Kawasaki KLR Forum banner

The great (informative) K&N filter debate. (here we go again)

5K views 93 replies 19 participants last post by  MN Willie 
#1 ·
It is with great pride that I'm able to start this conversation here today.

The purpose of this is to be informative, educational and last but not least controversial;)

There has been many a debate about the legendary K&N air filter with staunch arguments on both sides of the fence.

First, allow me to present some detailed instructions on how to properly maintain said filter (or any cotton gauze element type).

Then, I'll cover a case sample for further review and debate.

Last but not least I'll support everything with a short video from a man who is world renowned within the automotive industry (airflow research). When the OEM manufacturers have a problem they need solved this mans phone rings. His name is David Vizard, his level of experience and expertise is unmatched.

I know of several well respected figures who have done testing of their own in the past and those results have been repeated numerous times; here and elsewhere online. My intent is not to discredit those results in anyway. I'm merely presenting an entirely new set of facts and explanation of conclusion as to why it is the way it is and why those previous results ended up how they did.

Here's some initial food for thought: How much dirt and dust are we going to find behind this respectfully dirty K&N filter?
Glasses Automotive lighting Automotive tire Motor vehicle Automotive design

Automotive tire Sleeve Grey Wood Synthetic rubber


Stay tuned for part 2 coming soon!
 
See less See more
2
#4 ·
Yes, Welcome Back!

But I will say that sand is pretty coarse particulate and that filter is barely used compared to many air filters that I see, including my own oiled foams in KLR & KX500. Wyoming has a LOT of talcum powder dust.
I have measured <.0005 inches.
 
#10 ·
Well to reiterate what I've said on the subject in the past;

1) filtration ability; I'm skeptical and Dodge had a bulletin about voiding the warranty if a K&N filter was used on a Cummins turbo diesel. I'm not convinced they trap as much fine particulate as a proper oiled foam filter. There have been numerous tests over the years.

BUT, the biggest reason I don't recommend them in a KLR is 2) because they flow WORSE than the stock filter and much worse than a Uni-Filter due to the metal end plate design. I've seen convincing tests on this by two well respected and well known KLR gurus, here's a link to my thread containing KLRCary's (Schnitz Racing) notes on the subject;

A lot of missunderstanding with airbox issues.
First, the screen. Airflow gains are not linear. Removing the screen with an otherwise stock KLR airbox will only gain you 2 cfm. The engine won't know the differance. However, with a heavily modified airbox, the gain from removing the screen is 8 cfm. Depending on what else is done to the engine, you may make more power. I doubt that you'll feel it, but a dyno will show it. Butt-dyno's can detect very small low rpm changes, but don't detect higher rpm changes very well at all. You'll likely not detect it, but that does not mean it's not there.
Comparing screen removal to other models is wrong, particularly with the newer sportbikes. With them, the screen often serves another purpose as well. Air distribution in a 4 cyl sportbike can be a real problem, particularly with "ram air". Removing the screen on them can cause very real losses, depending on the model. That does NOT apply to the KLR.
Same thing with air filters. There is only about 2 cfm difference from the best filter (UNI), to the worst (K&N). With a modified airbox, that difference grows to 9 cfm.
Here is the flow chart:
Completely stock - 64.8cfm
Same - Remove snorkle - 74cfm
Same - With UNI filter - 76.2cfm
Same - Remove screen - 78.6cfm
Same - Small "L" cut - 85.1cfm
Same - Large "L" cut, open snorkle area further - 92.4
Same - Remove door - 103.2
Alternate - UNI filter, No snorkle, With screen, No door, No "L" cut - 95.4
All at 2" of water, tested at 1 1/2" and 3" and averaged to 2"
To answer the larger question, how much air can the KLR really use?
....................
A stock KLR about 70-80cfm. With a good pipe about 75-90cfm. A modified motor about 90-100cfm. Having a bit more capacity than you you need will not hurt anything. The effects are not linear though. Going from 65cfm to 75cfm you will likely notice, but going from 75 to 85 cfm you likely won't.

