K&N air filters?

[I812]

I use them in the cars but would like to know if any owners here used them on their RT/LT/etc?

Thanks!

Steve

[ShovelStrokeEd]

Here we go again!

 

Stock air filter will flow more air over its life and much more air than the motor can use.

 

Again, over its service interval, the K&N allows more particulate matter through than does the pleated paper air filter.

 

You don't have to buy a replacement filter at every service with the K&N but, you will spend another 15-30 minutes washing/drying/oiling the old element.

[I812]

I tried the search 1st.....From what K&N states in their info packet that their filter breaths better then stock and takes more dirt out of the inflow. Looking at the cage versions I find that part about filtering out better hard to believe. They have a warranty but I have heard things go bad when you are dealing with a factory covered vehicle. Mine are old so not an issue here.

[Joe Frickin' Friday]

Most of this is reprinted from a similar discussion that took place a couple of years ago.

 

These guys did a low-budget (but informative) road test on a Miata. According to their measurements, the K&N improved intake manifold pressure under WOT conditions by 0.12 percent. Yup, about one-eighth of one percent.

 

These guys did a rigorous flow/filtration bench test of nine aftermarket filters. (EDIT, May 2010: this link is broken, and I can't find the study anywhere on the web anymore. Anyone got a clue???) As you examine their graphs, it's important to point out that the zero of the Y-axis is not always located on the X-axis; so while one bar of the graph might look ten times as tall as another, they might actually be representing very similar values, so make sure you check out the numbers! Some conclusions to be drawn from their plots:

 

• Filter efficiency: K&N lets the most dirt get through.
   
  
• Accumulative capacity: Compared to all the other filters in the test except one, the K&N will accept relatively little dirt before presenting the maximum permissible increase in pressure drop (10 inches of water).
   
  
• Initial restriction: the pressure drop across a brand-new K&N under test conditions was 4.54 inches of water. The worst filter (the AC-Delco paper filter) came in at 6.23 inches of water. Atmospheric pressure is 408 inches of water, so the respective manifold pressures were 401.5 and 403.2, for a flow (and probable performance) improvement of 0.4 percent under maximum power (not max torque) condition; for max torque at any other RPM, the improvement will be less. Such a tiny improvement simply will not register on a butt dyno.

As to the engineering sense:

• a paper filter is made of...paper. It won't withstand much of a pressure drop before it collapses inward, so it stands to reason that there really can't be much of a pressure drop across the stock filter to begin with...which agrees nicely with the data that testers are providing.
   
  
• The K&N website is big on testimonials (a standard snake oil marketing ploy), but small on actual test data. They did link to a couple of "independent lab filter test results (flat filter and round filter), but you'll note that they're rather cryptic (a far cry from my earlier Duramax link), and there's no comparison whatsoever with their competitors. If their products are as superior to their competitors as they claim to be, they should be dying to show us some flow bench comparisons. Or some dyno comparisons. Or some 1/4 mile comparisons. Something, anything! All of that is conspicuously absent from their site, and objectively measured (i.e. no butt dyno) test results found elsewhere on the web consistently run counter to K&N's marketing claims.

So there's a fair collection of objective measurements that suggest K&N ain't so great, and a troubling lack of objective measurements affirming K&N's greatness.

 

When a single butt-dyno evaluation turns in a result that's contrary to all that objective data, I'm very inclined to dismiss it. Subjective evaluations are notoriously imprecise and subject to a long list of conscious and unconscious biases.

 

Not insignificantly, time separation affects perception, too. Example:

 

Test 1: Pick up a 10-pound rock in one hand and a 9-pound rock in the other at the same time, and you can probably tell which one is heavier.

 

Test 2: Pick up a 10-pound rock in one hand, get a feel for it, and put it down. Come back a half an hour later and pick up a 9-pound rock. You'll have a much harder time telling which one is heavier.

 

Unfortunately an informal "butt dyno" test is very much like Test #2 - except it's even worse, because the difference we're trying to observe is far less than ten percent. So when the results conflict with what cold hard instruments are reporting in repeated tests, the most prudent course of action is to discount the butt dyno results.

 

 

When it comes to testing that uses cold hard instruments, there's this plot of a series of dyno runs on an oilhead fitted with a stock air filter, a K&N filter, and a sock filter half covered with saran wrap. See if you can tell which is which:

 

 

Yeah, me neither. Looks like the stock filter flows pretty good, leaving little room for improvement. It's true that we are now talking about a hexhead rather than the oilhead featured in that plot, but I'd be berry, berry surprised if things were much different.

 

Bottom line, you are unlikely to achieve either improved filtration or improved breathing with a K&N.

[1NOTRED]

Have no experience with K&N, although filter useful life depends most on paper area: more is better, and the standard BMW has lots. Particulate trapping effiency is very high on all filters.

 

Unless a bike is ridden in dusty/muddy conditions, air filters will last a long time. With routine maintenance (removal for tapping and reverse-vacuuming to remove filtrates) the large designed-in surface area will perform well for 10s of thousands of miles. I recently replaced my RT filter at 112K miles even though the bike didn't exhibit any negative traits (fuel economy degradation and ultimately reduced top-end power).

