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Independent Filter Test, Paper vs Gauze vs foam. Key points:
Our story actually begins back in May of 1998 when I spent 3 glorious days at Fluid Technologies Inc. (FTI), an independent laboratory in Stillwater, Oklahoma hired by our company (NEUSPEED) to contact (sic) back-to-back testing of conventional paper air filters versus synthetic foam filters and pleated, reinforced cotton gauze filters. FTI is one of a handful of test laboratories equipped to perform the Society of Automotive Engineers' J726 test procedure for air filters.
the test results I am showing you here belong to an automotive panel filter similar, but not identical, in size and shape to the 2-valve 900SS/M900 panel filter. Our paper filters were manufactured by Fram.... Our cotton gauze filters were from K&N. Finally, our three-stage foam filters came from Ramair, a British company that has since gone bankrupt. A comparible motorcycle product to the Ramair foam filter would be a multi-stage ITG filter.
If you are choosing between a multistage foam filter (Uni, ITG, etc) and a K&N filter, there's no clear winner. The multi-stage foam filters have the ability to capture more dirt overall, but may cause slightly more initial restriction during the early period of use. In contrast, with the K&N you get superior airflow ability, but will have to settle with slightly lower dirt holding capacity. Hey, just clean it more frequently then! Nonetheless, they both outperform the stock paper filters
So, what I get from this is that the foam was superior to the K&N in filtering capability and dirt-holding capacity. IOW, it captured more dirt, and was able to hold more dirt before choking. This supports my contention that foam is a superior filtering media.
Flow is more complicated. When all the filters were clean, the foam had the worst flow numbers. Again, though, in the interest of science, this test was run with all filters of panel type, and of the same size in a stock airbox. I still think that this flow compromise can be overcome with a larger-than-stock filter, and that the gain in dirt-capture is worth it.
Just my humble opinion.
