RPM vs. Speed ?

[conv90]

Is there a formula or a table to calculate the rpm at a given speed?
Example: at 10k rpm which is the speed ?

 

[jjrandorin]

what about the RPMs on an electric motor is relevant?

 

[SSedan]

If you know rpm or speed you can figure out the other if you know tire diameter and gear ratio.

I don't really know what good this info is for an EV. In an ICE in know what can be done with this data but an EV not so much

 

[gavine]

I don't know how to do the math for this, but if you calculate the tire outer diameter and the 9.73:1 gear ratio, you can figure-out the motor RPM at any given speed. If I recall, the cars with 155mph top speed have a motor RPM of around 18,000.

 

[conv90]

Yes, is relevant.
Because the torque curve in a Model 3 (or any other ev car) is managed and corrected by software.
So, if I know for example that the LR AWD Torque curve is starting to fall (it's the software doing it..) at 5000Rpm and I know that 5000rpm is example 40 mph (or 50 or 70 or 25...) I know that past this speed the response to the pedal is slightly less than when at lower speed.
In a Model 3 the torque curve is maintained constant up to about 5000 rpm then via software it starts to decrease gradually.

 

[Zoomit]

calculate the tire outer diameter and the 9.73:1 gear ratio

BTW, this needs to be squashed tire diameter, not spec diameter.

 

[conv90]

I don't know how to do the math for this, but if you calculate the tire outer diameter and the 9.73:1 gear ratio, you can figure-out the motor RPM at any given speed. If I recall, the cars with 155mph top speed have a motor RPM of around 18,000.

...and yes, the 9.73:1 was my missing data.
Thanks!

 

[gavine]

...and yes, the 9.73:1 was my missing data.
Thanks!

The following link shows a lot of detail that might interest you. There, they say that the smaller motors have a different ratio -->

Undocumented | TeslaTap

 

[Zoomit]

The following link shows a lot of detail that might interest you. There, they say that the smaller motors have a different ratio -->

Undocumented | TeslaTap

This is the Model 3 subforum so I presume the ratio of interest here is 9.04:1. I haven't heard of any other gear reduction ratio for the Model 3.

My rough measurement of the rolling radius is 319mm (12 9/16"), as measured from the ground to wheel rotation axis. This compares to the tire radius spec of 336mm (13.2").

 

[kbecks13]

Here's some data from MPP dyno testing

https://i0.wp.com/www.mountainpassp...8/08/Tesla-Model-3-SOC-Dyno-Results.jpg?ssl=1