Part of the confusion might be due to the effects of the carb shimming. Since that mod is for a stock needle, the snorkle removal serves not just to add air, but to lean out the top end. The stock KLR till 07 is rich on the top. ( The 08 has a smaller main jet.) Airbox mods have much more effect on top end mixture, so, with the stock needle it also helps straighten out the fuel curve.

Finally the airbox door. You've got to carefull there. You don't have clean air there. It's flowing past that door when riding. You can easily create a partial low pressure area there, depending on wind direction, and where you place your leg!

Cary"


I do not recommend removing the backfire screen (PITA) or running without the airbox door for reasons that should be obvious.

Though a KLR isn't going to have a bunch more power no matter what you do, a KLX kit combined with the snorkle-ectomy and L mod or 4 - 1" holes will have it running properly. don't bother with the little 1" foam filters if you drill the holes - they are useless.



Given all of the above, I'm not sure why a person would bother switching from oiled foam to K&N; even IF you believe it filters as well and disbelieve the information on flow, what is the advantage? why bother?

2 cents,
Dave
 
#27 ·
because they flow WORSE than the stock filter and much worse than a Uni-Filter

It's that way on several. The yamaha grizzly filters from k&n gave up 50% of the surface area to the oem. One of my vehicles i remember had a flat panel filter and the stock filter has about double the surface area. Ive also had customers cars with K&N that the fit was simply not good enough to get a great seal.

I have K&N left in about half my road vehicles. Over the years I've came to not care so much for them. I'm not throwing away the ones I have.... but doubt I ever buy another
 
#11 ·
While this is a comparison for filters in a diesel truck, it's one of the more comprehensive I've seen, read it and take it for what it's worth;

 
#12 ·
K&N used to recommend Not Cleaning their air filters Too Often.
They instead recommended removing their air filters & ADDING more K&N Air Filter Oil from the Inside-Out. They claimed that the build-up of oil-soaked fine particulates on the outside of the pleats allowed ever finer filtration.

Does anyone have a copy of K&N's current instructions?

It's been many, many years since I have read the instructions which used to come/may still come with K&N Air Filters.
I've always dis-liked all the metal end caps that may have been used when the OEM factory air filter had filtration material in that area. Unless the OEM factory air box lids restricted/blocked air flow to that area also.
K&N does have some models of air filters that have a filtration material End Cap on larger filters, like real dirt bikes have.
 
#13 ·
K&N used to recommend Not Cleaning their air filters Too Often.
They instead recommended removing their air filters & ADDING more K&N Air Filter Oil from the Inside-Out. They claimed that the build-up of oil-soaked fine particulates on the outside of the pleats allowed ever finer filtration.
I have heard this as well, but couldn't tell you where from. Basically, filtration efficiency goes up as the filter gets dirtier.
 
#14 ·
where can i see what kind of dirt gets through these filters??
 
#15 ·
Here.
Below is an ATS 088 turbo I bought used. It required a complete rebuild, mainly due to the K&N filter that was run on it.
As you can see, it chewed up the compressor wheel pretty bad.

Another reason why many fleet companies no longer recommend the “million mile” K&N filter.
Junk I tell ya!

Silver Gas Petal Automotive wheel system Circle
 
#16 · (Edited)
All of the above comments are valid points and well respected.

The above comments about maintenance intervals in relation to filtration are on point.

Where folks run into issues is during the practical application of said maintenance which in turn causes damage to the element, typically going unnoticed by the operator. The damage begins once the filter is put into service.

