Just HOW bad is K&N

[Dantilla]

Some intake systems are very efficient from the factory, others are not.

944 turbo, Seattle Int'l Raceway (Now Pacific Raceways)- Coming out of turn 3B. Redline in second, shift to third, hit rev limiter at top of third just as it's time for threshold braking for 5A.

With K&N, Hit rev limiter not much past turn 4, grab a piece of fourth gear before braking for 5A.

This was with a brand new filter. No difference in street driving. Probably made a difference only over 6000 rpm.

[Randy W]

I'm with Dan. On a street driven car, I stick with the factory paper filter - less dirt gets by and the slight restriction is not noticeable with a factory intake/exhaust. On my race car, which is rarely driven on dusty roads, the K&N is less restrictive and with all the other intake and exhaust maximized it just makes sense. If you decide to use one, just make sure you clean and relubricate the K&N regularly.

[MarkY]

Originally posted by chuckr
OK,
I got 7 hp with K&N ! I have 175hp at the rear wheels

With ONLY a K&N, you claim an additional 7hp. Bologna or Baloney, whichever you prefer.

[stormcrow]

I don't have a K&N on my car but for those of you who do and are concerned about the efficiency with regard to particulate matter here's what you can do.

Most heating and air conditioning filters have been sprayed with a mist of oil to help trap particles. You can do the same with your K&N filter, just don't over do it. Spray a fine mist over it and check it out the next time it's due for cleaning - the results may surprise you. Any lightweight oil will do.

If any of you old timers remember, a few of the cars in years gone by had foam filters with an oil bath to keep them moist.

Steve

[Chuck Moreland]

cegerer

My "new to me" 73 has the watersheds on webers. How much are the pre-filters, where did you get them? Please post when you receive them and share your impression.

Does anyone make an oiled foam-element filter that fits the watersheds?

[sammyg2]

I have a K&N filter on my car, and I am not going to take it off.
The sky is not falling.

[cegerer]

Chuck, I special ordered mine at the local auto parts store - around $17 each (ouch!). Here's an on-line source:

http://www.4filters.com/

I'm sure Wayne could special order them as well since he sells K&N. -- Curt

[k9handler]

I have one...I like it and that is what matters to me. If you have one that you had purchased and no longer use, I am sure there are many others on the board who would gladly take it off your hands.

[Leland Pate]

I dumped my piece-of-garbage K&N filter over two years ago.
My story sounds very similar to another members... bought it from Perf Prod... before I knew "D-ick" about what I was doing with my car.
I gave it to an apprentice of my old mechanic... his eyes lit up... just "couldn't believe" I was just going to give it to him.

To me it's very simple... more dirt... less dirt...

Who cares if it's reusable... paper filters aren't THAT expensive!

If I ever end up selling my car I intend on putting a note in the ad about how I don't use K&N filters on my car.

[cegerer]

I'm not here to defend K&N, but with the pre-filter they're rated to 5 microns (I don't think anybody's ever done a test with the pre-filter on); without, they're 10-20 microns (probably dependant on oiling and dirt accumulation). The paper filters I've checked are anywhere from 10 to 40 microns. Most engine damage is supposedly caused by particles in the 5-20 micron range. Anybody else have specific micron ratings for various paper filters? -- Curt

[Wayne 962]

If I remember correctly, Bruce Anderson did many dyno tests with the stock filter, the K&N filter, and with no filter. All were exactly the same.

Keep in mind that dyno tests are highly subjective unless they are run under the EXACT same conditions. The intake is not a restriction area for the 911 engine, hence it would be suspect that a K&N filter would add anything.

We've had people on this board perform dyno tests with the filter on and off with no changes whatsoever.

The only advantage to the K&N is that it's reusable, in my opinion. I personally don't use them on my cars.

