K&N Air Filter

[Adirondack Bill]

HUNGRYEYE- in a recent post- pipes for the Valk., you basically indicated that a K&N air filter is a waste of money. Does'nt it  allow more air to get into the mix? I have put them on almost all of my bikes over the years- it (seemed) to make a difference. What is everyone's opinion on a K&N air filter? Is it worth the investment, or just a waste of money?

[Robert]

Yup just recently put one on and the difference was night and day. Must be 20 hp gain and the mileage has improved about 25% so I recommend them.   

Really the only advantages are they dont need to be changed as often as the stock air filter. On these fuel injected bikes the air filter is not really a restriction. On the 1500 Valk with 6 carbs it can vary the fuel mixture but not so with these bikes. The O2 sensors make sure that no matter what happens on the filter side the mixture stays steady. 

[Kidd]

Yup just recently put one on and the difference was night and day. Must be 20 hp gain and the mileage has improved about 25% so I recommend them.   

Reads like something Adrian would write , the other Adrian , just kidding , Adrian

[Adirondack Bill]

Robert, I like your sense of humor, and based on what you have written in your posts, I respect your opinion. I known an engine is a breathing machine. The more air you have going in and then out- (less restrictions) is a good thing. So are you saying (in your opinion), the K&N filter does not provide a less restricted air flow compared to the stock filter? AND- Fuel injected bikes don't run a little better with a less restricted air flow?

[Robert]

Robert, I like your sense of humor, and based on what you have written in your posts, I respect your opinion. I known an engine is a breathing machine. The more air you have going in and then out- (less restrictions) is a good thing. So are you saying (in your opinion), the K&N filter does not provide a less restricted air flow compared to the stock filter? AND- Fuel injected bikes don't run a little better with a less restricted air flow?

Almost, the K&N does provide less restricted air flow but the air has to be restricted before you put the filter in to feel a difference. The original filters on these bikes are really not very restrictive and coupled with 02 sensors and a computer constantly correcting the mix there is very little that would change.

  In this air pump by changing the filter you want more power from the volume of air. Since the 02 sensor and the computer compensate mixture how much more volume do you think you are really going to get out of a filter change? That is the question.

The engine design does not need to restrict incoming air with the air box or manifold to get the correct mix at different speeds like the 1500. The design allows the free movement of air into the engine then expects the fuel injection to do its job. This bike has a map sensor, baro sensor, tp sensor, and 02 sensor. What that means is the engine computer knows the air pressure the manifold vacuum, the throttle position, air temp, and the exhaust gas mix along with other engine parameters. Restrictions put more unnecessary variables into the programing of the engine ecu and engineers can use the engines computer much easier to regulate fuel with unrestricted air flow into the engine. I would say alter the exhaust then you may have something since I bet that is where most restriction is.

In some cars they replace the throttle body to get better performance from the increase in air to the engine. The throttle body is nothing more than a variable metered orifice. You can calculate the air flow through it and put it into a program but an intake or filter, its always going to change.



Sorry for the long explanation 

[Jess from VA]

My feeling on air filters go like this.

They can be a PITA to change.  It ought to be done once a year, but many like me are closer to once every two years. 

Yes K & N can be cleaned and reused, but at what point is the filter oil all dried out?  OE filters do not dry out.  So from the one to two year point of an unchanged, uncleaned filter, which one is working better?

50,000 miles between cleaning and oiling seems ridiculous.

I don't feel ripped off spending $25 for OE filters that last two years.

[Robert]

Reads like something Adrian would write , the other Adrian , just kidding , Adrian

  OH NO 

I think one reason I like this bike so much is the fact that its a complete package. The engineering is done the right way for being the bike it is. There are no real shortcuts on this bike like there were on the 1500. The air box and carb setup is one thing that is a compromise on the 1500, it works but its not the best solution. The 1800 was designed from the start to offer a certain hp with a certain riding condition and reliability. It kind of makes me wonder if the bike took so long to come out because the engineers wanted to make sure the wing platform could handle the different forces and uses it would be put through on this bike. When even the frame is designed with the engine as a supporting structure and done so well, (Lessons from the wing and cracked frames) it makes me have the feeling that the bike is a complete package.

