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MG MGB Technical - KN air filters

I had fitted on my new 1950 engine, twelve years ago, a pair of KN air filters. Washed, re-washed…
Can you give me your opinion about the true useful life for this component.
Regards
michel

Michel,
As far as I know, the filters are good for as long as they hold together! That's the beauty of the K&N's, they can be re-used over & over again, as long as the filter stays in shape. I've had mine on the B for 10 years also...
Robert Dougherty

I believe K&N says they are good for 1,000,000 miles if taken care of. I am guessing that has never been tried.
Carl W French

The last K&Ns I bought also said not to clean them more than every 50,000 miles or so in normal usage. They say the accumulated dirt acts as supplemental filtration...
Rob Edwards

The K&N will last a very long time if handled properly. The washing should be gentle! Submerging in a bath of soapy water (dish soap seems to cut the oil best) and gently swishing after a long soak, followed by similar rinse cycles seems to work best for me.

Dishwasher will kill them.

High pressure water or air will kill them.

Nasty solvents will kill them.

Insofar as being better when "dirty" or not, well...

Yes, they are much more effective at filtering out small particles once a layer of larger particles is trapped, etc...
You give up flow efficiency in order to have cleaner air. This is the case for all filters of any type.

The moral of the story is to not be too terribly anal about cleaning the filter, keep it oiled (but not sloppy) and clean it whenever it looks particularly nasty (annual is good in dirty places (like Nevada!)).

Mike!
mike!

FWIW, I have had the same set of K&Ns on my GT since 1989. The car is a daily driver. They get cleaned at least once a year, get re-oiled then also, and frankly, look prettyt much the same today as they did when new. The integrity of the filtering media has held up well as has the rest of the filter's structure. I have NOT put a 1,000,000 miles on them, but the way I look at it, what other filter could I have bought that I would still be using successfully 15 years later and would be expecting to use for many years to come?? I doubt that it would be a Fram, Mann, Purolator, or any other paper media filter. And, from what I have seen of other foam filters, probably not most of them either. You pays your money and takes your choice.
Bob Muenchausen

I rang K+N after fitting mine as I could not beleive that with the sort of mileage I cover the sum of maintenance before someone else looks after my car will be one cleaning .Well , they confirmed it , and 8 years on they are fine . I have washed and re-oiled them once , but I'm sure I did not need to . I have seen comments that they are less efficient at filtering out dirt then other elements , but have never seen this substantiated in testing.
S Best

Re: "what other filter could I have bought that I would still be using successfully 15 years later and would be expecting to use for many years to come??"

Well, there was that oil bath air cleaner on my '67 VW.

Sorry, couldn't resist.
Matt Kulka

No problem, Matt, I have used those too on Bugs and other cars/trucks. About the only other type with this sort of longevity. I note, however, that few auto/truck engines use these anymore, must not have filtered as well as the paper/media units.

S Best,
I have a photo posted on one of my websites, http://hometown.aol.com/idbritcars/MiscPage.html (bottom left) , which shows the mouth of one of my SUs immediately after removing the K&N filter from it after over a year's use. Untouched, unretouched. I could not find or feel any fine debris in it.

However, there was a dissenting view from someone in the Porsche camp recently and he refuses to use K&Ns, and will only use the Mann units. I would personally like to see a review as thorough and as candid as the Oil Filter Study about the whole lot of air filters.
Bob Muenchausen

Bob,
Here's a completely unbiased (ahem) comparison of several different filters:

http://www.performanceoiltechnology.com/k&nbitesthedust.htm

I had a friend who was an Amsoil distributor, and he showed me a video of the test described on the above page. It did show quite a lot of particulate getting through the K&N. However, K&N say that their filters don't acheive their maximum filtration until they've accumulated some dirt. So I think this is just an demonstration of the fact that you can structure a test to get the results you want. Or, as I saw it stated once, "After discarding the data to the contrary, the hypothesis was proven." ;-)
Rob Edwards

This may be an unbiased test.
http://www.mcagraphix.com/filter/test.htm

This week I have been reading David Vizard's (How to Build Horsepower, Vol.2). Volume 2 is a about carburetors and intake manifolds. In 1995 David was a believer in K & N filters and has some test data on air filters in chapter 1. In his comparative flow test K & N was best and Motorcraft was a distant second, Amsoil was last just behind Fram. On a Superflow dyno test a new K & N filter produced a little more power than any other filter. The test engine was a 305 Chevy. In another test a K & N was run 80 k miles without service with 25% of the mileage on unmade forestry roads. The dirty K & N flowed equal to a new Motorcraft filter and 25% better than a New Fram filter. A second opinion of sorts was published in Englang by Performance Tuning magazine. The author, Vish Seshadri presented some very through comparative tests of three brands of foam filters, one paper and one K & N. The K & N had the best flow rate and it's efficiency at 97.5% was less than 1% lower than two paper filters. The dry foam filters had efficiency ratings of 25.9% to 50.8%. The book does not say if K & N provides free filters to David Vizard. I'm not endorsing the K & N as the best filter, just repeating a condensed report, details of this information can be seen on pages 6-10 of How to Build Horsepower, Vol 1.
FWIW, Clifton
Clifton Gordon

The oil-bath filter was discarded by OEM for several reasons...
Service was a pain.
They were far more costly to produce than a housing for a paper unit.
Messy.
Heavy.
Emissions.
Low flow rates.

