Carlos

I have used K&N filters since 1971 with great results. However as a fairly new shark owner I have been paying attention to the "debris passes my K&N" comments. Let me say that when I first pulled my OEM filter there were bug components and other debris in the air box. Wanting to take as good care as possible of my shark I took a minute to email K&N. Within MINUTES I go the following reply. After reading it I am of the oppinion that the debris is BYPASSING whatever filter might be installed. I don't claim to be an expert but I think john is right. No motor can suck enough air to pull whole bug components through a K&N or any other filter. Here is the email from Rick Blum of K&N.

Dear customer,
Our filters are tested by an outside, independent laboratory. They have
been proven to stop at least 99% of particles on a SAE dust test. This test
uses particles as low as the 0 - 5 micron range and goes up to 20 microns.
For comparison, a paper filter also stops 99% on the same test and the OEM
minimum standard is 96%. Foam is generally the worst media with a typical
efficiency rating of 75 - 85%. To get higher ratings, the foam must be more
dense and therefore way more restrictive. The "tack" characteristic of a K&N
allows for increase filtration without loss of flow as well.
The testing procedure used is SAE J-726 using ISO Test Dust. This test
is the standard of the air filter industry. The test procedure consists of
flowing air through the filter at a constant rate (airflow rate is
determined by the application) while feeding test dust into the air stream
at a rate of 1 gram per cubic meter of air.
As the filter loads with dust the pressure drop across the filter is
increased to maintain the prescribed airflow rate. The test is continued
until the pressure drop increases 10" H2O above the initial restriction of
the clean element (in this case .78" to 10.78" H2O). At this point the test
is terminated. The dirty filter element is then weighed. This weight is
compared to the clean element weight to determine the total Dust Capacity.
The amount of dust retained by the filter is divided by the total amount of
dust fed during the test to determine the Cumulative Efficiency.


The K&N filter achieved the following results:

Dust Capacity: 305 grams

K&N Cumulative Efficiency: 99.05 %

Holding the filter to the light is useless, pin holes are normal. That
is what makes a K&N filter. There are actually hundreds of microscopic
fibers that cross these holes and when treated with oil, capture and hold
the very fine particles. On the same hand, they allow the filter to flow
more air than paper or foam. The filter is 4 ply cotton gauze unlike some
competitors synthetic material filters. The synthetics do not have the very
small fibers that natural cotton does. Also, the oil can be pulled off of a
foam filter contaminating electronic sensors. It will absorb into cotton
and stay in the media. In fact, Honda and Toyota only recommend K&N filters
when using aftermarket high flow filters as K&N is the only brand of filter
the oil does NOT come off of. They will not cover a failed sensor if foam
filters were used.
We got started over 30 years ago making filters for motorcycles and off
road racers. The filters did so well that these guys wanted them for their
cars and trucks. We started making filters for these applications and here
we are today. If they did not work, we would not still be here and growing
every year.
We now make filters for Chrysler/Mopar, Ford Motorsports, Edelbrock,
Rotax Engines, and Harley Davidson. We come as original equipment on the
2000 Ford Mustang Cobra-R. We even made filters for the Apache helicopters
used in Desert Storm because of maintenance problems with the original paper
design. If they work in these conditions they will work for you. Links to
the filtration tests are on the web site at http://www.knfilters.com/images/factstab1.gif and http://www.knfilters.com/images/factstab2.gif
Thanks for writing, Rick

IMHO we need a pipe & cold air kit similar to what is available for other Porsches in order to eliminate the leakage below the filter.

Abby Normal

Great post with info Carlos!!
Now someone else give that man some stars!!!!

Jay Wellwood

Very interesting reading to say the least.

Just to play devils advocate here - I wonder which company wouldn't beat their chest and roar loudly that their products are the best?


Anyway...still good reading - thanks for taking the time to pass it on.

John Struthers

Carlos,
Thanks Guy! You saved my lazy butt a bit of effort ringing up the K&N people.
I appreciate the effort.
AND, with the proverbial grain of salt, I'm taking the supplied test matierial to heart.