[Kidd]

The CEO of Honda said before he left his place  at Honda , he'd  develop the EVO6 and our bikes are a byproduct of the EVO6  , hp power wise , a long way from the EVO6.
Or , the new Valkyrie was modeled after the EVO6 , I guess

[AdrianR]

Robert, I like your sense of humor, and based on what you have written in your posts, I respect your opinion. I known an engine is a breathing machine. The more air you have going in and then out- (less restrictions) is a good thing. So are you saying (in your opinion), the K&N filter does not provide a less restricted air flow compared to the stock filter? AND- Fuel injected bikes don't run a little better with a less restricted air flow?

Almost, the K&N does provide less restricted air flow but the air has to be restricted before you put the filter in to feel a difference. The original filters on these bikes are really not very restrictive and coupled with 02 sensors and a computer constantly correcting the mix there is very little that would change.

  In this air pump by changing the filter you want more power from the volume of air. Since the 02 sensor and the computer compensate mixture how much more volume do you think you are really going to get out of a filter change? That is the question.

The engine design does not need to restrict incoming air with the air box or manifold to get the correct mix at different speeds like the 1500. The design allows the free movement of air into the engine then expects the fuel injection to do its job. This bike has a map sensor, baro sensor, tp sensor, and 02 sensor. What that means is the engine computer knows the air pressure the manifold vacuum, the throttle position, air temp, and the exhaust gas mix along with other engine parameters. Restrictions put more unnecessary variables into the programing of the engine ecu and engineers can use the engines computer much easier to regulate fuel with unrestricted air flow into the engine. I would say alter the exhaust then you may have something since I bet that is where most restriction is.

In some cars they replace the throttle body to get better performance from the increase in air to the engine. The throttle body is nothing more than a variable metered orifice. You can calculate the air flow through it and put it into a program but an intake or filter, its always going to change.



Sorry for the long explanation  

This imo, is all correct.  Engines are designed for a specific type of induction, and back pressure in the exhaust manifold/system based on combustion parameters determined by displacement, stroke, compression..etc. It's a balance that is predetermined to produce max power for a given design.  Of course another variable is complying with emission standards..  this too is included in this balance.

This is why fuel injected engines are far superior to those equipped with carburetors.   With carburetors the 'balance' is fixed based on the amount air intake and exhaust back pressure.  Changes in barometric pressure and temperature cannot be adjusted for automatically.  You end up with an engine that must be tuned for your local environment..and specific intake/exhaust.   A fuel injected engine and it's equipped sensors, monitor the engine's working environment and adjust accordingly.

Same thing applies if you switch out the air cleaner to a less restrictive one.  The system would just account for it and make the necessary changes...The hope in gaining more HP would be negligible at best assuming this factor is within the adjustment parameter of the system. (enough throw in a lever/set screw).

[Adirondack Bill]

Robert, I am humbled by your knowledge of engines. Also, do not apologize for your long post, I found it interesting. It is good to have a few (gear-heads) on this site. I have had some type of motorcycle since 1970, and know a little about how they work. But now I am a little confused. I already purchased a K&N filter, but I have not installed it. It is a pain in the but to remove the tank ect.  All of my other bikes-(for the most part) had exposed air filters. Either way I will have to replace the air filter at some point, but now I feel I have wasted my money. Oh-well, thanks for your input, you are a very valuable member of this club.

[Robert]

Robert, I am humbled by your knowledge of engines. Also, do not apologize for your long post, I found it interesting. It is good to have a few (gear-heads) on this site. I have had some type of motorcycle since 1970, and know a little about how they work. But now I am a little confused. I already purchased a K&N filter, but I have not installed it. It is a pain in the but to remove the tank ect.  All of my other bikes-(for the most part) had exposed air filters. Either way I will have to replace the air filter at some point, but now I feel I have wasted my money. Oh-well, thanks for your input, you are a very valuable member of this club.

I like you bought a K&N filter and installed it on my bike. I like you look for that little easy extra hp's that were undiscovered. Even knowing what I know. So that should tell you something. I waited to install it till I had 11k miles on the bike.

   Its not hard to install and the real benefit is you can do less maintenance because it doesn't require the same service interval as the stock filter. I also while off lubed the radiator pod supports, checked the engine mounting bolts, lubed the throttle cable and a bunch of other small maintenance things. I only say its not going to make the bike fly but that doesn't mean we cant keep trying.

When I change my oil I swear up and down the bike feels so much better, but really does it?  Maybe yes, or maybe not but who really cares its our baby. I have a term psychosomatic service syndrome that moment when you do any change and you swear you gained 25hp. Its a blast for the time it lasts. Kind of like a pretty girl you swear is hitting on you and you swear up and down she really likes you, but really she was looking at the guy next to you. Its all part of the fun of making changes and enjoying our toys.

