[S_Cal968]

<!--quoteo-->QUOTE <!--quotec-->oil vapor recirculation into throttle body has a blowback into MAF<!--QuoteEnd--><!--QuoteEEnd-->
Not sure how it can be "more"[?] Most of the vapor is sucked into the engine by down-stream of the MAF[?]. Since the filter is up-stream, I would think the filter oil would have a greater affect. I keep a close eye on my MAF and it rarely requires cleaning.

It seems the trade-off for more power is an engine that may wear out sooner as a result of finer particles getting into the engine. I've read about this from other sources and until it's disproved I'm not willing to take the gamble. To each his own... If I was out for a track day, I'd pop one in, but not in a daily driver.
Keep in mind the original K&N filter was designed for off-road racing where power is more important than longevity. I have one on my 4x4 because there are no components that may be affected by the oil and the engine costs less to replace.

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[jfrahm]

One of my bikes came (used) with K&N pod filters and I found a scary amount of grit on the 'clean' side of the filter, collecting on the inside of the intake tubes and presumably also going through the motor. No thanks, not for me. I have a few K&N filters I have taken off used cars and can see pinholes in them when they are held up to the light.

There are a few tests out there, here is one:

http://duramax-diesel.com/spicer/index.htm

A fleet test in a quarry was also interesting. I do not have a link to that one.

A filter should filter, screw the extra HP if it's indeed even there.
-Joel.

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[PorscheDude]

Your concerns are valid.
If one is lazy, then use a paper filter.
If one is a fanatic about keeping things tidy, then there are
no worries.

Reports of problems are very few among all autos, more than likely those reported faults were from idiot owners
who did not properly maintain the filter.

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[firefish]

<!--quoteo(post=76248:date=Jul 28 2009, 06:20 AM:name=PorscheDude)-->QUOTE (PorscheDude @ Jul 28 2009, 06:20 AM) <{POST_SNAPBACK}><!--quotec-->Your concerns are valid.
If one is lazy, then use a paper filter.
If one is a fanatic about keeping things tidy, then there are
no worries.

Reports of problems are very few among all autos, more than likely those reported faults were from idiot owners
who did not properly maintain the filter.<!--QuoteEnd--><!--QuoteEEnd-->

Agreed on idiot owners. Had a friend who cleaned his K&N the other day, unfortunately when I came to his place he was already done, using pressurized air and some kind of solvent for cleaning greasy engine parts. Afterwards he rinsed the filter from both sides with the maximum pressure of hot water from the tap. It was "How To Destroy Expensive Filters 101".

This being said I am reluctant to use filters that I haven't bought and maintained myself.

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[jfrahm]

<!--quoteo(post=76251:date=Jul 28 2009, 02:00 AM:name=firefish)-->QUOTE (firefish @ Jul 28 2009, 02:00 AM) <{POST_SNAPBACK}><!--quotec-->Agreed on idiot owners. Had a friend who cleaned his K&N the other day, unfortunately when I came to his place he was already done, using pressurized air and some kind of solvent for cleaning greasy engine parts. Afterwards he rinsed the filter from both sides with the maximum pressure of hot water from the tap. It was "How To Destroy Expensive Filters 101".

This being said I am reluctant to use filters that I haven't bought and maintained myself.<!--QuoteEnd--><!--QuoteEEnd-->

I disagree that the care of the filters is a big issue. Compressed air might make little blowholes in the filter, but generally I think it is the nature of the gauze media that allows it to pass harmful particles.

As I understand it, the way a K&N works is that you have a several layer weave of cotton gauze, which is carefully oiled to make the threads sticky. When a particle passes through it, it probably strikes a string or two and usually sticks to one of them. Sometimes (one or two % of the time) it does not get stuck and moves on through. A standard filter, on the other hand, is made of a material that should not have any holes in it big enough for a harmful particle to pass through, the fibers being much smaller and more randomized.

The nature of the K&N media is such that there is more likely to be pathways through it that encounter few strands of the cotton string.
Less restrictive, sure, but more likely to pass some dust. I live in a dusty environment. Pass.

K&N's own spiel is that the filter gets more effective as it loads up, if that does not indicate that holes in the filter are getting plugged up with dirt and dust I don't know what does.

Anyway it's your motor. Performance has it's cost.
-Joel.

