So I buy the K&N cleaner kit and read through the instructions.

#11. Performance Hints: Service every 50,000-100,000 miles on street driven applications. Service more often in off-road or heavy dust conditions or when air filter reaches 18" of restrictions. Let the dirt "build-up" work for you; it will not hurt the performance and actually help filter the air.


50k miles! And what does "when air filter reaches 18" of restrictions?" My application is on an AEM-type CAI. Help is appreciated.

Skip

 

18" represent the amount of negative pressure the system will draw. The more plugged the filter the more inches (of mercury) it will draw. I wouldn't worry too much about this frame of reference. When I had my AEM, driving it through our winters really got the thing filthy, so I cleaned it every spring. If you don't drive yours through the winter muck, clean it every couple of years.

 

Thanks, xviper. Just hard to believe you can let it go that long!

 

I've seen it posted here that although a K&N filter flows good air and thus contributes to intake gains, it really doesn't filter all that well. Letting it get a bit dirty helps its filtration at the expense of some reduced flow, so you kinda have to decide which one is more important to you.

 

I clean mine on my QUAD once a year. They can (and should) take on quite a bit of dirt and still flow well.

 

Longer is probably better, since the larger holes will be filled, and it will do a better job of filtering, which is not its strength. All filters do a better job of filtering when they have some miles on them.

When i used K&N's (have not after I did some research), I threw them away after a few years - never cleaned them.

Why? Well, i found that they did not go back to their original performance level. Remember, they claim to work by having lots of little threads in the airstream, catching dirt. (Like dendrites in your neurons). I sectioned a piece of a new filter, and examined it in oen of our lab grade microscopes. It looked like it had a fair number of these little thingies (and some huge gaps). Anyway, I then serviced the small section (cleaned and re-oiled). What I found was that the mechanical process of cleaning, reoiling, resulted in a filter media that did not look as good as the original.

The other thing is I exposed the filter section to an air pump, and those little "dendrites" rolled back from the force of the wind, leaving nothing to catch dirt other than the main threads and the larger dendrites. IMO, that is nto a very good filter action, so that is why i say a slightly dirty filter may be better. (Actually that si true of all fiklter media, since in a "paper" filter thge lkarger holes get plugged).

And theirt are different grades of cotton gauze, from different parts of the world. K&N now sources its coptton from Asia - Accel and other gauze users source differently. One can see a difference in the gauze under a microscope. I did it myself, using an old K&N from about 20 years ago, a new one, and an Accel Blue.

The Accel looked the best and had more/deeper pleats, and the older K&N looked better than the new.

Other quality gauzes I examined were S&B, and AFE.

There is no doubt that the K&N's let in more air - and more of things not so benign. Unless the stock filter is undersized for the engine's needs (which it isn't in our case), I do nto see the benefit of the gauze filters, since you will not produce more power unless thr engine is not getting the air it requires, and the other big selling point - 1 million mile warranty - does nto hold up if the filter degrades in its service protocol. Here, a foam would have an advatage froma reuseability point of view, if you can bear the cleaning and having to massage the oil into the foam. I have no time for that.

So for me, the high quality "paper" (they are usually composites of some sort) filters are better: they filter better, flow adequately, and do not have degradation - they are just tossed.

 

Guess my question wasn't as dumb as I originally thought it might be. Thanks for the responses!

 

if I might humbly add:

a good way to see if your current filter setup is letting in too much contaminants, you can have your oil analyzed when you get it changed. ideally you will have put the new filter on when you last changed your oil, so as to have a complete picture of it's filtration ability.

high silica counts indicate that your air filter is letting in a lot of dirt.

most people on s2ki are pretty happy with blackstone-labs.com for their oil analysis, but I believe Road Rage was happy with Quaker State's lab (url unknown).

$.02

 

[QUOTE]Originally posted by tritium_pie
if I might humbly add:

a good way to see if your current filter setup is letting in too much contaminants, you can have your oil analyzed when you get it changed.

 

[QUOTE]Originally posted by Road Rage