How to determine the size of air cleaner/filter needed?

Is there any formula and or method to determine the needed air filter size per cubic inch ? Bigger seems to be always better but in limited space what is adequate for a 466 with decent heads turning around 72-7500 rpm. I know this would be dependent on the quality and cleanliness of the filter.

A=(CID X RPM) / 20,839

A = effective filtering area
CID = cubic inch displacement
RPM = revolutions per minute
at maximum power

Pulled from K&N site for use as a base line. Lots of other things to take into account but it gives you a number to look at.

Just for reference, I use a 14" standard round K & N filter with the filtering lid on my 514" racecar, typically from 6600 to 6800 rpm.   Some clowns have seen my car in the pits and suggested that it would run better without the air filter.  My tests say otherwise, as on different occasions I have run several successive passes, alternating them with and without the air filter.  Result?  Just like on any other day, I couldn't tell one timeslip from another.

Thanks Guys!

paperman wrote:A=(CID X RPM) / 20,839

A = effective filtering area
CID = cubic inch displacement
RPM = revolutions per minute
at maximum power

Pulled from K&N site for use as a base line.  Lots of other things to take into account but it gives you a number to look at.  

There is more to it for figuring what size element you need. I found this on another site:

Once you have determined the proper shape, you can determine element size. Two factors dictate the filter size: the engine’s cubic inch displacement and RPM at maximum horsepower. Knowing those figures, use this formula to determine the minimum effective filtering area an engine requires, where A equals filtering area:

A = (C.I.D. x RPM) / 25,500

With the effective filtering area established, we can determine the required element height (including the rubber sealing edges), where H equals height and D the estimated maximum element diameter that will fit in the engine bay. The .75 figure is to account for the element’s rubber sealing edges:

H = A / (D x 3.14) + .75

I was just trying to give him area. Some folks like to built boxes for air filters and use flat filters, in tight spots in can really help free up some room.

I know, I was just giving the rest of the formula to help determine the element by size. Some manufacturer's don't always list the surface area of their filters.

kjett wrote:I know, I was just giving the rest of the formula to help determine the element by size. Some manufacturer's don't always list the surface area of their filters.

Thanks for posting that up Karl. The more information you have the better.