WHAAAAT? A DOWNSIDE to K&N filters?!?!

[Guest ratchethack]

Exec Summary

(paragraph exerpted from the text of the Sept. ‘04 ISO 5011 Duramax Air Filter Test at link below):

 

“Gentlemen and Ladies, Marketing and the lure of profit is VERY POWERFUL! It is amazing how many people believe that better airflow = more power! Unless you have modifications out the wazoo, a more porous filter will just dirty your oil! Some will say "I have used aftermarket brand X for XXX # years with no problems." The PROBLEM is you spent a chunk of ching on a product that not only DID NOT increase your horsepower, but also let in a lot of dirt while doing it! Now how much is a lot? ANY MORE THAN NECESSARY is TOO MUCH!”

 

Gents, since this is my thread (so far) there’s no escaping my editorial spin and a slightly overly windy trip down memory lane :

 

So you found yourself with some spare time over the holidays? Me too. How better to spend that extra time, than by opening up a favorite perennial can-o-worms that’s sure to uncork a little o' that spitting-viper fanaticism and bile-spewing, raw acrimony that lurks just beneath the level of self-control of every reader of every Technical Forum? The year’s almost over with, and you haven’t had a single aneurism, Binky. Time to let ‘er rip!

 

Lest I open myself up too far too fast for the most spurious of attacks on my own biases, let’s see if I might head at least a few of ‘em off at the pass by airing ‘em up front. Warning - a trace of sarcasm and even a pinch of gloating may be evident.

 

When I was 12, I built my first motorbike out of a Briggs & Stratton lawnmower engine and a “balloon tire” Huffy bicycle. The rear wheel hub broke going over railroad tracks at the blistering pace of 30 mph, and I sold it to a kid down the street. Then came motorbike #2, a well-used Suzuki 80. The Suzuki was the first “real motorcycle”. One of the first things in my young mind that made it a “real motorcycle” was the realization on the glorious day I brought it home, that I actually had a selection of several aftermarket air filters to choose from.

 

By that time in my early development as a young rider/shade-tree mechanic, I had read a few things in the tech columns of Cycle Magazine, and had acquired some basic hands-on principles of internal combustion engine theory and operation, including the operating principle behind air filtration. It seemed to me that the new “Go Faster” K&N filters of the day, as advertised in the back pages of Cycle, which touted increased horsepower over any other filter on the planet, must have a down-side to them if there were any basis at all to their claims. It also occurred to me that there must be a "cost" to removing the dirt from the air and that this "cost" must be paid in terms of restricting air flow.

 

My 16-year-old reasoning told me that there was a trade-off in design here, and that if the K&Ns flowed more air, they must also pass more dirt. This made the K&N a poor choice for me at the time, since I knew that the only function of the air filter was to keep dirt and abrasives out of the engine and away from critical tolerance parts. It seemed pretty obvious to me that more dirt in the intake would not be a good thing. It also seemed to me from my budding powers of observation that lots of knuckleheads of every description appeared to be supporting entire cottage industries producing lots of goofy stuff in and betwixt the truly valuable stuff in the motorcycle aftermarket. Some discretion was clearly called for here.

 

Since then, every apparently credible air filter comparison test I’ve read has more or less upheld the logic of my 16-year-old brain. Today, nearly 40 years later, I run into motorcyclists who not only swear by K&N filters to the point of never considering an alternative, but some of ‘em have evidently been doing this non-stop over the same 40 year period.

 

That’s all well and good, and to each his own. But to do so in denial of the facts and in ignorance of the trade-offs – especially for so long – still doesn’t make any sense in my book. If you’re going to swear by something and adhere to it with unwavering fealty, best not be blindly justifying your "commitment" to an arbitrary prior point of view based on sales claims and marketing hype, or at least have a somewhat educated understanding of what your position is actually based on, using logic at the very least. Some attention to hard facts can't hurt either, it seems to me.

 

“They’re the BEST because I’ve used ‘em my entire life, and all my engines run perfectly, dammit!” Hmmmmm…I'm sure that's true in many cases and wouldn't question some real probability of this - even high probability. But nothing less than repeatable, scientifically derived data and rational conclusions add up to hard facts, to the best of my understanding. But that’s just me.

 

I’ll just wind up my pre-emptive defense quickly here and get out of the way. You’re welcome.

 

My Guzzi gets 10-15K miles per year, and I plan on keeping it “forever”. With this in mind, I’d never consider a K&N air filter for this bike, believing as I do that many other kinds of filters are more effective in terms of providing the kind of protection that air filters are meant to provide. There may in fact be some measure of “performance” given up by using my current choice of the BMC re-usable filter relative to a K&N, however small (and however temporary - see test) that may be. You see, it's not important. If there IS any loss (or gain) between flow rates (temporary or otherwise - see test results), it’s so small that it’s not noticeable to me, and I consider it 100% irrelevant to my riding style and objectives either way. Any difference in peak horsepower on the road is so negligible that it’s off the charts and out of consideration.