Its never a waste when in comes to accessories for the Valkyrie, because even if it only adds 1 hp its 1 hp I didn't have and its just cool to have a K&N filter 

[dans2014]

  Go talk to a bike-atv shop about K&N filters.  Why do you think they let more air in? They also let more dirt in and will wear your engine down to failure. A lot of people get away with it however a lot don't. Most warranties are void with one. If you never ride in dusty or muddy conditions, you may get away with it

[ledany]

When my bike had 15,000 miles last year, I had to have the valves checked for warranty reasons though I knew it wouldn't be necessary. I asked the dealer to install the K&N filter, I think it took him about an hour and a half. My dealer is used to ordinary Goldwings, most of his clients are the bike cabs of Paris and he is cheap (66 US$/hour when others ask 88,6 $/hour) but I guess I'm the only Valk he knows.
I must confess that the K&N air filter didn't change a thing  . I had one on my BMW K1200 GT and the gain was obvious.
I 'll change the oil today and Robert, I know the bike will run cleaner and smoother   

[Robert]

Go talk to a bike-atv shop about K&N filters.  Why do you think they let more air in? They also let more dirt in and will wear your engine down to failure. A lot of people get away with it however a lot don't. Most warranties are void with one. If you never ride in dusty or muddy conditions, you may get away with it

I know what all the specs say and I know the good and the bad of what some say but I think this is more hype than truth. Let me explain why I feel this way.

On the cars that I have seen with air flow meters and K&N filters have not fared any worse off than those with normal filters. The air flow meter sits in the air coming into the engine like a mini air scoop so if there was excess dirt this thing would have taken the hit and replacement would be frequent at 200.00 to 600.00 per vehicle. But I have not seen any frequent replacement. As for motorcycles on the 1500 I would say that most run the K&N and some there have 300k on their bikes. Mine I have 60k and there is no wear and tear that I can attribute to the K&N. So in the engineering world yes I have to agree with the fact that K&N not only flows better but lets in more dirt. But in the real world I would have to say it does not make a significant difference. I also believe even with the K&N filter that some have had installed at the dealer will not void your warranty, I am not absolutely sure of this but K&N says it does not void the warranty and the dealers would not install it if it did.

[F6Dave]

After buying my F6B 2 years ago I thought about using a K&N air filter.  There are a lot of K&N evangelists out there who fervently recommend the brand.  So I did some research and found data disproving some K&N myths.  Here's what I posted back in 2014:

I've used both K&N and another 'serviceable' oiled air filter in the past, on bikes I rode for nearly 100K combined miles.  So I've had several opportunities to clean, dry, and re-oil these things.  That process is a pain.  It's so much easier to just drop in a new replacement filter.  And if that's not enough, a K&N isn't cheap.  I've never paid more than $20 for an OEM filter for my Valkyrie or GL1800.  A K&N will cost about 3X that much, or 4X if you include the cleaning/oiling kit.  At that price you need to ride years just to break even.

The high price of a K&N might be acceptable if they worked as well as paper filters, but they don't.  Over time I've seen informal tests indicating they don't filter well, but those tests were somewhat basic and short on specifics.  Then I recently found results of a comprehensive ISO 5011 test that compared a K&N with 8 other air filters of the same size.  This test uses a high tech (and high $$) machine to flow air and test dust (with a specific distribution of particle sizes) at a precise rate.  After testing, dirt captured by the filter is weighed, as is dirt that passed through the filter, to calculate filter efficiency.  The test also determines how quickly a filter clogs up, by measuring how long it can flow a constant mix of air and dust before air restriction causes a pressure drop of 10 IN-H2O greater than the initial restriction.

The results of this test are posted in multiple internet locations.  I found it on a Nissan/Infinity Car Owner (nicoclub.com) discussion board, though other sites include more detailed tabular data.  You can read it (search:  K&N air filter test results) if you're interested in the details.  I'll just summarize in terms of efficiency and capacity, which is what matters to me.

As far as efficiency, the best filter tested was an AC-Delco, at 99.93%.  The K&N was the least efficient, capturing only 96.8% of the test dust.  The paper element filters were consistently much more efficient than the serviceable (foam and fabric) filters, so this is useful data even though the tested filters were not sized for our bikes.

