K&N vs. paper air filters

[Speed_Racer]

It's time to replace the air filter on my MR2.

The previous owner replaced the OEM air filter with a K&N knock-off that's in pretty bad shape - clogged, rusting, etc. I would go for the K&N but I've also heard that the increased air flow = increased engine wear (it lets in more dust and dirt particles). Truth or fiction?

EDIT: Another issue I've heard is that the oil impregnated in the K&N can come off and damage the MAF.

[Gotta-Qik-C7]

I have K&N filters in my bike and Z28. I don't know if they make more power or cause more engine wear,but all the power junkies I know swear by them. I like the fact that I can wash and reuse them (they have a million mile warranty) as long as I own the vehicle.

[Gotta-Qik-C7]

I've never had any oil problems with mine.

[Rupert]

I think most things said about K & N's is a myth, except that they'll last forever if you take care of them. I bet they would give enough power to notice if the old air filter was reeeaaallllyyy clogged, or if you replaced the stock filter with a bigger K & N. I actually have foam filters on the MG.

[JWC]

Improperly maintaining the K&N will damage an MAF. 

The other thing to keep in mind is why they use oil as part of the filtration system.  Think about it.

[r0tor]

at worst (well given correct usage) the maf becomes dirty and can be cleaned in 5 seconds with some electrical cleaning spray.  The use oil because it allows them to get similar filtration with less resistance....

[S204STi]

I've never had any oil problems with mine.

You don't have any sensors to contaminate.

It's time to replace the air filter on my MR2.

The previous owner replaced the OEM air filter with a K&N knock-off that's in pretty bad shape - clogged, rusting, etc. I would go for the K&N but I've also heard that the increased air flow = increased engine wear (it lets in more dust and dirt particles). Truth or fiction?

EDIT: Another issue I've heard is that the oil impregnated in the K&N can come off and damage the MAF.

I would put a paper filter in there.  I use paper filters in everything, including the WRX.  Not enough of a difference can be felt in the butt dyno to use them, IMHO.  The paper filters keep out more dirt, flow more or less the same, and you don't have to worry about it effecting sensors.  That said, I still recommend periodically cleaning off the MAF with a plastic-friendly cleaner like CRC's MAF Cleaner.

[Byteme]

It's time to replace the air filter on my MR2.

The previous owner replaced the OEM air filter with a K&N knock-off that's in pretty bad shape - clogged, rusting, etc. I would go for the K&N but I've also heard that the increased air flow = increased engine wear (it lets in more dust and dirt particles). Truth or fiction?

EDIT: Another issue I've heard is that the oil impregnated in the K&N can come off and damage the MAF.

K&N filters are a waste of money, pure and simple.  The let in more dirt don't add much if anything to HP, and if they do it's generally near the redline (how often do you drive at that RPM).

http://www.nicoclub.com/articles.php?id=180100

See:  http://www.bobistheoilguy.com/airfilter/airtest1.htm

http://www.metrompg.com/posts/air-filter-part-1.htm    No, or virtually no mpg gains.

http://www.autoblog.com/2005/09/07/how-well-do-k-n-air-filters-work/   Might save you a few bucks after a quarter of a million miles but how much is an engine rebuild?

[GoCougs]

K&N filters have only one benefit: intake roar. They do not add power or increase MPG, despite their claims.

No automaker is going to spend $25MM+ developing an engine only to hamstring it with an overly restrictive air filter.

And as we have seen, and true to aftermarket part performance, they are neither as reliable nor as robust as the factory stuff.

[Eye of the Tiger]

K&N filters have only one benefit: intake roar. They do not add power or increase MPG, despite their claims.

No automaker is going to spend $25MM+ developing an engine only to hamstring it with an overly restrictive air filter.

And as we have seen, and true to aftermarket part performance, they are neither as reliable nor as robust as the factory stuff.

Unfortunately for you, Ayn Rand doesn't know jack shit about cars. Try reading some automotive literature, perhaps.

[S204STi]

Unfortunately for you, Ayn Rand doesn't know jack shit about cars. Try reading some automotive literature, perhaps.

What was the point of this post?  He's absolutely right, you know.

[Eye of the Tiger]

What was the point of this post?  He's absolutely right, you know.

He is not right right at all, and is obviously talking straight out of his ass, as usual. Are you trying to tell me that every single test that shows improved performance with a K&N filter was a phony? I've seen so many of tests from so many different sources, that I do not think it is possible for K&N to be paying off all of them. Actually, all of those links that Byteme just posted (except for the first one) prove that a K&N is less restrictive and improves performance over paper filters.

[GoCougs]

What was the point of this post?  He's absolutely right, you know.

