The following website contains a data intensive study of air filters for a General Motors Duramax diesel. Lots of data measured scientifically with flow rates, filtration efficiency and capacities to an ISO 5011 standard.

http://www.duramax-diesel.com/spicer/index.htm


I was considering a K&N...........

 

and?

are you surprised? you can't have both filtration and performance. if you want a performance gain, you're going to have to pass more air. the only way to do that is to reduce filtration. it's a trade off. what's more important to you, picking up a couple HP or limiting the amount of debris in your motor? depending on where you live, i can't imagine the slight reduction in filtration is going to be a big deal.

 

Interesting

 

I still rock OE paper filter in the S. Works fine and my software is designed for the stock (RS4) airbox.

 

You can have filtration and performance if you incresase the surface area of the filter. These tests tell you what the filter will do per filter. To increase performance you must decrease the delta p (pressure, inches H2O) across the filter. Since delta p is fixed by the vacuum of the engine, the variable to be adjusted is in surface area with filtration size at a constant. These filters were not rated as to the amount of surface area they have, this would greatly effect the effeciency graph if all were tested with a given surface area. Also, a micron is pretty small 10 to the -6 meters .000006, the particles in test were 2.5 to 80 microns in size. They also do not tell you the size of the particles that get through, only the accumulative mass. The larger ones will get caught and the smaller ones will get through. These particles in this size range that actually stay in your engine will only dirty your oil.
Ask your accountant how you did last year and a good one will ask you how you do you want to do. It is all subjective.

 

i don't think surface area is a variable with this test. i could be wrong, but i was under the assumption that they were all "drop in" air filters to replace the stock one for the same vehicle. i agree with your point though in general about increasing the surface area.

 

On my dodge truck with the diesel, I had a K & N and when I went to change out the turbo, to a much larger one, I found dust and grit in the intake tube. I replaced the filte with an AFE and after a few thousand miles, have found no dust or grit. So it all depends on what you find acceptable. Most of the higher flow elements sacrifice filtration efficiency.