 

I’m not chasing world speed records on dry lake beds, I'm not after higher peaks on a dyno chart, nor am I racing anybody. Though the BMC filter wasn't included in this study, It’s clear from other tests I’ve read that the BMC stacks up similarly in every measurement to the performance of a range of the more mundane “high efficiency” filters. The BMC and others are clearly significantly better for my Guzzi than a K&N in terms of protecting the engine over the long run. In critical measurements with real-world consequences in terms of likely engine wear, the K&N's are in many cases on their own and IMHO, "out on a limb".

 

So may a desire for Truth trump emotion and ego, Gents, when and if you consider the following study (see link below). I found it to be well-conducted, and both comprehensively prepared and scientifically executed. I could find no reason to suspect that the comparisons were anything but what's claimed - “accurate and unbiased”.

 

For those who’re still reading this, may any potential enlightenment that may exist here find it’s way into your understanding of air filters, and if such a thing DOES exist, may this be a welcomed thing!

 

UPDATE: Here's the latest link to the Sept. ‘04 ISO 5011 Duramax Air Filter Test:

 

http://www.duramax-diesel.com/spicer/index.htm

 

Now let the festivities begin!

[big J]

Bollocks

[Guest ratchethack]

Bollocks

Eh? Is that all y'got? No bile and venom?

 

Ain't you at least gonna take any shots at the results of the test?

[Ouiji Veck]

Again I am in complete agreement with ol' ratchethack.

Though I don't see a K&N as potentially threatning to the long life of

my Guzzi. In that my passion for Guzzi lays in my perception that

I could throw a handful of sand down the carbs,fill the tank with kerosene and

ride my old SP out to Ca. and give ol' ratchethack a visit rather than I could tweak

another pony out of the motor and go straffing GSXRs.

I've always been a devotee of the KISS school of enginering which harkens back

to before the days of picking up my buddy to go dirt biking but ended up packing it in because he had no "Yamah Lube" No amount of frantic arm waving discourse on the

properties and origins of petroleum could convince him that Yamaha did not infact

have thier own oil well in down town Tokyo that was specifically designed to pump

the only black gold that was suitable for the divine chariot that was his YZ.

Madison avenue had done it's job all to well. And still does, judging by sitting here watching C-Span.

[badmotogoozer]

Obviously sponsored by AC Delco...

 

More flow = more go! It's an air pump fer crimey. Better cylinder fill is better performance. period.

 

I don't even know what filter I put in the Goose... But my 57 chevy pickup with a stock straight six and a single barrel carb sure had more power on the hills with the K&N. It was an obvious difference.

 

Rj

[Guest ratchethack]

...my 57 chevy pickup with a stock straight six and a single barrel carb sure had more power on the hills with the K&N.  It was an obvious difference.

OK, I'll bite. Many's the time I've replaced a filter with other than a K&N, and experienced an immediate power increase. Makes sense, since they all load up. Since this happens gradually over time, of course, it's very difficult to notice the change, and the change at replacement is instant. One of the results of the test was the finding that K&N's load up significantly faster than others, having a tendency to negate any initial flow benefit. They also hit the restriction limit faster than others, which again points to dramatically inferior air flow (and decreased engine performance) over time relative to others.

 

You can doubt the independence of the test, but if you actually read the comprehensive source information, it at least has a fairly compelling appearance of legitimacy and independence. Since the results corroborate and parallel the results of many many other similar kinds of tests done over many years, this would also tend to uphold a lack of bias.

[badmotogoozer]

I try to stick with what I know from personal experiences...

 

I've learned to be skeptical of everything I read on the net. Even here on this forum I've found some great info and a lot of trurh, but there have been times when the info wasn't correct - see the Yamaha springs sitting in the corner of my garage...

 

the 57 was a slug, even with the K&N. the difference between the K&N and a fresh filter was noticeable, especially when I stuck my foot in her going up hill. I always washed and reoiled it when I changed the oil, never seemed to get that dirty or plugged.

 

my only experience with K&N...

 

Rj

[big J]

Many,many race teams use K&N filters.

 

Gullible fools all,obviously.

 

David Vizard,one of the foremost engine tuners in the world reccommends K&N filters(amongst others) when improving through-engine airflow.

 

Another mug.

 

 

Your engine will wear out,whether you want it to or not.Any air filter will remove most of the airborne grit, what comes through will probably pass through most filters,so I'd say changing your oil is far more important than fussing about whether a 2 nano-micron particle is better than a 3 nano-micron one.

 

You have to hand it to K&N though, they've got the world buying airfilters that are marginally better than a sieve. What a lark.

 

 

BTW,I put a K&N on because the performance improvement has been independantly dyno-proven,on many different engines.

 

And they do a nice line in stickers.

[Guest mtiberio]

clean your K&N filter

 

let whatever you use to clean it with, dry off

do not oil it

 

hold it up to the light

 

you will never trust a K&N to filter dirt again...

[badmotogoozer]

Ya! The stickers! I forgot the stickers!

 

When's the last time an AC Delco filter came with a little sumthin sumthin for the tool crib?

 

Rj :

[felix42o]

Let's not forget the all-important "fluuurp" sound you get with the K&N. Stickers+added noise=free horspower. Duh. The logic is there, people...