I already knew the K&N was less efficient, so that result was no surprise.  But I didn't expect the paper filters to have such higher dirt retention capacity.  I had believed the claim that oiled filters had longer service intervals, which apparently is a myth.  Here the AC-Delco was again the best, running for 60 hours before plugging up, and capturing 574 grams of dirt while passing only 0.4 grams.  The K&N plugged up in 24 hours (next to last of the 9 tested) and captured 212 grams of dirt while passing 7.  The author didn't mention why paper filters had such a greater capacity, though I suspect the tightly packed corrugated paper allows more total surface area (and more pores to clog) than the thicker fabric media.

To be fair, the author pointed out situations where foam or fabric filters make sense, such as off-road vehicles where water or mud can cause paper filters to collapse, or competition engines where high airflow is more important than high filtration efficient.

In the real world a lower efficiency filter may not make a difference.  GL1500 and GL1800 engines can last hundreds of thousands of miles with minimal maintenance.  Since the vast majority of owners never come close to wearing these motors out, some extra dirt may only show up as higher silica contamination in an oil analysis, and barely measurable wear on internal parts.  With this in mind, when I bought my F6B I seriously considered trying a K&N again.  Since a Goldwing filter change is so difficult, a longer service interval would be attractive even at the expense of more dirt in the engine.  But if an oiled filter like K&N traps less dirt, and also clogs up faster than a paper filter, it's hard to justify the cost or effort .  I'll stick with the OEM Honda filters.

[98valk]

search Spicer air filter test.  u will see HOW much dirt a k-n lets into an engine, wearing it out faster and making the oil dirtier faster.
Honda OEM filters are a synthetic/paper design which allows great airflow and provides top filtration.
if the GL18 OEM filter has a metal screen on the bottom remove it for even more airflow.
I do this for my Valkyrie GL15 and just made 106 HP on a mustang design dyno which would be about 116 HP on a dynajet dyno. I also am doing some OEM filter tests, one oem has 30k miles on it looks dirty yet still flows the same as a new OEM.

k-n is a race track only item, it lets too much dirt in, but it's your rings and cylinder walls.

[F6Dave]

I also am doing some OEM filter tests, one oem has 30k miles on it looks dirty yet still flows the same as a new OEM.

That's good to know.  With my F6B I plan on changing the filter at about 30K since the job is such a PITA.  There seems to be a consensus on the GL1800 boards to change air filters at about that mileage.

How/where do you flow test an air filter?  I'd be curious how my old one will flow.

[98valk]

I also am doing some OEM filter tests, one oem has 30k miles on it looks dirty yet still flows the same as a new OEM.

That's good to know.  With my F6B I plan on changing the filter at about 30K since the job is such a PITA.  There seems to be a consensus on the GL1800 boards to change air filters at about that mileage.

How/where do you flow test an air filter?  I'd be curious how my old one will flow.

until a filter is causing plugs to turn dark, engine performance goes down,  or darker smoke out the exhaust the air filter is still good. dirt on a filter actually helps it filter better. unless one rides/drives on dirt roads all of the time, air filters are usually good for at least 60k miles and a lot of times more. the 12k number is a joke and just there to sell air filters, like the 3k mile oil change.
http://filterminder.com/resources/learn-more.html

picked up a spare air box from pin wall $19 shipped, actually had a brand new filter in it. So I just seal off all of the outlets except one which gets an air flow meter attached. I modified the lid, put the inlet in the front and sealed off the existing, then tape an electric leaf blower to the inlet, and test away.

[Jess from VA]

I also am doing some OEM filter tests, one oem has 30k miles on it looks dirty yet still flows the same as a new OEM.

That's good to know.  With my F6B I plan on changing the filter at about 30K since the job is such a PITA.  There seems to be a consensus on the GL1800 boards to change air filters at about that mileage.

How/where do you flow test an air filter?  I'd be curious how my old one will flow.

until a filter is causing plugs to turn dark, engine performance goes down,  or darker smoke out the exhaust the air filter is still good. dirt on a filter actually helps it filter better. unless one rides/drives on dirt roads all of the time, air filters are usually good for at least 60k miles and a lot of times more. the 12k number is a joke and just there to sell air filters, like the 3k mile oil change.
http://filterminder.com/resources/learn-more.html

picked up a spare air box from pin wall $19 shipped, actually had a brand new filter in it. So I just seal off all of the outlets except one which gets an air flow meter attached. I modified the lid, put the inlet in the front and sealed off the existing, then tape an electric leaf blower to the inlet, and test away.

