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Old 05-02-2020, 01:33 AM   #10 (permalink)
Cyborg ECU
California98Civic's Avatar
Join Date: Mar 2011
Location: Coastal Southern California
Posts: 6,297

Black and Green - '98 Honda Civic DX Coupe
Team Honda
90 day: 66.42 mpg (US)

Black and Red - '00 Nashbar Custom built eBike
90 day: 3671.43 mpg (US)
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Originally Posted by JulianEdgar View Post
I got impatient and tried some testing in very strong winds. However, the results were too inconsistent to be useful. So while you can test in some wind, really strong winds appear to be too variable, even over a 5 second or so average of top speed.
Yes. That makes sense. Real world conditions are not really an advantage because we are talking about uncontrolled variables changing willy-nilly. When I did my coast down testing of my flat decklid spoiler in spring 2019 in the desert at El Mirage heat changes as the sun rose in the sky were noticable. Your method would be an interesting way to retest my flat decklid spoiler after I finish rebuilding it. It would take less time.

My coast down method was different than the one you describe. Rather than measuring time between two speeds, I coasted from X speed to a full stop, measuring distance with GPS. But I think I need better GPS. Mine was reporting accuracy of only to within 20 to 50 feet. I was coasting 2600 to 3500 feet to stop, so that's roughly 0.75 to 1.9 % inaccuracy in my calcs from just the GPS. Not awful but not great. What GPS are you using to confirm speed?

Here is my El Mirage data:
See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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