Quote:
Originally Posted by aerohead
here are some numbers I pencil-whipped for the Chevy BOLT I'll be getting in September.
I used Cd 0.31, Af 25.7-sq-ft, 0.00238 slugs air density, and 3,880-lb test weight.
Aerodynamic horsepower requirements are presented in 5-mph increments, from zero-to 100-mph:
0-mph = 0
5-mph = 0.0067
10-mph = 0.054
15-mph = 0.183
20-mph = 0.435
25-mph = 0.8497
30-mph = 1.4683
35-mph = 2.3316
40-mph = 3.4805
45-mph = 4.9557
50-mph = 6.7979
55-mph = 9.048
60-mph = 11.7468
65-mph = 14.9351
70-mph = 18.6535
75-mph = 22.943
80-mph = 27.8444
85-mph = 33.3983
90-mph = 39.6456
95-mph = 46.6371
100-mph = 54.3836
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Over the same speed spread, power absorbed from rolling-resistance increased linearly, from zero, to 8.9873-hp ( using a Cfrr of 0.008686291 ( probably 'high' )) [ Bridgestone Ecopia is around 0.005 ].
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If everyone constructs one of these tables from 'day one', 'curves' can be constructed from the data-plots for aero and R-R, plus adjustment for mechanical efficiency, and presuming a constant BSFC, or BSFC-e for BEVs, one can predict, at any chosen velocity, what mpg, or 'range' their vehicle will return.
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With EV's the speed has a greater effect on range since the efficiency of the motor doesn't go down so much at lower speeds.
I remember when I had the Nissan Leaf that someone had done the work to figure out what speed would give the Leaf the greatest range, and it was 12mph.
I would sometimes start a long trip creeping along at 25mph which would give me quite a range advantage, sometimes getting over 100 miles with juice to spare in an EV that had an advertised range of 71 miles at that point.