Except for the leaf blower and meter, this sounds suspiciously like a custom valkyrie airbox bong.   

I read all your posts with interest; do you really think 60K is OK on any air filter? 

Valk filters always come out dirty on about the rear third or quarter of the element (in back where the intake is).  Do you believe so long as there is clean element, it's still OK? 

[98valk]

I also am doing some OEM filter tests, one oem has 30k miles on it looks dirty yet still flows the same as a new OEM.

That's good to know.  With my F6B I plan on changing the filter at about 30K since the job is such a PITA.  There seems to be a consensus on the GL1800 boards to change air filters at about that mileage.

How/where do you flow test an air filter?  I'd be curious how my old one will flow.

until a filter is causing plugs to turn dark, engine performance goes down,  or darker smoke out the exhaust the air filter is still good. dirt on a filter actually helps it filter better. unless one rides/drives on dirt roads all of the time, air filters are usually good for at least 60k miles and a lot of times more. the 12k number is a joke and just there to sell air filters, like the 3k mile oil change.
http://filterminder.com/resources/learn-more.html

picked up a spare air box from pin wall $19 shipped, actually had a brand new filter in it. So I just seal off all of the outlets except one which gets an air flow meter attached. I modified the lid, put the inlet in the front and sealed off the existing, then tape an electric leaf blower to the inlet, and test away.

Except for the leaf blower and meter, this sounds suspiciously like a custom valkyrie airbox bong.  

I read all your posts with interest; do you really think 60K is OK on any air filter?  

Valk filters always come out dirty on about the rear third or quarter of the element (in back where the intake is).  Do you believe so long as there is clean element, it's still OK?  

its still good and with the dirt is actually filtering the dirt better. the intakes are actually drawing air from the air volume in front of them which is downstream of the filter, so one area that looks dirty really doesn't mean anything.
read the link I provided much, much info. actually its Donaldson filters and they talk against changing air filters too soon and they sell air filters. the post facts not fiction/emotion about all of their filters, and they're filters are known to be one of the best out there.

[hungryeye]

Others have given the same answer I would have, simply more air flows along with more dirt, good for race machines of all kinds where winning is more important than engine longevity. I think most of us here want a clean running long lasting engine.

[Robert]

Interesting reply's on the KN air filters but I have a couple of questions.

How many engines have you replaced traceable to the KN air filters letting in to much grit.

How many other parts have you replaced traceable to the excess dirt the KN let in.

I am also kind of interested to know the speed, cfm, of the air and sq inch of the filters being tested compared to our engines. These ratios will make a difference in the efficiency of the filter and determine the validity of the tests.

I am not a real fan of KN and I pretty much agree the stock filter is a synthetic paper that is a good filter but really the way you guys make it sound your engines will die a quick death. Quite honestly I am amazed at the amount of crap an engine can take in and not get bothered. Ialso agree with the longer interval to change the oem filter. But if you extend the interval for the stock filter maybe there is not that much dirt out there to contend with. So either filter will fair better than expected.

[F6Dave]

Interesting reply's on the KN air filters but I have a couple of questions.

How many engines have you replaced traceable to the KN air filters letting in to much grit.

How many other parts have you replaced traceable to the excess dirt the KN let in.

I am also kind of interested to know the speed, cfm, of the air and sq inch of the filters being tested compared to our engines. These ratios will make a difference in the efficiency of the filter and determine the validity of the tests.

I am not a real fan of KN and I pretty much agree the stock filter is a synthetic paper that is a good filter but really the way you guys make it sound your engines will die a quick death. Quite honestly I am amazed at the amount of crap an engine can take in and not get bothered. Ialso agree with the longer interval to change the oem filter. But if you extend the interval for the stock filter maybe there is not that much dirt out there to contend with. So either filter will fair better than expected.

If you re-read the last paragraph of my post you'll see I said the extra dirt a K&N filter lets through may not matter:

' In the real world a lower efficiency filter may not make a difference.  GL1500 and GL1800 engines can last hundreds of thousands of miles with minimal maintenance.  Since the vast majority of owners never come close to wearing these motors out, some extra dirt may only show up as higher silica contamination in an oil analysis, and barely measurable wear on internal parts. '

But why bother if the less efficient filter costs more, and clogs up faster?

