How to figure square inches of air filter.

[oldhp]

Do you figure the doubled pleats as if they were laid out when figuring square inches of a air filter? 13.78"X9.4"=129.53" is the square inches of my 2012 RAM air filter. K&N calculator says it should be 475sq.in. If you laid out the doubled pleats, 35 pleats, 35X2=70 70X1.75 height=122.5 it would figure out to be 122.5X13.78=1688sq. in. Is this right?

 

[MolaKule]

Because the height of each pleat is 1.75," if you stretched out each pleat, the effective length would be slightly greater than 3.5" long, since it has rounded hills and valleys.

So let's assume the rounded hills and valleys contribute an extra 0.17" of length, then the the effective length is 3.5" + 0.17" equals 3.67."

3.67 X 13.78 X 9.4 = 475.38" is effective area of filtration.

 

[Dufus2]

I may be new here, but why does anyone want to waste their time to determine the actual size of the filter element? If you are concerned, buy the heavy duty option

 

[oldhp]

A. Because I like to know things.
B. I've looked at a lot of filter sites with no luck on a HD thicker filter. Do you know the number of one?

Thanks for answering MolaKule.

 

[Jim Allen]

Originally Posted By: oldhp
A. Because I like to know things.


Good answer! ( : < )

What are you trying to achieve, more filter area?

 

[oldhp]

Was reading a old HOT ROD. Article on how to figure out how much sq inches of air filter a engine needs. Here's 2 of them.
1.Square inches of filter required for a motor = CID x Maximum RPM / 20839
2.CFM required for a 4 stroke motor = CID x Maximum RPM / 3456

After reading this I wondered how the pleats were figured in. My 345c.i. Hemi @ 5600RPM = 92.71sq. in. of filter area. My filter measures L/13.78 X W/9.4 = 129.53 sq.in. So I should be good there.
Now this is square inches. But wouldn't you figure the pleats by laying them out length wise using that length X width???

Remember my PM on rearend gear oil? ...and why I sent it to you?

 

[ZeeOSix]

Yes, the real square area of the filter media would be as if it was all laid out flat. That has more to do with what kind of pressure drop you will see across the filter based on the flow resistance and the area of the media.

Unknown how the old "Hot Rod magazine" article came up with their formula. It's basically the engine's volumetric displacement at max RPM divided by a constant which is probably base on many factors. But it seems evident that it is calculating the frame opening area of the filter, and not the pleated area. In other words, you could easily get 129.53 sq-in of pleated media area into a lot smaller filter frame opening than 13.78" L X 9.4" W.

 

[oldhp]

Yes there are different ways to figure size needed by engine.
Another way is c.i. X Max RPM X volumetric efficiency DIVIDED BY 3456.
I just like to figure out things.
I was looking for a thicker filter, more area less restriction. But no luck.