Yeah, I'm not sure if he was joking, or serious, trying to make a funny, or just trundling in out of boredom...

What I have read about the subject is that automakers spend quite a bit of money on intake filter/box/tract design, to take advantage of the pulsing effect of the intake charge WRT to the firing of the cylinders. This advantage is along the lines of throttle response, and otherwise maximizing performance.

The specifics are well beyond my knowledge, but it's enough for me to say I think that yeah, a team of dozens, scores, maybe hundreds of power train engineers, who are are spending tens or hundreds of millions of $$$ developing an engine, aren't going to botch the whole process with an overly restrictive air cleaner.

K&N are for intake noise, and one risks contamination and other hassles.

[Eye of the Tiger]

Yeah, I'm not sure if he was joking, or serious, or trying to make a funny...

What I have read about the subject is that automakers spend quite a bit of money on intake filter/box/tract design, to take advantage of the pulsing effect of the intake charge WRT to the firing of the cylinders. This advantage is along the lines of throttle response, and otherwise maximizing performance.

The specifics are well beyond my knowledge, but it's enough for me to say I think that yeah, a team of dozens, scores, maybe hundreds of power train engineers, who are are spending tens or hundreds of millions of $$$ developing an engine, aren't going to botch the whole process with an overly restrictive air cleaner.

K&N are for intake noise, and one risks contamination and other hassles.

You are denying the results of thousands of tests because of a subject that you admit is "well beyond my knowledge".

Your "pulsing" effect of intake flow takes place most importantly in the intake ports and the manifold, and is almost irrelevant by the time it gets upstream of the throttle body. We're talking about air filters, not intake design. Any restriction in the intake path that is not designed to increase velocity or induce swirl is going to decrease the volumetric efficiency of the engine. K&N's flow better than paper. Period.

[Speed_Racer]

Wow, this is an exact cross-section of what I've read on other parts of the internet.

[S204STi]

He is not right right at all, and is obviously talking straight out of his ass, as usual. Are you trying to tell me that every single test that shows improved performance with a K&N filter was a phony? I've seen so many of tests from so many different sources, that I do not think it is possible for K&N to be paying off all of them. Actually, all of those links that Byteme just posted (except for the first one) prove that a K&N is less restrictive and improves performance over paper filters.

We've gone over this a million times.  A huge engine or one with forced induction may see an increase in performance, but the butt dyno isn't going to register it in most cases, and neither will your pocket book.  This is particularly the case in cars with normally anemic engines.  You are allowing largely unfiltered air to enter your engine, contaminating intake sensors on its way, for the sake of a very minor increase in HP.  Most cars are limited by the size of the throttle body and the tuning of the engine.  Changing something that far away from the real action simply doesn't have that much of an effect, and I am not willing to risk damage to my engine for the hell of it.

I noticed Z28 chimed in about his motorcycle; on a vehicle weighing 400lbs you are probably going to notice even minor changes to the power curve, but in a 3000lbs vehicle not so much.

[r0tor]

Yeah, I'm not sure if he was joking, or serious, trying to make a funny, or just trundling in out of boredom...

What I have read about the subject is that automakers spend quite a bit of money on intake filter/box/tract design, to take advantage of the pulsing effect of the intake charge WRT to the firing of the cylinders. This advantage is along the lines of throttle response, and otherwise maximizing performance.

The specifics are well beyond my knowledge, but it's enough for me to say I think that yeah, a team of dozens, scores, maybe hundreds of power train engineers, who are are spending tens or hundreds of millions of $$$ developing an engine, aren't going to botch the whole process with an overly restrictive air cleaner.

K&N are for intake noise, and one risks contamination and other hassles.

To counter your thoughts, many OEM's have their performance branches that are selling intakes that come with higher flowing K&N style filters.  Mazdaspeed for instance uses AEM intakes and their filters.

[S204STi]

To counter your thoughts, many OEM's have their performance branches that are selling intakes that come with higher flowing K&N style filters.

Probably because people like to buy them anyway.

Look, case in point.  I drive GTOs on a regular basis here.  Many have stock airboxes, many have K&N or equivalent air boxes.  I can never feel the difference between them.  I get lots of vehicles of all types with K&N panel filters.  Guess what, same deal.  I''ve never thought to myself, "Oh my, this one clearly makes more HP than the one I drove in a few minutes ago."

[r0tor]

Did you ever have to fix one because the engine died from sucking in too much dirt?


FWIW I bought a K&N for the RX-8 because it wwas cheaper then a OEM paper filter -shrug-

[Eye of the Tiger]

We've gone over this a million times.  A huge engine or one with forced induction may see an increase in performance, but the butt dyno isn't going to register it in most cases, and neither will your pocket book.  This is particularly the case in cars with normally anemic engines.  You are allowing largely unfiltered air to enter your engine, contaminating intake sensors on its way, for the sake of a very minor increase in HP.  Most cars are limited by the size of the throttle body and the tuning of the engine.  Changing something that far away from the real action simply doesn't have that much of an effect, and I am not willing to risk damage to my engine for the hell of it.

