K&N Air Filter long-term side effects

[radman]

Not sure what filter SkooterBoh was running, but mine was OEM and replaced frequently. My guess is the PAIR system.?
From here

PAIR uses air from the filtered side of the airbox, and directs it to the exhaust ports bypassing the TB's altogether. Overcleaning of the K&N may have contributed to the problem-the dirtier the filter gets, the more efficient it is at removing dirt. Both K&N and UNI caution against over-oiling in their user instructions. Franks had a UNI for 45K or so, and exhibits none of the issues shown here. But then, he's always been a good boy. Well........ B)

 

[Denver_FJR]

What did I learn...?The K&N air filter system, IMO, allows larger particles of contaminants to pass than the OEM filter. The K&N filter oil lacks sufficient tack when applied in a way that makes me personally comfortable with it's filtration level. And the big lesson learned... I'm going back to OEM filters on FJRs.

Yep, same here.

I (and apparently like many others here) have given up on K&M for cars and bikes because of insufficient filtration. A while back I had fuel injection problems on a Tacoma, turns out the excess oil and particles had collected on mass air sensor, causing invalid readings. The benefit is not worth the hassle and especially the risk of engine damage.

Anyone know where I can get a sticker that says "OEM" for my toolbox? :blink:

 

[HaulinAshe]

Mine were not as bad as ScooterG's, but the same problem for sure.

 

[exskibum]

Only use OEM filters anymore. Once upon a time, I used to put K&N's in everything -- bikes, cars, trucks. I think that ended when I sold my '85 Toyota SR5 4x4 in 1992 and started using OEMs in everything again. No particular reasons, except that my butt dynos didn't indicate much, if any, boost in performance with the K&N.

Then a few years ago, I read a few threads on the net comparing air filters and reaching unconfirmable, but unflattering conclusions about possible deficiencies in filtration, HP boost claims, etc. Not that I really bought the conclusions on the strength of the evidence and others' anecdotal claims, but it was another perspective to consider against potential benefits. Finally, jestal 'splained about OEM oil and air filters here in a thread -- tested by manufacturers, you know it's good enough for their warranty exposure, etc. That sealed it for me -- not that I was planning to go back to K&Ns, but neither the cost savings of reusable nor any minimal performance gain was important enough to me to go that route. The Yamaha paper filters work well.

 

[Warchild]

I am pretty sure my 2003 FJR will explode in a million pieces when I try to take it to World Superbike races tomorrow evening.

Because it has had a K&N filter on it for 72,000 miles.... so tragedy is imminent, according to this thread....

I have had K&N's in every bike I've owned since 1995.... maybe I am just lucky. Currently, the FJR runs like a scalded cat, has no throttle issues, gets 42-46 mpg depending on throttle discipline, intake tubes are clean and dry... and here in the High Desert, we have some pretty intense dust. If the K&N was going to have trouble trapping dust, this environment is the place it would happen.

So I dunno what to tell all youse guys having issues.... I can only suspect you're doing something with the filters that I am not. Or, vice versa. Why else would all these bikes, with well, well over a combined half million miles of use for over the past decade and a half, all perform so well if the K&N air filter was so evil?

Like exskibum, I never really bought into the K&N air filter's alleged "great flow, more power" hype. I use them strictly for the maintenance longevity, and costs savings. I haven't bought one of those spendy OEM paper filters since 2003... and while I look at the K&N once or twice a year during some maintenance action, I've only cleaned it once, at around 45,000 miles.... that was a couple years ago.

Like tires, oil, spark plugs, etc, everyone has their own opinions on a maintenance item that they are convinced is correct based on their own observations. That's why we have NEPRT, and that's where we are off to... B)

 

[Fred W]

Not sure what filter SkooterBoh was running, but mine was OEM and replaced frequently. My guess is the PAIR system.?
From here

PAIR uses air from the filtered side of the airbox, and directs it to the exhaust ports bypassing the TB's altogether.

