Interesting data, jdean!
I wonder if you could tell us what the other numbers indicate--is the % figure the filtration rate (my guess), no idea what the number after the % sign is, perhaps square inches of filter area (again, my guess)?
I drove a '65 GTO for a while, opened up the hood scoop and used an aftermarket air filter that used foam at the top of the "funnel", or venturi, shaped base. I was not happy with the filtration and feared that a backfire would start a fire in the engine compartment. I don't know that I felt any positive difference in the performance of the car, but it didn't seem any slower, either.
One thing is sure, with my stock-block 302/5.0 HO, I won't need to worry about having enough airlfow with a 9" X 2" or 2 1/4" K&N. That relieves my concern about going to a shorter filter!
I'd bet there is HP to be found with experimentation regarding the structures inside the air cleaner assembly, such as the "vanes" you mentioned in the Airaid. I could see a "funnel" shaped insert (for lack of a better term) inside the air cleaner that would force the air to make the 90* turn into the carb's venturis a bit less turbulent....much like the swirl patterns on some intake valves increase the flow rate.
Interesting.....thanks!
Cheers from Dugly
