Exclusive first Model 3 Dyno

[MountainPass]

Don't worry about the "speed" displayed on the dyno plot. The dyno just uses a standard tire circumference to display speed, and it is irrelevant as we don't use that value for anything, nor does it play into the calculation of torque or power - this is a hub dyno, so the dyno measures hub RPM directly.

Here is a dyno plot with Motor RPM and accurate wheel speed on the X-axis.

 

[D3xDt3Reaction]

Don't worry about the "speed" displayed on the dyno plot. The dyno just uses a standard tire circumference to display speed, and it is irrelevant as we don't use that value for anything, nor does it play into the calculation of torque or power - this is a hub dyno, so the dyno measures hub RPM directly.

Here is a dyno plot with Motor RPM and accurate wheel speed on the X-axis.

View attachment 328001

Thanks - that looks better, although at e.g. 10000 rpm I would have expected a ground speed of 140 kph instead of 134 kph. What am I missing?

10000 rpm / 9 final drive ratio = 1111 hub rpm / 60 sec/min * 82.7 in tire cir / 12 in/ft = 127.6 ft/s * 3600 sec/h / 3280.84 feet/km = 140 kph

 

[JRP3]

Is the final drive ratio in fact exactly 9?

 

[MountainPass]

Thanks - that looks better, although at e.g. 10000 rpm I would have expected a ground speed of 140 kph instead of 134 kph. What am I missing?

10000 rpm / 9 final drive ratio = 1111 hub rpm / 60 sec/min * 82.7 in tire cir / 12 in/ft = 127.6 ft/s * 3600 sec/h / 3280.84 feet/km = 140 kph

Small difference in tire circumference. You also need to measure rollout to get true circumference - not just whatever it measures out or a tire calculator website calculates. This is based on speeds reported by the car's CAN bus and matched to our GPS antenna +/- 1.5%

 

[insaneoctane]

Don't worry about the "speed" displayed on the dyno plot. The dyno just uses a standard tire circumference to display speed, and it is irrelevant as we don't use that value for anything, nor does it play into the calculation of torque or power - this is a hub dyno, so the dyno measures hub RPM directly.

Here is a dyno plot with Motor RPM and accurate wheel speed on the X-axis.

View attachment 328001

Didn't you guys do SOC of 100%?

 

[D3xDt3Reaction]

Small difference in tire circumference. You also need to measure rollout to get true circumference - not just whatever it measures out or a tire calculator website calculates. This is based on speeds reported by the car's CAN bus and matched to our GPS antenna +/- 1.5%

Fair. I realized I may not have even started with exactly the right theoretical circumference and you guys could have easily burned off some tread. Thanks for the explanation.

 

[SD_Engnr]

Next Wednesday, my Model 3 Performance and I have a date with a Dyno Dynamics AWD dyno.

Any tips/advice to help this date go smoothly, and to achieve accurate data?

@MountainPass @Mysterylectric

 

[Krash]

...I have a date with a Dyno Dynamics AWD dyno...Any tips...?

I would love a copy of the data in a CSV or similar format for the Performance Metrics. Think they'd give you that? Are you going to do multiple runs at different states of charge?

 

[SD_Engnr]

I would love a copy of the data in a CSV or similar format for the Performance Metrics. Think they'd give you that? Are you going to do multiple runs at different states of charge?

I will ask. The plan is 3 runs at whatever SOC I'm at when I get there. It's a 30 mile drive from work, which is a 13 mile drive from home. So, it may end up being less than ideal. There are a couple of destination chargers near the dyno, but I doubt I'll have luck with just driving up and plugging in. I'll give it a shot.

 

[Krash]

Definately charge to 100% at work and bring your mobile charger to top off at the dyno when they are setting up if you can't destination charge nearby. Looked like the RWD power topped off at 90%, so if you can get back to 90 that is a plus.

 

[SD_Engnr]

Definately charge to 100% at work and bring your mobile charger to top off at the dyno when they are setting up if you can't destination charge nearby. Looked like the RWD power topped off at 90%, so if you can get back to 90 that is a plus.

Unfortunately, there's no charging available at my workplace. I checked with the dyno place, and they don't even have a 14-50. My best bet is trying my luck with the 4 nearby places with destination chargers. I'll do my best to get it to 90% or higher.

 

[Krash]

Worst case, charge to 100% at home and moble charge at work before mobile charging at the dyno. It won’t hurt your car at all to do that once.

 

[Mysterylectric]

Next Wednesday, my Model 3 Performance and I have a date with a Dyno Dynamics AWD dyno.

Any tips/advice to help this date go smoothly, and to achieve accurate data?

@MountainPass @Mysterylectric

Dyno dynamics dynos read high. They also are funky with the torque, and the operator needs to be able to set the dyno up properly, or you’ll get a wild horsepower number and 200lb/ft of torque. This is what happened with the first model 3 we ran, and got 393hp for a car that should be getting 300-320. The dynojet and mustang dynos are both much more accurate. The dynojet we used during the dyno day was set very conservative, as we really didn’t want wild horsepower numbers. I think with some tweaking, we’d be able to get some spot on numbers, and with a lot of math, we should be able to get power per axle on a non linked dyno.