Let's look further into proper maintenance here:

When maintaining the filter you'll need a bucket with clean water and some K&N cleaner.
Food Automotive tire Drink Liquid Font

(The water already looks dirty because in this picture I've already sprayed the filter with cleaner which causes dirt to instantly start running out of the medium and some had dripped into the bucket, no problem)

Once you've liberally sprayed the filter with cleaner (must use K&N cleaner, do NOT use any other type of cleaner or soap) I usually let it soak in for a few minutes at least (not terribly long).
Hand Liquid Fluid Gesture Plumbing fixture




At this point you're now ready to begin 'dunking' the filter as seen here:
Fluid Ingredient Serveware Cuisine Dish

Lifting filter and dunking it repeatedly(more dirt comes out each time)
Food Ingredient Cuisine Dish Thickening agent

After a dozen or so dunks it should be looking clean like this below
Tire Automotive tire Hood Grille Tread


Typically at this point(above filter) I will dump out the dirty bucket add fresh water and dunk the filter a few more times just to rinse out any residual cleaner/dirt.

Next it's time to dry:

IMPORTANT: do NOT
use any sort of compressed air to dry the filter. It MUST be left alone to "air dry". This step is where 90% of damage to the filter occurs from. Using any other method except open air drying causes separation of the cotton fibers, in turn, causing a condition known as a "blown filter" once this happens the filter is no good and must be discarded. (Don't be that guy).

Choosing to oil and use a "blown filter" most likely results in fine dust ingestion. (Hence the black looking substance coating the surfaces of the intake tract and or turbocharger compressor blades)

Further on in this article we will talk about how a K&N filter actually works to remove particulate from the air.

Once the filter is dry you must re-oil with the correct K&N filter oil. (Do not use any other type of oil, period.)
Cosmetics Automotive tire Font Tints and shades Liquid




Additionally, I'll be posting a video by Mr. Vizard addressing the flow aspect of the debate. (You'll be quite surprised at the results)

Next: we'll look at the filtering capability and what this filter trapped. We'll also have a look at what this filter looked like on the inside before it was cleaned. Stay tuned coming soon.
 
#18 ·
All of the above comments are valid points and well respected.
Interesting. Thanks for sharing all this. I'm not a K&N hater. I use it on my VStrom despite dire warnings from half the owners saying my engine will die an early death, mixed in with other VStrom owners stating they got 100's of thousands of miles on their VStrom using K&N Filters with no early failures. I do use the Uni Filter on my KLR though.
 
#17 ·
That's an interesting method of cleaning the filter. I've always used low-pressure water (kitchen sink) from the inside of the filter, obviously with liberal use of the K&N filter cleaner.

And definitely no compressed air. Ever. Every hot rodder by now should know that you shouldn't blow out air filters of any type for risk of blowing holes in the filter media.
 
#20 · (Edited)
I want everyone to chime in with their thoughts and experiences.

Once the filter is sufficiently dry I apply a liberal coat of fresh K&N oil. Inside and out. It should look something like this when finished (sufficiently saturated but not soaked)
Automotive tire Tread Automotive lighting Musical instrument Tire

If it looks as though you just pulled it out of the package for the first time then you're on the right track.
 
#21 · (Edited)
Next let's look at the dirt that was trapped in the filter.

For the purposes of this experiment I let the contents of the bucket settle overnight. At which point I poured off the water to reveal the dirt left behind in the bottom of the bucket.
Wood Beige Tints and shades Circle Landscape

The amount of ultra fine silt material is astounding. As well as a decent amount of fine magnetic black sand material 'aka' magnetite. That stuff can and will kill an engine in short order if it gets inside.

Additionally, when I pulled the filter from the box the inside of it look like this(before cleaning)
Shoe Automotive tire Wood Tints and shades Bicycle part

Notice the glossy black rubber sections that have zero "dust" accumulated. Likewise the wires containing the filter medium have zero dust residue. What makes those parts glossy is the light coating of oil residue that exists; surely any dust making it's way past the filter would stick to this oil covered surface. (Let's hear what y'all have to say).

The inlet to the intake track looked as follows:
Automotive lighting Automotive tire Audio equipment Grille Automotive exterior

Again, same results. No indication of dust build up on the glossy oil coated intake surfaces.

