[Engo]

Originally Posted by lust4speed

Except K&N has taken the folds into account with their stated flow rating of 6CFM per square inch of (exterior) filter medium.

Using the 6CFM figure, my 121 square inch sized round filter would flow 783CFM -- which wouldn't be enough to satisfy the needed 829CFM requirement of the 462 at 6,200 RPM. Since we proved on the dyno that the filter size was sufficient up to 6,500 RPM, I'd say that their estimate is somewhat conservative. That nice even 6CFM number was probably rounded down. I'd say that it would be entirely safe to use the 6CFM figure for figuring minimum filter size.

I avoided splitting hairs and simply installed a 5x14 K&N filter on the drag car. Probably didn't need it, but had the room so why not?

Were did you get that 6cfm figure from? Is it an approximation for all KN filters or an exact no valid for the 3x9 filter only?

Reason I question this, is the fact that even the foldings on different sizes KN filters are different. I have the KN 3x9 filter were the foldings are 10mm deep and a KN 16x3.5 filter were the foldings are twice as deep 20 mm. Because of this fact, the 6cfm figure cannot be correct for both these filters.