That is true, Rad. I think the theory here may be that some of the exhaust may be leaking backwards past the PAIR reeds into airbox after the filter. That might explain the sooty spooge in those intakes. It sure doesn't look like "normal" intake deposits to me, and quite likely not related to lack of air filtration.

 

[Constant Mesh]

More likely oil fumes from the crankcase breather hose. Or, maybe exhaust particles from the engine. There's a 55 degree rotational interval when the exhaust and intake valves are both partially open at the end of the exhaust stroke and beginning of the intake stroke. Maybe the engine is coughing a few soot particles back to the throttle valves.

Are the intake tubes in the airbox covered with oily residue? Any fumes from the crankcase breather hose or the air induction system would have to transit the outside of the tubes before entering the tubes on their way to the engine.

 

[Fred W]

More likely oil fumes from the crankcase breather hose. Or, maybe exhaust particles from the engine. There's a 55 degree rotational interval when the exhaust and intake valves are both partially open at the end of the exhaust stroke and beginning of the intake stroke. Maybe the engine is coughing a few soot particles back to the throttle valves.
Are the intake tubes in the airbox covered with oily residue? Any fumes from the crankcase breather hose or the air induction system would have to transit the outside of the tubes before entering the tubes on their way to the engine.

Hey... Now you're thinking. I wonder how many of the guys that end up with residue on the forward end of their intakes have a habit of running their bikes at lower RPMs a lot. When RPMs are lower the valve overlap would theoretically allow a longer actual duration for exhaust pressure to travel back up the intake and foul those regions. I think everyone automatically assumes that the intake flow is fairly linear and unidirectional, but that may not be the reality at all rpms.

 

[Bounce]

Both K&N and UNI caution against over-oiling in their user instructions.

BTDT got the bill to figure out why my 98se GL1500 was choking on accel (after trouble shooting fuel and fire it turned out to be air... the lack of it from an over-oiled K&N). I got a Uni for my 2003 back during the initial group buy. So far, so good.

I'm not going oil filtered on the STi because it would then need a custom map to balance the flow. Before I do that, I have some other bits to accumulate (catless up pipe, CAI, replacement catted down pipe, etc.).

 

[HotRodZilla]

Not sure what filter SkooterBoh was running, but mine was OEM and replaced frequently. My guess is the PAIR system.?

I will say that I don't really get the entire PAIR system deal and like others wonder why it is on the bike if it is totally unnecessary. That being said, if all that crud was enabled by the PAIR system, where will all that crud end up when the system is removed and the caps put on? Does it blow out the pipes, or does it end up stuck to the bottom of the caps? I have been wishy-washy as to whether or not I really need to take that stuff off and cap my system.

 

[slapnpop]

Because it has had a K&N filter on it for 72,000 miles.... so tragedy is imminent, according to this thread....

Maybe not, but Metzlers make the baby Jesus cry.

 

[CRMH Eagle]

Not an engineer here and don't have the riding experience you guys have. However, I put a k&n in my 1996 Nissan Maxima which at the time had 110k miles. I drove that thing to 300K miles with the engine pulling just as strong the day I sold it from the day I bought it. I put a k&n in my 2001 4runner when I bought it 2.5 years ago. Both the 4runner and maxima had a little extra pick-up with the k&n.

Agree with Warchild - for me the cost savings is a big plus. With the vast majority of riders on this forum shouldn't we have had someone witnessing detrimental damage by now? Just asking...

However HaulinAshe's desire to protect the bike is shared by me as well. At least we're not a bunch of hd riders who only care about adding shining pretty things to the bike...

I put the k&n on my bike when it had less than 4k miles. Clean it 1-2 times per year.

I'm more concerned with the additives & blends being put into the gas than with my k&n filter.

 

[slapnpop]

Everyone should remember this is a posting of opinion. I don't see Jeff telling anyone they should immediately remove their K&N and throw it in the garbage. He's merely sharing the information he learned from his experiences.

A single point of failure can not determine causality. A lack of failure cannot determine fitness of application. This entire thread is *more* information for each person to base their own decisions around.

 

[charismaticmegafauna]

To quote 'Denver FJR':

Oil threads are proof that marketing works.

