K & N air filter
 

A guy at the local Subaru autowrecker told me today that he has reason to suspect that the oil in a K & N air filter may cause premature failure of the MAF sensor. Chime in here if you've had a MAF sensor failure and let us know if you're using a K & N filter.

Re: K & N air filter
 

Won't cause it to fail but will cause it to be coated in the oil and cause inaccurate readings to the ECU causing problems;)

Re: K & N air filter
 

What this guy said is he thinks it causes the plastic to break down.

Re: K & N air filter
 

Nah, the MAF is solid-state and would have to experience some serious plastic warpage to have the output signal even slightly affected.

Im more of a fan of the high-flow filter being relocated into the fenderwell anyways, that way it wouldnt even be a concern.

Re: K & N air filter
 

I've used a K&N FIPK on my truck for 8 years and an oiled filter CAI on my wife's Vibe for 5 years with no issues at all except the one time I over oiled the Vibe filter and threw a CEL. I cleaned the MAF and it was fine.

Re: K & N air filter
 

I'd heed what he said.. I had this exact problem on my 2001 Legacy GT-B. I bought the car new and during a subsequent service I enquired about installing a K&N filter to improve "breathability". Long story short, the dealer sold it to me and installed it during the service. Everything was fine for about 6 months and then the car started running really rough and surging terribly. I took it back to the dealer a few times until finally getting someone with more experience to diagnose the problem as being a faulty MAF and that it was'nt under warranty as I had installed a K&N filter. I argued that they sold the filter to me and installed it and produced reciepts as evidence afterwhich they replaced the MAF as well as refunded the cost of the K&N and fitted a factory filter.

The problem is that the oil particals from the K&N (and other oil-impregnated filters) comes out of the filter material and deposits on the very fine sensor wire in the MAF unit eventually causing it to warp due to uneven temperature and potentially break (as happened to me) if left unchecked. The wire cannot be replaced or repaired and so the whole MAF unit need to be replaced, sometimes at significant cost.

Like others I had used K&N filters on previous cars for years and swore by them, but none of those vehicles had the MAF setup that any of my Subarus have.

Re: K & N air filter
 

And they let alot more dirt into your engine than a normal filter would.

This page is a good read if you are considering going to a K&N
http://www.duramax-diesel.com/spicer/index.htm

Re: K & N air filter
 

I prefer dry filters like Green, AEM, Apexi etc. Oiled filters can cause havoc on MAF sensor equipped cars. Though usually thats due to the owners coating them excessively with oil.

Re: K & N air filter
 

I've run a K&N filter for a few years in an '89 Honda, and have experienced no problems. However, recently I did send off an oil sample to one of the analysis companies, and the report came back that the oil had an unusually high level of silica. I'm thinking that the filter is not working as well as the standard paper filter, and that I'm not doing my engine any favors by leaving in the K&N. I'll send off another sample to see, and then if it's high, go back to paper, then send a 3rd and see if the silica has come down.

The late 80's Honda engines are famous for going 3 or 400k. Mine has 225k, and I'd hate to think I'm compromising it for the sake of a couple of extra hp.

Re: K & N air filter
 

And if you look @ the dyno numbers, in most cases the horsepower gains from air filters like that are usually AFTER your peak HP, so they're pretty much useless. Just some numbers to make the Johnny Andretti Eclipse/Civic owners think that $100 "cold air" intake, $80 fart pipe and $120 Erector set wing really make their car faster :lol:

Re: K & N air filter
 

Excellent link, sheds some light on something I always wondered about.

Re: K & N air filter
 

I never had any problems with my K&N filters. It's a good practice to clean your MAF every so often anyway. Usually I clean mine everytime I service the car. Plus since my filter's in the fenderwell I don't think it's as big of a deal.

That said I think I'll switch to an AEM dryflow sooner or later.

And STILL clean my MAF every once in a while. haha

Re: K & N air filter
 

This is a lot more than a good and should go into the how too stuff, or become a sticky. Please can someone make this happen.

Re: K & N air filter
 

A legitimate question: How much "dirt" is negligible, and how much is harmful? Anyone who's eaten anything has pretty much consumed some number of bugs or rat hairs, which is OK with the FDA if not one's own body.

Can we relate to the amount of dirt that actually gets through these filters? Remember, we're talking about enough introduced to suffocate the filter pretty well. That's some poor car maintenance - likely several oil changes, even in a reasonably dusty environment.

Take any given number of grams of dirt, remove the amount that the oil filter would remove, and divide it by the number of oil changes that your properly maintained car would have before its air filter was restricted to over double its resistance as new? Not much.

FWIW, I don't care how much the test stand cost. That seems like fluff, and in a third party article, it seems to want you to believe it's honest. That's shaky as a debate tactic. I'm not saying it's untrue; I'm saying that it seems to be trying hard to be seen as true. Please see disclaimer below. ;)

Re: K & N air filter
 

Good questions to be sure. I have found that anyone with an agenda can pretty much pick apart anything. Use what you feel comfortable with and whats readily available to you. I have used pretty much everything out there. Though I prefer dry filters only due to oil covered MAF's causing problems in the past (for me personally).

I have a Stock STi red panel filter in my SVX if that makes any sense! LOL

Re: K & N air filter
 

I will make it happen Trevor. We are about to do the upgrade in software and a new how-to section. :) I will sticky it for the time.

Re: K & N air filter
 

interesting...could this be the cause of the chugging, as i call it?

Re: K & N air filter
 

Thank you Earl,

The "how to" section is certainly due for an edit and sort out, as it forms such a very valuable part of this forum.

