Victor Tikhonov wrote: > Mark Farver wrote: > > > > I ran my Ranger on a chassis dyno, both before and after > > conversion.
[...] > > but the results are interesting. > This is interesting data! > > Question 1: - the cliff position where constant torque turns into > constant power (4,400 RPM in your case) depends on the voltage. > What was the battery voltage during test? Looking at theoretical > curves for 5133 motor, sounds like the voltage was lower than 280VDC > during the test. http://www.metricmind.com/line_art/plot_all.gif > > Question 2: Why the curves end at 5,700 RPM? Question 3: what is the relationship between driveshaft RPM and motor RPM during the test? (If the ICE test was measuring engine speed while the EV test measured driveshaft speed, and the difference was not accounted for (implied by the remaining offset to the EV curves), then it seems like the power curves at least cannot really be interpreted as shown since power is proportional to torque x speed, and the speeds are not being measured at the same place... assuming they are measuring torque/HP at the drive wheels and using the RPM signal to compute HP/torque at the engine - and if they weren't, it seems they wouldn't need the sensor since rear wheel HP/torque could be obtained directly from the roller RPM & torque.) Question 4: why is the electric motor torque not flat all the way to 0 RPM (or at least to whatever RPM the test started at), as Victor's plots all show the drive is capable of? We EVers take pride in our vehicles' ability to beat most any ICE at low end torque, yet this dyno run makes it look like the EV has wimpy low end torque compared to the 2.5L ICE it replaced. Question 5: I gather from prior posts that you are running a string of Optima YTs; what is the pack voltage (I can't seem to find a message identifying that detail)? One wouldn't expect a healthy string of YTs to break a sweat delivering all the current your inverter can demand, so it seems odd that you shouldn't have gone home with a *really* head-turning dyno plot showing the flat torque from 0 to at least 2000RPM, and flat power until the rev limiter shuts things down (it does seem a shame to limit yourself to just 4500RPM when you could spin up to at least 8K (flywheel and clutch integrity allowing; 6000-6500RPM otherwise) and really turn heads at the dyno shop ;^> I suspect you would come away with a more impressive set of plots if you return for another run once your pack is cycled in a bit and in better balance, and at a decent state-of-charge. Thanks for sharing the data! Cheers, Roger.
