the distance. It didn't felt like he covered a lot of distance. The GPS after the run showed 1625m / ~1 mile and that's including the scooter ride.(600-800m)
Click to expand...
I remember a video of his where he claimed a record was shared in a speedrun group on Facebook, and everyone was in an uproar because of the bridge and the tires. I think he had a Garmin on the car at the time so distance wasn’t shown.
 
More guys running large 1/5 scale motors putting up big numbers!

I know a guy running the TP5660 1460kv (y-wind) who is running well into the 170-175mph range now.

A new guy on the scene Peter Dirks appears to be using a TP 5680? Unknown KV, but I have seen his RPMs are around 38-40k in logs. This tells me the KV would be in the 1640Kv (+/-300kv) range. One of his logs pulled over 19kW, and he reached 190mph recently with the Limitless GT. One of his secrets is running parallel 8s (using 4 packs) This helps him only sag down to around 27-28.5v versus the normal 23-25 volts. More volts = more RPMS = more speed. The cost is significant weight addition. This weight will mean longer distances for acceleration and braking.

A picture he shared on Facebook shows his clever setup to reduce wire length:

1624280233208.png
 
Last edited:
LibertyMKiii said:
I figure now that we have a speedrun section of the site it would be good to post a thread about motor KV selection. Motor selection is a mystery to many and although I don't have it all figured out (I am not the experienced expert) I believe I have a pretty good understanding.

First I want to say that Castle ESCs like the XLX and MMX8s are really the only 2 good options. This is because you will need high amps and data logs to make informed decisions on adjusting your setup.

Running a Typhon as a buggy you would likely be limited to a 6s setup or running a Limitless you could run up to 8s. First things first you must know what power level you plan to run and how large of battery you plan to run. As of today the top 3 batteries for speed running would be the Turnigy Graphene/Panther, CNHL 70c, and SMC True Spec Extreme V2. You will need the best of the best LiPo due to their amperage delivery and reduced voltage sag. On the topic of voltage sag higher mAh values will help. This is why you will see many guys run 2 packs in parallel. A parallel 6,000 mAh setup would effectively give you 12Ah!

Next to begin the discussion on KV of motors you must know that most if not all motors are hand wound. This means no 2 motors are the same. Some are power hogs and some are highly efficient. I recently purchased the SkyRC motor analyzer and if you are serious about speed running this would be a wise purchase. The 2 big things this tool will give you is actual KV and how efficient in amperage draw your motor is.

This first example is a good TP4070 with the D-wind 2080KV
This is a good motor that my friend has done 159 mph with on a 1/8 Mugen. You can see here the amperage draw is “efficient” at 3.6A
View attachment 86853

The next was another TP4070 with the D-wind 2080kv it would be an ok motor, but it will draw more amps (around 2x the other motor) and run hot! Also notice the KV difference of these 2 motors both sold as 2080KV. While higher KV would pull slightly more amps we wouldn't expect it to be this much higher. Ideally TP Power should have taken this motor back as "bad".
View attachment 86854

(note I had tried charging my 2s testing LiPo fully to 8.4V and same results came out.)

Back on topic to selecting a motor. The Magic is shooting for your motor to run around 51-55k rpm knowing it wont quite get there. Reviewing logs of people who have truly gone fast, their motor RPMS are in the high 45-49k rpm range to as much as 52krpms.
KV multiplied by the voltage = the motor RPM

The topic of voltage sag here and data logs is key! Without testing your motor, gearing, and battery... the best thing we can do is use typical numbers.
Typical value of a 6s Lipo drops during a speed run to around 19 volts. On 8s it drops somewhere to around 26 volts. These numbers are for 5000 to 6000 mAh packs as described above as "best LiPos" I have seen far worse sag on low end LiPos.

