Justin Short, engineering supervisor, motorcycle powertrain development, at this point noted that, "We make sure that the hardware we build actually confirms their assumptions."
How do you measure such fuel-air charge motion in an engine cylinder? Not so long ago it was done with an actual wind gage, an anemometer, in the cylinder. Today the method is Particle Image Velocimetry—basically adding dust to the intake flow and analyzing its motion to give a clear picture of in-cylinder dynamics. Metrics of charge rotation are derived from that. Call or write AVL Tippelmann for details.
Another problem of traditional air-cooled engines, much as many love them, is that of excessive piston temperature. Anything that heats the fuel-air charge entering an engine pushes engine combustion closer to detonation, or "knock." Because knock can be destructive, it must be avoided. A primary source of heat flowing into the fresh charge is the piston crown. It is cooled mainly by the piston's close contact with the cylinder wall. If that cylinder wall is cooled by air alone, its temperature can be quite high, resulting in hotter pistons. Because of that, air-cooled engines must be given lower compression ratios. Because compression ratio is a prime determinant of engine torque, that reduces torque.