Trevor.

Re: K & N air filter
 

I think the point is that the dirt makes it into your intake, past the valves, down to the pistons, past the rings and cylinder wall, and then chugs around in your pan while mixing in with the oil where it is again passed up to your crank bearings, etc until it would finally make it to your oil filter to be removed.

All the while possibly damaging anything in it's path.
The question is - are the size of the particles passed large enough to do damage with the clearances in our engines?


To me it's irrelevant. I simply don't want to put that much extra dirt into my engine when I plan on keeping my cars for hundreds of thousands of miles.

A while ago I calculated the cfm at peak torque for our 08 tribeca to determine if the stock paper filter was starving it. It was not. It flowed more than enough. With 0.3 L less displacement and the larger filter that the svx has, I feel confident that a paper filter in our airbox also flows more than enough air. This makes the performance claim of K&N simply not true in a stock svx.


So - more dirt and no more performance. What is the point of the K&N? Oh yeah, it lasts a million miles. :WTF:

Re: K & N air filter
 

Legitimate question: How much extra dirt?

How long would you say it takes for your airbox to see a pound of dirt? Miles or time - your choice.

How big (volume) is a pound of dirt? How about 6.6 grams (the difference between the thread-subject-chosen K&N and the best-in-test AC Delco)?

Would you eat 6.6 grams of dirt for a dollar? How about over the course of a year?

Don't let percentages and bench tests that don't reflect real world situations scare you; look at real, raw numbers before declaring that the end is nigh.

Re: K & N air filter
 

I had a k&n on my little red wagon for a long time. The oil was black before I even hit 3k mile change interval every time. I always hated that but didn't know the filter was the cause. I put that same piece of junk filter into my svx when I first got it with the same results. Only later did I realize the filter was at fault and I threw that pos into the trash. With a paper filter my oil is still clean on the dipstick when I change it. I like that.

The test shows real numbers proving that the oiled filters let more dirt in. Whether they represent a minute, hour, week, month, or year of driving in the real world to achieve the specific weight is not estimated and would be difficult to test or guesstimate.

You can subscribe to the k&n advertisement pitch of more horsepower with no downside or you can choose to protect your engine as best as you can with a filter that is scientifically shown to filter more efficiently.

Re: K & N air filter
 

The only thing I'm subscribing to is the fact that you can make numbers out to be whatever you want them to be.

It took damn near a quarter pound of dirt to end the test for the K&N (our topic subject, remember, and a filter bashed by SPICER pre-test, fwiw) and 0.22 cubic inch of the stuff got through the filter. That's smaller than a sugar cube!

I don't think that the sum of the dirt that found its way to the airbox in my Legacy and that in my SVX (combined, over 80k miles) has met a quarter pound. That would work its way out to a gram a year if SPICER's test's figures hold true.

In a four-oil-change year, that's a quarter gram. That's probably the size of a sesame seed. That's smaller than this emoticon: :tard:

I'm not going to tell you which filter is best for you, or which one is worst, and I'm not defending the K&N because it's in my car. I'm telling you that the numbers in the test are hype at best.

Numbers are numbers. What they mean is up to their appropriate interpretation.

I suppose you could decide that whether you eat a regular hamburger or a Big 'n' Tasty before you hit the dragstrip might critically influence your ET. After all, the Big 'n' Tasty is bigger, right? ;)

Re: K & N air filter
 

What about oilless high flow air filters? How do those perform in comparison? ie a Green 2019? Does anybody run one of these and how does it perform?

Re: K & N air filter
 

If there was cheap horsepower to be had without compromising reliability don't you think the manufacturer would be all over it?

Instead of K&N why not fabricate some expanded metal screening, rice cakes and Wesson Oil for your filter? I can see this idea going viral in about 45 seconds... :rolleyes:

Re: K & N air filter
 

My '96 59k miler is on it's 3rd MAF with a standard air filter. It has a flat spot (half power) between 1,800 rpm and 2,400 rpm. After that, it's amazing - pulls like a train. Oh, and it's fine when cold. It's on it's second brand new MAF from Subaru but they last 1/2 a day and show up code 23 and the car runs like a moped. Any ideas anyone? There are only about 35 RHD left in the Uk so no-one has a clue here.....

Re: K & N air filter
 

I'm convinced the dirt deal is settled science, I abandoned my K&N for stock. Way more dirt particles pass through the K&N than most any other AF.:eek:

Re: K & N air filter
 

based on this video, which seems to be based on real data, air filters don't add power
http://www.youtube.com/watch?v=PAIxeQUSg-Q
now for the engine protection purposes, I doubt that a high flow air filter would do any better than the cheaper ones...but I haven't done tests on either...

Re: K & N air filter
 

An alternative would be the spectre filter.

http://www.autozone.com/autozone/par...3939_378103_0_

Re: K & N air filter
 

BACK IN THE OLD DAYS I had a 1966 Dodge Dart GT 273 4 barrel . Someone stole my air cleaner. I replaced it with a small paper air leaner. Sounded great when that 4 barrel opened. Well after 35,000 miles the car was using a qt of oil in 500 miles. We took the motor apart and found that the motor was actually bored out by all the dirt that the crappy air filter let in . The ring gap was .050 over size . So between the ring wear and bore wear the rings lost there spring, and allowed the oil to pass. Moral of this story clean air is better than that 1/2 HP gain. <LOL> :rolleyes:

Re: K & N air filter
 

I put one of these in about a year ago. I doubt it caused the problems I am having now, but this is an interesting thread. I will go back to a stock filter.