[another TV program driven question from enquiring minds!]
Background:
Dad drives the 100 Series normally aspirated manual diesel at about 90 k's.
When The Chancellor of the Exchequer is in the passenger
seat Dad likes to show how frugal he can be (with the diesel that is).
So he turns off the AC and winds down the windows and tells the kids to send their complaints to the bureaucrats at the Chancellory - of course, says he, it is more efficient to drive with the AC off.
Then, kids watch Jamie & crew of Mythbusters fame on SBS, and tell dad he doesn't know what he is talking about, and send a stinging letter to the Chancellory. Windows up and AC on is more efficient, they say.
Surprise, surprise, Mythbusters revisit the question with some more real-world testing (yeah sure), and to everyone's surprise, prove that this holds only (for their
test vehicle) at speeds above 50 mph.
The situation:
Now - Dad's cruiser has an added burden and higher coefficient of drag than your everyday San Franscisco runabout rental car that Mythbusters use. Especially with the Sahara bar on the front, the tyres on the back, the roof rack and everyone's luggage on the roof, the whip antennae, etc.
It also has different power/weight ratio, power curve and air-con compressor than the Mythbuster's
test vehicles. On the first, I'd guess that my gutless cruiser has a considerably lower power/weight ratio.
The critical question:
So, theoretically speaking, will these factors (and any others you can think of) serve to increase or decrease the critical speed at which is becomes more efficient to wind the windows up, and put the AC on?
Enquiring minds need to know ;-)
Andrew, who can't wait to see the contributions from this esteemed mythbusting crowd