So I researched into air filtration technologies and published research articles on airborne particle sizes and concentrations, particle size affect on engine wear, and factors in predicting engine wear based on air contaminates. I take back what I said about the filter being saturated with flour and I believe the filter was properly oiled. Turns out it's way more complicated than it seems and even academic researchers are struggling to reach a consensus on many of the basic points. K&N claims between a 96-99% cumulative filtration in ISO 5011 testing (https://www.knfilters.com/efficiency_testing.htm
). Dry filters on the other hand should see nearly 100% filtration down to their pore size (which we saw in you testing). But there's a catch, once you go below the pore size nearly all of the particulate matter should pass straight through the dry filter (though they can actually act like finer filters as they clog at the significant expense of airflow), where as the oiled filter should continue to filter out 96-99% of the particulates no matter the size. Typical flower is 89-98% 10-41μm and 41-300μm particulates, and 2-11% 10μm or smaller (https://www.sciencedirect.com/science/article/abs/pii/S0733521084710587
). In conclusion, it appears that neither dry filters or oiled filters alone can fully protect an engine from wear but dry filter are by far more effective at stopping the most dangerous debris. I wouldn't be surprised if we eventually saw a high performance car intake system that uses both technologies with the oiled filter being a maintenance free item and large replaceable dry filters being the primary flirtation.
I think the fact that you had no filter-less control to show what the count would have been with flour going straight through the system may have skewed everyone's interpretation of what's going on. Long story short, without a filter less control to compare to I could predict only vaguely similar results as what your testing indicated (and I do agree that in the continuous flow test that the particulates probably passed the counter before you checked it) but I don't think most peoples' interpretation of the results really reflects what is going on or the difference between oiled vs dry filters. Despite what simulated testing (yours and others I've found) have shown, oiled filters are doing at least a similar job at preventing engine wear as dry filters. So either the effects of 40 times the pass through of particulates is only marginal (but no less an important factor when selecting a filter) OR 60mph airflow in your system is more than real world air velocity's through the filters causing more pass through than normal OR the distribution of flour particulate sizes is vastly dissimulator compared to the vast majority of ambient air particulate sizes across the USA.
I'd love to see a control test with flour to find out if the pass through we saw is within the 1-4% K&N is promising and some measurement of how much of the 3-6um particles made it through the dry filters because I think it's way more than what viewers think and it has been shown to cause significant engine wear (https://www.researchgate.net/public...and_filtration_on_automobile_engine_wear