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Okay so I finally found a farm road during my Idaho road trip to do coast down testing
There was one stretch of flat road that was perfect but not very long
Found 2 marker signs and did a base line test with windows up
Test started around 73 mph and when I reached the second marker, the speed was 68 mph
Did the windows down test, and it was 66 mph at the second marker
So 2 mph drop thanks to drag
Did my cardboard wheel skirts, speed dropped from 73 down to 69 mph
Only a 1 mph change. But it clearly worked. The results show that all 4 windows rolled down causes more drag than the gain you get from wheel skirts ( obviously!) also- with the wheel skirts, acceleration out of the parking lot felt more stable and actually faster. Hard to explain.
So what I’m asking is- how many cd points does the windows down add to your average vehicle, or how much drag percent is added based on the 2 mph slower test I just mentioned. Once we find that out, we could half that and say that’s how many cd points I’d be lowering with rear fender spats?
Math anyone?
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