John Struthers

Ed,
Please use eyeballs and brain.
No reference made, inferred, or, intended that referenced you to STOCK filter passing trash .
Referenced myself and others on that topic.
Referenced you on the straps, and earlier post concerning your doubts on the K&N filter test data hype. I actually, agree with your opinion on the hype, but hold the STOCK filter test data to the same flame-HYPE-. Essentially, the mention of your esteemed family name was intended to include you in the debate, not to use your name in vain. However, judging by the content of your post you are just as bullheaded on this topic as you are with performance mods - the only two subjects you are unreasonable about, so far as I have noticed -.
AGAIN, performance(K&N) no longer the issue.
Trash bypass is! 'I' still believe the trash bypass is a combination of owner inspection methods - I, too, was guilty and have since become fastidious -, and the filter box. AGAIN, the Porche Owners Manual recommends cleaning the filter box. WHY? Think about it.
No intent on my part to missrepresent you would appreciate same consideration in your posts. One other item. Out of the bag... IMO there is to much oil on the K&N resulting in a light coating in the throat area, etc. I have since air blown and whacked some of the excess off and have had no further, discernable, coating of the internals. ZERO dust or debris either.
Later,
Keep em' rolling.
John & Pattycakes

John Struthers

Roy,
Not an either-or-question.
Yes, as I stated, the filter issue is STILL a concern but secondary to the fact that we have posts from users of both STOCK and K&N filters saying that debris is getting on the wrong side of both filters. And yes, I, too, am concerned about the oil - not vapor - mist being drawn of the K&N by both air intake/engine vacuum. Since, we were writing responses at about the same time - mine to Ed - my quick fix cure to the oil misting is in the post above. FYI, while I don't race on the track the Tach needle in my 'Pattycakes' spends a lot of time between 3800 and 5000 rpm. Most of my vac. hoses are reasonably snug and I believe I am pulling a fair amout of vacuum. Results, so far, indicate no discernable oil film. Admittedly, this is less of a concern for my 81' than Louis Ott's 90'.
Roy, like yourself,I can point at seemingly odd statements.
NO DOUBT IN MY MIND -square business-, Louis knows more about 928's than I do. However, if he is THE shark guru YOU make him out to be. Where does the mechanic fit into his
life? From my point of view I will consider
Louis's mechanic's opinion but not Louis's vitriol on keeping his two K&N's in a bag and away from his air box. If he doesn't want them -and they are in good shape- I'll give him 25 cents on the dollar for them and I will pay the freight.
Bottom line Roy, if you can look in a mirror, and tell yourself that bug parts are passing thru ANY filter to end up in the airbox or on the MAF screen... and believe that....
AGAIN, the problem this extended post is NOW focused on is: the how/where/why debris is getting past ANY filter element.
And any post concerning the problem or cure should be considered by any and all sHARk
owners.
This isn't a put down, read over all the posts here to see what we are getting at O.K.? I believe the guy's over in the 924/944/951/968 and performance forums are posting on the K&N performance side of the issue. I don't care for gottcha's and would really appreciate new info. but if that's your thing, this is, after all, a forum, knock yourself out.
later,
Keep em' rolling
John S. & Pattycakes

2V4V

This topic just may outlive Jesse Helms...

To echo/defend John's point - and dredge mine up again - where does this "stuff" come from?

If ANYONE can demonstrate the passing of a bug/bug piece, THROUGH filter media (K&N or OEM), and then it's reappearence on the other side of the filter in recognizable form, I'll put you in touch with some folks at Stanford Physics who'd LOVE to know how you did it.

I only ask that you think carefully about the following - whatever "stuff" you found on your MAF screen did NOT get sucked into your motor. Your MAF screen is SCREEN. ALL the air volume just passed through that (comparatively) HUGE filter area is now accelerated through that one (comparatively) TINY opening. If it can't pass through that MAF SCREEN, how could it possibly pass THROUGH that filter media? Remember, lots more area on the filter, far less air flow per sq. in. on the filter than on the MAF screen.

Unless you have physical hole the size of a bug in your filter media, it did NOT go through. It went AROUND.

Somehow. I don't know exactly what the sealing issue is with the airbox. IMHO, it is a lousy design (see my previous posts in this thread).

I DO believe those who have had issues with their K&N filters. I'm sure that stuff is getting BY their filters. But, it is no more possible for a bug/bug piece to go THROUGH that filter media and show up on the other side unscathed than it is for one of us humanoid types to be injested by a large jet engine and leave the exhaust as anything much more than a chunky red mist.

Greg

Carlos

Well said GB.

Ed Ruiz

Sorry, but I know what I know. I've only owned 928s for nearly 12 years. For most of those years I've used OEM and K&N filters.

