Quote:
Originally Posted by Vman455
That^.
Unfortunately, despite its complication coast down testing is still probably the most viable means of aerodynamic testing for enthusiasts like us. The instructable is a very approximated version, so it will only give you a general idea of drag coefficient and rolling resistance coefficient. Some things you could do to improve accuracy:
-following SAE J1263, do it on a day with wind speeds <10 mph and 10 runs total (5 in each direction) for any one configuration
-take a photo of your car from a distance and get an accurate cross-sectional area measurement rather than estimating
-weigh it on a truck scale and get a reasonably accurate curb weight rather than estimating
-use as flat a road as you can find, throw out any runs with traffic interference and redo them
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That is what I did the last time I did a coast down test, except I only did 3 runs in each direction.
I use the national weather service to find a day when winds are calm.
We have a truck scale at work tha I can use to get the weight to within 20 lbs.
I know of a pretty flat road to do the coast down test on.
The cross sectional measurement I can probably get from the last coast down test I did.
This is a copy of the last coast down test I did.
