Yes, I'm sure K&N makes a really crappy product, and that's why it's the #1 selling filter on the market. Put a piece of plywood in there, it wouldn't let any dust thru..........
Some people are such sceptics...........
Well, when the marketing keeps repeating in your ear often enough, some people start to believe it. That's not at all unusual.
Here's a good reference, but there've been a number over the years just like it:
http://www.nicoclub.com/articles.php?id=180100
Basically, whenever anybody independent bothers to actually try measuring the filtering capability of K&N media and flow after dust loading, the results are always the same: they don't live up to the hype.
So I dug up the pics I took myself when I looked into this quite a few years ago:
First three pics of typical holes in a K&N filter, at only 60x magnification,
These are what you can see quite easily just by holding a K&N filter up to a light or to a bright sky. K&N says in some of their literature or on various sites that these are okay because there are fibers going across these to trap dust, but it's clear in these shots that that's not the case, as you can easily see all the way through. To more clearly demonstrate that these are genuine, let-a-bus-through holes, here's a backlit shot, also at 60x:
For comparison, here's a common blue paper shop towel at 60x:
It'd make a better dust filter than a K&N, but it wouldn't hold up very well.
For comparison, here's a generic, cheap paper filter at 60x:
The focal depth on the microscope is pretty narrow, so I could only shoot the top of the pleats. Still, it's clear that there aren't holes anything close to what the K&N has. I couldn't do a backlit shot exposing holes as the paper blocked the light too much, and there weren't any holes.
Here's a closer look at the paper media at 200x, just to be sure about the holes:
The paper media, just by visual inspection, will clearly do a much, much better job of keeping dust out of the intake. Flow measurements, like shown in the cited website, don't show much difference. A paper filter with deep pleats will have many, many times the surface are of a K&N, which typically has big holes and shallow pleats, and will, therefore, make a pretty good compromise between stopping dust and allowing air through. A number of folks over the years have done back-to-back dyno tests with a paper filter and NO filter and seen negligible difference on a SHO. Why people think a K&N will give them an advantage worth the price has always baffled me, especially given the reduction in filtering capability.
FWIW, I live in Arizona, so dust is a big deal. In more humid or low-dust climates people have done oil analyses and demonstrated that a K&N filter was performing satisfactorily in many cases. But is it enough "better" to justify the cost? I've not seen evidence of that, but I do see a risk in using them due to the potential for poor filtration, especially when they're kept clean.
FWIW, YMMV, don't try this at home, etc., etc.
