Then Argess (John) sent me this Filter Flow Test comparison:
WOW. Does that K&N filter result look great or what!
But wait. What do we know about about those other filters?
Nothing. Because no filter manufacturers actually publish any technical specs about their filters.
How many pleats per inch?
How deep are the pleats?
How thick is the filter material?
What is the filter material?
What is the micron spec of the material?
On the foam filters tested, what is the PPI (Pores Per Inch) spec?
This was a test of brands, not filter material performance.
As apples to oranges as you can get.
Now don't get me wrong, K&N filter do flow the best. But compared to?
As an example. Road & Track magazine did a fiter test of a number of filters compared to K&N on a small sports sedan with 130 rwhp. (yeah I know, not 400 or 500 hp like our cars)
A K&N filter was better than stock by 4%. (almost the margin of error)
But a cheapo K-Mart filter was almost as good at 3% better than the stock filter.
Why were the K&N and K-Mart filters better than the stock filter?
Fewer pleats per inch and thinner more porous filter material. (K&N makes up for porosity by oiling the filter material to trap particles.)
So they flowed better.
So the test chart is interesting but not very helpful.
Cheers
Greg