 

Interesting characteristic of paper & foam filters is that efficiency (highest % of particles caught) is lowest when new, before initial particulates help plug any built-in microscopic leak paths. And, filter efficiency doesn't go down with use, as dirt simply adds up to clog and plug up the media and (if we're watching) reduce engine performance.

[I812]

^^ was very informative!

Thanks!

[Don_Eilenberger]

When it comes to testing that uses cold hard instruments, there's this plot of a series of dyno runs on an oilhead fitted with a stock air filter, a K&N filter, and a sock filter half covered with saran wrap. See if you can tell which is which:

 

 

Yeah, me neither. Looks like the stock filter flows pretty good, leaving little room for improvement. It's true that we are now talking about a hexhead rather than the oilhead featured in that plot, but I'd be berry, berry surprised if things were much different.

 

Bottom line, you are unlikely to achieve either improved filtration or improved breathing with a K&N.

For more info on the dyno runs that Joe Frickin' Friday posted about..

 

http://www.eilenberger.net/R1100R/index.htm <-- original data on my website..

 

That was close - the plot above was three runs: One - no filter; one - stock filter; one - K&N. Shows the claim of more power to be bogus..

 

We also did a buncha runs with and without various CAT-CODE plugs.. and then the one with the stock filter 1/2 blocked off with SaranWrap..

 

Stock oilhead filter - and same filter half-blocked off..:

 

There were also dyno runs done on my old '85 K100RT.. stock vs K&N vs none vs blocked stock..

 

http://www.ibmwr.org/ktech/dyno/index.shtml <-- IBMWR K-tech website

 

Since the K100 engine was only pulling in air for 250cc's at a time, the difference was even less:

 

Stock vs None:

 

 

Stock vs K&N:

 

 

While the site doesn't show it - the stock vs stock-half-wrapped with SaranWrap - the plots were identical. The large panel filter on the early K bike is apparently good for a 3L BMW car engine.. and WAY oversized for the 1,000cc engine.

 

I do agree - K&N does nothing useful to your engine, and I've seen enough tests (including one by a fleet-diesel heavy equipment operator who had lots of $$ invested in his equipment) indicating that they simply don't filter as well as the stock filter.

 

BTW - the only REAL test if the stock filter is causing a restriction is a top-speed test. Any slight difference in airflow caused by a filter restriction will be automatically compensated for by the closed-loop O2 sensors circuit. So - do a top-speed run on your bike, then go 24,000 miles and do it again. If you're still within a few MPH - your filter is just fine.

 

 

 

[racer7]

Agree with Don and Mitch. Data is king and K&N never show anything useful.

 

I used to run a filter test lab and while I've never done comparative tests on K&N stuff, I think you'll find that most experienced testers would automatically expect the K&N material to load up the fastest and pass the most dirt based on material and construction. Your engine won't self destruct in 10 seconds if you do use them but why would you, absent any real proof of claims? Remember that racing uses are not relevant to street use - race engines always get torn down and rebuilt/replaced after a few 10s of hours of service, at most, so grit related wear that is important for street longevity is of no real concern as long as you keep enough of the grit out so the race engine runs well for its expected (few) hours. Note that air prefilters are often used in desert racing to slow plugging of the main filter, something you wouldn't do on the street.

Some racing stuff uses wire mesh screen oil filters and these are definitely NOT reasonable for street use.

[Rinkydink]

Don't use them but have one of their stickers on my tool box!

[sardineone]

K&N = good bug screens.

While not exactly apples & oranges, I've had some real life experience with a bike with a K&N installed. An 83' Honda 1100F with a K&N that at 12,000 miles was already getting tired compaired to when new. My Moto Guzzi with stock paper filters @ 55,000 miles feels as strong as at 5,000 miles. My current BMW with the stock BMW filter needed at least 12,000 miles to achieve full power and at 22,000 miles has never run better. I can live with not seeing daylight through my filter to have a longer lived and stronger motor in the long run.

[Lmar]

I have used them in my BMW vehicles, never tried them on my bikes.

[AZRTRDR]

Isn't it true that an increase in airflow through a filter could only increase the power making capabilities if that is the highest restriction in the entire engine intake/exhaust system?

Much like the reported increase in engine scavenging that aftermarket exhaust manufacturers claim.

Can the valve/s flow any more air that the factory filter or the factory exhaust?

Or am I way off base here ?

[kenthewrench]

Bikemaster makes one that sells through TuckerRocky for $39.95 and does the same thing as the K&N for alot less.I'm not as much worried about flow as I am buying another OEM filter when the time comes. Its nice to know when I service my bike that I'm not gonna have to have my bike apart waitng on a filter or buy an extra on "just" to have around. The idea of a "lifetime" filter is what I'm after. Just FYI. Ken

 

P.S.---TuckerRocky part# is 45-7001

[AllenW]

 

 

 

Tim, I think what your asking is, if the most restrictive point in a motors intake cycle is the air cleaner would removing that restriction increase volumetric efficiency/power and the answer I believe is yes.