Notice the K&N air filter sealing grease around the flange. This is an important step not to be overlooked. The only filters that do not utilize this grease are the typical 'clamp-on' style elements. All other 'press to seal' type elements must use this grease around any sealing surfaces for them to be effective. Here is said grease:
Automotive tire Motor vehicle Road surface Asphalt Wood


The sealing lid looked as follows upon removal:
Dishware Serveware Circle Close-up Tableware

The center portion exposed to "clean air" has a similar thin oil residue coating. Yet when wiped no dirt/dust appears on the rag. Nor is any visible upon inspection.

Before we dive into the airflow research side of this conversation I'd first like to share some thoughts about why these filters have such a love/hate relationship among performance enthusiasts and everyday folks it seems.

Here's a few to consider

Price: These filters are not cheap. No matter the application they're at a premium price point above 'most' other options.

Availability: While it's not as much of an issue these days with all the online options but, most places don't 'stock' many options of K&N filters so some additional leg work must be done to aquire one. Again still at a premium.

Application: Even though there are tons of applications available not all models have a K&N option.

Maintenance: I know for a fact that some folks just don't want to hassle with having to clean the darn thing every so often. Plus the expense of the cleaning kit. Just grabbing a brand new filter each time and tossing it in is just plain easier.

Stay tuned for the next post as you won't want to miss this video about K&N filters in relation to airflow testing. It's all about the how and why.
 
#22 ·
Nice looking clean filter. Back when I was in the auto industry, I saw a lot of them over-oiled.

I prefer the squeeze bottle over the aerosol. I find it easier to apply the oil in a controlled manner.

When re-oiling, I add a small bead to the outside edge of the pleats, moving my way around the filter. By the time I make it around the filter, I can usually see if the oil hasn't seeped down into the bottoms of the pleats. If not, I apply a small amount to any potentially dry sections.
When done, I let the filter sit overnight. In the morning, I check to see if the oil has seeped to the inside of the filter media (it's "media", btw, not "medium"). If there are any light spots, I add a bit more oil to the dry areas and let it soak in. But if everything looks a nice light red (like Biggs's previously posted picture), I call it good.
 
#26 ·
(it's "media", btw, not "medium").
The root word is medium. See plural (-dia) & #3 but I understand where you're coming from(plural), same difference. Best wishes as always.
Newspaper Publication Font Material property News
 

Attachments

  • Like
Reactions: AntonK and JimR
#25 ·
After much anticipation I'm happy to present the video with the answers. It's about a 20min flick and well worth watching it through to the end as it all comes together and answers those difficult questions.



I'm interested to hear from those well in tune with this topic. Enjoy!

Ps. Anybody not familiar with David Vizard is encouraged to do a little research, especially if you're a motor head type of person.

Best wishes
 
#30 ·
I like David too and I don't know much about ICE but I'm not buying his logic there unless he backs it up with a research. He criticized Todd and his 'constant velocity' compressor while somehow he forgot how the air has mass and doesn't just stop in the intake manifold when there's no suction stroke. Based on his 'logic' the K&N filter will benefit thumper more than multi cylinders or engine with long intake runner. Doesn't make any sense to me.
 
#31 ·
Precisely why I'm running the K&N on the KLR, I live in Baja like conditions. It's not for everyone though and I don't advocate that everyone should be running one.

Glad you enjoyed this thread and I hope you got something from it. Best wishes

I like David too and I don't know much about ICE but I'm not buying his logic there unless he backs it up with a research. He criticized Todd and his 'constant velocity' compressor while somehow he forgot how the air has mass and doesn't just stop in the intake manifold when there's no suction stroke. Based on his 'logic' the K&N filter will benefit thumper more than multi cylinders or engine with long intake runner. Doesn't make any sense to me.
That good because he's not selling it. He has tested these filters in the lab and on the track. The air inside an intake pulses back and forth. On short runner setups air fuel mixture can actually come back out the air filter.

Your observation is correct in that having individual filters/runners is beneficial over a large common intake plenum. The wave dynamics of each cylinder can be tuned separately.