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[flash]

i ran my mgb for 20 years with NO filter - just velocity stacks - no damage at all - no signs of crud anywhere either - it just combusted whatever got in there

on the flipside, we ran nylons OVER our oiled K&N filters on the sandrail

i don't think it's nearly as big of a problem as it is made out to be - gravity is your friend here - the higher the pickup point, the lower the need for filtering - the stock location is a bad one - mine is pretty high - it is difficult for airborne particles to find their way to the intake to begin with - i don't generally see a lot in my airbox or on my filter, and what i do see is really big, and would be caught with just about anything - i've had this thing in there for over 5 years now, and about 25k miles - no signs of much of anything - there was more sand when i was closer to the beach, but again, anything would have caught that

by the way, you usually can't "see" when the maf is dirty - but if you clean it and set it down on a paper towel, you'll see the black gunk

lol - i guess a lot of this comes down to whether you want to be in the front or in the back - do what makes you comfortable

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[PorscheDude]

I have had a K&N for well over 40k miles.
Not one problem other.
I clean my MAF when I service the filter.

If you have a concern, don't do it.

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[jfrahm]

Rereading that Duramax test, I converted the units to try to quantify the restriction difference between the K&N and other filters. The most restrictive filter showed 6.23 in H2O restriction and the K&N was the least at 4.54 in H2O at 350cfm (350cfm is pretty close to a 968's requirements at full honk.)

Converting those numbers to psi, I find the pressure difference between those two filters is .009 psi. Really? That is pretty tiny.

The interweb tells me "1 PSI is equal to 27.6807 INH20 @ 4 C" so a hundredth of a psi sounds possible, and it's looking like the pressure drop for a filter is not really much to write home about. 0.10 psi might mean something but 0.01 psi, not so much. If we were making 237 crank hp at 14.7 psi that's about 16 hp per psi, so 1.6hp IF we could prevent a .1 psi pressure drop. 0.16 if we only got 0.01 psi.

So what is on the table? Maybe as much as 3hp between running a filter and going commando. But from the Duramax test and the bobistheoilguy test it looks like the K&N is allowing 0.01 or 0.02 more pounds of pressure in the airbox over a stock-type paper element, or (roughly) 0.16 to 0.32 crank HP.

I would not use a K&N even if it netted 2 HP, which I think is not real likely, being 10x more than the data suggests.

It'd be interesting to get a handful of MAP sensors and try to measure it though myself. One could also try to see what sort of ram air effect we can get too. Might be in the error range for a MAP sensor though... might need manometers in the cockpit instead. I do have a four-stick mercury one for motorcycle carbs. Hmmm.

I guess there is a reason why they use manometers and not pressure gauges for this sort of test. They need the resolution down to a thousandth of a psi to measure anything.

-Joel.

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[flash]

well, you are entitled to your opinion, but dyno tests i conducted myself on 2 different 968s, showed about 5hp gain with the K&N over the paper filter, when used with the airbox mod - these tests were done on the same cars on the same dyno on the same day - it was literally, take measurements of conditions, test this, swap out, take measurements of conditions, test that - it did the same thing on both cars

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[S_Cal968]

I'd bet the gains were mostly at high rpm which is only seen for a short duration on a street car. As I mentioned, if at a DE or track day, I'd pop in a K&N for the day.

After doing the airbox mod I did noticed a little more power too, so all is not lost. IMO, the bottleneck is the throttle-plate; the air filter is only part of the equation.

BTW, there are a lot of variables that determine who ends up in the front...

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[ds968]

<!--quoteo(post=76392:date=Jul 29 2009, 07:16 PM:name=S_Cal968)-->QUOTE (S_Cal968 @ Jul 29 2009, 07:16 PM) <{POST_SNAPBACK}><!--quotec-->BTW, there are a lot of variables that determine who ends up in the front...<!--QuoteEnd--><!--QuoteEEnd-->

Absolutely true.

However, same car, the same driver, exact repeated conditions of the "race", with the only variable being the K&N vs. stock filter I'd bet money on the
K&N insert winning by a half a car or more every single time at the end of a 1/4 or 1/2 mi race.

I've had K&Ns in all my cars, several of which have gone past 150,000 miles and a 944 with more than 250,000 miles and all without a single problem
to the engines.. from so called particles the filter may let trough, so I tend to doubt reports of inefficiency, no material gains, or those alleging greater risk vs paper filters.

