Ace,
All this about increasing air flow, now let me date myself. years ago it was desirable to use "dead air space" with a large volume to allow the engine to draw what it needed in the manner it was needed.
I'd be interested in hearing (reading) your thoughts or commentson "normal" aspiration.
Good question, Phil.
The dead air space is basically a requirement for throttle responsiveness.
With current technology, this dead air space requirement has been pared-down to approximately double the engine displacement. In a 500cc engine, then we'd be looking for about a liter of dead air space on the engine side of the filter barrier. This includes the air in the port and in the carb, as well as inside the airbox and filter body itself.
In some cases, this size of dead air space is partially compromised for space to fit it on the bike. Such as Ducati is currently using about 1.3 liters of dead air space in their 999. But, a bit more than that is desired when space permits.
Now, the dead air space, as I understand it, is primarily to allow a big gulp of air on initial throttle openings, for rapid throttle response.
I don't think that it really has much to do with turbulent air in the vicinity of the intake throat.
And there is little(if any) benefit to provide more dead air space than is actually needed for the purpose, Because the dead air space will replenish itself thru the filter by natural movement of the air. It's when the dead air space becomes less than the engine displacement where it can show itself as a flow problem, primarily as lag in throttle response time..
So, current practices would be to use always more than engine displacement volume in the inlet tract on the engine side of the filter barrier. And preferred to provide double the displacement volume if it is practical to do.
Is that sufficient? Or do you want discussion about how to optimize inlet flow in normally aspirated engines? That's quite a big discussion, in fact there's whole books written just on that alone. But, the wave tuning stuff that I've been discussing on this thread is part of that.