Best wishes
 
#32 ·
Wow, quite the primer on the K&N filter. on my A9 (1995 Barbie) I was tracking some info and took to the K&N filter advertisements. I can not say I ever knew of any difference in performance of the bike. I thought they were supposed to be "high flow" and thus a an HP or two or something . . . . . I never experienced any difference in my own mind. That bike ran great no matter how hard it was flogged. Now my A16 got a UNI and after discovering all of the advice of the topic of "how to properly maintain and oil your filter" the UNI has been in about 4 - 500 miles worth and all is well. Have not been on gravel or dusty trails enough (sadly) for me to dive into maintaining it. I still have the OEM cleaned and stored and ready for an oiling should I decide I need to service the UNI. It is likely this summer I will get out on the gravel in dusty conditions. If anyone needs advice on proper maintenance of the air filter you will find it here. be careful as there are "specific methods" and those who do not heed them shall atone. (kidding) L6
 
#33 ·
Id say 9 of 10 bikes that I see in my shop come in with a foam filter that's never been oiled. Lol. VERY rarely do any have an engine issue. I have a Grizzly in right now with a bad starter relay. 6k hours and never any oil on filter. Ridden only in dusty conditions and hay fields.

So id say any oiling or maintenance puts you ahead of the curve
 
#34 ·
I watched the video. .....The concept of the little "waving hairs" being the reason that the K&N can outflow paper filters and still offer superior filtration is an interesting one. I'd also point out that the comparison between paper and oiled cotton is one thing and between oiled cotton and oiled foam is something else but lets leave that alone for a moment.

As I said in post #10 there are two areas of concern; filtration AND flow. IF we eliminate the filtration portion of the question, we are left with flow and going back to Cary Aspy's flow testing of a K&N designed for a KLR650 inside a KLR airbox, the K&N underperformed compared to the top oiled foam filters; it appears that the big metal end cap on the filter simply cuts off too much flow compared to the stock or aftermarket foam filters.

Giving the whole idea presented in the video due consideration, it may be possible that the K&N's initial poor flow as compared to an oiled foam filter would be overcome as the restriction increases due to loading and that at some point the dirty K&N may outflow a dirty foam filter even though a clean foam filter outflows the K&N. In most real dirt bikes, the engineers significantly oversize the filter to allow for the decrease in flow as the filter gets dirty; on the KLR, the filter area is far more limited which means that filter maintenance and maintenance intervals become more urgent in dusty/dirty conditions.

My takeaway is that the video offers a compelling potential rationalization for a difference between the opening size in the media vs. filtration results. OTOH, nothing presented makes me question Cary Aspy's flow testing and though maybe the 9CFM flow gap (10 - 15% ) between an oiled Uni-filter vs. a K&N closes as the filters load, the best flow was obtained by a clean oiled foam filter.

Additional areas of thought are around oiled foam media vs. paper and the oiled cotton gauze; I think it's quite possible that oiled foam resists restriction at a greater rate than typical paper media. There are also several tests that show K&N's letting it far more dirt than paper (which is why Dodge and others voided their engine warranties if K&N's were used) but maybe that's more of an issue on forced induction motors...If memory serves, even K&N had a disclaimer on their site at one point for forced induction motors.

Anyhow, I'm sticking with my Uni filters and Bel Ray filter oil at this point. Flow testing with various types of KLR filters in an airbox showing results at various % of dirt loading and combined with an oil analysis experiment may convince me to switch depending on results but I'm very skeptical that will ever happen.

2 cents,
Dave
 
#36 ·
@DPelletier you make some valid points.

I'd like to hear some opinions as to why you guys think the foam filters never caught on with the automotive industry or the greater off-road racing industry (excluding most dirt scooters).

It seems that the only major market using those oiled foam filters is in dirt bike applications. Now, yes, I understand there are other applications available; I'm simply saying that in general it's the dirt bikes where applied the most from an OEM standpoint.

I'd also like to point out that quite a lot of 'newer' dirt bikes are using a flat paper element type. Ex. Crf300 rally.... perhaps cost cutting is to blame??