Just my $ .02

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[flash]

actually, while the upper end power did also increase, the biggest area of improved gains when using the K&N in the airbox mod versus the paper filter was from 2k to 3200, where there was about 10 ft/lb more torque

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[S_Cal968]

<!--quoteo-->QUOTE <!--quotec-->same car, the same driver, exact repeated conditions of the "race", with the only variable being the K&N vs. stock filter I'd bet money on the
K&N insert winning by a half a car or more every single time at the end of a 1/4 or 1/2 mi race.<!--QuoteEnd--><!--QuoteEEnd-->
Hmm well that's profound - we all know there's a power increase; so why bring up an unrealistic situation[?].

As mentioned 3x now, if I was going to go racing I'd install a K&N... [img]style_emoticons/<#EMO_DIR#>/rolleyes.gif[/img]

A few more ft/lbs on the street would be nice, but not a big deal for what I use the car for, [I'm already faster than most of cars out there]...

re gain @ 2K; I find that a little suprizing. Even the paper filter has a lot of surface area and the velosity/volume is still relatively low at that rpm. If that is true great...

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[ds968]

<!--quoteo(post=76271:date=Jul 28 2009, 09:09 AM:name=jfrahm)-->QUOTE (jfrahm @ Jul 28 2009, 09:09 AM) <{POST_SNAPBACK}><!--quotec-->...it looks like the K&N is allowing 0.01 or 0.02 more pounds of pressure in the airbox over a stock-type paper element, or (roughly) 0.16 to 0.32 crank HP.<!--QuoteEnd--><!--QuoteEEnd-->

That's why I brought up the so-called "unrealsitic situation" - it seems from the above statement ( were it true..) that a K&N vs. stock would make ABSOLUTELY ZERO difference in performance, insofar as a O.32 crank HP delta would be equivalent the the push force generated by a driver's fart escaping trough the hatchback .. [img]style_emoticons/<#EMO_DIR#>/tongue.gif[/img] , so I was just pointing out that from personal experience the K&N does without a doubt make a seat of the pants difference.. and further proven by dyno tests to add about 5 hp, so it's a heck of a lot more than merely a third of a pony..in this car, with the air box mod. And in my cars there have been no drawbacks whatsoever..

But hey, everyone reaches their own conclusions based on personal research or experience, so perhpas yours is different, and it's all ok .. 0.32hp, or 5hp, not that huge of a diff in the overall scheme of things..

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[flash]

i do have the dyno charts to prove it - i just haven't been able to get them to convert to anything i can post here - happy to show them to you though the next time you come to an event down here - in fact, you could come to the one on saturday

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[S_Cal968]

DS,
It was Joel who posted those numbers not me...
The numbers I've seen in the past were closer to what Bob has mentioned.

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[jlm968]

Bobistheoilguy article

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[ds968]

<!--quoteo(post=76510:date=Jul 30 2009, 09:58 PM:name=S_Cal968)-->QUOTE (S_Cal968 @ Jul 30 2009, 09:58 PM) <{POST_SNAPBACK}><!--quotec-->DS,
It was Joel who posted those numbers not me...
The numbers I've seen in the past were closer to what Bob has mentioned.<!--QuoteEnd--><!--QuoteEEnd-->

sorry, must have been dazed and confused.. [img]style_emoticons/<#EMO_DIR#>/rolleyes.gif[/img] anyway, point was just that while I've never had a problem with any the engines where I used KN
for hundreds of thousands of miles ( and I also am not too diligent about maintaining the filters as often as I should ) the resulting gains in this particular car are significantly more pronounced than a lot of data in articles out there would lead one to believe..

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[flash]

i am a bit surprised that the article did not actually include any dyno results - we did both manometer and dyno testing - while the differences on the manometer were small (.15), the differences on the dyno very clearly were not

bottom line though, do what you want - i'm going to continue to run it because i have seen the data with my own two eyes

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[biotechee]

Effective immediately, I am removing my K&N filter and my whole airbox and then covering the inlet to the MAF with some old fishnet stockings. So there! I'm going for sexy versus functional.

In all seriousness, I'm tired of hearing the debate between the regular filter and the K&N. With proper maintenance, either appears to be just fine. So install whichever filter you deem makes you happy/comfortable/thrilled/excited/relieved/warm&fuzzy.

Let us not discuss air filters anymore - PLEASE! [img]style_emoticons/<#EMO_DIR#>/tongue.gif[/img]

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