But not necessarily the same as exhaust scavenging as that's a bit different story, one side deals with vacuum and the other pressure and notably exhaust pulses.

 

As far as valve flowing, we add valve lift, duration, location of valve in head and a few things I'm sure I'm missing here, not always a simple explanation.

imho the air filter rarely restricts enough to make a difference.

Al

 

 

Isn't it true that an increase in airflow through a filter could only increase the power making capabilities if that is the highest restriction in the entire engine intake/exhaust system?

Much like the reported increase in engine scavenging that aftermarket exhaust manufacturers claim.

Can the valve/s flow any more air that the factory filter or the factory exhaust?

Or am I way off base here ?

 

[billS]

I have a Uni Filter fitted now. Been on for nearly 10000 km now, will be interesting to see how dirty it is at the next service which is not far off. I change the sock that goes on the intake tube evrey 2000 km or so, it catches quite a bit or dust and stones. I do ride gravel a bit at times.

 

http://www.uniflow.com.au/contents/en-us/d320.html

[I812]

http://www.unifilter.com/online%20catalog/streetbmw.html

[kenthewrench]

I have a Uni Filter fitted now. Been on for nearly 10000 km now, will be interesting to see how dirty it is at the next service which is not far off. I change the sock that goes on the intake tube evrey 2000 km or so, it catches quite a bit or dust and stones. I do ride gravel a bit at times.

 

http://www.uniflow.com.au/contents/en-us/d320.html

Little pricey compared to the Bikemaster or even the K&N don'tcha think ? Not a big fan of foam filters anyway as they tend to let more dirt and debri through than the traditional cheese cloth style oiled ones.

[I812]

I have used Unifilters and the same type in Motocross bikes for years. I would think they would be the best at keeping out dirt/dust as many mfg's equip their dirt bikes with them.

[Penforhire]

Not a huge fan of K&N style filters. I've used them a few times in cars. Last application registered a whole 3 HP increase from a 350 RWHP base value. Big whoop. Like others said, they don't filter as well as paper. I know some racers who keep virgin paper filters in plastic baggies and just swap it in for a race.

 

Additionally I know a couple of people who screwed up their intake MAF sensors by over-oiling the K&N. I'm not certain the "correct" amount of oil is all that safe either. The oil gets on the heating element stretched across the intake and messes up the readings.

[kenthewrench]

I have used Unifilters and the same type in Motocross bikes for years. I would think they would be the best at keeping out dirt/dust as many mfg's equip their dirt bikes with them.

Ok if you say so. Just offering an opinion like the rest. To each his own.

[billS]

I have a Uni Filter fitted now. Been on for nearly 10000 km now, will be interesting to see how dirty it is at the next service which is not far off. I change the sock that goes on the intake tube evrey 2000 km or so, it catches quite a bit or dust and stones. I do ride gravel a bit at times.

 

http://www.uniflow.com.au/contents/en-us/d320.html

Little pricey compared to the Bikemaster or even the K&N don'tcha think ? Not a big fan of foam filters anyway as they tend to let more dirt and debri through than the traditional cheese cloth style oiled ones.

 

I think it will pay for itself fairly quickly as paper filters out here are around $40.00 each. Foam works fine if it is maintained correctly, as stated most dirt bikes use them and they get more dust than my 1200.

 

Will check it this weekend and see how it looks and report back.

[Rob]

I have used Unifilters and the same type in Motocross bikes for years. I would think they would be the best at keeping out dirt/dust as many mfg's equip their dirt bikes with them.

 

How often do you change them on the MX bikes, every moto or race? I did that also. I also replaced rings every few races too.

 

I dont' want that type of maintaince on my street bikes. The OEM lasted 40,000 miles on my RT. I only changed it because I had one waiting.

 

Best,

 

 

[I812]

I have used Unifilters and the same type in Motocross bikes for years. I would think they would be the best at keeping out dirt/dust as many mfg's equip their dirt bikes with them.

 

How often do you change them on the MX bikes, every moto or race? I did that also. I also replaced rings every few races too.

 

Best,

 

Depends on riding conditio9ns. Sometimes 4-6 moto's . Others 2 and some 1. Ring's on H2O cooled motor did not need the replacement near as often as the Air cooled. CR500 1 season. Smaller displacement require shorter intervals.

[kenthewrench]

I have used Unifilters and the same type in Motocross bikes for years. I would think they would be the best at keeping out dirt/dust as many mfg's equip their dirt bikes with them.

 

How often do you change them on the MX bikes, every moto or race? I did that also. I also replaced rings every few races too.

 

I dont' want that type of maintaince on my street bikes. The OEM lasted 40,000 miles on my RT. I only changed it because I had one waiting.

 

Best,

 

 

Thats kinda what I was thinkin too. MX/dirtbikes require alot more constant maintenence and repair for the amount of ride time spent on them vs. a street/touring bike. Theres a reason foam types aren't popular with street bikes and I believe you hit it on the head with the amount of constant attention they require.

I also understand BillS position to in that being far removed from easy accessability makes one "creative".