I had lunch with David Vizard not long ago and we discussed this tuning a little bit, I asked him specifically about cylinder filling particularly as it related to long intake durations where the valve is closing well past BDC and the piston is rapidly moving back up the cylinder removing effective displacement with every degree.

He mentioned the one fact that manyt people don't completely comprehend...something a motor depends on but we're not really concieous of...the fact that air has mass and a column of air mass in motion has momentum. The very notion that VE's can exceed 100% in a race engine is testament to that fact. You also see and understand how variables in the air density effect power output if there is more or less pressure in the intake tract.

What dry flow benches do not take into account is the fuel atomization and if or how it stays in suspension at various RPM (proportional velocities) through the powerband, Also it's imprtant to realize that with an example 12.5:1 A/F ratio, ~7.5% of the potential flow is displaced by the fuel the air is carrying in suspension...especially in a carburetted motor. to muddy the waters further, on a bench we tend to only look at air moving one way (either into or out of the cylinder)...the effects of reversion when the rapidly moving column of air suddenly gets the door slammed shut as the valve closes and has to regain it's momentum. Then you think that all the airflow moving through an engine in a minute's time when we know that any intake or exhaust valve is closed roughly 2/3'd of the time....regardless of crankshaft RPM this is a mechanical constant.