Then there's the matter of air restriction.  Keep in mind that any engine can only flow a finite amount of air, which is a factor of displacement, RPM, induction and exhaust design, and cam profiles.  A properly designed airbox and filter will flow all the air a given engine can handle.  I've read that Honda designs their intake systems as well as any manufacturer -- the filter is as large as I've seen on some cars!  I find it hard to believe that a company with as much engineering expertise as Honda would sacrifice 'free' power and fuel mileage by under-sizing the F6 intake system.

[98valk]

there will not be total engine failure.
But what will happen over the miles, the piston walls keep getting scorn from the extra dirt being let in, thereby increasing blown-by and lost compression. this all results in less mpg and HP/TQ.
So the question is does one want their engine to be the same as new at 100+k miles or not?
If one checks the used oil analysis sites every set of results WILL always tell the technician if a k-n is being used or there is an air filter problem.  some people have used k-n see the dirt results and then switch to an oem or eqiv filter and they will certain numbers go to zero.

[Robert]

I agree and respect both of your opinions as well as your answers but a person who is not a gearhead may think that their engine will flame down to a cinder in an instant if they put the KN filter in it.

We all know the facts sometimes do not present the real world scenarios that we all see and go, HUH? Although we can extrapolate real world results from tests but they may or maynot be lived out in the real usage of the vehicle.

[Fsixer]

I used to run K&N on every vehicle I had. My son put one on his Harley Low Rider. 3 months later he called me up and said you gota come over here. I went over and he had his breather cover off and shined his flashlight down the throttlebody and to my horror there was dirt yes dirt lining the throttle body as far as you could see. Well that pretty much did it for me. I seen it come out of the wraper and it was impregnated with oil when he installed it.. I felt bad because I bought it for him for a birthday present.
I'm not here to bash anyone just letting you know what I seem with my own two eyes and know to be a cold hearted fact.
He didn't trust the engine after that and sold the bike.
Yes it was on tight and sealed up properly, I've been wrenching dang near 50 year and he's certified.
To bad because I've seen K&N pull a couple more ponies on the dyno.

[98valk]

I used to run K&N on every vehicle I had. My son put one on his Harley Low Rider. 3 months later he called me up and said you gota come over here. I went over and he had his breather cover off and shined his flashlight down the throttlebody and to my horror there was dirt yes dirt lining the throttle body as far as you could see. Well that pretty much did it for me. I seen it come out of the wraper and it was impregnated with oil when he installed it.. I felt bad because I bought it for him for a birthday present.
I'm not here to bash anyone just letting you know what I seem with my own two eyes and know to be a cold hearted fact.
He didn't trust the engine after that and sold the bike.
Yes it was on tight and sealed up properly, I've been wrenching dang near 50 year and he's certified.
To bad because I've seen K&N pull a couple more ponies on the dyno.

many reports similar esp by some BMW sites yrs ago. one guy actually put some grease inside the air box, road the bike for a while and then saw all of the dirt which got by.

if a correctly sized air filter with enough surface area to provide all of the air the engine wants is used, it would make the same HP as the smaller k-n. this has always been the slight of hand by k-n who originally used a car with an under sized air cleaner and installed their filter, wow 2-5 more HP and only at the very top end, I believe this was a 4 cylinder '80s eco car they used.

[Glenlivet]

Go talk to a bike-atv shop about K&N filters.  Why do you think they let more air in? They also let more dirt in and will wear your engine down to failure. A lot of people get away with it however a lot don't. Most warranties are void with one. If you never ride in dusty or muddy conditions, you may get away with it

Nailed it, and F6Dave proved it. My own experience  with K&N has been in ATV applications and these often operate in very high dust conditions. The K&N is an abysmal air filter.
Basically the K&N has huge product recognition and is associated with air filtration in our minds through years of exposure, but really, what are they?

The K&N air filter was designed for show vehicles, period. They look good on polished and chromes engines where their purple oil stained cotton gauze and chrome stretch metal retainer is their signature look, perfectly complementing the show car. As far as actually filtering, all they have to do is protect the motor from ingesting the odd blade of closely trimmed grass at a concours d'elegance show, as the vehicle is driven off and onto its trailer.
But then the K&N filters became popular, and people began to assume they were a great filter for actual service duty (when in fact they are ill suited to real world work) What was K&N to do? They want to sell as many filters as they can and yet they were married to their signature look, which really didn't work so good. At all.

