What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

K&N Air Cleaners

Tony_T

Tony_T

Well Known Member
Patron
Working on an annual condition inspection and cleaning the K&Ns. A bit of a hassle, spray with cleaner, rinse with water, let dry, reoil.

After a year of service they were gray in color, I assume when the pink color dissappears the cleaners are dirty.

For any gearheads out there here is an interestin' study: http://www.gmtruckcentral.com/articles/air-filter-study.html

Note the relative poor performance of this brand with respect to contaminants passed.

I would not use this product in my other vehicles, in the airplane nothing else probably would fit.

Is anyone cleaning the filters on a shorter schedule than 100 hour or annual?

Tony
 
Last edited:
Tony_T said:
Working on an annual condition inspection and cleaning the K&Ns. A bit of a hassle, spray with cleaner, wash with soap and water, dry, reoil.

Is anyone cleaning the filters on a shorter schedule than 100 hour or annual?

Tony
Click to expand...

I do it based on condition/appearance.


BTW you are not supposed to put anything on the filter other than cleaner, water or oil (no soap)
 
Tony, thanks for the interesting article. My initial comment is does the type filter we use in the 12 perform any better than the 1795 type tested? Could go either way I suppose. Interesting that the flow rate differed little, but the filter rate effectiveness was very different. Wonder if the aerosol propellent may have been a factor for the oiled filter? At my first annual I did nothing to the filters other than to examine them closely, and they appeared as they did when new. The K&N used on my 6A served for 5 years with an annual cleaning and re oiling and I did not detect any deterioration with a visual check. Considering that filter had a direct ram airflow for that period of time I would say it performed well from a durability perspective. However I don't know how well it filtered as there is no test. My engine never indicated any excessive wear in over 500 hrs of use. Another thought is that our RV12 filters are not exposed to the the ram air the 6A was so perhaps they will do better as a result. I don't really know other than how they look and how much crud is found in them (little to none so far). I also like to think that if Rotax had a concern about a particular filter we would hear about it, hopefully. Maybe I'll take another look at them in my oil change next weekend. Anxius to see comments from others. Thanks for the info.
Dick Seiders
 
I flew my 10 year old RANS S-12S with a 912S (pusher configuration) from a dirt strip in Southern Arizona for about a year. When I checked the filters they appeared not filtering much if anything. At some edges the filter material was deteriorating. Browsing through the engine log I couldn't find any entry for a filter change and the way the looked, I'd say these were the OEM filters that came with the engine. I replaced them with new K&Ns and I also installed the optional pre-filter socks that you can pull over them. They suggest that for dirt bikes, ATV and other off-road vehicles that stir up a lot of dust. I did not notice a power reduction or any change in engine behavior with the socks on and it sure adds another layer of protection, probably even enhancing the cleaning intervals for the filter. They were cheap and gave me peace of mind ... About half a year later the plane got sold and so I cannot report what the filters looked like after a year of flying from the dirt strip..
 
Last edited:
Interesting that for my Toyota Tacoma pickup truck, the NAPA gold filter is $13.23 and the K&N is $48.24 (ouch!) (same store.)

Bob Bogash
N737G
 
flyingriki said:
One's a throw away, the other is reusable?
Click to expand...

That's the point. To reuse it you must buy a cleaning kit for $12 and spend time cleaning and reoiling it. Unless there really is a performance enhancement, see the study about that, it is hardy worth the effort if you have a choice of brands. For the airplane there is not a choice. But that's ok; I'm just saying...

Tony
 
The study you referenced shows dry filters were consistently better than the oiled ones. And, the picture of the K&N filter shows a filter appearance very similar to the Rotax filter. Their filtering is probably exactly the same, the only differences being in filter physical configuration construction, while using the same media.

The K&N filter was dead last - 12 out of 12 - for the contaminants passed. It passed about 35% compared to, say, the NAPA gold, that passed 2.5%. That's not even close - and on an absolute basis, is just abysmal.

