I just cleaned a boatload of grime out of my AEM filter and my friend directed my attention to these two links:

http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm
http://www.mkiv.com/techarticles/filters_test/2/

It seems the K&N style filters (and the AEM filter is most definitely the same style) let the most dirt though, the least air through, and plug up the fastest. Pretty much the worst of all worlds.

Anyone using anything else with the AEM intakes?

 

Did you even read those pages you linked?

Neither of them say that the K&N flows the least

And I quote from the first link: "The less efficient filters correspondingly had less restriction to flow. This illustrates the apparent trade-offs between optimizing a filter for dirt capturing ability and maximum airflow."

It goes to follow though that flowing the most air comes at a price

 

On the first link, there's a big chart at the beginning for efficiency at catching dirt. K&N was wost there. The second diagram shows it catchse the second least amount of dirt. The third diagram shows it let the second most amount of dirt through.

But you're right, I did read some of the other diagrams backwards right before I fell asleep. Sleep deprivation due to new animal in the house.

 

I'm missing something here. For some reason, the K&N and AFE filters were fed *fine* dust compared to the "course" (coarse?) dust of all the others. That invalidates the test of those two filters since they aren't under the same test conditions. I may have missed it but I don't even see it mentioned anyplace in the text as to why the difference.

I would fully expect any filter that has low restriction due to average filter hole size (the average size of the holes in the medium) to pass more dirt initially. As time goes on, the average size decreases since dirt starts to accumulate, (partially) blocking each hole. Obviously, the rate at which the filter plugs is important as is the amount of dirt passed. An initial surge of dirt passage followed by superior filtering may still pass more overall dirt because of the initial surge. Hence, one should be careful as to cleaning something like a K&N filter too often.

I have one of the JR filters and have yet to clean it after ~4 years. It may be past it's efficient filtration point but I live in a not-so-dusty area (except winter with road salt dust). It *looks* like it's still clean enough but I probably ought to pull it out, examine it more closely and clean it after this amount of time. It still lets me run with the big dogs at our regional SCCA autocrosses so it can't be too far off.

Anyways, I'd like to see a reason for the difference in the dust size for these filters...

 

First off - don't pay much attention to the second link, as the test method they used looks like a junior high science project. The first link looks pretty good, but I don't understand why they changed dusts in the middle of the test (from coarse to fine).

I'm an engineer for a large filter company (no we don't make consumer automotive filters) so I'll look at the Duramax air filter report and write up opinions over the weekend.

There was an earlier discussion on somewhat the same subject about a year ago.

inlet filter discussion

I'm glad someone has done this work, as I think it has been needed very badly to put some truth to the "free-flow" filters marketing hype.