Quote:
Originally Posted by mans
he gained 5 mpg with the doughnuts on his rear wheels. that would show that doughnuts are pretty good, way better than stock tires!
whats up with that?
thats a total conflict of results.
can anyone explain how this can be?
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If you use this calculator, (
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com) you will see that the tires he took off may have had a Crr of .012 (who knows to what pressure they were filled?). The donuts may have been .009 at 60 psi. If you put in good guesses for a Metro, you can get 55 mpg at 50 mph. Then change only the Crr to .009. You get a little over 60.
I think MetroMPG used better controls.