First we can look at a 6s setup. If I want 51k RPM I will take 51,000 divided by 19 volts and come up with 2684 KV. This is why many people like the 2700KV motor for 6s use!
The major key with this setup is that you cannot over gear it. The higher KV motor like this will pull some serious amperage. I would recommend starting conservative and use you data logs as you make adjustments. You would be keeping an eye on RPMs, voltage sag, amperage, and ESC temps. With a Typhon/Limitless differential running GRP tires you could expect as much as 154 mph with 27 pinion and 34t spur gear. (assuming your car gets there safely and has the aerodynamics to do it) Given that you should not go out your first time and do 150mph I highly recommend gearing way down on this setup and work up to that gearing.

There is a mobile app called "RC Car GearCalc" that I use. this one does not have you pick 6s 8s 5s etc. Instead it allows you to input a specific voltage so that you can use it to properly adjust for voltage sag.

Next we will look at 8s!
For this again our around 34 volts will sag to 26 volts. (this could differ depending on the batteries you choose.)
Again shooting for 51,000 rpms divided by 26 volts provides a motor of 1961 KV. This would be why speed runners recommend 2000 KV up to 2200 for 8s use. (This is why I purchased the 2080kv TP 4070 motor)
Also why I am using my BLX 2050KV on 8s! Which that motor is actually closer to 1900kv

View attachment 86856

Most scenarios we find that staying under 1:1 gearing is ideal for 40mm motors due to the gearing torque loss. Also keep in mind that the gearing creates the amperage load for the ESC and if you over gear you will not reach the desired RPM range. Always start low and work your way up. Read the data logs and adjust accordingly. At a certain point the car will not go faster but the motor heat and ESC heat will go way up. At that point you have reached the limits of the setup. You have 2 options. Try a different motor or in my mind the better option is to improve the aerodynamics.

People are now playing with large 1/5 motors which are around 1000 - 1350 kv. I am not certain yet how all of this will play out as their power band will be different and requires some gearing way beyond 1:1
It is also worth noting that TP Power 1/5 motors are 6 poles and the more poles of the motor will provide more timing stress on the motor as it has less time between each pole to do its "job".

I hope this is helpful and again I am not a proven expert on motor selection, but I believe this is at least a good ballpark for you!
Click to expand...
Super informative and helpful. Thank you for taking the time to post this.
 
LibertyMKiii said:
I figure now that we have a speedrun section of the site it would be good to post a thread about motor KV selection. Motor selection is a mystery to many and although I don't have it all figured out (I am not the experienced expert) I believe I have a pretty good understanding.

First I want to say that Castle ESCs like the XLX and MMX8s are really the only 2 good options. This is because you will need high amps and data logs to make informed decisions on adjusting your setup.

Running a Typhon as a buggy you would likely be limited to a 6s setup or running a Limitless you could run up to 8s. First things first you must know what power level you plan to run and how large of battery you plan to run. As of today the top 3 batteries for speed running would be the Turnigy Graphene/Panther, CNHL 70c, and SMC True Spec Extreme V2. You will need the best of the best LiPo due to their amperage delivery and reduced voltage sag. On the topic of voltage sag higher mAh values will help. This is why you will see many guys run 2 packs in parallel. A parallel 6,000 mAh setup would effectively give you 12Ah!

Next to begin the discussion on KV of motors you must know that most if not all motors are hand wound. This means no 2 motors are the same. Some are power hogs and some are highly efficient. I recently purchased the SkyRC motor analyzer and if you are serious about speed running this would be a wise purchase. The 2 big things this tool will give you is actual KV and how efficient in amperage draw your motor is.

This first example is a good TP4070 with the D-wind 2080KV
This is a good motor that my friend has done 159 mph with on a 1/8 Mugen. You can see here the amperage draw is “efficient” at 3.6A
View attachment 86853

The next was another TP4070 with the D-wind 2080kv it would be an ok motor, but it will draw more amps (around 2x the other motor) and run hot! Also notice the KV difference of these 2 motors both sold as 2080KV. While higher KV would pull slightly more amps we wouldn't expect it to be this much higher. Ideally TP Power should have taken this motor back as "bad".
View attachment 86854

(note I had tried charging my 2s testing LiPo fully to 8.4V and same results came out.)