It's worth noting that in drag racing, an industry centered around "maximum performance" we don't see the application of foam. Rather tons and tons of cotton gauze.

Now, like I said at the beginning, nothing about my intent was to discredit any of those previous tests; for they are valid tests indeed.

Likewise, I don't wish to "convert" anyone by coercion.

I think it's healthy to present as many facts as possible in order to make educated informed decisions. Likely, it leads to positive outcomes.

As an aside, has anyone ever seen one of those old school retail parts counter displays by K&N where it tests filter restrictions?

It was a device the had a vacuum motor attached to an inlet box and a tube with a png ping ball to measure resistance. You could switch out different filter types on the front of the machine and the ball would rise or fall depending on airflow (basically a crude little flow bench).

We had one on our counter and man let me tell you with that machine we sold truckloads of K&N filters.

I'll look for a picture or video of one to post up.

In the meantime, Best wishes.
 
  • Like
Reactions: DPelletier
#56 ·
I'd like to hear some opinions as to why you guys think the foam filters never caught on with the automotive industry or the greater off-road racing industry (excluding most dirt scooters).
Like I said. Of the hundreds of atv/bike I get in my shop....I could count the foam filters that ive seen oiled by an owner on one had probably. People just don't do it. Lol . In cars any K&N or paper is better than a non oiled foam filter and I suspect that even fewer cars are properly maintained by their owners than Toys like bikes/atv/and sxs. Ill recommend a K&N over a dry foam filter anyday. Lol.

And oiling isn't terribly cheap or fun either. Maintaining our 20 or so vehicle fleet would just suck more in general if we had to clean, dry, and reoil.

Ask me about overcarburating :p
. I see a LOT of old cars in my shop come in with a 350 or 400 CI engine, stock heads and nearly stock cam..... and an 850 CFM edelbrock. Lol. Can flood and kill them on demand if you open the secondary lol. I had a one small block with a pretty mild cam and little if any head work come in with dual 550s. Lol. Enough carb for a 9k RPM 460 or 454.

Even with my afr meter people won't usually let me put a smaller carb on. One can only jet and needle down so far. Lol. Adding a big carb spacer can help dumb down the issue too.

For filters, a stock engine only needs so much air. An NA engine will likely NEVER be built enough to need more air than the stock filter or air intake will flow, yet people spend millions on intakes/cold air/filters.

Turbo are a different beast. A tune (or even a different restrictor pill or some other cheat can gain 100 HP or more and more air may well be needed. Even without touching impellers or the snell itself

Id also wonder how many maf would be damaged by oiled foam. It's not so much of an issue now but back in the 90s and 00s we seen several K&N filters oil coat the maf and cause issues.
 
#37 ·
I worked auto parts professionally in a previous life. I've seen tons of those K&N displays, and you can still find some here and there.

I think paper filters have been the norm in automotive because they're easy for the average vehicle owner (and shop tech) to inspect and replace. Pop a housing, inspect, replace if dirty. Pretty idiot proof, and low on labor. They're also predictably effective, so manufacturers can rely on them to not affect warranty claims. There aren't many ways to screw up a paper filter replacement.

Motorcycles, particularly dirt bikes, are a different beast. Maintenance intervals are shortened, a larger percentage of owners do their own maintenance, production is far more limited (thousands instead of hundreds of thousands), and motorcycles tend to end up in a lot dustier conditions than most automobiles. Oiled foam filters are more effective, vs paper filters that get clogged easily. They're also more compact and provide more surface area for that volume vs a flat filter panel.
 
#38 ·
Just to throw in more controversy, Suzuki's all new VStrom 800 DE comes with a hybrid air filter. The first layer is the traditional paper element that you remove/replace like all the other OEM filters. But in front of that paper element is an oiled foam layer that during service, requires cleaning and re-oiling. Suzuki intends the 800DE to be the most off road oriented VStrom in its history.

Food for thought.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top