So are threads about K&N -- sadly, successful marketing too (IMO).

The answer is found in this post:

Not surprised one bit. I've abandoned K&N all together in my trucks and bikes. The proof is in the oil. Oil Analysis that is. ...flags from Blackstone ...K&N's were installed...high Silicon contents STEP AWAY FROM THE K&N KOOL-AID

 

[Fred W]

I will say that I don't really get the entire PAIR system deal and like others wonder why it is on the bike if it is totally unnecessary. That being said, if all that crud was enabled by the PAIR system, where will all that crud end up when the system is removed and the caps put on? Does it blow out the pipes, or does it end up stuck to the bottom of the caps? I have been wishy-washy as to whether or not I really need to take that stuff off and cap my system.

The intent of the PAIR system is to allow fresh air to be drawn into into the exhaust stream (under certain ECU controlled circumstances) to improve the efficiency of the catalytic converters in burning up any unspent fuel in the exhaust. That's why there is no change in performance when it has removed. It only effects the exhaust emissions.

So, the "crud", which I theorized may be getting back into the intake, would be normally exhausted out the pipes.

But as someone already pointed out, if my theory was correct then there should be crud through the entire intake manifold, not just the forward (engine) end. I like the back flow due to valve overlap theory to cover that angle.

PS - You guys want "cost savings" on your air filters? Quit changing them so often. The Yamaha service schedule only call for blowing them out with compressed air every 4k miles. Says replace when necessary. That may be never unless you have mice chew it up. A dirty air filter is a better filter-er of air than a brand new clean one, so you are not risking damaging your engine. The reason to replace an air filter would be because of lack of flow, which would result in loss of top end horsepower and potentially a loss of fuel mileage.

I'd guess there have been a lot of stock, paper air filters replaced unnecessarily.

 

[Constant Mesh]

I just clean the OEM filter and swap ends and reinstall it. The inlet nozzle seems to impede the air flow for a portion of the filter. So that portion accumulates less dust. I flip the filter to even out the dust distribution.

 

[Geezer]

Just to clarify a data point,

Jeff, did you always use K&N oil on your K&N filter?

I ask that because I use a UNI but I do not use UNI oil.

 

[JamesK]

Just to clarify a data point,
Jeff, did you always use K&N oil on your K&N filter?

I ask that because I use a UNI but I do not use UNI oil.

I don't know about Jeff, but as i was told, with the K&N you have to use their oil since it's not a foam filter like the UNI, but with the UNI you can use any oil designed for a foam filter. I followed these rules with both filters, using the K&N kit on the K&N filter and Belray foam filter oil on the UNI. Whilst i've not pulled my airbox off yet i am fairly certain i'll find something similar to what Jeff found on his FJR when i get around to doing it since i do have some of these same issues...

 

[Warchild]

A single point of failure can not determine causality. A lack of failure cannot determine fitness of application. This entire thread is *more* information for each person to base their own decisions around.

Exactly so!

This nicely sums up why NERPT exists.

 

[Grumpy]

More likely oil fumes from the crankcase breather hose. Or, maybe exhaust particles from the engine. There's a 55 degree rotational interval when the exhaust and intake valves are both partially open at the end of the exhaust stroke and beginning of the intake stroke. Maybe the engine is coughing a few soot particles back to the throttle valves.
Are the intake tubes in the airbox covered with oily residue? Any fumes from the crankcase breather hose or the air induction system would have to transit the outside of the tubes before entering the tubes on their way to the engine.

Hey... Now you're thinking. I wonder how many of the guys that end up with residue on the forward end of their intakes have a habit of running their bikes at lower RPMs a lot. When RPMs are lower the valve overlap would theoretically allow a longer actual duration for exhaust pressure to travel back up the intake and foul those regions. I think everyone automatically assumes that the intake flow is fairly linear and unidirectional, but that may not be the reality at all rpms.

Fred, you've obviously not tried to keep Mr. Ashe in sight or you wouldn't make this observation. Shall we say he's never ever been guilty of "lugging" his engine in almost 100, 000 miles.