Back on topic to selecting a motor. The Magic is shooting for your motor to run around 51-55k rpm knowing it wont quite get there. Reviewing logs of people who have truly gone fast, their motor RPMS are in the high 45-49k rpm range to as much as 52krpms.
KV multiplied by the voltage = the motor RPM

The topic of voltage sag here and data logs is key! Without testing your motor, gearing, and battery... the best thing we can do is use typical numbers.
Typical value of a 6s Lipo drops during a speed run to around 19 volts. On 8s it drops somewhere to around 26 volts. These numbers are for 5000 to 6000 mAh packs as described above as "best LiPos" I have seen far worse sag on low end LiPos.

First we can look at a 6s setup. If I want 51k RPM I will take 51,000 divided by 19 volts and come up with 2684 KV. This is why many people like the 2700KV motor for 6s use!
The major key with this setup is that you cannot over gear it. The higher KV motor like this will pull some serious amperage. I would recommend starting conservative and use you data logs as you make adjustments. You would be keeping an eye on RPMs, voltage sag, amperage, and ESC temps. With a Typhon/Limitless differential running GRP tires you could expect as much as 154 mph with 27 pinion and 34t spur gear. (assuming your car gets there safely and has the aerodynamics to do it) Given that you should not go out your first time and do 150mph I highly recommend gearing way down on this setup and work up to that gearing.

There is a mobile app called "RC Car GearCalc" that I use. this one does not have you pick 6s 8s 5s etc. Instead it allows you to input a specific voltage so that you can use it to properly adjust for voltage sag.

Next we will look at 8s!
For this again our around 34 volts will sag to 26 volts. (this could differ depending on the batteries you choose.)
Again shooting for 51,000 rpms divided by 26 volts provides a motor of 1961 KV. This would be why speed runners recommend 2000 KV up to 2200 for 8s use. (This is why I purchased the 2080kv TP 4070 motor)
Also why I am using my BLX 2050KV on 8s! Which that motor is actually closer to 1900kv

View attachment 86856

Most scenarios we find that staying under 1:1 gearing is ideal for 40mm motors due to the gearing torque loss. Also keep in mind that the gearing creates the amperage load for the ESC and if you over gear you will not reach the desired RPM range. Always start low and work your way up. Read the data logs and adjust accordingly. At a certain point the car will not go faster but the motor heat and ESC heat will go way up. At that point you have reached the limits of the setup. You have 2 options. Try a different motor or in my mind the better option is to improve the aerodynamics.

People are now playing with large 1/5 motors which are around 1000 - 1350 kv. I am not certain yet how all of this will play out as their power band will be different and requires some gearing way beyond 1:1
It is also worth noting that TP Power 1/5 motors are 6 poles and the more poles of the motor will provide more timing stress on the motor as it has less time between each pole to do its "job".

I hope this is helpful and again I am not a proven expert on motor selection, but I believe this is at least a good ballpark for you!
Click to expand...

Follow up on this motor tester post.
Jason Flores (flo packs) posted a video that if you change the connections ABC to BCA or ACB etc. then retest you might find the motor runs more efficiently in a certain configuration.

Great idea and worth trying to find the optimum efficiency for your motor.
 
LibertyMKiii said:
I figure now that we have a speedrun section of the site it would be good to post a thread about motor KV selection. Motor selection is a mystery to many and although I don't have it all figured out (I am not the experienced expert) I believe I have a pretty good understanding.

First I want to say that Castle ESCs like the XLX and MMX8s are really the only 2 good options. This is because you will need high amps and data logs to make informed decisions on adjusting your setup.

