# Warp 9 on an engine dyno



## dcb (Dec 5, 2009)

re: 84s, do you mean 7.5vx84 or 3.75vx84?

"Obviously" we want to know motor voltage and current vs battery voltage and current vs rpm and torque, and motor temp (might do battery temp/controller temp). Not sure what to add.


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## jwiger (Oct 18, 2014)

3.75x84
The pulls will be shorter than a drag run, so not sure how relevant the motor temps will be. 

I'm tempted to find peak torque, then basic fractions of that to map out efficiency. 

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## dcb (Dec 5, 2009)

oh sure, if you can do multiple runs definitely would be interesting to see battery power vs motor electrical power vs different rpms and torques at something besides full throttle (though motor temp might come in to play).


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## jwiger (Oct 18, 2014)

Yeah, agreed on the temp there. 

He is used to people bringing in newly built engines that need initial start, break-in, then tuning. So the lack of break-in and tuning is what he's looking forward to most. 

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## brian_ (Feb 7, 2017)

jwiger said:


> I found a nearby engine dyno cell that is very interested is seeing what an electric motor does on their dyno.





jwiger said:


> The pulls will be shorter than a drag run, so not sure how relevant the motor temps will be.


If they're that short, that suggests to me that it's not much of a dyno - probably just one of those flywheel machines that can't apply a sustained load. Unless you're assessing performance specifically for drag racing, I'm not sure how useful this will be, and all data will be peak values rather than continuous.

It would be nice if the run could start from zero speed, run to the maximum operating speed of the motor, and as dcb suggested be repeated at different voltages. If you really want to map out efficiency, you need to cover the map, not just the full-power edge of it. The dyno probably won't measure anything other than the speed of the rollers/flywheel, and will calculate power and torque from that.


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## dcb (Dec 5, 2009)

brian_ said:


> and all data will be peak values rather than continuous.


Well, it will be continuous acceleration data 




brian_ said:


> and as dcb suggested be repeated at different voltages.


FWIW I Wasn't suggesting different voltages (i.e. change pack voltage), just different motor current levels. i.e. a run at 2000 amps (probably gotta limit the pack above 1000 rpm), 1500, 1000, 500, 100. I don't expect any surprises, just something of an efficiency map in the data. Or to keep it simple, just different throttle settings. Oh don't forget to capture throttle setting.

edit: evtv did a number of pulls @ 1000 amps. They got a more complete picture with it in top gear.
http://evtv.me/2011/11/elecobra-the-thrill-of-victory-and-the-agony-of-the-feet/


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## brian_ (Feb 7, 2017)

brian_ said:


> It would be nice if the run could start from zero speed, run to the maximum operating speed of the motor, and as dcb suggested be repeated at different voltages. If you really want to map out efficiency, you need to cover the map, not just the full-power edge of it.





dcb said:


> FWIW I Wasn't suggesting different voltages (i.e. change pack voltage), just different motor current levels.


Sure, that would probably be easier to manage, and achieves the same result of covering the range of operating conditions. Different motor current (at the same speed) will mean different motor voltages (at that same speed)... and of course I did mean *motor* voltage, not pack voltage; why would anyone change the pack to test the motor? That would be like changing the entire fuel and induction systems of an engine instead of just running at part-throttle.


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## dcb (Dec 5, 2009)

brian_ said:


> and of course I did mean *motor* voltage, not pack voltage; why would anyone change the pack to test the motor?


I don't know, that is why I made the correction to motor CURRENT (~throttle/torque) not voltage. The current is what is being controlled, so why would you suggest controlling the motor voltage?


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## brian_ (Feb 7, 2017)

dcb said:


> ... that is why I made the correction to motor CURRENT (~throttle/torque) not voltage.


It's not a correction, since there was nothing incorrect; however, since you're still beating the dead horse with essentially the same remark, the answer is the same:


brian_ said:


> Sure, that would probably be easier to manage, and achieves the same result of covering the range of operating conditions. Different motor current (at the same speed) will mean different motor voltages (at that same speed)...





dcb said:


> The current is what is being controlled, so why would you suggest controlling the motor voltage?


Again...


brian_ said:


> If you really want to map out efficiency, you need to cover the map, not just the full-power edge of it.


If all you have is the throttle pedal input to a controller, then it would make sense to run the thing at something like 1/4, 1/2, 3/4, and full, because that will still cover the operating condition range.


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## dcb (Dec 5, 2009)

brian_ said:


> and as dcb suggested be repeated at different *voltages*.


I didn't suggest that, because it is stupid.


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## Frank (Dec 6, 2008)

Any feedback you could share from these tests?


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## jwiger (Oct 18, 2014)

Frank said:


> Any feedback you could share from these tests?


I'm still in Europe. I won't be able to get it before January. 

Thank you for the interest!

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## John Metric (Feb 26, 2009)

Maybe we could go with you. I would like to dyno my motor. We are in houston. What part of central TX are you?


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## GoElectric (Nov 15, 2015)

Keep us posted.


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## coleasterling (Feb 29, 2012)

I'd be interested in seeing this, as well. I'm in BCS.


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## jwiger (Oct 18, 2014)

John Metric said:


> Maybe we could go with you. I would like to dyno my motor. We are in houston. What part of central TX are you?


John, I'm in the Ft. Hood area, an hour north of Austin. Unfortunately I still haven't been paid from my last deployment, so I still don't have batteries to test with. 

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