Subject: [FlyRotary] Re: Area calcuation for Cone air filters was [FlyRotary] Re: Air = filters

I’m just going to make my educated guess that for a minimal/neglible loss of pressure head you would want a filter element area of 10 to 15 times the required inlet area of the scoop. So the surface area that you = have, Jerry, is getting into the ballpark. What is K&N’s criteria?

Ed, the surface area of the filter is much greater than its circumference x = height due to the folding of the element. I just checked mine and each inch = equals 4 inches if stretched out. Thus the surface area on my 5.5 in. round x 5 = inch high filter would be over 300 sq. in. Jerry

On Monday, April 18, 2005, at 07:00 PM, Ed Anderson = wrote:

Bill,

I did some research on the K&N = site - they have a formula for determining filter area needed - the trouble is = there is no correlation (I could find) between the area you calculate and the = surface area of their filters. So I just did a rough calculation of their = filters surface area based on small end - large end and length. On their = double cone types I assume the inner cone is only 10% the area of their = outer cone (which is probably very conservative). I used the 160 CID 4 = stroke equivalent displacement area for the 13B and the below formula. = Which gave me at 7000 rpm a minimum of 53 sq inches required.

Then I did the calculation using = the attached spreadsheet to compare their different size filters for area - = since they don't give it. Attached is the spreadsheet for using the = below formula and the calculations for a truncated cone surface area.

Use the formula below to compute the minimum size filter = required for your particular application. The usable portion of the filter is = called the EFFECTIVE FILTERING AREA which is determined by multiplying the diameter = of the filter times Pi (3.1416) times the height of the air filter in inches, = then subtracting .75-inch. We subtract .75-inch to compensate for the rubber = seals on each end of the element and the filter material near them since very = little air flows through this area.

<image.tiff>

Ed A

----- Original Message -----
From: William
To: Rotary motors in aircraft
Sent: = Monday, April 18, 2005 5:54 PM
Subject: [FlyRotary] Re: = Air filters

If one looks at the K&N cone = filters, how big a one is required?
Bill Schertz (really tight under my cowl)
KIS Cruiser # 4045

<affform1.gif><affform2.gif><Filter Size Cone.xls> = Homepage: http://www.flyrotary.com/

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