LEAF Dyno Run

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TLeaf

Well-known member
Joined
Aug 7, 2010
Messages
247
Location
Renton, WA
So I finally caved and scheduled an appointment with a dyno for last Friday.. Though I have to admit to being a bit nervous about the whole process (I've watched a few too many dyno failure videos), the whole thing turned out to be pretty fun. Showing up at the shop "early" in the morning (they had only just opened up at 10:30am), it took a bit of time for them to clear away the dyno area, but once that was done, the car was hooked up and ready to go sooner than I would have expected (once again, cue fear of car flying off of dyno).

The first few minutes on the dyno were spent slowly ramping the motor up in speed in order to make sure everything was tied down securely. This was also a good time for the tech to learn how to operate the car and share a few laughs with his co-workers ("Hey, you better turn off those headlights to get another 5hp!"). After that, it was time for the real deal! Though this is where some car owners would turn away, I watched in fascination as the tires on the car first squealed in protest and then quickly ramped up to a reported 97mph. The procedure happened a second time and, before I knew it, the whole endeavor was over. 30 minutes, start to finish.

Shown here is the graph for the two official dyno runs. In both cases the car was in 'drive', but one involved mashing the accelerator while the other involved a neutral drop. Though the lines do look a bit different between the two, I'd be highly dubious about both lines below 30mph as the wheels on the LEAF were definitely outpacing the dyno on both runs at this point. As much as I'd like to say that the LEAF simply had too much torque for the the dyno to keep up, I'm sure it was some combination of both high torque and the low rolling resistance tires. In any case, note that this is a horsepower vs. speed graph as we had no way to measure motor RPMs. Since we're talking about a single-speed car, however, the two graphs should look identical.

On the matter of torque, owing to the same lack of RPM monitoring, I'm afraid we couldn't get any official torque numbers.. Though some would therefore consider this a wasted outing, the changed attitude of the tech after the dyno runs was priceless. Whereas before he was indifferent to the whole matter of testing an electric car, after the fact I believe he was an EV convert. Besides, since we're talking about a single-speed car, I wonder if we could do some back-calculating to go from vehicle speed to RPMs. According to this link, the relation between horsepower and torque is straightforward enough in which case we should end up with something very similar to the typical declining torque "curve" of a DC motor. This has me a bit confused as I could have sworn the LEAF has an AC synchronous motor which operates a bit differently. Any takers??
 
Awesome stuff there.

Figuring the motor RPM should be very straight forward, and at 95-ish mph, you should have had 10,300 RPM, therefore 47.5 mph would be 5,150 RPM. Right there is your torque / hp equal mark, so 105 hp was about 105 ft/lbs of torque.

I get about 212 ft/lbs of torque at [edit: about 3200 RPM], assuming 105hp there. The motor is definitely AC, as there is an inverter for the battery (your valve cover under the hood).

You could reasonably guessimate the RPM at various points to determine torque using the classic formula, HP = (Torque x RPM) / 5252

http://en.wikipedia.org/wiki/Horsepower
 
That is an impressively flat horsepower curve right there!

Most ICE vehicles would die to get a curve that flat, though the 105 hp peak isn't much to write home about. :)

Thanks for doing this - given the wheelspin you were seeing I'd have to assume that the actual peak may be a bit higher at lower speeds...
 
I watched with great interest as they do a rolling/dyno tested on each LEAF as they come off the line at the Nissan Oppama factory. They take each car up to about 100 kpm with no tie downs! Saw one Juke really squirling (sp?) around for half a second but the driver got it all straightened out.

Most disappointing thing about the factory tour? NO PICTURES. ARGHHH!!!
 
BTW, where are the directions for uploading pictures? I see where you can give a URL link, but can't I just upload pics? I DO have some pictures from both the Factory tour and Nissan's global world HQ, and would like to post them with the details of both places.

Got a great screen shot showing all the local L2 an L3 charging stations in an area about the same size as Seattle Metro area. GREEN with envy on the availability of free charging stations all over the place.
 
Some years back when we picked up our BMW at the factory in Munich on the EDP, we were given a factory tour that was incredible, and sure to give U.S. OSHA heart attacks! Among many other things, we were walking between the robotic chassis wielders with sparks flying right over our heads and no hard hats! One person even had a spark land in their hair. The tour was about three hours long and they actually encouraged us to take pictures. Due to demand and very small groups, the tours had to be scheduled months in advance (though if you were picking up a new car, they would fit you in regardless). Most fascinating!

GoSolar said:
I watched with great interest as they do a rolling/dyno tested on each LEAF as they come off the line at the Nissan Oppama factory. They take each car up to about 100 kpm with no tie downs! Saw one Juke really squirling (sp?) around for half a second but the driver got it all straightened out.
Most disappointing thing about the factory tour? NO PICTURES. ARGHHH!!!
 
