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Old 05-22-2008, 10:05 AM   #11 (permalink)
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Pushrod - '02 Chevrolet Cavalier
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That's not my experience using one in controlled conditions. The last series of back-to-back runs I did testing vortex generators had a standard deviation of .6%. I'd call that decent resolution. It's less important that the absolute MPG readings are 100% accurate, as long as the relative differences are consistent.
Don't confuse resolution with accuracy. SG only correctly accounts for stoich, no other mixture. Even then, it's flawed. Just because it ends up being pretty close when you fill up doesn't mean that trip averages in certain conditions are accurate. While it can be accurate for external factors like aero drag, it cannot give results for things that affect the quality of combustion, like lean burn and acetone. Because it is an air meter, it can't tell you that you traveled the same distance using less fuel. If you used the same amount of air during that trip, it will report no difference.

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