Over those years I've seen bug parts on top of the MAF screen after using the K&N filter, but there is nothing to clean after using the OEM filter. I've seen this too many times to dismiss it as a poorly fitting filter cover or loose straps. Sorry, I just don't buy it. They are the same straps and cover in both cases.

K&N claims their filters allow more air-flow than OEM filters. Anyone care to guess how they do that? If you said their filters are less restrictive, give yourself a pat on the back. What does "less restrictive" mean? Does it mean the K&N filter air passages are not as small as those on OEM filters? If so, can objects get through it that would be caught by the OEM filter? I know the answer for me. YMMV.

John Struthers

Ed,
One of us is in a shrinking box...
If the lip seal of the K&N and everything above the filter is bug tight that leaves a reduced area...from the top of the filter surface to the bottom airbox seal.
No one has denied that debris is getting on the wrong side of the filter. No one has denied that the K&N is less restrictive.
I have already stated that IMO there is way to much oil on/in the K&N as delivered which in all likelyhood is responsible for the oil misting of intake internals -can be fixed-.
And yes it is possible if not likely that a less resrictive filter will pass more fine particles of dust/grit than a more resrictive filter.
Having said that, I would like to see you put YOUR cards on the table. Are you saying that the BUG PARTS are passing through the K&N filter?
I hope not - see Greg's post -
I don't want to be snide about this but you have yet to come right out and say "the bug parts are going thru the filter" yet to anyone reading your posts on this subject you seem to infer that. Am I mistaken ? If you are saying the bug parts are going thru the filter we can argue the merits, weaknesses, anecdotal and provable data.
Honest differences are alot easier to cope with than inference. Let's hash this out If i'm wrong then I'm wrong, if you are wrong then you are wrong. But one or both of us need to stop misleading other posters and get the straight scoop to them. The box is getting smaller!
later, keep em' rolling
John S. & Pattycakes

pd'83SC

...I have used a K&N filter in my '80 928 for about 5 years now and have NEVER found anything large enough to see with the naked eye BELOW the air filter....and I live at the end of 1100 feet of gravel drive that goes thru 7 acres of hardwood forest (leaves, seed pods, bugs galore). Count me as a satisfied customer even if there is no significant performance gain with the K&N. The cleaning and re-oiling ritual makes one realize just what a tough job this filter element has to do in a hostile environment.
PD

pd'83SC

...and one more thing, on the '80, there is one hose connection into the filter box below the air filter...an emissions connection I think, that could pass a few bug parts, leaves, etc...if left disconnected. A simple point that I am sure you guys have considered, but I haven't seen it mentioned here...
PD

Ed Ruiz

Since we no longer want to mince words, I'll be perfectly clear. The fit around the filters are tight regardless of which filter I use. So (IMO), the bug parts (wings, small legs) I see on top of the MAF screen after using a K&N filter ARE getting past that filter. They are not getting past the filter box, which is well sealed.

When I use an OEM filter, absolutely nothing can be seen on top of the MAF screen. That's why I use the OEM filter 95% of the time.

You can do as you like and believe what you like. I KNOW the K&N filter is allowing "stuff" to go through that the OEM filter does not. YMMV.

Donald

All:
Has it been discussed whether the difference in flow rate between OEM & K&N may result in a change of pressure in the airbox, thus the differential in front of and behind the filter element is also greater when using one than the other? This would lead to a difference in distortion of the element, and possibly flexing a portion of the box as well. Could even be specific to a car (or batch) rather than systemic 928.
I liked PD's hose point, will check mine when it's back home.
Lest we all forget, everyone knew the world was flat, when all they knew was that it appears flat.

Donald

John Struthers

PD,
Thanks for the post.
I hope that gravel is packed!!!
You are correct. We haven't mentioned 'that'
connector stub before. I noticed it sometime back but, didn't comment on it for several reasons:
1. I have not MADE the time to track down its function though the smog pump removal post is probably tied in there somewhere.
2. Before I sealed that puppy off I wanted to see if being fastidious during clean-up,
service/inspection, insuring the lip seal wasn't cocked off to one side or the other,
etc... wasn't part of the problem/cure.
Yeah, its a slow process waiting to service the air filter, but, if you are going to say, " THIS is what I did to eliminate A problem" some repetion is involved so as to prevent a visit to a professional to have a foot or feet removed from my mouth down the road.
3. I am, both, curious and lazy -earlier Abby & Carlos posts- . I am perfectly happy to let someone do ALL the work and benefit from their labor -the American way-.
4. This is probably the most important. Seeing someone else get involved and actually look at the problem ,offering some insight from a different perspective, hands on and all that good stuff. I feel that there is a positive benefit for all concerned
when we get our hands dirty and learn a little more about our sHARKs.
I won't get around to sealing that 'emissions' tube until I finish with the K&N then service a OEM filter around 5 or 6 times -will require a few miles- to see if my efforts do keep out the nasty stuff when using either filter or not.
Again, thanks for your post, ideas, and thoughts.
Later
Keep em' rolling
John S. 82' Weissach, Auto. 'Pattycakes'

