Quote:
Originally Posted by California98Civic
I'm glad you're still at it. I'm working on my own coast down testing and so I'd be happy to see your thoughts. I too considered testing even when there were significant winds, but I changed my mind.
Re: your chart. The yellow is with gap fillers and box and the blue is the box without the fillers? How did you calculate Cd? Because the stock Cd listing for the 1996-2000 Civic coupe was 0.32, while the hatch was something like 0.36 ... so something just does not look right, or else I am not getting it. You recorded speeds or distances and calculated Cd somehow? Did you start by assuming 0.36?
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Blue is with the gap fillers (reduction in Cd), and yellow is without gap fillers. The calc is very similar to the Instructable, basically model and minimize Chi-squared. Crr shook out to be 0.012 BTW. Using a GPS for data capture.
Yes, 0.36 would be a surprisingly high figure for this car, even if the AHB was hurting it. But don't be alarmed just yet, I know I have at least one gremlin in my data since I coast better traveling east than west. There are several exercises I need to finish: error propagation on bumps and wind, GPS hysteresis, hill cross check, Euler method step size ... I'd like to start a new coast-down thread sooner than later, I'm just swamped for the next two weeks. But it's my kind of physics problem, it should be fun.
For the moment the point is that in A-B-A the gap filler had a significant benefit.