After I removed my K&N, I took a swipe on the downstream side of my airbox to check how well the K&N was cleaning things up.

Looks like the K&N is doing a good job.  There was virtually no sign of any sort of dirt.

Here we have the standard K&N filter oil.  I would have preferred the aerosol spray, but the speed shop only had this.  I applied it with a brush and it seemed to cover and penetrate OK.

This is the mock frame for the poly-fil material.  It has a screen across the bottom just like the stock frame.  The screen is sealed to the wood with clear latex calking.

This photo shows the stock element installed on the rig.  It’s held down by a screw on one side, and a zip tie with small clamp on the other.

This shows the poly-fil frame installed on the test fixture.

As you can see, the underside was dry.

I started the test using a 51.85mm orifice which is rated 209 CFM @ 15” H2O.  As I said, I was hoping I would have at least enough restriction to test @ 5” H2O and then convert the data.  I wasn’t able to achieve 5” H20 test pressure.  There just isn’t enough restriction.  So, I started trying to test at the maximum depression I could achieve.  At first, that seemed to be working OK, but then I started having trouble with repeatability.  As the day wore on, and the temperature, humidity, and barometric pressure changed, the test results changed.  I was frustrated, so I sat down and thought things out.  

The main reason I built this contraption was to be able to test components on a level playing field.  Always test at the same pressure from one test piece to another.  Then it dawned on me, find out which element had the lowest depression at full flow, and then test each filter at that pressure.  If you have to apply a higher test pressure to achieve the same flow, the filter under test obviously doesn’t perform as well.  Note that on this test, when I use the term “test pressure”, it refers to a negative value (vacuum).

So, I started over.  I tested each filter with all bleed valves closed to find out which one resulted in the smallest test pressure.  I did baseline runs using the 51.85mm orifice on all the filter elements to determine which element resulted in the lowest pressure.  Then I did a single run using a 42.38mm orifice on the best performing element.  I felt that two sets of data would allow cross checks to make sure things made sense.  The K&N pulled the smallest test pressure, so it was already evident which element performs best.  But I wanted to practice and learn, so I continued with the full test.

Full Pull Test Pressures (51.85mm orifice, all bleeds closed)

Stock:                  1-7/8” H2O
K&N:                          1” H2O
Poly-fil dry:            2” H2O
Poly-fil canola oil:      2-3/4” H2O
Pol-fil K&N oil:            2-1/2” H2O

Full Pull Test Pressures (42.38mm orifice, all bleeds closed)

K&N:                          ¾” H2O