I noticed Z28 chimed in about his motorcycle; on a vehicle weighing 400lbs you are probably going to notice even minor changes to the power curve, but in a 3000lbs vehicle not so much.

I never said the butt dyno would notice, but a real dyno does. As far as the effectiveness of the filters, they are also proven less effective than paper under dry conditions, but like r0t0r said, Mazda and others seem to think they're good enough to still honor the warranty. The bottom line is, paper filters better and is cheaper than K&N, and that is why they are used on factory vehicles. If they can save $20/vehicle x a few hundered thousand, that's a lot of money, all for a filter that will cost them more to "maintain", rather than passing the expense onto the consumer to just replace it.

[r0tor]

An OEM mazda filter costs the customer $50.  They probably buy them from Fram or Puralator for $5 a piece.  They then require you to change it once a year.  Its rather obvious why OEMs will never go away from paper filters...

[S204STi]

Frankly this is one of those arguments, like oil, that is more emotional than anything else.  Some people "feel" better having a paper filter and a couple fewer HP, other people "feel" better having a couple more HP at a calculated risk to their engine.  Do what feels best I guess, but go into it with a very low expectation.  That is all I can say really.

[Byteme]

You are denying the results of thousands of tests because of a subject that you admit is "well beyond my knowledge".

Your "pulsing" effect of intake flow takes place most importantly in the intake ports and the manifold, and is almost irrelevant by the time it gets upstream of the throttle body. We're talking about air filters, not intake design. Any restriction in the intake path that is not designed to increase velocity or induce swirl is going to decrease the volumetric efficiency of the engine. K&N's flow better than paper. Period.

Interesting.

I just looked at K&N's web site.  They have buried the HP gains in the information on specific filters. 

I looked at 2002 Mustangs.  Average about 7-8 HP at about 5,000 RPM.  Big whoop, you think you will notice that?  And who drives at that RPM anyway and for how long.  Also note that is for their intake and filter, not just the filter.

Next I tried a 2004 RX8.  They make no claims about additional HP from using their filter.

I do see that Mazda does sell intakes for about $400.  There are no claims regarding HP increases and at least one for the MazdaSpeed 3 isn't legal in california.  Also, no guarantee the filters perform the same as the K&N filters.

I have also yet to see a test in which K&N outfilters the OEM filters.  One would think if such a test existed K&N would proudly display the outcome on it's website.

Lastly we come to the testamonials on the K&N site.  I saw none where the claims were backup up with hard data.  Just "wow, I bought a K&N filter and just having the filter in the trunk on the way home reduced my 0-60 times and doubled my gas mileage".

Then there is the old argument that racers use K&N filters.  You bet many of them do.  Most race teams worry a lot less about engine wear than winning.  They want to filter out large foreign objects like birds and beer cans, not 1 micron dust.  And the sponsorship money doesn't hurt the team's bottom line either.   

[GoCougs]

You are denying the results of thousands of tests because of a subject that you admit is "well beyond my knowledge".

Your "pulsing" effect of intake flow takes place most importantly in the intake ports and the manifold, and is almost irrelevant by the time it gets upstream of the throttle body. We're talking about air filters, not intake design. Any restriction in the intake path that is not designed to increase velocity or induce swirl is going to decrease the volumetric efficiency of the engine. K&N's flow better than paper. Period.

"Results", "tests" and volumetric efficiency however are within my area of basic knowledge.

From K&N's website: "Our horsepower/torque testing is performed on wheel-based dynamometers, which measure actual brake horsepower and torque at the wheel(s) receiving power from the drive train. This is different and we believe more reliable than horsepower/torque testing done at the flywheel of an engine."

This alone invalidates all of K&N's claims, and clearly shows that they don't know what they are doing, or do know what they are doing, but are hucksters. An engine dyno provides far more reliable testing results simply because not only are the atmospheric conditions controlled, virtually all variables that affect power on a chassis dyno are eliminated - from transmission and differential oil temp (viscosity) to tire pressure to other goodies. K&N uses a chassis dyno because it is cheap and quick, and also easier to manipulate the results. Think an automaker spending $300MM to develop a new engine uses a chassis dyno? Not on your life.

And then look at this ditty: "We attempt to hold all other variables constant to generate a reliable measurement of changes in horsepower and torque on a vehicle before and after a K&N product is installed." Uh, I'm sure they do attempt to, but on a chassis dyno it's next to impossible. Atmospheric conditions? Temperature of drive train fluids? Sorry, I don't buy it. "Attempt" is a legal out because they know that they can't with a chassis dyno.

