Castle Datalog Question

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KiTris ExtremeRC

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Arrma RC's
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So I was doing some speed runs last week with my new MMX8s and I need some help regarding the data logs.
First of all is there still an amp limit/bug on the MMX8s like there is on the XLX? And how accurate is the motor rpm and is there a difference between sensored/sensorless operation in terms of reading accuracy.
I want to calculate my speed with the motor rpm as my current GPS is really inaccurate. With 2 similar passes one was 60mph and the other one 112mph accordingly to the GPS.
I'm not planning on breaking any speed records I just want to have more or less accurate way to measure my speed as I don't want to spent a lot of money on a nice GPS currently, maybe at some point in the future though :)
 
You can grab that GSM020 SKYRC from RcJuice for 69.00 shipped. I bought one a few days ago. It should be here today. I have no experience with it but it was recommended by a well known user up here and a ton of people online (youtube) use it.
I live in Germany so that's not an option for me but they are sold here as well I think. Would be still interesting to know how accurate the Datalog is. I might be doing a test with 60mph gearing and then compare it to the datalog.
 
So I was doing some speed runs last week with my new MMX8s and I need some help regarding the data logs.
First of all is there still an amp limit/bug on the MMX8s like there is on the XLX? And how accurate is the motor rpm and is there a difference between sensored/sensorless operation in terms of reading accuracy.
I want to calculate my speed with the motor rpm as my current GPS is really inaccurate. With 2 similar passes one was 60mph and the other one 112mph accordingly to the GPS.
I'm not planning on breaking any speed records I just want to have more or less accurate way to measure my speed as I don't want to spent a lot of money on a nice GPS currently, maybe at some point in the future though :)

I can tell you there has not been any seen Amp limiting so far on the MMX8s.
I can help you break down the actual speed based on motor RPMs if you have not figured it out already. Not sure about RPMs in logs with sensored versus un-sensored. That would be interesting to see. The ESC knows where the motor is at all times otherwise it wouldn't run right at all. Plus it reads the back emf. I suspect the RPM values are pretty darn accurate. The amperage values on the other hand are an estimated number based on an algorithm.

This was my Typhon 6s using the MMX8s (no cap pack) factory BLX2050kv motor.
The speed was 119 on GPS. You can see the dark red line was held at that peak speed a very short time. GPS saw 119 and my calculations show it was likely closer to 130 but the GPS didn't get enough time to read that speed. Also the throttle at 1.848 was not full throttle ;)
Typhon 119mph 8s Capture.PNG
 
I can tell you there has not been any seen Amp limiting so far on the MMX8s.
I can help you break down the actual speed based on motor RPMs if you have not figured it out already. Not sure about RPMs in logs with sensored versus un-sensored. That would be interesting to see. The ESC knows where the motor is at all times otherwise it wouldn't run right at all. Plus it reads the back emf. I suspect the RPM values are pretty darn accurate. The amperage values on the other hand are an estimated number based on an algorithm.

This was my Typhon 6s using the MMX8s (no cap pack) factory BLX2050kv motor.
The speed was 119 on GPS. You can see the dark red line was held at that peak speed a very short time. GPS saw 119 and my calculations show it was likely closer to 130 but the GPS didn't get enough time to read that speed. Also the throttle at 1.848 was not full throttle ;)
View attachment 95584
Thank you for the detailed feedback, this is really helpful. With the amp limiting I meant the "bug" the XLX has where the reading is only accurate to something around 270A or so. And would be interesting to know if the MMX8s has the same issue/bug.
That's great to know that the RPMs are really accurate. That would mean that I went 120mph (112mph on GPS) with a 2200kv sensored on 8s with the Infraction.
My goal is to reach 125mph. It should be possible with this setup I think. My biggest issue now is finding a suitable road (kind of difficult here in Germany ?).
 
Thank you for the detailed feedback, this is really helpful. With the amp limiting I meant the "bug" the XLX has where the reading is only accurate to something around 270A or so. And would be interesting to know if the MMX8s has the same issue/bug.
That's great to know that the RPMs are really accurate. That would mean that I went 120mph (112mph on GPS) with a 2200kv sensored on 8s with the Infraction.
My goal is to reach 125mph. It should be possible with this setup I think. My biggest issue now is finding a suitable road (kind of difficult here in Germany ?).
As far as I know the MMX8s does not measure amps, but makes a calculation so the readings for amps are imaginary.

I have the same issue related to roads. My best road is over 1 hour away. And honestly its not good enough...
I wish airports were more open to RC cars running

It sounds like you are too close to your goal. Time to up that goal ;)
 
I haven’t heard of anyone reporting a max amp output report on the MMX8S. I’ve seen mine report over 350A on a pass. I will let you know how my pass goes tomorrow if weather allows. Was hoping for today but work is holding me back.
 
I can tell you there has not been any seen Amp limiting so far on the MMX8s.
I can help you break down the actual speed based on motor RPMs if you have not figured it out already. Not sure about RPMs in logs with sensored versus un-sensored. That would be interesting to see. The ESC knows where the motor is at all times otherwise it wouldn't run right at all. Plus it reads the back emf. I suspect the RPM values are pretty darn accurate. The amperage values on the other hand are an estimated number based on an algorithm.

This was my Typhon 6s using the MMX8s (no cap pack) factory BLX2050kv motor.
The speed was 119 on GPS. You can see the dark red line was held at that peak speed a very short time. GPS saw 119 and my calculations show it was likely closer to 130 but the GPS didn't get enough time to read that speed. Also the throttle at 1.848 was not full throttle ;)
View attachment 95584
Watch that voltage ripple!
 
As far as I know the MMX8s does not measure amps, but makes a calculation so the readings for amps are imaginary.

I have the same issue related to roads. My best road is over 1 hour away. And honestly its not good enough...
I wish airports were more open to RC cars running

It sounds like you are too close to your goal. Time to up that goal ;)
Yeah I was on vacation for a few days and the area where I went is way less populated (still in Germany). And before sunset there was no one on the road left so I was able to make a few passes. I wanted to try out different motor combinations (CC 2200kv / TP 2300kv / CC 1650 1717) but I only managed to really test out the 1515 and two passes with the TP but both ended up in crashes at 110mph+. Only managed to break one body mount which is quite impressive?.
But I keep my eyes open for a suitable road.
I haven’t heard of anyone reporting a max amp output report on the MMX8S. I’ve seen mine report over 350A on a pass. I will let you know how my pass goes tomorrow if weather allows. Was hoping for today but work is holding me back.
My datalog showed over 390A that's why I asked about the bug. Because it seems really high for the 27/34 gearing I went with :)
 
Another ignorant question about these gsm's: can they be used to track your vehicle too, say if it were stolen or lost in the woods?
 
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