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cool
 
TLeaf said:
So I finally caved and scheduled an appointment with a dyno for last Friday.
Thanks for doing that! Very interesting stuff!

TLeaf said:
In both cases the car was in 'drive', but one involved mashing the accelerator while the other involved a neutral drop.
[...]
Though the lines do look a bit different between the two, I'd be highly dubious about both lines below 30mph as the wheels on the LEAF were definitely outpacing the dyno on both runs at this point. As much as I'd like to say that the LEAF simply had too much torque for the the dyno to keep up, I'm sure it was some combination of both high torque and the low rolling resistance tires.
Plus, dynos rarely produce measurements below 2000 rpm or so. A quick search of dyno graphs bears that out. The straight lines below 20 mph (about 2200 rpm) in your graph seem to be extrapolated values and not actual values.
 
My interpretation of this curve is the LEAF would benefit from a two speed transmission if you were optimizing for highway mileage. It appears after 30 mph the increase in RPM is decreasing the torque such that the horsepower is remaining flat.

The Tesla Roadster originally had a two speed transmission - they just couldn't get it to work in time so they gave up.

To me this explains why the highway energy consumption is so high - the electric motor is not very efficient at high RPM. This goes beyond the v squared issue of wind resistance.

This is also confirmed by the Chevy Volt which has a highway mode which couples the electric generator to the engine so the traction motor can spin slower.
 
evmike said:
The Tesla Roadster originally had a two speed transmission - they just couldn't get it to work in time so they gave up.
Yeah - but instead they improved the efficiency of the power electronics which allowed them to meet their performance requirements (the primary reason for the transmission - they _really_ wanted a < 4s 0-60 time) AND the overall efficiency went up a good amount, too!

The LEAF would be better off getting the Cd reduced from 0.29 to 0.27 or lower - doing that would improve highway range by 5% without any extra complexity. If a Toyota Camry can get a Cd that low...
 
Considering the car is rated for 110HP, that is very little drive line loss. An automatic ICE would lose anywhere from 15% to 20%. This only loses 4.5%!

Thank you for doing this!

-Alex
 
drees said:
The LEAF would be better off getting the Cd reduced from 0.29 to 0.27 or lower - doing that would improve highway range by 5% without any extra complexity. If a Toyota Camry can get a Cd that low...

But I doubt a Camry has less wind noise. I will take less wind noise any day to a lower cd with more wind noise.
 
Herm said:
You would suffer the headache of a transmission to get at extra 5% at 75mph?.. please..

Where did you get the extra 5 % number? Does Nissan publish data for the motor?
 
evmike said:
Herm said:
You would suffer the headache of a transmission to get at extra 5% at 75mph?.. please..

Where did you get the extra 5 % number? Does Nissan publish data for the motor?

There is a graph in a magazine published by the SAE people, but I got it from the chart posted at the top of this thread.. its a typical number for this class of automotive motor/inverter.. obviously it has been designed for its optimum point to be around 40 mph, right at the average speed most people drive and the EPA does its city and highway cycle tests.. Volt is the same way.

Damn, Google is good, here is the magazine, I think its the one, will download and check it later:

http://www.electricauto.org/resource/resmgr/media/nissan_leaf_sae_2_11.pdf" onclick="window.open(this.href);return false;
 
GoSolar said:
BTW, where are the directions for uploading pictures? I see where you can give a URL link, but can't I just upload pics? I DO have some pictures from both the Factory tour and Nissan's global world HQ, and would like to post them with the details of both places.
You can't upload pics directly from your local computer on this forum. That feature has not been turned on in this implemention of the phpBB software, probably to save storage space and bandwidth charges, as images greatly increase hosting requirements. The pictures that appear here must be hosted on another internet site and then linked in your post with the function of the BBCode (see [url=http://www.mynissanleaf.com/faq.php?mode=bbcode#f5r0]this link[/url] and the [url=http://www.mynissanleaf.com/viewtopic.php?f=6&t=2456]image FAQ here[/url]). If you don't have a personal website to upload the images to, get an account at one of the popular hosting sites (Flickr, Photobucket, Imageshack, etc.) and upload them there.

TT
 
Cd alone is not the whole picture. You need to look at both Cd and frontal area. Thus a car with a low Cd but high frontal area can have more drag that a car with a high Cd but low frontal area. You need to look at the product of both to get the true drag picture.

drees said:
The LEAF would be better off getting the Cd reduced from 0.29 to 0.27 or lower - doing that would improve highway range by 5% without any extra complexity. If a Toyota Camry can get a Cd that low...
 
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