In a stroke of genius (or out of desperation) they came up with the 'pre-filter', basically a sock of dense material that you pull over the K&N in the effort to increase the technical performance of the old filter.
Which raises a few questions: Why should you need a filter to filter the air filter's air so you can use THAT air filter? And with that sock pulled over it, what's the good of having that fancy chrome and purple gauze housing when you can't see it anymore?
To top it off, the thin purple oil that the K&N uses tends to bleed off the cotton medium into the intake air stream and contaminate the mass 02 sensor in fuel injected engines.
 There have been many mass 02 sensors and IAP sensors that needed replacing from K&N oil contamination.
Any number of internet searchable technical performance comparisons and measurements of the K&N air filter give the same results: It's a poor technical performer until one buries it in prefilters, and then it becomes a mediocre filter with a higher air resistance than alternate options that are less expensive and less fussy.

My humble opinion is to leave the K&N to it's original purpose, screening the bumblebees out of the intakes of show cars.  

[hungryeye]

I'm sure there are a lot of show vehicles that use K&N, but they are a performance street filter. They let more air in so you can spray more fuel in. But more dirt goes in also. I haven't used K&N in years, I was one of the first to condemn K&N filters on this board.

[Robert]

Just wanted to show how dirty my original air filter was after 10k miles. Its not bad at all and if the KN was installed I dont think it would have any problem keeping this dirt out.

[ledany]

Buon giorno a tutti,

I would like to clean my K&N filter but I have no idea how to remove the fairing and the fuel tank 

Woofred, à l'aide ! 

[98valk]

Just wanted to show how dirty my original air filter was after 10k miles. Its not bad at all and if the KN was installed I dont think it would have any problem keeping this dirt out.

Spicer air filter test (your favorite search engine) will show u different. k&n lets in a lot of dirt.

[dans2014]

My mechanics love K&N. It gives them lots of business with bad engines. They are for track and no dusty conditions. They do not filter as well as a good paper

[Robert]

Buon giorno a tutti,

I would like to clean my K&N filter but I have no idea how to remove the fairing and the fuel tank 

Woofred, à l'aide ! 

Just saw this and if you would like an explanation on how to remove the air filter I would be more than happy to show you.   

[Robert]

My mechanics love K&N. It gives them lots of business with bad engines. They are for track and no dusty conditions. They do not filter as well as a good paper

I know that there are opinions that they dont filter as well and ruin engines, but really I have NEVER seen one failure due to the air filter. I also do not dispute the ability of the filter to do its job either better or worse than a stock air filter. Actually I have seen cars come in with no air filter run better than those with one. Unless you are a high mileage truck driver I see no ill effects due to a K&N air filter. Now in reality though, I see few good reasons to have one also.


Now I have seen mas air flow sensors go bad more than likely due to dirt. But ironically not on cars with K&N filters in them. These sensors are in the flow of air, extremely sensitive and would be the first to show some form of problems if the dirt were really the problem.

Its like us as humans, something is going to get to us one day and we could spend all our time worrying about this or that, thinking its going to shorten our life. But when the time comes it will more than likely have nothing to do with what we were worried about.

[98valk]

My mechanics love K&N. It gives them lots of business with bad engines. They are for track and no dusty conditions. They do not filter as well as a good paper

I know that there are opinions that they dont filter as well and ruin engines, but really I have NEVER seen one failure due to the air filter. I also do not dispute the ability of the filter to do its job either better or worse than a stock air filter. Actually I have seen cars come in with no air filter run better than those with one. Unless you are a high mileage truck driver I see no ill effects due to a K&N air filter. Now in reality though, I see few good reasons to have one also.


Now I have seen mas air flow sensors go bad more than likely due to dirt. But ironically not on cars with K&N filters in them. These sensors are in the flow of air, extremely sensitive and would be the first to show some form of problems if the dirt were really the problem.

Its like us as humans, something is going to get to us one day and we could spend all our time worrying about this or that, thinking its going to shorten our life. But when the time comes it will more than likely have nothing to do with what we were worried about.

read the spicer air filter test. it's a slow extra wear on the engine, meaning, oil get dirtier faster and HP and MPG goes down over the yrs from the increased wear and compression getting less.  stating as many have "never seen a failure" is a very poor statement. The oem filter lets in plenty of air and filters very well. Honda filters are not pure paper filters. There are many dyno runs out there showing a reduction in HP when using a k&n.
 http://www.billswebspace.com/AirFilterTest.htm

[Robert]

read the spicer air filter test. it's a slow extra wear on the engine, meaning, oil get dirtier faster and HP and MPG goes down over the yrs from the increased wear and compression getting less.  stating as many have "never seen a failure" is a very poor statement. The oem filter lets in plenty of air and filters very well. Honda filters are not pure paper filters. There are many dyno runs out there showing a reduction in HP when using a k&n.
 http://www.billswebspace.com/AirFilterTest.htm

This is the test you quoted:

The results of an ISO 5011 test of several air filters designed for the GM Duramax Diesel
and the K&N has a 96.8 efficiency compared to the best at 99 percent a 2 to 3 percent difference.

