TEST: K&N vs stock air filter...

[Gary - K7GLD]

WELL, the BEGINNING of one...



We have all heard or been involved in the "K&N filter wars" over a period of time - some users have claimed that they don't like the daylight they can see thru the filters, others claim too much dirt can be found on their turbo hubs and impellers with K&N filters...



But what most DON'T tell us, is how visually clean their STOCK filters have kept their intake tract by comparison, and whether they have had similar visual problems with STOCK air filters...



THUS, my own little non-scientific "test"...



After about 5000 miles with the stock filter in my new truck, I have carefully swabbed the intake to my turbo with a clean white paper napkin - the results:







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I have now installed a slightly used K&N filter kindly contributed by Garrett (greatwhitebeast) at a generous price, and will now proceed to put similar mileage and use on it - then make the same test with the same napkin, and post results here...



Like I said, this IS NOT a scientific test, merely an informal visual test to see how this K&N will do on my particular truck...

 

[Mundgyver]

Question Did you swab out the system before you did your test to ensure a base line for comparison? I would assume that you swabed it out again before installing the K&N. This should prove an interesting test

 

[Gary - K7GLD]

NO, I had no idea a test of this nature was in my future, so did not swab out the turbo inlet right off the dealer's lot - nor would it be practical to do it NOW, and then pile up ANOTHER 5000 miles or so for a test - but realistically, I seriously doubt that there would be any significant buildup of intake dirt right off the DC assembly line - NOR do I particularly expect this informal "test" to change anyone's mind one way or another concerning K&N filters - it's for general info and entertainment ONLY...



Mine as much as anyone elses...

 

[Crazy Horse]

Gary I'll be interested in seeing what your test yeilds. I did some airbox mods awhile back and posted my finding. Prior to the installation of the K&N I did note black crap on my turbo fins. After cleaning the fins and installing the K&N, I never saw that black crap on the fins again. Turbo Blades



Proper sealing on that filter to the airhousing is very important. Last year after that trip was over, I checked the turbo blades when I got home they were still clean with almost 21,000 miles on the truck.

 

[illflem]

Gary, just wondering if you were going to do before and after oil analysis but guess that it wouldn't be very representative on an engine that isn't broken in yet.

 

[Gary - K7GLD]

"Proper sealing on that filter to the airhousing is very important. "



Exactly - and one of my main points - fellas get REAL critical of the K&N - but like any other filter, it's only as good as it's fit and installation - JUST LIKE a stock filter!



For the record, a very careful inspection of my STOCK filter, as it came installed right off the assembly line, revealed traces of fine dust particles leaking past the filter seal - undoubtedly why there was dust buildup in the turbo intake.



Illflem asks:



"Gary, just wondering if you were going to do before and after oil analysis but guess that it wouldn't be very representative on an engine that isn't broken in yet.



Yeah - pretty much the way I see it too - I'll probably upgrade to a BHAF after playing around with the K&N - I've used the K&N's for years, on different vehicles, and always been completely happy with the lack of visual dirt in the intake tract over long miles in use - as was the case in my '91 Dodge/Cummins with well over 100,000 of K&N use - and typical silicon oil analysis was at 3 ppm in 5000-7000 miles oil changes. After another 5000 miles on the new engine, 10,000 miles total, I'll do an oil analysis, then I'll install my Frantz bypass oil filter and do another oil analysis after another 5000 miles or so. I'm pretty sure a BHAF will be my final air filter after all the playing around...

 

[Gary - K7GLD]

Once again - this is NOT intended as a "scientific" test - just a visual inspection to see what sort of dirt might be getting past a K&N, as compared to a stock paper filter - here's a comparison after 2000 miles SOME of it in VERY dirty conditions in Sierra powdery red dust!



The tissue on the LEFT is the "after" test...



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And here's a shot into my turbo before wiping it out for the above photo - appearances are deceiving - the inlet and impellers are VERY clean, shadows might seem otherwise no dirt, no "oily build-up" or other nasties - and I also carefully wiped the inside of the top lid of the airbox, and inside the rubber connector boot - NO observable dirt to be seen!



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*I* am satisfied the K&N is doing a perfectly satisfactory job - the filter was a second-hand unit, somewhat dirty right outta the box it came in - the filter minder has never moved from it's lowest setting - all seems quite proper... I did this as a test to see whether I wanted to stick with the K&N, or go to the BHAF - as good as this looks so far (same as my experience with K&N on my '91 for 100,000 miles!), I will stick with the K&N!



Draw your own conclusions...

 

[COBRAJET]

Three years ago I ran oil analysis for a year on my 99. 5 PSD. They check for silica... which is dirt. I ran 55K in a year. The first 15K with a stock filter. I changed the oil five times and had it analyzed. The remaining 40K was with a K/N. There was virtually no difference whatsoever in the silica reading. The K/N was actually slightly less... . CJ

 

[Crazy Horse]

Gary,

Thanks for the "test" results. It confirms what I believed all along, and my past personal findings.

 

[illflem]

For your next test Gary try over oiling the K&N then installing it without the sealing grease. Then pop open the box every couple of days to see if it's ok.