Running a Typhon as a buggy you would likely be limited to a 6s setup or running a Limitless you could run up to 8s. First things first you must know what power level you plan to run and how large of battery you plan to run. As of today the top 3 batteries for speed running would be the Turnigy Graphene/Panther, CNHL 70c, and SMC True Spec Extreme V2. You will need the best of the best LiPo due to their amperage delivery and reduced voltage sag. On the topic of voltage sag higher mAh values will help. This is why you will see many guys run 2 packs in parallel. A parallel 6,000 mAh setup would effectively give you 12Ah!

Next to begin the discussion on KV of motors you must know that most if not all motors are hand wound. This means no 2 motors are the same. Some are power hogs and some are highly efficient. I recently purchased the SkyRC motor analyzer and if you are serious about speed running this would be a wise purchase. The 2 big things this tool will give you is actual KV and how efficient in amperage draw your motor is.

This first example is a good TP4070 with the D-wind 2080KV
This is a good motor that my friend has done 159 mph with on a 1/8 Mugen. You can see here the amperage draw is “efficient” at 3.6A
View attachment 86853

The next was another TP4070 with the D-wind 2080kv it would be an ok motor, but it will draw more amps (around 2x the other motor) and run hot! Also notice the KV difference of these 2 motors both sold as 2080KV. While higher KV would pull slightly more amps we wouldn't expect it to be this much higher. Ideally TP Power should have taken this motor back as "bad".
View attachment 86854

(note I had tried charging my 2s testing LiPo fully to 8.4V and same results came out.)

Back on topic to selecting a motor. The Magic is shooting for your motor to run around 51-55k rpm knowing it wont quite get there. Reviewing logs of people who have truly gone fast, their motor RPMS are in the high 45-49k rpm range to as much as 52krpms.
KV multiplied by the voltage = the motor RPM

The topic of voltage sag here and data logs is key! Without testing your motor, gearing, and battery... the best thing we can do is use typical numbers.
Typical value of a 6s Lipo drops during a speed run to around 19 volts. On 8s it drops somewhere to around 26 volts. These numbers are for 5000 to 6000 mAh packs as described above as "best LiPos" I have seen far worse sag on low end LiPos.

First we can look at a 6s setup. If I want 51k RPM I will take 51,000 divided by 19 volts and come up with 2684 KV. This is why many people like the 2700KV motor for 6s use!
The major key with this setup is that you cannot over gear it. The higher KV motor like this will pull some serious amperage. I would recommend starting conservative and use you data logs as you make adjustments. You would be keeping an eye on RPMs, voltage sag, amperage, and ESC temps. With a Typhon/Limitless differential running GRP tires you could expect as much as 154 mph with 27 pinion and 34t spur gear. (assuming your car gets there safely and has the aerodynamics to do it) Given that you should not go out your first time and do 150mph I highly recommend gearing way down on this setup and work up to that gearing.

There is a mobile app called "RC Car GearCalc" that I use. this one does not have you pick 6s 8s 5s etc. Instead it allows you to input a specific voltage so that you can use it to properly adjust for voltage sag.

Next we will look at 8s!
For this again our around 34 volts will sag to 26 volts. (this could differ depending on the batteries you choose.)
Again shooting for 51,000 rpms divided by 26 volts provides a motor of 1961 KV. This would be why speed runners recommend 2000 KV up to 2200 for 8s use. (This is why I purchased the 2080kv TP 4070 motor)
Also why I am using my BLX 2050KV on 8s! Which that motor is actually closer to 1900kv

View attachment 86856

Most scenarios we find that staying under 1:1 gearing is ideal for 40mm motors due to the gearing torque loss. Also keep in mind that the gearing creates the amperage load for the ESC and if you over gear you will not reach the desired RPM range. Always start low and work your way up. Read the data logs and adjust accordingly. At a certain point the car will not go faster but the motor heat and ESC heat will go way up. At that point you have reached the limits of the setup. You have 2 options. Try a different motor or in my mind the better option is to improve the aerodynamics.

