I've always wondered if vortex generators would a worthwhile addition to a commuter car because any money not spend on work related expenses is like giving oneself a little raise. Youtube and forum responses are either exaggerating fan-boy or doubting cynic. My last car was a jeep liberty diesel and with the aero of a medium-sized cinder block I've never had the opportunity to find out. Enter Nissan Leaf. I 3d printed some vortex generators from thingaverse and taped them to the roof of my 2012 leaf and did test to see if it would help improve the economy and so increase the range. in short, the result was yes but not very much, adding about 1 mile range to the 60 miles the car can go now, or almost 2% better (.1 m/kwh) economy. The air temperature did increase from 47F to 54F, because I was driving outside, and it might the case that the thinner, warmer air is partly attributable for the .1m/kwh because the control mileage did increase a little. Also a better design for the vortex forming chute, more like the airplane/aerospace design and less like the gimmick airtab design might make the improvement more dramatic.
I ran two control tests to warm everything up, 1.25miles back and forth on a strait flat country road. 47F-54F, 5 bars on the battery temperature meter for the whole test. stead 55mph with the cruise on, no HVAC, seat heaters, radio, lights, etc. tires were pumped to 45PSI cold. I reset the instant economy calculation once at the 55mph test speed and no regen braking was applied in the 1.25 miles, I recorded the number with the cruise still on, when I stopped the car and turned around the economy really jumped up due to the regen braking so the was defintly not included in the data. I repeated the test two time in the sequence control-control-1-2-3-control-2-3. location 1 was not an improvement after the first test so I did not repeat it.
location 1 was 10x vortex tabs at the seam where the hatch meet the roof, typically where these things are placed on race cars with huge rear wings, it reduced m/kwh economy 1% meaning the additional drag was outweighing any benifit. location 2 was right over the B pillar at the highest point on the roof line, giving fast, clean air. this location improved m/kwh economy 1.8%. the last test location was on the hood right up at the cowl, that improved m/kwh economy 1%. here are photos of the test locations. and the data summery spreadsheet.
raw data and data summary: