K&N Air Filter Maintenence

[erod]

how often do you guys clean and oil your air filters? i recently had my cruise control serviced at the dealer and they said i was due...looked at the filter and its dirty but not overly dirty, or at least thats how i see it. instructions say every 50-100,000 street miles, more often off road or heavy dust. we drive a good amount of dirt roads and dusty conditions. also says...or when filter reaches 18" of restrictions (not even sure what this means). continues to say...dirt "build up" works for you and will actually help filter air. heres a few pics. thanks, as always, in advance. oh yea, i do have a supercharger...seems like that would matter due to increased air intake...

also, anyone know why they don't manufacture a K&N filter kit (think its the generation II or FIPK kit) for motors outfittted with the supercharger?

 

[erin]

I would say you are probably real close to needing to clean it. I read that the atfter market cold air intakes can create a lean situation w/ super chargers on the yotas, unless you add the 7th injector and remap the fueling.

 

[adventureduo]

After every trip in the dirt, but i have no life

 

[ntsqd]

I should first say that I do not like the K&N type air filters. I have seen them pass dirt. I know that they are at fault as the sealing ends were greased and the wing-nut had a fender washer brazed to it with a greased rubber washer under that. The bottom of the filter assembly always had grit trapped in the filter oil I intentionally sprayed there.

With that being said, I think you do yourself a disservice if you clean a K&N filter too often. The nature of a K&N is that the built-up filth on the filter increases it's ability to trap small particles while unfortunately at the same time increasing the pressure drop of the filter. I doubt it will reduce the smallest size that can be trapped, but it will aid in trapping the minimum size that the filter is capable of stopping.

Reportedly the UNI type of oiled foam filter works better at stopping fine particulates than do the K&N type. I believe this is because the depth of the filter element is much greater in the foam filter. I've no personal experience with these filters. If Uni doesn't list your application I understand that Amsoil makes a similar air filter. Personally I have an anti-Amsoil bias, but this might be an option for those not afflicted with my disease.

Delta P is what they're talking about when they say "depression." This is the pressure drop across the filter. Say (for some dumb reason) you put the filter after the supercharger and before the engine. Then say that you're boosting the engine to 20 inches of Water Column (WC) (that's not a lot). The filter, at it's worst, then has an 18 inches of WC pressure drop ("Depression"). This means that the engine is only getting 2" WC worth of boost. You went from 0.72 psi of boost to 0.07psi of boost just due to the restriction of the filter.

Most of the US diesel fueled pick-ups now have a filter depression gauge on them. This is usually a clear plastic cylinder with a multi-colored piston inside it. One end of the cylinder is ported into the intake tract downstream of the filter and the other end is referenced to ambient pressure. When the pressure drop across the filter gets high enough the piston moves within the cylinder far enough to put it's red portion into the plugged filter indication zone.
With the popularity of putting cold air kits on those trucks, finding one of these depression gauges to fit to your truck shouldn't be too hard. Then you would have a reliable method for knowing when the filter needs to be cleaned.

 

[stevenmd]

After every trip in the dirt, but i have no life

LOL... x2...

As for the K&N passes dirt thing... a lot of rover guys run the K&N air filter and have had no problems. If you know rovers, you know we have a sensitive MAF (Mass Air Flow Sensor). If the K&N didn't do it's job, a lot of us would be replacing our MAF's a lot more.

 

[flyingwil]

I used to have a K&N, but ditched it place of an Amsoil filter. After every dusty trail we would run it would requiring "recharging." Upon inspection of the intake I found oil (from over oiling it) and that scared me enough to switch. With the Amsoil filter you can not over oil it, as you blot off the excess oil, which you can not do with the K&N. I think that most filters are designed for street use, and the recommended change intervals become obsolete. I check the air filter every 3,000 miles (especially with the snorkel) and clean and re-oil as needed.

 

[Willman]

I used to have a K&N, but ditched it place of an Amsoil filter. After every dusty trail we would run it would requiring "recharging." Upon inspection of the intake I found oil (from over oiling it) and that scared me enough to switch. With the Amsoil filter you can not over oil it, as you blot off the excess oil, which you can not do with the K&N. I think that most filters are designed for street use, and the recommended change intervals become obsolete. I check the air filter every 3,000 miles (especially with the snorkel) and clean and re-oil as needed.

Ditto for the most part!!!!!

I use to have a K&N.....Same as Wil.....but decided to go back to oem paper filters!!!

 

[Incusus]

The Trooper came with a K&N from the previous owner. I ditched it after its first cleaning as the MAF is so close to the airbox on my truck that any fresh oil would coat the MAF and cause the CEL to come on. I'd rather not under-oil it and pass too much dirt to the engine, so... back to paper filters until I can find a reasonable alternative.

 

[mountainpete]

I have been using an Amsoil filter for a few years but just recently went back to OEM paper. With the snorkel installed you do get more particles inside the box so my current feel is to just replace a cheaper filter more often. We'll see if I feel the same in a year.

Pete

 

[DaveInDenver]

I think that most filters are designed for street use, and the recommended change intervals become obsolete.

I thought the K&N was originally conceived because paper filters on the guy's motorcycles clogged up quickly. So it was designed not for the street, but the dusty tracks of SoCAL. Which is weird because it was the dusty conditions here in CO that prompted me to switch back to OEM filters. I started getting dust collecting in the wrinkles of the intake tube at the 90 degree bend before the throttle body. But you are right, Wil. The change interval for most filters is based on miles of road driving, one good trip in a caravan will clog a filter. But I figure that if my paper filter /didn't/ clog, where is that junk going? Right into my engine was my guess. In a K&N some of that is being collected on the oil film, but once that is completely coated the only stuff filtered is what is getting caught, so it should in my mind clog just about as quickly as a regular filter and that they don't bothered me.

 

[erod]

Thanks for the advice guys...I have been happy with the K&N so far so I am sticking with it and I decided to clean it as well but maybe down the road i'll look into the AMSoil air filters. Thanks again!