They are pretty effective at getting dirt out of the airstream but at a HUGE loss of flow.


Mike!
mike!

Well, so far some very interesting info and sites have emerged. I thank those who have given us these sites to review. Interesting that the Amsoil filter proved no better than the K&N in the tests Clifton mentions, and that it did so much better in Amsoil's own tests. I think the same people write Amsoil's copy as do for OxiClean.

I am not about to tell anyone that K&N is the best at filtering out sub atomic particles. It may not be. But I can tell them as best I can the truth of my limited experience with them. And for the claims that they have made, their performance has generally proven true more often than most of their competitors. Some of what must get through must also be in the oil and oil filtration system and I have to wonder if the old standby oil testing for engines might not shed some light on this question, particularly in terms of foreign matter accumulated over a 3000 mile period. I would think that the density of this material and its type would point towards a confirmation of anyone's air filter tests. Just a thought.

Also, thanks Mike! for the insights into Oil bath filters.
Bob Muenchausen

Clifton ,

Even Peter Burgess did confirm the K&N supériority. For instance, read his book "how to power tune B serie engine" , all his tests carried on various tuning stages heads show up a better flow if K&N equipped.
Another reason that goes to K&N choice too comes from the solution payed for itself on time and even more for the look .
Renou

Renou,

Thanks for your comments, I have K & N filters on two MGB's and replaced the stock filter in my Mazda Protege 5 with a K & N. I also have the Peter Burgess book and have read his tests on K & N filters. Peters's comments on the K & N filter convinced me to to try them on my MGB's. I like the K & N filters and as Bob stated, I have seen no indication they do not provide adequate filtering, when I remove the filters I find no dust or grime inside the carbs.

Regards, Clifton
Clifton Gordon

Until a few years ago GM used to provide a test dust for Air Cleaner testing, typically known as ACFTD (Air Cleaner Fine Test Dust) which was used for a number of other purposes. It is no longer sold but is offered as ISO Medium Test Dust. This sort of dust could be used to establish the performance. the trouble is an air cleaner is like a fuel filter, it is single pass and has one chance to capture the dirt, unilke an oil filter which is multi-pass. Unfortunately, automotive filers are sold down to a price, but industrial fluid power filters are tested for for their capture efficiency. There is work to try and get automotive filters rated in a similar way to allow consumers to make sound judgements on choice of brand and performance.
As to the K&Ns, Bob, indeed, taking oil samples and measuring the elemental levels of silicon and alumin(i)um would indicate the possible ingress of atmospheric dust, although silicon would be a more reliable indicator. On commercial diesels this is regularly done and increases in Si usually indicate a fault with the air intakes.

HTH
Martin
Martin ZT

Quick question, Are K&N air filters available for Z-S carberator ? My B is a 79 and would like to fit one if it is available, Thanks, Davy
Davy Crocker

Martin,
Thanks for the interesting information.

For total air flow through an air filter I don't think you can match ITG.
Leland Bradley

Why do you say that Leland? You have good experience with them, I am sure, what has convinced you? I am sure it was more than their advertising. I am just curious as we see so little info on this and other BBS's about them.
Bob Muenchausen

Bob,

For what it's worth: on my car, there also is a pair of ITG filters (for sidedraught carbs though). They do not have a metal back plate, the back plate's made of foam too.
The guy that initially did the engine set up here in Belgium claimed that ITG filters cause less losses than even K&N does in his experience. Peter Burgess on the other hand said he'd never seen them before when Chris and I went over there to have him tweaking the setup (which he obviously did splendidly!!!)

Alex
Alexander M

Davy,

Yes, there is a K & N that fits the Z-S airbox, I have one in my 77. I don't remember what the number is, I will try to find out. K & N doesn't list this application, but the filter in question fits perfectly. I'll try to find the number and post it.

Cheers, Paul K
Paul K

Bob,
I use them on my race engine and do not have to change mixture settings with or without the filters. Also the ITGs have a great deal more filter area. See Alex’s comment.
Leland Bradley

Thanks, Leland and Alexander. I knew, Leland, that you did some racing and demand some real performance from your car(s) so I figured you had good reasons. I will look up what I can on them. Thanks for the tip!
Bob Muenchausen

This thread was discussed between 02/08/2004 and 14/08/2004

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