Quote:
Originally Posted by jime57
...Very high speed coastdowns might help, but those can't be conducted on public roads.
No amount of sophisticated data gathering is going to compensate for shifts in the environmental conditions during the test. I don't think we have any accurate models for environmental shift other than perhaps averaging the two "A" segments, which sandwitch the "B" segment, but then that violates the primary philosophy of the A-B-A test itself. What am I missing?....
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Jim,
One way that I compensated for daily shifts, is to continue to collect data on the same mods for many numerous days.
I did this back in 2009 and 2010, and collected data all winter into summer, with basically the same setup on the car. Who is going to dramatically change their Eco-Mods in the middle of the winter? Right?
Anyway, my data acquisition methods turned out to be too coarse and not repetitive enough. The sampling rate was not high enough.
Looking at the data did start to show just how much the Crr changes in cold weather versus summer, but I was not convinced enough of the accuracy to post anything here at EM.
For those that like to speculate, the 50 coast down runs showed at least a 17% increase in rolling drag for winter temps versus summer, but again, I was not convinced that from a statistical standpoint the data was that valid.
If one were to test a MOD over many days, and see the same decrease in Cd or the same increase in mileage, then one could assume that environmental conditions were properly addressed, not just one run over the coarse of a single day of testing.
Sorry to say, but without a wind tunnel, I think that is what we have to resort to. Multiple tests over multiple days.
Actually it's rather interesting to perform multiple tests in this way, as it shows just how consistent (or inconsistent) tests of this nature really are in the real world, so we learn something even though we may not actually know how big of an improvement our latest aero mod is worth.
Jim.