6 year old study of air filters, including the venerable K&N!

[Gillbot]

Yeah, the mpg claim is pure bullshit. HP? Probably also bullshit.

Both are definitely plausible but not the norm IMHO.

 

[IcePickFreak]

Was curious about what kind of flow they put through the filters since that's going to be kinda important when determining pressure drops across the filter. I found it in ThrockMorton's link, 350scfm. Would be curious to see what the outcome would be at a higher flow rate since we're talking dyno results, which is going to be pulling more than 350scfm though the filter.

And before the AT K&N hate wagon jumps all over me, I'm not defending them. It's just that some things about these tests seem a bit off though. From ThrockMorton's link for instance:

Compared to the AC, the K&N “plugged up” nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt. See the data tables for a complete summary of these comparisons.

How does a filter that flows more and traps less and passes more dirt plug up faster than a filter that flows less and traps more dirt and passes less dirt? Magical disappearing fairy dust?

 

[mwmorph]

Was curious about what kind of flow they put through the filters since that's going to be kinda important when determining pressure drops across the filter. I found it in ThrockMorton's link, 350scfm. Would be curious to see what the outcome would be at a higher flow rate since we're talking dyno results, which is going to be pulling more than 350scfm though the filter.

And before the AT K&N hate wagon jumps all over me, I'm not defending them. It's just that some things about these tests seem a bit off though. From ThrockMorton's link for instance:

How does a filter that flows more and traps less and passes more dirt plug up faster than a filter that flows less and traps more dirt and passes less dirt? Magical disappearing fairy dust?

350CFM isn't a lot, but it's not trivial. A 3.7L VQ37VHR found in Nissan's V6s use about 400cfm at 7000rpm when max power is made.

Either way at 350CFM the difference in PSI restriction between the best and worst is 0.06psi which is negligible at best.

As for the dirt issue, easy. For example if 1 filter flows
350CFM @ 99.5% efficency, and there's 10grams of dust in the airstream per 100CFM, it would let 0.0175g of dust by.

If the K&N flows 370CFM at 98% efficency, it would allow 0.074g of dirt by.

Also filters have a point at which dirt has accumulated enough that the filter cannot hold more, a higher flow, lower restriction filter typically has less filter surface area/volume, bigger holes ore both, so the delta at which the filter is saturated and filtering efficiency decreases dramatically is reached sooner.

 

[Greenman]

Because it was probably user error. Like I said, I've had no issues with mine and the same can be said for my old "ricer" that had a K&N cone filter.

I agree that for the most part K&N won't damage an engine, but it won't help either, so why bother?