-Wayne

[cegerer]

But what about air filtration. I'm assuming that the K&N pre-filter wrap provides a relatively constant 5 micron protection (they don't need to be oiled so there shouldn't be much variance). Is there a paper filter that provides 5 micron or better filtration? -- Curt

[RSupdate]

I guess if your 911 is your daily driver one could be concerned over the issue, but if one's 911 is just their weekend "fun-car" then odds are that you're putting alot less miles on it and the wear and tear issue of any add'l dirt is minimized to a certian degree.

To each his own !!

[JuiceMan]

Actually for those of you who doubt the K&Ns performance gains you may want to check this out:

http://forums.corvetteforum.com/zerothread?id=325971

Some good dyno sheets and such there showing the power difference a K&N element CAN make with some combinations.

[hobieboy]

Wayne must have read my mind...

In my mind, it boils down to whether the K&N can increase your intake air flow. If that's not the limiting factor, then like Wayne said, why bothered.

Having said that, I put it on my 87 930. Subjectively, it gives a very slightly better throttle response...

[TimT]

LOL this is funny....... I would call this thread "paralysis by analysis"

K&N filters work just fine.....

Maybe they dont give you some extra hp........... but they last forever..

I had an early Toyota 4 runner..... that I i installled a K&N filter on. I sold this truck with 193000 on the clock and it was still running strong.....BTW I installed the K&N at about 10000 miles.

I would and I do use K&N filters to this day

if you guys collect the <5 micron particles your worried about. Im sure you would see there is really nothing to worry about

[N11Porsche]

In the Corvette test, the K&N may have made more h.p. but that doesn't relate to a Porsche. The Vette may have a filter restriction with the stock filter which would explain why the K&N makes more power. This isn't the case with a P-Car. Bruce Anerson did the dyno test with a stock filter, a K&N and with no filter. The K&N did NOT do as well as the stock filter. If the K&N would give 7 h.p. as someone suggested, they would be selling thousands of them to Porsche owners. Also the factory would gladly supply K&N's as the factory filter if they could add 7 h.p. so cheaply.

[Kurt B]

Well, the exhaust of 911s is usually the bottleneck. If you have less restrictive exhaust, you may benfit from improved airflow. Because tests using ssi, mass airflow etc on 3.2 Carreras made a considerable HP increase as noted by Bruce in 911 P.H.

I put on the paper filter for a few days. Remembered where I live and the fact that 'dirt' is not a problem and not only took the paper filter out, I put my K&N cone back in.

Except the problem was before without the black box, there is no support for the air flow meter. This was remedied by cutting the air box up so that you could resuse it to support the air flow meter while still mounting the cone.

Seat-of-pants told me, with my other modifications, the paper filter seemed to bog it down.
I believe this to be true because after I swapped the K&N back in, the idle was too high until the DME adjusted for it.
It ran at 1500, then it figured out there was something different and adjusted.

This is not proof, but it can be an indicator.

In any case, this is how I mounted the cone this time to properly support the air flow meter while still using the cone.

You know ef it. A paper filter ain't gonna save my car from me. I will run it until it explodes in great glory, and then I will pick up the pieces, reassemble it, and destroy it again in greater glory. This my friends, is Manhood. Welcome aboard.

[Rick Lee]

From now on, Kurt B is only person whose advice I will heed. He seems to have the right attitude for Porsche ownership.

[cegerer]

OK, my K&N "Pre-Chargers" finally arrived. Just installed them and it's kinda like putting a goll-darn supercharger on - it really flies! Just kidding of course.

Actually, the purpose was to improve filtration - these take it down to 5 microns, about as good as it gets no matter the filter. One tip: order BLACK - not the colored versions!!!! I got yellow because I thought it would be a nice accent to my red watershields. Well, one small problem: they absorb the oil sprayed on the filters and look absolutely terrible. But since these filter wraps, essentially, make the actual filters redundant I will probably completely clean the filters of oil, clean the 'Pre-Charger' wraps and reinstall! Nothing's ever easy ..... -- Curt