We found that out waaay back. Proof: Remember when Chrysler slapped that neat Turbo sticker on the side of a Dodge Omni? It hauled ass as a result!

[Guest ratchethack]

Aaaaah, then! I just knew you had some o' that pent-up bile in you, BigJ!

Many,many race teams use K&N filters.

Yes indeed. I might point out that many, many race teams also use open velocity stacks. They've used stacks with or without different size screens to keep large debris out of open venturis in many kinds of racing probably since before commercial air filters were available. Typically, air filtration is very low on the priority scale when designing a race engine, since many race engines are built for a service life of anywhere from a few seasons at the most, down to as short as a single race before a complete teardown and rebuild or alternately, discarded. So of course race engines' air filtration requirements are a considerable departure - not remotely in the same ballpark, actually - from the requirements of a road-going vehicle, for which a primary design goal is almost always longevity and infrequency of service. For the last 50 years or so, this translates to a hard requirement for the elimination entirely of any need for teardown within the entire lifespan of a vehicle.

 

I'm currently driving a car with 245K miles that still uses no oil between changes. Nope, per the results of the Duramax test cited above and the the rest of the tests that have shown the same kinds of results for many years, I never have, and wouldn't ever consider a K&N for this car. If I had, I'd expect it to have started using oil long ago.

David Vizard,one of the foremost engine tuners in the world reccommends K&N filters(amongst others) when improving through-engine airflow.

It's nice to know (but not too revealing) that K&N hires professionals to promote their products.

Any air filter will remove most of the airborne grit, what comes through will probably pass through most filters...

Evidently not, according to the results of the "Filter Efficiency" and "Accumulative Gain" tests in the study in question, as well as the results of many other filter tests. Do you have access to a credible test that would counter these findings? I've never seen one, they all seem to find K&N's pretty far out there.

I'd say changing your oil is far more important than fussing about whether a 2 nano-micron particle is better than a 3 nano-micron one.

A fair enough statement, but does the importance of oil changes make the quality of air filtration any less important? Why not change your oil AND use a filter that has been repeatedly and scientifically proven to do a better job of protecting the engine than the K&N's - especially if it costs less?

You have to hand it to K&N though, they've got the world buying airfilters that are marginally better than a sieve. What a lark.

A lark indeed! You've certainly got to give credit where due here! Getting people to pay more money for a competitive product that does LESS of what it's designed to do than it's competitors is nothing less than pure marketing genius. It's like getting people to vote for a government that actually creates more of the very problems that it purports to solve by taking more and more taxes to do it! Absolutely brilliant!

BTW,I put a K&N on because the performance improvement has been independantly dyno-proven,on many different engines.

This is clearly what sells 'em alright. Too bad that instead of using brand-new filters, they don't typically take dyno readings on K&N's after they've loaded up for a few tens of thousands of miles on the road, and THEN compare the dyno outputs to competitive filters - sorta like what they've done in the Duramax test....

 

You can feel free to claim that the Duramax test was entirely fabricated. Maybe it was dreamed up for the purpose of trying to run K&N out of business. Maybe Amsoil and UNI too. But I rather think not. Again, it agrees with so many similar test results that this is beyond highly unlikely IMHO.

 

If you actually read and try to understand the comparative data in the Duramax tests, it's quite illustrative, and very decisively so. Looking first at the "Initial Restriction" bar chart, the K&N shows it's strength. The chickens come home to roost, however, when the trade-offs start to show up. Next, take a gander at the "Dirt Passed vs. Total Test Time" and "Dust Loading" tests, then "Accumulative Gain" and "Accumulated Dirt Capacity". Well, I rest my case.

 

Thanks for the response, BigJ. I was sorta hoping to get some dialog going. The Truth, and it's supporting facts, tend to be damn stubborn things, don't they?

[badmotogoozer]

It's like getting people to vote for a government that actually creates more of the very problems that it purports to solve by taking more and more taxes to do it!  Brilliant!

 

71332[/snapback]

 

So you've lived in Canada then!

 

My velocity stacks do a fine job of keeping the sparrows out of the carbies. The other crap rinses out with the oil.

 

Can we talk about oil again??? There are at least two schools of thought on every topic - one man's idiot is another man's genious. For every oil article that says use dino juice, there is one that says use synth. One study says to change your oil as often as possible, another says that this will damage the engine...

 

IMHO there is no such thing as a reliable source or study.

 

Rj

[Alex-Corsa]

Bollocks

 

I second that,in the way that

A) the dust particles that will be able to pass that kind of "open" filters are more dangerous to us than an engine.

B)The fact that the factories release now bikes that are so lean (due to specs) their motor is perhaps more "damaged" ,in the long run, than from an air filters like these.

So ,no more bull , if my motor packs it in ,I'll repair it or buy another one.

Still having perfect cylinders after 66K. and "open" filter.

 

Well put though, ratchet

 

 

P.S. (edit) I use K&N mostly because it saves me that hassle and money to finding new ones every once and a while, just proper clean and go.

[badmotogoozer]

I regard Science and Law as best guesses to date. My education into Science, Mathematics, Electronics, Mechanics and Engineering have led me to the belief that we know fook all about most things we think we've figured out.

 

Rj