I've heard people complaining of deposits downstream of their K&Ns. I would like some input on this... any real data out there on it's FILTERING ability?
First, WELCOME!
I'll take a stab at one of your two questions. I have not seen any really hard data on filtering ability under lab conditions such as micron ratings, etc. Data has been posted on oil analyses done the K&N in place. If the filtering data was really superior, I would expect K&N to post it all over the place, just like they do air flow resistance data. For this reason I do not believe the K&N is a significantly better dirt filter; I think it flows more air while achieving "acceptable" filtration. But this is JMO.
Summarizing what must have been 100's of posts on this topic, I would have the following bullet points:
1) A number of people have posted better oil analysis (Si) results with the K&N than with the original, but a few have received defective K&N's and were very unhappy. K&N has been good about replacements, but you may have to do oil analysis to prove you have a problem.
2) If your K&N is in the factory airbox, then poor filter sealing can render it worthless. But in some cases the factory filters seem to be subject to the same problem. Be sure to use the sealing grease that comes with the K&N.
3) The tendency seems to be for us to "over oil" these filters. Try not to, since an oil coating on the intercooler will collect dirt and render it less effective at heat transfer.
4) Charges of "oil on turbo blades" have been thrown back and forth. I don't know what the real truth is, but unless someone steps forward and says the oil was "K&N red" then I would be more likely to suspect minor oil leakage from turbo seals as an equally likely source that has nothing to do with the K&N.
You may want to try using the search engine over in the "Products" forum if you haven't already - there really are 100's of opinions out there on the K&N.
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2001 ETH, QC, LWB, 4WD, 3. 54, SPA Pyro & Boost, K&N RE-880 w/foam pre-cleaner, ARE Z-series Cab-high shell, Rear ARB locker, and all kinds of synthetic fluids...