However,
there is still the problem some folks are having with whatever is causing the Grit to end up on the wrong side of the filter and potentally in the air stream feeding our 'FAB'German motors. When I finish this I'm going to pull the K&N, clean any oil residue from the box and roar around town at low speed and high rev's for an hour or so.
I'll re-check the box in a day or so - My urologist is blasting the remaining stones on Thursday- for any grit or oil. I want to suck as much air as possible to see if like that 7.3L Ford vacuum and air velocity might be PART of the problem. Though, like you, I tend to think the air box is the culprit - how and why (vacuum and a poor fit?) and the focus of the problem MIGHT shift that way.
In any case I want to see if there is a large field of of 928 users out there and if there is a significant number of them experiencing problems like Ed, Vince and Kaz.
Which leads me to another question; are other Porsche's equipped with a similar airbox...924's? 944's? ....?
Any long time Porsche abusers out there? Feel free to enter the fray with solid or anecdotal info.
Danke again , Carlos. Und how ist der Snowball?
Keep em' rolling.
John S. 82' Weissach, Auto. 'Pattycakes'

Ed Ruiz

Sorry, but I don't buy the K&N hype. If insect parts get through, then so can other particles. Sand is very abraisive, and I'm not about to chance damage just for a little better engine breathing.

Like I said, I use the K&N for track event. For day-to-day driving I use the OEM filter. YMMV.

John Struthers

Ed,
All of that is well and good , I don't blame you or anyone else for being concerned about possible premature cylinder/bearing wear and damage. If its' a bad filter so be it, if its' a flawed airbox/intake system, also, so be it. But, does the **** crow at the morning light or does his crowing summon it? I am more than willing to agree with anyone who has found debris on the MAF screen and or in the airbox proper, there is a problem. I and others wonder why we had/have debris BEFORE changing to the K&N just like you and others are wondering about the debris AFTER the change to a K&N. I'm looking to narrow the field after rounding up the usual suspects. Is this a couple of problems working in tandem or a single problem? As of yet'I' don't know! And ,yes, if you stop using the K&N you do eliminate a
part of YOUR problem, but, do you cure 'the problem', everybodies problem? Remains to be seen. Let's get 'some more' info instead of re-hashing what we already have.
So, jump on the 928oc list and ask for some member participation.
WE need input from 928 owners who 1. Have used or are using the K&N, and for that matter a stock filter and see if there is a debris bypass problem with either type.
2. Who are having filter oil migration from the K&N to the box.
3. Do other Porsche's 924/944 etc. have a similar air box/intake system? Are they having similar debris bypass problems with the stock and/or the K&N?
As VInce has stated there is a problem outside the 928 community but for the time being I'd like to attack this from a 928/Porsche problem , if possible.
Keep em' rolling.
John S. 'Pattycakes'

Carlos

Guys I am 100% certain that there was junk in the airbox whin I took my (relatively clean) stock filter out for the first time. I removed the airbox to clean the crap out of it, and used a brush to clean off the maf screen. We can discuss filter properties till the cows come home, but it would take The Amazing Kresgin to move an entact insect wing through ANY filter. What we need IMO is a pipe & cold air kit.

John Struthers

Carlos,
We are in agreement but it won't do Ed and some of the other guy's any good if we can't PROVE there is a glitch in the intake system by getting enough 928 people to look at the system installed by the Factory on the Sharks.
Ed says he won't buy into the K&N hype and that's fine and dandy but if he were to call the Porsche Zuffenhausen crew they ( I believe ) would give us the same hype.
I moto crossed my old Maico 250, 400, and Enduroed'/jack-pined my Maico 502cc thruogh some incredably bad country -Ah, to be really young again- and if you ever rode through that strip mine clay dust which seemed like it didn't settle until the next weekend you -and I'm sure I'm preaching to the choir here- would be at least curious that anything made it past any K&N. My only problem back then was over reefing the clamps and deforming the Intake throat.
John

Carlos

John, I ran motorcycles on the street w/ K&Ns and the carb throats stayed pristene. Never found the first insect or rock. I put a post on the 924 board to see if I could get some input from folks using pipes instead of airboxes. I'd be willing to bet they're bug free.

Ed Ruiz

As the saying goes, "There is no free lunch."

You don't get something for nothing. In order to get increased airflow - the filter must be a bit less restrictive. How much less and still be OK is a matter of debate.

For those of you who have not had any problems with K&N filters - great! I have, and so have others. BTW, I think I know how to properly install an air-filter. YMMV.

