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.
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??