air filters

[okeehandyman]

has anyone had any experience with excessive dirt passing through k&n filters or any other aftermarket filters? i read lots of bad reports about the oiled filter's dirt catching ability on RV.net posts. also, a good link to a test performed by independent tester on many filter brands at Testand. poses some real questions!

[More Power]

Good test data is expensive, time consuming to acquire and all air filter tests can be challenged on many levels. People who have a favorite filter will question the validity of any test if their filter of choice did poorly, and every individual will likely experience a slightly (or significantly) different result from what the "test" data showed.

In my mind, the best air filter test will include a complete air intake system that duplicates what we have in our trucks, with a range of airflow CFM's that matches what the engine actually consumes. The circuitous path taken by the incoming air will have an effect on the air filter's ability in removing dirt particles, and will have an effect on both the velocity and amount of particles actually making it to the air filter media.

Some tests (performed by both filter manufacturers & third parties) introduce graded particles directly onto the air filter media at a right angle or some fraction thereof. This does not replicate dirt entry into air box in an actual truck.

We did an air filter test about 8 years ago, where we used an actual pickup truck airbox, and a fan that pulled the equivalent of 540 CFM (which replicates a non-turbo 6.2L diesel at 3600 rpm). While all three passed some dirt, we found that an oiled foam air filter performed best, when compared to a new AC paper filter and a new out of the box K&N. Particles were trapped downstream of the air filter in the airflow path on a white 5" square ceramic plate coated with a tacky oil. There was a significant visual difference between the various filter's ability to trap graded/weighed samples.

I use an oiled foam air filter...

Perhaps the best way to know whether your choice in air filter is doing a good job is to have your engine oil analyzed after 3-5K miles. The silicon level in the engine oil will show you how effective your air filter has been for the type of driving you do. We all should choose an air filter that produces single digit silicon levels.

MP

[DA BIG ONE]

I have been using K&N w/great results for as long as they have been around on everything from a 2.3 high pressure turbo race motor, my current 6.5TD, and my HD V-Rod.

But, a pre-filter is required for best filtering in some sandy, or dusty areas "I always use some type of prefilter".

I will get a K&N larger than stock if it fits univ. filter that flows 2 times cfm the engine actually needs at WOT, then use a prefilter.

Prefilter can be what K&N sells which reduces filter flow about 10%, or any of the various "panty hose" on the market. "Panty hose" can be had in a extreme fine mesh and restrict flow even more, but this is why a larger filter.

A prefilter can be adapted to any other filter too, but results will vary.

I like it when I can open filter box, or remove upper intake manifold and find the prefilter is doin its job.

[Idle_Chatter]

I'm a believer in oiled foam. Have been using two generations of Amsoil foam filters and most recently a UNI for a total of 102,000 miles and nearly four years with excellent silicon numbers in my oil analyses (single digits mostly - highest a 12) in some very dusty conditions.

[Onebigcanuck]

I just installed a K & N on my truck. I got it from my Dealer and they installed it. The service manager gave me the "Be careful when cleaning and oiling the unit". I intend to discard it after 50K.

Here is a web site with some testing by K & N:

http://knfilters.com/facts.htm#RESULTS