Your test confirms what I've known all along, as long as you follow K&N's instructions you'll have no problem

 

[Chipstien]

Oh come now Bill, are you insinuating that the consumer is at fault. :-laf :-laf

 

[Vaughn MacKenzie]

Gary, if you would've done your "test" on the K&N RE0880 I used to run, it woulda flunked for sure! It was sealed very well and after only a couple thousand miles I could swab out all kinds of dity brown dust. This was with the red foam prefilter. The high Si in my oil analysis results backed it up.



My conclusion is most K&Ns are good, but there are definitely some bad ones out there! I think their QC is a bit weak.



Vaughn

 

[JR2]

Vaughn,

I had exactly the opposite experience with the RE0880. I ran it for two oil cycles and then ran a BHAF for two changes. All the oil analysis came back practicaly the same and the same as the stock filter that I ran for one oil cycle.



I chose the BHAF because they flow more and you don't have to mess with cleaning or oiling, you just buy a new one.





JR2

 

[Joe G.]

I agree with Gary on this one (can't believe I said that). I use the same kind of check he does, but mine is a little more hi-tec. I lick my finger and wipe the inside of the turbo. So far, no mud. My K&N looks horrible looking thru the holes in the bottom of the air box. No sign of any dirt in the air system. The filter minder never moves. Even with a clean stock filter it would move before with WOT up a hill.

 

[Dane]

Cool! These air filter threads are almost as fun to watch as the oil war threads



I'm doing my own research, but I use the taste test



Mmmm turbo gunk... Tastes kinda like chicken

 

[pwr2tow]

My results, The numbers may be off a little as I do not have my maintenance schedule at this computer.



20,000 miles using original filter---Clean turbo blades



next 8,000 miles using K&N RE0880 and red prefilter---black crud on turbo blades.



next 20,000 miles using fleetguard filter---Clean turbo blades.



Conclusion---I would not use another oil type filter on my turbo diesel truck no matter if someone gave one to me, Oh by the way Someone was giving a oil type filter away just the other day on the TDR and I declined



Ron

 

[pdolan]

I don't like to have to pick sides, but I guess there isn't any way to avoid it:



We race 160 and 200cc Honda-powered go karts (all paved track), and my team mate has insisted for years that foam filters were the ultimate in protection. They have worked for us, but when adding a couple of new engines two years ago, I decided to try genuine K&N elements. Much to my horror, the inlet air horn and carb were showing lots of road dirt in a few races. I tried more oil, less oil (all K&N oil) whatever, but the end result was dirt passed both elements (no pre-filter) very easily. These things are clamped onto the air horn with a hose clamp and absolutely DO NOT leak.



If these things are so critical in either design, manufacturing or some nuance of service that they won't reliably filter air, what's the point of having one on an engine???



Pat

 

[Gary - K7GLD]

I really think there are 2 major issues where use of a K&N type filter is used - one is that you MUST make absolutely certain that it fits securely - and that goes for ANY filter - as pointed out in my first post, I could see clear evidence the OEM filter had leakage right from the factory - but few bother to check or complain about that!



Second, the properly sized filter must be used - NO filter, paper or oiled-type will function properly if the VOLUME of air being sucked thru it exceeds its design flow rate or real-life capabilities! I suspect that is why SOME oil-type elements seem to perform better than others in actual use - and I suspect the conical types many are using on later Cummins engines simply are not up to the task.



An UN-turboed 5. 9 Cummins near sea-level will draw something like 360 cubic inches of air thru the filter - at roughly 14 psi boost with a turbo, that doubles to about 720 cubic inches - for those adding a Comp as I have, that doubles again at 30 psi boost to nearly 1500 cubic inches at maximun boost! If those numbers aren't properly designed and factored into the element used, you WILL have problems, and probably faster with a K&N type than a paper filter, due to availability of some of the larger visible holes in the material that normally have very fine "hairs" across them to provide filtering at NORMAL flow - but can allow contaminents to be sucked thru them at excess flow. A paper filter under those conditions simply deforms or collapses...

 

[Evan A. Beck]

I see rigs come in with all sorts of filters, K&N, Amsoil, AFE, etc... The dirtiest turbos are the ones with a K&N RE-0880 and the red prefilter "sock" thing. The difference with & without the sock is pretty big. The intake is far cleaner, with little or no oil residue--when the sock is NOT installed. I think it is because both the sock AND filter are oiled, allowing more oil to get sucked in... Just a theory...



Currently I am running an AFE filter in my Psychotty system, and the turbo inlet is cleaner than with the RE-0880... IMHO, the AFE filters are of better quality construction, and seem to filter better. Also, when using an AFE filter in the stock box, the fit is MUCH better than with a K&N. WHo uses a stock box anyways? :-laf

 

[Chipstien]

Evan, I wasn't aware that you were supposed to oil the red filter sock. I am 90% sure the the instructions that came with my pre-filter said "not" to oil it. Regardless I wouldn't oil the pre-filter anyways as I don't feel it is neccesary. I run 2 separate pre-filters on mine..... seems to be working great.