Here's another blatant error: "These plots show the median run of a specific vehicle, which had three runs with the original stock intake system and three runs with the K&N intake kit installed." With so many variables, only three runs? Anyone with basic manufacturing engineering experience would fail this test methodology in a heartbeat.

And here is Final Indictment to K&N's testing process: "The vehicles our R&D department uses for testing are loaned to us by consumers residing near our test facilities." wat?

As to volumetric efficiency, it's an extremely basic equation to determine the maximum air flow of an engine; VE% * CID displacement * RPM / 3456, and use 100% VE. A team of power train engineers aren't going to duff this. Sure, the K&N filters may flow more, but it simply doesn't matter. A 600 cfm filter on an engine that will only ever flow 500 cfm is wasted effort in terms of power and MPG.

Take a visit to their site and you'll see they are now pimping environmental benefits (as in, throwing away fewer filters). That IMO is an indication of the dubious value proposition. I think they and others of their ilk are snake oil hucksters along the lines of grounding kits, 3000 mile oil changes, and myriad other automotive myths.

[Eye of the Tiger]

You don't think 7-8 hp + saving money on replacement filters is a good thing? I think you have entirely the wrong attitude - and that's all you have, an attitude. 

[S204STi]

You don't think 7-8 hp + saving money on replacement filters is a good thing? I think you have entirely the wrong attitude - and that's all you have, an attitude. 

No that's all YOU have dude.

I think you should sort out whatever it is that's putting you in a bad mood today, and then come back when you can deal with the arguments in this thread.

[S204STi]

As to volumetric efficiency, it's an extremely basic equation to determine the maximum air flow of an engine; VE% * CID displacement * RPM / 3456, and use 100% VE. A team of power train engineers aren't going to duff this. Sure, the K&N filters may flow more, but it simply doesn't matter. A 600 cfm filter on an engine that will only ever flow 500 cfm is wasted effort in terms of power and MPG.

Yes, thank you.

[GoCougs]

Interesting.

I just looked at K&N's web site.  They have buried the HP gains in the information on specific filters. 

I looked at 2002 Mustangs.  Average about 7-8 HP at about 5,000 RPM.  Big whoop, you think you will notice that?  And who drives at that RPM anyway and for how long.  Also note that is for their intake and filter, not just the filter.

Next I tried a 2004 RX8.  They make no claims about additional HP from using their filter.

I do see that Mazda does sell intakes for about $400.  There are no claims regarding HP increases and at least one for the MazdaSpeed 3 isn't legal in california.  Also, no guarantee the filters perform the same as the K&N filters.

I have also yet to see a test in which K&N outfilters the OEM filters.  One would think if such a test existed K&N would proudly display the outcome on it's website.

Lastly we come to the testamonials on the K&N site.  I saw none where the claims were backup up with hard data.  Just "wow, I bought a K&N filter and just having the filter in the trunk on the way home reduced my 0-60 times and doubled my gas mileage".

Then there is the old argument that racers use K&N filters.  You bet many of them do.  Most race teams worry a lot less about engine wear than winning.  They want to filter out large foreign objects like birds and beer cans, not 1 micron dust.  And the sponsorship money doesn't hurt the team's bottom line either.  

So let's say with the stock filter and a cold car they do a dyno pull. Now let's say they do a dyno pull with a K&N filter but with a warm car (i.e., warm drive train fluids). There's easily 7-8 hp difference right there.

After learning of the chassis dyno test methodology to pick up variances of 1-10 hp I have no choice but to suspect that they manipulate test parameters for their own means.

[Eye of the Tiger]

No that's all YOU have dude.

I think you should sort out whatever it is that's putting you in a bad mood today, and then come back when you can deal with the arguments in this thread.

Hey, I'm not the one who declared the holy war against K&N. I call just bullshit when I see it, and your snake oil hunt is based on nothing but opinions, backed up bt contradictory evidence.  For fuck's sake, it's just a damn air filter.

[Byteme]

You don't think 7-8 hp + saving money on replacement filters is a good thing? I think you have entirely the wrong attitude - and that's all you have, an attitude. 

The last engine I rebuilt was the Jaguar's and the cost was about $6,000  in parts and machine work and labour.  The engine develops 265 HP so 8 HP at 5,000 doesn't mean much at all;  new plugs would probably give me that kind of gain.  Neither does saving a couple of hundred dollars when compared with the cost of a rebuild.  I'll just suffer along with an unoptimized engine while replacing the air filter annually, knowing, not just hoping, my engine is getting properly filtered air.