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13.5 boost timing question

Got some questions for motor timing. I see people using Skyrc analyzer to find the 6amp optimized timing. And I doubted about:

1. How accurate is this Skyrc optimized timing under no load compare on a real dyno? There is no torque measurement....
2. What is the point of finding the Skyrc optimized timing then adjust the boost/turbo on the ESC? Isn't it making the Skyrc optimized timing pointless?

This 3 part write up should answer your questions. Read it all, and ask any questions you have after that.

There is a linear relationship between current and torque if timing is correct. the sky rc does not look at timing in a way that allows you tp correct the timing errors. it does a good job of telling you the physical relationship between the sensors and the rotor. it does not help you correct the timing as the magnetic fields distort from torque and rpm increase.

lets look at this from the opposite side of the logic. Your motor can be efficient (heat to power ratio) or very powerful (torques per rpms). it can never be both at the same time but you can manipulate timing to do 3 things. it can be neither powerful or efficient. it can be one or the other and everything in between.

in terms of how we apply this in onroad. Powerful means you can have a higher frequency of accelerations or higher amplitude of acceleration at the expense of how long you can do it for. efficiency means you sacrifice a little frequency or amplitude of the car to be able to extend the duration you can run the RC for.

A motor dyno can help you calculate the timing plus timing distortions that get you peak power or efficiency. a chassis dyno allows you to measure the influence the mechanical system of the car has on the motor and also include the ability to understand the previous sentence. You still cannot get an understanding of duration with a chassis dyno... just efficiency and peaks are possible the same as a motor dyno. All previous comments about a dyno were specifically about an inertia dyno.

A load dyno will help you understand the previous paragraph plus duration (heat).

Lets go back to the beginning. torque and current are linear or to simplify lets say equal if your distortions (timing) are accounted for. the sky rc only tells you the relationship between the sensors and the rotor. the number that the manufacturer provides is an average torque/rpm that they calculated so that the sky rc does something more than just the sensor relationship. its a number that they decided was somewhere below the duration curve (continuous duty). this number has real torque curve for peak and continuous data behind it. behind that is efficiency, heat, frequency, amplitude, and a massive amount of assumptions about ESC efficiency and mechanical load (which also includes the influence the track has on the motor).

this is why the number they give you may or may not be good to use in the sky rc. we dont race in a lab but the number is usually very robust. it takes into account a range of all of these things. it may get you all the results you can feel or measure but its rarely perfect. that is why its considered a starting point.

Quote:

Originally Posted by Bry195 (Post 15374542)

there is a linear relationship between current and torque if the timing is correct. the sky rc does not look at timing in a way that allows correct the timing errors when it in your RC. it does a good job of telling you the physical relationship between the sensors and the rotor. it does not help you correct the timing corrections that need to be made as the magnet fields distort as torque and rpm increase.

lets look at this from the opposite side of the logic. Your motor can be efficient (heat to power ratio) or very powerful (torques per rpms). it can never be both at the same time but you can manipulate timing to do 3 things. it can be neither powerful or efficient. it can be one or the other and everything in between.

in terms of how we apply this in onroad. Powerful means you can have a higher frequency of accelerations or higher amplitude of acceleration at the expense of how long you can do it for. efficiency means you sacrifice a little frequency or amplitude of the car to be able to extend the duration you can run the RC for.

A motor dyno can help you calculate the timing plus timing distortions that get you peak power or efficiency. a chassis dyno allows you to measure the influence the mechanical system of the car has on the motor and also include the ability to understand the previous sentence. You still cannot get an understanding of duration with a chassis dyno just efficiency and peaks are possible the same as a motor dyno. All previous comments about a dyno were specifically about an inertia dyno.

A load dyno will help you understand the previous paragraph plus duration (heat).

Lets go back to the beginning. torque and current are linear or to simplify lets say equal if your distortions (timing) are accounted for. the sky rc only tells you the relationship between the sensors and the rotor. the number that the manufacturer provides is an average torque/rpm that they calculated so that the sky rc does something more than just the sensor relationship. its a number that they decided was somewhere below the duration curve (continuous duty). this number has real torque curve for peak and continuous data behind it. behind that is efficiency, heat, frequency, amplitude, and a massive amount of assumptions about ESC efficiency and mechanical load (which also includes the influence the track has on the motor).

this is why the number they give you may or may not be good to use in the sky rc. we dont race in a lab but the number is usually very robust. it takes into account a range of all of these things. it may get you all the results you can feel or measure but its rarely perfect. that is why its considered a starting point.

Well put!!

The Sky RC motor analyzer is also useful for approximating the point of diminishing return with timing adjustment. You can make a table whereby you do a Kv/RPM measurement at different timing settings within the motor's usable range. Looking at the range, it should be apparent where Kv and RPM are no longer rising at a beneficial rate against a timing adjustment. I found the new "short stack" motors I have like less timing (and consequently, show a lower unloaded amp draw), which I am guessing is because of lower resistance winding, while a couple of my older motors responded better to higher timing settings. It's by no means as useful as a loaded dyno, but it's better than simply "timing to temperature", and the difference is noticeable in how the car runs.

You had a second question about using the sky RC to get timing and current and then adjust boost.

The target number the MFG provides is a well thought out number but its usually not perfect for all the reasons i mentioned previously. Boost makes up for the difference between the prediction the mfg made about the application in a laboratory (very conservative number) and what you need for your drive train, ambient temp, track, wear, ...

I discovered (maybe others have too) that if I set the end bell to say 5.6 amps and it results in 47 degrees of timing that the power/efficiency curve below 10k is not as good as if i set the end bell to something less. On the 17.5 I squeezed what i wanted out of the low rpms of the motor at about 39 degrees and it was significant. Then i trickled in timing at about 8k in the form of boost. You can look at some of the pictures i posted previously and you will see the transition point im talking about as a small notch in the torque curve.