Unfortunately, I call the mythbusters "attempt" Bad Science. Nice try, but too many potentially significant variables have not been addressed. Even the test itself is flawed, thusly.
One: true that the engine (indirectly) measures intake air flow through the AFM. But the engine computer does know how much fuel the engine is getting, via the pulse width signal sent to the injectors. Some cars will report the mpg to the driver using that data... of which no mention was made.
Two: the "test" was only run once, with one car using AC, the other using windows. We can't/don't know the state of tune of these two vehicles, surely they are not identical. Therefore, for the test to be valid, the "AC versus windows down" test should be run with the vehicles reversed.
Three... even if the test was run correctly (see item two above) the test is only valid for the vehicles used. Aerodynamics for other vehicles will of course vary. The coefficient of drag for these SUVs was not mentioned. The results will be different for vehicles with a different Cd, ECU, state of tune, and numerous other factors.
Overall, this was a pretty lightweight attempt to address the question, and in my opinion the "results" are meaningless. |