Montblack wrote:
How much does the 15 minutes of air weigh - that you run through an
(average) rotax engine?

At 4 gallons per hour, the fuel rate is 6*4=24 pounds per hour. (aprox
60% power)

The air / fuel ratio of gasoline engines is about 14 / 1, so the
airflow rate would be 336 pounds of air per hour. At standard
conditions, air weighs about 0.075 pounds per cubic foot, so the air
flow rate expressed in cubic feet per minute would be 336/0.075/60=75
cfm.

tom