John Struthers

Donald,
I was wondering about about vacuum draw deforming the box -not the filter- and had my son run the rpm's up to 3800 rpm slowly, hold then blip up to 4500 rpm. Then tried gunning across the idle to 4800 range. the box -sturdier than it looks- really didn't flex enough to make a difference so I moved on to other things. But, I am running out of areas to check that would let BIG STUFF get drawn around or under the filter.
There has to be something letting things get by though. Unless the Zuffenhausen guys' developed a smaller version of the Enterprise - Star Trek - Transporter Room the only way I can imagine bug parts and leaves etc. getting thru the filter itself would be to armor plate them and shoot them thru.
I fear Ed and I are both flatlanders. Thanks for the tact. I think I'll be lazy again and let YOUR post be MY response to Ed's last post with the codicile that it applies to the both of us.
Again thanks for your thoughts and insight.
John S. and Pattycakes

Ed Ruiz

I don't know where all this is heading, but I'll add just a bit more fuel to the fire.

On my 928s, the smog pump connection to the air box is before the filter, and the smog pump itself has its own filter to boot. (Interesting that K&N doesn't make a filter for the smog pump )

Years ago while trying to determine how bug parts were finding their way to the top of the MAF screen, I did a test of the K&N and OEM filters. The test was rather simple. Since my wife is a hair dresser I grabbed some dark hair from her trash can. I then took a long single strand and tried to pass it through the respective filters. I could not get it to pass through the OEM filter, but I was able to get it through the K&N filter. I wonder what else can get through?

Donald

John-
I knew you were a flatlander, Midland makes College Station look like the Alps

Thanks for having done the work on observing the airbox at revs, saved me the effort. What I was getting at is that in addition to the box deformation from drawing a vacuum, the pressure on either side of the filter element should not be the same at least for the moment of airflow acceleration or decelaration. Then, a pressure differential will cause the element to bow either in a "lift" or "push" depending on which side has lower pressure. If this bowing is large enough, or is exacerbated by a slight airbox distortion (or weak straps), could it be sufficient for a small gap (say, wide enough for insect bits) to open on one side of the element? It can even be a vertical gap, not just a horizontal one.
There is a lot going on in the airflow. I have not yet had intrusion past the filter, but I have found cigarette butts on top of the filter- and that takes quite a a bit of suction to get it there from the pavement. Then again, maybe I should check the ride height.
Just another idea to shoot down. I personally like the transporter room theory. Perhaps that was the next-gen to the flagship 928 being tested on a small scale, but it flunked the survival test (of the pilot).

Donald

John Struthers

Ed,
Obviously, not common sense! Which I will now prove by demonstrating that the two of us are like a couple of arguing drunks. In the spirit of good natured dementia,
I will try to reproduce your experiment.
But, wait!
That's not all!
After I try to duplicate the hair experiment,
- don't tell the animal rights people - I will tape not one but two cats to the air filter, san cover with the filter duct taped to the lower housing and go for a twenty minute romp. The cats are kind of skinny with lots of loose fine hair and I'll try to use as much of the rpm range as possible .
In the hope of representing the test fairly, I'll weigh the cats with the duct tape bindings before and after the experiment but I'm sure one or both will have an 'accident' somewhere during the course of the test so I will also record the weight of the filter prior to and after the test. Ed, since the FBI is running Raptor full time now I'll have a courier deliver photographs of anything larger than test devices' claw, tail, or, eyeball found in the lower airbox.
LABEL epending on bypass residue test results may cause nausea, fainting and in extreme cases remorse.
To prevent injury sturdy gloves should be used when collecting test data and, or, cats.
This test may be duplicated by anyone without fear of litigation by the author of said test - whoever that might be -.
Litigation by representatives of any number of government agencies is another story altogether and if the word gets out about the tests subjects-willing or otherwise- may lead to extended conversations with any number of law enforcement, judicial and psyhiciatric hospice representatives.

Don't have a cow! This is just humor...Isn't it?

Anyone know how to put a cat to sleep for short periods of time ...say 20 - 30 minutes?
Later
Keep em' rolling
John S. and a somewhat disturbed Pattycakes
P.S. Assuming Ed is right does anyone know how to remove caked on hair from the intake plenem and valves?