People are now playing with large 1/5 motors which are around 1000 - 1350 kv. I am not certain yet how all of this will play out as their power band will be different and requires some gearing way beyond 1:1
It is also worth noting that TP Power 1/5 motors are 6 poles and the more poles of the motor will provide more timing stress on the motor as it has less time between each pole to do its "job".

I hope this is helpful and again I am not a proven expert on motor selection, but I believe this is at least a good ballpark for you!
Click to expand...
I think xlx2 has alot to do with 40k-45k runs guys are over gearing there motors and thanks to xlx2 and new 2p lipos the esc will supply it .with the old xlx if you over geared it would smoke .I still try for higher rpm runs over low rpm torque run the power band at 50k rpm sounds badass . I have a video series you won't want to miss any talks about this and what I actually gain mph buy going down teeth .started high went low ..
 
J-florc said:
I think xlx2 has alot to do with 40k-45k runs guys are over gearing there motors and thanks to xlx2 and new 2p lipos the esc will supply it .with the old xlx if you over geared it would smoke .I still try for higher rpm runs over low rpm torque run the power band at 50k rpm sounds badass . I have a video series you won't want to miss any talks about this and what I actually gain mph buy going down teeth .started high went low ..
Click to expand...
For sure... Everyone wants to jump up big gearing for more speed.
I tell people they should start with some baseline runs with light gearing so that you have data logs showing what health the system is in.
From there as you gear up you will see voltage dropping and rpms dropping letting you know the system is getting pushed hard. At some point the RPMs and volts keep dropping and you are not gaining speed, yet pulling more amps and heat. It is over with at that point.
 
Interesting. Wish i could test my arrma 2000kv motor. My nero gets very hot on the stock gearing. Reminds me of my oitcast 4s by how hot the motor and wires get. My second old pair of lipos puffed slightly and shrunk.. the nero i bough came with 4 hrbs 6000mah puffed. But i though it was because of the adaptor he use. I have a firma 2050kv motor. If the new spektrum motors are around 1900kv and the 2000kv one is around 2000kv or more would it be more suitable to put the 2050kv in @LibertyMKiii ? I know its not speed run related but i think these are pretty interesting findings about the true KV ratings. People upgrading to lower kv but turns out they are not really getting an upgrade( for example if you buy a 1700kv motor who is the same lenght but turns out its truly a 1800kv motor so 100kv lower than stock instead of 350kv.)
 
Surchaufeur said:
Interesting. Wish i could test my arrma 2000kv motor. My nero gets very hot on the stock gearing. Reminds me of my oitcast 4s by how hot the motor and wires get. My second old pair of lipos puffed slightly and shrunk.. the nero i bough came with 4 hrbs 6000mah puffed. But i though it was because of the adaptor he use. I have a firma 2050kv motor. If the new spektrum motors are around 1900kv and the 2000kv one is around 2000kv or more would it be more suitable to put the 2050kv in @LibertyMKiii ? I know its not speed run related but i think these are pretty interesting findings about the true KV ratings. People upgrading to lower kv but turns out they are not really getting an upgrade( for example if you buy a 1700kv motor who is the same lenght but turns out its truly a 1800kv motor so 100kv lower than stock instead of 350kv.)
Click to expand...

Unless the original motor has an issue, I doubt that motor change will make a big enough difference. I am not well versed in bashing motor setups but it seems people like the 1600-1700kv range a lot from what I read.
 
LibertyMKiii said:
Unless the original motor has an issue, I doubt that motor change will make a big enough difference. I am not well versed in bashing motor setups but it seems people like the 1600-1700kv range a lot from what I read.
Click to expand...
I seem to be the only one complaining about the stock nero motor. I have to hold back. Even then the motor gets boiling hot, wires too hot to touch. Something is funny with it i have an increased ride height so it goes over pretty much everything effortlessly
 
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