Exactly what I said, the test is a diesel that flows much more air at higher rates than a motorcycle or car. Also what is the wear difference between the best at 99% compared to K&N at 96%. I doubt you can tell me exactly. while I agree with you on many points I find the claims of catastrophic differences a bit over stated.


You state:

"stating as many have "never seen a failure" is a very poor statement."

So my question to you is,  tell me what failures have you seen that are directly related to this 2 to 3 percent filter efficiency difference.

Also what did they use as dirt and dust and how much? I doubt anyone would ride through that much dirt and dust since they plugged up the best filter in short order.

[98valk]

read the spicer air filter test. it's a slow extra wear on the engine, meaning, oil get dirtier faster and HP and MPG goes down over the yrs from the increased wear and compression getting less.  stating as many have "never seen a failure" is a very poor statement. The oem filter lets in plenty of air and filters very well. Honda filters are not pure paper filters. There are many dyno runs out there showing a reduction in HP when using a k&n.
 http://www.billswebspace.com/AirFilterTest.htm

This is the test you quoted:

The results of an ISO 5011 test of several air filters designed for the GM Duramax Diesel
and the K&N has a 96.8 efficiency compared to the best at 99 percent a 2 to 3 percent difference.

Exactly what I said, the test is a diesel that flows much more air at higher rates than a motorcycle or car. Also what is the wear difference between the best at 99% compared to K&N at 96%. I doubt you can tell me exactly. while I agree with you on many points I find the claims of catastrophic differences a bit over stated.


You state:

"stating as many have "never seen a failure" is a very poor statement."

So my question to you is,  tell me what failures have you seen that are directly related to this 2 to 3 percent filter efficiency difference.

Also what did they use as dirt and dust and how much? I doubt anyone would ride through that much dirt and dust since they plugged up the best filter in short order.

u have to read the full report.  that 96.8% eff is at the end of the test however until that point the k&n is letting in a ton of dirt. see the chart where it shows how much dirt is passed through.

[Robert]

The test ran for 60 minutes do you really think there is enough dirt in the air unless we went through volcanic ash in the air from an eruption that the normal filter would get that much dirt in that little space in time and what kind of mileage does that really represent in the real world? So in the real world by the time the K&N gets enough dirt in it to pass that much dirt someone would clean it and re oil it.

Also in all fairness to the K&N it partially works by oil holding the dirt, so in that short a time the oil would not be able to hold the dirt and spread to the particles that have just attached themselves to the filter.

I do not deny that the K&N lets more dirt pass, I just say I have never and I feel pretty safe to say no one has seen a failure from this.

 Heck they cannot even find the wear that this 3 percent causes. I feel pretty much like most things in cars like people all  have an end of life, usually it has nothing to do with the causes we were worried about and more to do with something unplanned. People overeat, eat the wrong foods, party to much, and the list goes on and yet people do live and most times like machinery its not those causes that did them in. Sometimes everything is done correctly and still something else takes them out, so it is with any machinery.

I have seen more motorcycles taken out by accidents than K&N filters. So the hysterical claims of severely shortened life and increased repair costs I take with a grain of salt. Been tinkering to many years and lost to many vehicles to be to worried about this topic.

So personally I have no problem in saying they may shorten engine life but no one including  yourself can pinpoint anything that is a technically ensured conclusion to this.

Did you ever think of becoming a politician LOL

[F6Dave]

I posted an oil analysis from my F6B last month.  One user replied that his analysis had above average silicon levels, which dropped to below average when he switched from a K&N to an OEM air filter.  That's good evidence that K&Ns let more dirt into you engine.

Below are pictures of my F6B's OEM filter and a K&N.  The OEM has nearly 50% more pleats.  That much more surface area could be the reason tests have shown that OEM filters actually last longer.  Even worse, I've read some posts about the filter oil drying out when a K&N is left in a bike for years.  Surely that makes those filters even less effective.