I wonder if Rotax is even aware of this study.

Bob Bogash
N737G
 
Interesting study.

Of course, beware the law of unintended consequences.
For example, several years ago, a member of VAF suggested using certain automotive fuel filters that would effectively block any water in the fuel.

The problem is, that with enough water trapped, the fuel flow would stop and the engine would quit. It's better to allow small amounts of water to flow and flush through the system than to accumulate and stop all fuel flow.

I'm wondering if there is a similar issue here: My Lycoming and my Cummins Diesels in my boat both use K&N air filters. Perhaps they are both tolerant of certain contaminants as long as the larger particles are trapped. Field servicability may be more critical in the marine and aeromotive applications than in automotive.

Nevertheless, it seems obvious that stopping more dirt is better. Unfortunately, in a standard RV with the FAB, the filter is modified to custom fit. This means that re-use is easier than replacement.
 
NASA515 said:
The study you referenced shows dry filters were consistently better than the oiled ones. And, the picture of the K&N filter shows a filter appearance very similar to the Rotax filter. Their filtering is probably exactly the same, the only differences being in filter physical configuration construction, while using the same media.

The K&N filter was dead last - 12 out of 12 - for the contaminants passed. It passed about 35% compared to, say, the NAPA gold, that passed 2.5%. That's not even close - and on an absolute basis, is just abysmal.

I wonder if Rotax is even aware of this study.

Bob Bogash
N737G
Click to expand...

I recall reading a test some years back which showed that the filtration effectiveness of the K&N was degraded significantly after cleaning. Racers I know, believing they flow well, discard them rather than cleaning them. I believe they are inferior filters.

Jerre
 
how to choose a better filter?

I believe Van's may have spec'd the K&N because it's readily available, and the construction is sturdy enough to withstand the junk that gets rammed into it at 200 mph...including rain, sleet etc.
....not for it's stellar filtering ability?
another data point; if you throw a variety of airborne stuff at a filter, from seagulls to talc, the big stuff plugs up the big holes first, then the material passed continues to change over time as the oil becomes less sticky, and the amount of clear space degrades. ( ie. the front of the filter becomes blocked, and more flow is thru the back.)
The fact remains, I'd like to protect a $30,000 engine, so perhaps a screen and foam pre-filter at the inlet for the big chunks, and a disposable fibre element downstream would be a good compromise.
I know after having to taxi thru tall grass, I really wanted to clean the filter right then, not at the next 50 hr!
 
Don't clean it too often; Filter inspection may be sufficient

flyboy1963 said:
another data point; if you throw a variety of airborne stuff at a filter, from seagulls to talc, the big stuff plugs up the big holes first, then the material passed continues to change over time as the oil becomes less sticky, and the amount of clear space degrades. ( ie. the front of the filter becomes blocked, and more flow is thru the back.)
Click to expand...

It is somewhat counter intuitive, however K&N claims that the filtering capability of the K&N improves as it picks up dirt. A fresh clean filter is not as good at filtering:eek:

http://www.knfilters.com/faq.htm#4

I clean my filter on an annual basis, however I may now defer some of those automatic yearly cleanings as per K&N recommendations, by inspecting the filter:

4. How often do I need to clean my K&N air filter?

If you have not experienced a decrease in mileage or engine performance, chances are your filter is fine and does not yet need cleaning. To be more specific, the filter does not require cleaning if you can still see the wire screen on the entire air filter regardless of how dirty it may appear. When the screen is no longer visible some place on the filter, it is time to clean it. When used in normal paved road, street or highway conditions, our replacement air filters that fit in the factory air box should require cleaning every 50,000 miles and our large conical filters on an intake system should require cleaning every 100,000 miles. When used in dusty or off-road environments, our filters will require cleaning more often. We recommend that you visually inspect your filter once every 25,000 miles to determine if the screen is still visible.
​

