Quote:
Originally Posted by plasticuser
From the baseline of 17 mpg, at 68mph that's 4 gallons/hr. That means 58.8 gallons of air would be consumed in an hour at a fuel:air ratio of 1:14.7, or a gallon a minute. That sounds like a lot less than I'd imagined, so I suspect my math is wrong? Anyone in the know want to weigh in?
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Fuel air ratio is figured by weight. That 4 gallons of gasoline weighs about 24 lbs, so 24 X 14.7 = 353 lbs of air. Next you need the density of air, which comes from a pschrometric chart (Google is your friend to find one). Air density depends on temperature, humidity, barometric pressure, and altitude. Psychrometric charts assume the altitude is at sea level, and standard barometric pressure.
Air density can range from over 15 cubic feet per lb (hot and humid) down to less than 12 cubic feet per lb (cold). Air at 70 deg F and 50% RH has density 13.5 cubic feet per lb.
Next, multiply 353 lbs X 13.5 cubic feet per lb = 4763 cubic feet per hour = 79 cubic feet per minute. And that's your air flow.