John Struthers

Ed,
No one is taking you to task here.
No one said you couldn't install a filter properly.
No one denied the fact that you and others have detected debris on the MAF screen.
But you have determined that a particular filter is at fault. And from your posts REFUSE to believe that anything other than the filtration element side of the house is at fault and that's all there is to it.
All I am asking for is additional info from more sources. Already, we have MORE people advising that they have debris bypassing the filter in some manner or another. We also have some people advising that the stock filter gave the same bypass results.
No one is defending a given filter but everyone is concerned about the amount, type of debris and the possibility of damage this debris presents to our engines.
You are a founder, amongst other things, of
the 928 OC. You almost always make a timely, informative and educational post. But on two posts you are/were adamant and more bullheaded than one would expect. This was never meant to be the personal affront you have taken it to be. Simply a request for info. So, you gonna use some of your healthy influence to help or hinder the search for ADDITIONAL info.
John Say you wouldn't be related to Command Sargeant Major Ed 'Batman' Ruiz, recently of the 160th Special Operations Aviation Regiment, would you?

Ed Ruiz

By all means, gather the data. More information is always better than less. Try to include actual dyno HP increases (if any).

BTW, I'm not the only one who is not too keen on K&N 928 filters. One of the premier 928 engine tuners and rebuilders does not think very highly of them either. They ought to know, as they tear these engines down everyday. They also sell the K&N filters, so are they cutting off their nose to spike their face?!

Lastly, my 928 tech guru thinks they are much to do about nothing, and he sells them too. YMMV.

sergeant5

John,

I just changed my air filter today. I found a number of small pieces of debris on the MAF screen. I also found 1 intact leaf measuring approximately 1.5" x .75". There is no way that this came through the filter. The old filter was Purolator. I know that the debris was not in there a 4 weeks ago, as I had the filter out to check it, just after purchasing the vehicle. As I recall there was debris in there at that time as well. I vacuumed the debris out then, and again today. I'll keep an eye on it. I can't see how the debris is getting in there. I checked as well as I could to see if there are any openings that would allow entry. I couldn't find any. Just a thought, but could the debris be getting in when the filter is removed? (maybe lurking out of sight waiting for an opening) Next time I look I'll blow that area clean first.

As far as I know this car as never seen a K&N, although it might in the future.



Since I never introduced my car. I borrowed a digital camera, and took a few shots. Any way here she is.

2V4V

I have no doubts of the veracity of anyone's bad K&N experiences, I just think some are still not giving this a logical analysis.

I have said before, and so has Carlos, a whole bug is NOT passing through a filter - be it paper or K&N. If a bug couldn't go through the screen on your MAF - where the air velocity is far more concentrated and steady than it is across the wide surface of a filter - how could it go THROUGH a filter???

When we're talking about big, visible bug chunks, the real issue is that well as Hans und Frans usually do the engineering, sometimes they're, well, WRONG. The airbox design is highly functional in many respects, but it's held together with 4 BIG RUBBER BANDS. Yes, I'm sure it worked well when they tested it, no, it doesn't for very long in the real world. My former MB and BMW products all used metal clamps, LOTSA clamps, ALL the way around the air box to keep things snugged down. As opposed to the 4 cheesy rubber band/ bungee cords, that only provide tension across part of the box, and don't cover directly a good section at either end.

My point is just this - I recently spent the (absolutely ridiculous) sum of $120 to replace my straps, and my airbox is now TIGHT. There was a scary difference between the new and old straps ability to generate tension (rubber bands in an engine compartment, remember?) and I see a huge difference in the amount of "squish" in my filter gasket. I also bet that 2 years of heat-cycling will make those $30 apiece rubberbands worthless yet again.

As Carlos has pointed out, the best solution would probably be a complete 'cold-air kit', thus eliminating the poorly done airbox - which is the real issue at hand if we're talking about visible bug parts.

If people are having the same issue with either filter, then the issue isn't the filter, it's the box that holds the filter.

FWIW,

Greg

Ed Ruiz

I've modified my straps so that they provide a tight and good fit over the filter. YMMV.

When I use the OEM filter (which is 95% of the time), no debris accumulates on the MAF screen. When I use the K&N filter (even for ony 5% of the time) I see stuff on the MAF screen. Again, YMMV.

[BTW, YMMV means "Your situation or condition or experience may vary from mine."]

One last comment. A few 928ers have told me that their dyno runs were no better with the K&N than with the OEM filter. In at least two cases, the HP was less with the K&N filter.