http://www.knfilters.com/filter_facts.htm

The dirt particles collected on the surface of a K&N element have little effect on air flow during much of its service life because there are no small holes to clog. Particles are stopped by layers of crisscrossed cotton fibers and held in suspension by the oil. As the filter begins to collect debris, an additional form of filter action begins to take place because air must first pass through the dirt particles trapped on the surface. That means a K&N air filter continues to exhibit high air flow throughout the life of the filter while it is accumulating dirt. At the same time, the air flow for an average paper air filter can decrease dramatically as the paper element gets dirty. So as dirt accumulates, the performance advantages of a K&N air filter can increase! Tests performed by an independent laboratory commonly known as the Frazier Permeability Test have shown that the Medium used in K&N air filters flows more than 300% more air than paper air filter medium when compared on a square inch per square inch basis. A Square inch comparison is not directly proportional to the increase you can expect from installing a K&N air filter in replacement of a paper air filter due to the effect of such things as filter size, number and depth of pleats. However, you can be assured a K&N air filter will provide dramatically more air flow which can enhance engine performance.​

There is also some good advice on how to recharge the filters, advising against over-oiling them (more is not better).
 
My first airplane with its Continental 65 engine flew with no air filter for it's first 1200 hours. I flew it another 600 without. I still see it from time to time, still flying around, happily eating bugs and dust.
I know of at least one RV owned by a prominent RV enthusiast locally that has no filter at all, no airbox, and has never had one. Not sure how many hours on it now, but it is a bunch.

Now, I would not advocate a filterless install. I am happy to have a K&N on my RV and a Napa Gold on my Bucker. They are what was recommended.
I rarely fly the Bucker in the rain, but I might be concerned about how it might hold up if it was continuously wet. Not sure. Not an issue with the K&N.

However, I would not get too hung up on it either. If I flew off a dusty dirt strip I might feel differently.
 
Tony_T said:
Working on an annual condition inspection and cleaning the K&Ns. A bit of a hassle, spray with cleaner, rinse with water, let dry, reoil.

After a year of service they were gray in color, I assume when the pink color dissappears the cleaners are dirty.

For any gearheads out there here is an interestin' study: http://www.gmtruckcentral.com/articles/air-filter-study.html

Note the relative poor performance of this brand with respect to contaminants passed.

I would not use this product in my other vehicles, in the airplane nothing else probably would fit.

Is anyone cleaning the filters on a shorter schedule than 100 hour or annual?

Tony
Click to expand...

Tony,
As a professional auto mechanic, I totally agree with not using K&N air filters on cars and trucks. The oil gets on the expensive [$100 to $400] Mass Air Flow sensor and ruins the sensor. I've seen lots of "stupid owner" tricks like that through the years.
That said, our aircraft engines operate for the most part at altitude, where the air is not so contaminated. We really only need an air filter for ground operations and low altitude [pattern] operations.
The "hot rod" car guys use them because of their low restriction to air flow, not because they are the greatest thing since sliced bread. For an RV, they work well. Cleaning it more often is a good idea. As you said, when it turns gray.
Just my opinion and worth what you paid for it.
Charlie
PS I only found this thread while using the search engine to locate another.
 
Not just Vans recommends the K&N ...

My Sam James cowl and alt-air intake are also designed around the K&N model 995 (cone shaped, $47).
And yes, virtually all air filters get more efficient as they get dirty. As an old pro in the HVAC business once explained to me, "Heck, the most efficient air filter in the world is a sheet of plywood." :) A somewhat dirty air filter hurts nothing ....it's only when the dirt accumulates to the point of reducing airflow to some critical point. In the commercial HVAC business, we used to put in Magnahelic gauges to measure pressure drop across the filters... which told us when to replace them. Some pressure drop was fine; too much was replacement time.
 
I used to own a Yak-52 that had neither air nor oil filter. I put 500 hours on it in dusty Arizona with no problem and the guy I sold it to went to 1000 hrs before overhaul. Not bad considering the Ruskies overhaul them every 500 hrs.
 
You must log in or register to reply here.
Back
Top