Richard.

Maybe its me but after a short drive with K&N filters filters on my Boxster GTS, the car is quieter with the K&N Filter than the OEM ???

DBH

I've used K&M air filters on most all of my cars and have found both a marginal increase in HP (on butt dyno ) as well as a noticeable boost in the intake sound. I cannot comment on my CGTS as I felt it was too much trouble to install air filters for any small incremental increases in power/sound.

JCtx

Well, what you can bank on for sure is a lot more dirt getting into your engine. Not worth it, even if it made more noise, but to each his own. I assume you don't think a basically see-thru RACING filter is going to trap more dirt than a proper factory paper filter, but if you're one of those, you can find out for yourself with a simple test using a shopvac. And yes, the factory filters provide all the air the engine needs even at WOT, so any illusion of more power is just that.

extanker

a test rig for evaluating air filters built out of a shop vac............WOW .....just when ya thought you have read everything here

khoahtran

I noticed that I have to drive really HARD to notice an increase sound and change in tone.

PorscheAddict

Haven't installed mine yet, but the folks always crapping on aftermarket filters are sort of skipping a link in the causation chain here. People have run K&N on hundreds of thousands or millions of vehicles for a long time, and the only substantiated issues I've ever seen relate to MAF and oil, not dirt. A lab test showing X% dirt gets in doesn't really mean much without a showing that the small incremental increase actually caused some sort of issue (at least in some engine in history, obviously not every engine). The data is not out there to condemn it, IMO. I've ran them on BMW, Porsche, Audi, everything I've had (not K&N necessarily, but aftermarket cone-style). Just my opinion, in the same way others may opine that a 1 or 5 or 10% dirt increase automatically means there is catastrophe going on in there.

Scooby921

What link is being skipped? Higher flow comes from reduced restriction. Reduced restriction comes from larger holes in the filter element. Larger holes allow more and larger bits of debris to pass through. At some point in time this will affect the engine. Do you not accept this? Maybe it doesn't lead to immediate catastrophic engine failure, but the larger debris will slowly increase wear on cylinder walls and valve guides. Whether that reduces engine life by 1% or 40% is agreeably unknown, but there is guaranteed to be increased wear and reduced life.

PorscheAddict

Nope, I don't. Without knowing the size of the particles and many other factors I don't think any of us can conclude either way. It seems to me that if the effect was significant at all there would be some sort of evidence as to engine wear (not just evidence as to increased dirt flow, which does exist to some degree and under certain conditions). Tiny particles get in already to no or little ill effect.

Also, to be clear, I'm not saying you're wrong and I'm also not saying more dirt particles don't cause damage or wear. I'm saying there's no evidence to support that, beyond speculation and assumption.

I do know that I've ran them for hundreds of thousands of miles in a wide variety of applications and never had an issue, and while I'm but one small data point, tens or hundreds of thousands of other folks have done the same.

Didn't mean to derail thread, so we should probably just agree to disagree and both enjoy our cars

terbiumactivated

I wrote K&N once and they provided a lot of research to refute the claim that always arises about filtration particulate, it's their research so I guess it could be biased. IMO, almost all the failures associated with K&N or BMC arise from improper cleaning and over oiling of the element. I never hear anyone flipping their #$% over old 911's with velocity stacks and rough gauge screen on the tops. Personally, I'd be a lot more concerned with a launch control addict than an aftermarket air filter and LC is a factory add. Given the longevity, I will split the difference and never put a cleaned BMC back in the spyder but instead just replace it.

DBH

Everybody seems to be missing two things here...1) I've seen people with 100,000+ miles on engines that have always run with K&M (or similar) filters with no apparent issues (caused by the filters) - how many miles do you intend to put on your car before replacing it?? And 2) proactive motor oil/filter replacement. This probably has more to do with a healthy engine than anything else you can do. In the "good old days" this meant doing an oil/filter change every 3k miles. Now, with fully synthetic oil, I replace every 7.5K miles or one year whichever comes first.

Oh, and I've never experienced any (K&N) air filter related issues on nine cars over the last 30+ years.

JCtx

If you lived in the dusty desert southwest, you probably would have had different results. It's like saying because you're never lost money on the stock market, there's no risk. Or more appropriate, saying eating crap food doesn't afect your longevity because you're still alive. Like Scooby said, it's just common sense. But yes, it's impossible to quantify because nobody drives under the same conditions. But that doesn't mean any reasonable person knows which way is better in both cases. I leave this discussion with one much simpler test that is not subject to a million different scenarios: Do a dino run back to back with and without a K&N. I'd be very surprised if there's any advantage (981s have TWO huge filters), and it'd only be at the very top of the rpm band, if at all. Then judge if that's worth potentially damaging your engine. K&N is a great racing filter, but a lousy street filter, especially in dusty places. Still surprised by the power of (false) advertising in this country, but to each his own. Have a great weekend gang.

terbiumactivated

"I'd be very surprised if there's any advantage" "K&N is a great racing filter"

One of these things is not like the other, one of these things just doesn't belong....

MrMoose

If you look at actual test data and not just marketing materials you will never use one of those filters. The increase in flow is negligible, they plug up faster than paper filters, and they let a lot more dirt into your engine. Couple of decent tests linked below.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

https://www.bobistheoilguy.com/airfilter/airtest1.htm

I wouldn't use one on a car I cared about. It's not going to make your engine explode or anything, but it has the potential to increase wear over the car's life for basically zero gain.

PorscheAddict

FWIW, I installed K&N over the weekend and the induction noise above 4-5k is way louder. It has a sort of growl and resonance that was not present before. It sounds exactly to same to my ears at normal idle-4k rpm operation. My paper filters were very dirty at 20k miles; hard to believe Porsche specs 40k intervals.

Richard.

Seems the mid engine cars take it a lot more dirt & they are so f*king difficult to change