Vi posto per chiarezza informativa tutta la discussione sui test che sono stati fatti su questo filtro. E' un po' lunga, ed in inglese purtroppo, ma credo che possa meglio rendere l'idea sulla qualità non eccelsa di questo filtro: si parla dell’olio usato dalla K&N, testato in laboratorio, che trattiene molto ma lascia passare certi tipi di polveri che addirittura un filtro normale di carta tratterrebbe…risultato: il motore “respira” sporco con questo filtro, quindi non potete certo venirmi a dire che è il miglior filtro in circolazione!
<<I don't "hate" them, and haven't always - in fact, I have owned K&N filters in the past. However, that test I linked is no opinion - it's the most scientific, controlled air filter test I've yet seen, and the FACT is that the K&N filter performed very poorly. (To the suggestion that they simply got a bad filter - no, I've seen quite a few less well controlled tests that gave similar results with the K&N filter filtering less effectively).What I don't like is bullshit marketing claims, and in that regard K&N is one of the leaders of the pack, just behind Splitfire and Slik50!
The point is that the K&N was next to the worst filter of the bunch. NOT the best by any means, which is what K&N claims. As far as filtering goes, 95% isn't bad - but when your OEM filter actually does a better job of filtering, then it isn't great either. After all, filtering is what those things are supposed to do, right? And there are a LOT of better filters out there. What's the big deal with K&N filters then, when they are certainly no better than the other alternatives?If we see a test between several filters and the test includes extremely fine particulate matter of a micron or less and the worst filter is still above 95% efficient, that is pretty damn good. Gordon makes it out like the K&N are only 75% efficient and you are going to destroy your engine if you use one. Nothing and I stress nothing, can be farther from the truth.
That test was run by a professional independent lab according to the ISO 5011 test procedure. Hard to argue with that or complain that the test wasn't conducted correctly, isn't it? As for the "proven fact" - actually, the results of that test showed that the K&N clogged sooner than the paper filters they tested, even though it also passed more dirt. An amazing feat, as I mentioned! All the data is there, just go look at it. That test just disproved the "proven fact" that K&N claims. PS - they did test the K&N with both coarse and fine dust - the K&N clogged even faster with the fine dust.I don't know how well that test in that article was run but it is a proven fact that the K&N filters flow more in a clogged state than paper filters do.
Real world? Let's consider - in the real world of street cars, the air filter is NOT a restriction that is costing horsepower. Take out the filter completely, and an RX-8 will not dyno more than 1 HP higher. Put in a K&N, and it doesn't make any more HP. Who cares that it can theoretically flow more air, when any paper filter can flow as much air as the engine needs??? Real world, a K&N doesn't provide any more HP. Even changing out the stock panel filter to a K&N cone filter does NOT provide any more power - look at all the tests and experiences on this board for proof of that fact in the RX-8 street world. The nit-picking is to insist that the K&N flows better, when THAT DOESN'T MAKE ANY DIFFERENCE! So what? That's as relevant as to insist that it's red instead of white, and red is better. In the real world, the colour of the air filter doesn't matter.So we have two major requirements for an air filter - flow capacity, and filtering dirt out. We know that flow capacity is NOT an issue, as all of them will perform the same on our street application. Therefore, the difference between air filters comes down to their filtering capability - and this test (along with pretty much every other independent test I've seen) proves that K&N filters do NOT filter as well. Tell me again why I'd ever want to spend extra dollars for an inferior filter?This above test proves absolutely nothing beneficial in real world applications. There comes a point where nit picking doesn't do anything anymore. Paper filters don't flow as well. Do they filter better? Maybe. But they don't stop anymore harmful particulate matter than a K&N. Anything that small is not much to worry about.
Racers? Come on, what a lame argument. Their filter requirements are much different than street filtering requirements, and you certainly understand the engineering analysis of requirements that goes in to selecting a race air filter will be much different than the requirements for selecting a street filter. If you insist, I can list them, but you actually cover a bunch of them yourself. Yes, in race use, ultimate flow capacity will be a much bigger factor, and engine durability in the hundreds of thousands of miles range will not. I would never base oil selection for a street car based on what Ferrari runs in their Formula1 engines, either, because their requirements are much different than mine (That also points out that the use of Redline in race engines isn't really a great recommendation that Redline is the best oil for street use, for example. I'm NOT saying anything against Redline, please note, just pointing out that products that are great on race applications aren't necessarily great on street applications, because of the vastly different requirements).
I don't know about you, but I run an oil filter on my engines. The best one that I can find, for that matter - in terms of its filtering capability.The oil that your oil metering system is injecting into the engine is putting far larger and harmful things into the engine than a K&N filter is. If you can see metal shavings or a silver sledge in your oil, these shavings are also getting into your engine through the omp! Oh yeah, no one remembered that!
However, if you're familiar with oil analysis, then you know that oil analysis actually shows the differences between air filters. I've seen several tests where people find that silicate content in oil increases when they run K&N filters. Why? Because the K&N filters are letting more particulates (ie fine particles of sand, composed of silica) through into the engine. Yeah, your oil pumps stuff around the engine that can cause wear - your argument about the oil, then, is actually another argument AGAINST using K&N filters.
Nitpicking? How many people here discuss and debate the best oil filter for their engine? The best oil? People want to know what products will provide for the longest life and will do the best job preventing wear. Air filter choice obviously contributes to that as well - and it is NOT nit-picky to want people to know that some filters protect better than others (especially when those others do NOT provide ANY benefits beyond noise in our specific application), despite the marketing department's claims. I don't buy the hype for Splitfire plugs, Nology plug wires, Slik50, and I don't buy the hype for K&N. That doesn't mean I hate them, by any means - for different engineering requirements (where long life of componentry is not a primary concern), then obviously my criteria would be different and a K&N filtercould be an excellent choice. Not ever (not ever again, that is) in one of my street cars, however!
Ho preferito postare l'intera discussione e non farne un riassunto, perchè credo che in questo modo ognuno possa avere più chiarezza sull'argomento senza inutili travisazioni (soprattutto proveniendo da una lingua straniera)!