Testing wet filters on something that resembles a flow bench is completely useless and will get you false results - you need to test them on an actual engine.
Not all oiled filters are similarly bad to K&N...
- Thread starter SubieRubyRoo
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I’ve got almost 100K on my AFE prodry drop in. I lightly blow it out every 30K.
Really, why is that?
Engines don't have a constant suction like test benches, engines pulse.
Wet "gauze" filters like K&N are depended on those pulses - no pulsing = no filtering.
Mhm, okay.
Has anyone actually done an official efficiency test with simulated "engine intake pulsations" compared to a non-pulsating air flow? If so, please link the test info, I'd be interested in seeing it.
The only engine I see remotely fitting "pulsations" into its M.O. is a single cylinder, and since the lowest cylinder count one can get in the US is 3 cylinders, its a moot point.
Mentioning "testing pulsations" seems like there's one of these in the mix:
Here is a chart from Experimental and Numerical Study on Automotive Pleated Air Filters, showing filtration efficiency rising with dirt loading at a few different air speeds through the media. Efficiency rapidly increases with dirt loading (actually much more rapidly than the chart suggests since it doesn't actually rise linearly), but there is a drop in efficiency at high dirt loading and high air speeds due to particle shedding.
Using high air flow rates in an ISO 5011 test would result in higher initial efficiency, but lower efficiency at end of test, and probably doesn't typically have a huge effect on average efficiency. The average air speed is affected by the total media area, and local air speeds vary across the pleat and are affected by the pleat design, so some filter designs will have less particle shedding at the expense of lower initial efficiency or vice-versa.
Not that I know, but here is an explanation from one of the most respected living engine builders.
Interesting paper ... thanks for the link. Yes, makes sense that the total filter media area and pleat design would have effects on the local air velocity through the media. Total media area is basically always advantageous (all other factors held constant) for performance aspects (lower dP, higher efficiency due to less velocity, less debris shedding, etc) in any filter.Here is a chart from Experimental and Numerical Study on Automotive Pleated Air Filters, showing filtration efficiency rising with dirt loading at a few different air speeds through the media. Efficiency rapidly increases with dirt loading (actually much more rapidly than the chart suggests since it doesn't actually rise linearly), but there is a drop in efficiency at high dirt loading and high air speeds due to particle shedding.
Using high air flow rates in an ISO 5011 test would result in higher initial efficiency, but lower efficiency at end of test, and probably doesn't typically have a huge effect on average efficiency. The average air speed is affected by the total media area, and local air speeds vary across the pleat and are affected by the pleat design, so some filter designs will have less particle shedding at the expense of lower initial efficiency or vice-versa.
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Engine builder ... not an engineer or scientist. He claims a K&N would be "way more efficient than a paper filter when on the engine" ... so according to that it would be way over 99+% and even better than those paper filters tested in the Duramax ISO 5011 tests? ... I doubt it.
And he references "when our friend at Project Farms" ... what? That was not SAE or ISO testing. If this guy thinks so then he has zero credibility.
What he's saying is all "theory" with no controlled testing to prove the claim. I'll believe it when I see a valid controlled test with the data of the test done with smooth air flow and engine "pulsing" air flow. Would also like to see slow motion, up close video of the cotton fiber dynamics while on an engine with "intake pulses" going on.
If you can do data logging off an engine that uses a MAF sensor, you can do those comparisons.
Injen air filters are 8-layer oiled cotton gauze
AFE has 5 and 7 layer oiled filters
Well you don't have to be an engineer or scientist, to do such a test, but actually he is an engineer.
No "theory" ether, he had several of them (new and dirty) on the flow bench.
And yeah, if you want to see those tests, why don't you do them?
You missed my whole point. He only has a "theory" that K&N air filters are more efficient when on an engine because the intake "pulses" do some "magic" with the cotton that makes them "way more efficient than any paper air filter". Nobody has proved that with any official credible testing, unless you have a link to the test report that proves it. Until I see that, I'll chaulk it up to a "flat earth" theory with zero proof, lol.
His testing on his flow bench wasn't simulating an engine's intake system pulsation, it was just a simple smooth flow vs pressure drop test. So yeah, he's only got a "theory" with no proof.
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You don't get it. The flow bench tests was just for flow new vs. dirty and have nothing to do with the filtering performance - just sheer flow.
Regarding the pulsing vs steady flow - since you don't have a test ether, I consider your theory also in the flat earth territory.
David - on the other hand - did a ton of tests and extensive research to figure out how K&N does the filtering, (sorry he didn't write a paper on it), you - did nothing, nothing at all - all you have to show is a lot of opinion.
David is a living legend when it comes to those things, while you are (no offense) just a random guy on the internet - so guess where my trust is?
Track record is everything.
Regarding the pulsing vs steady flow - since you don't have a test ether, I consider your theory also in the flat earth territory.
David - on the other hand - did a ton of tests and extensive research to figure out how K&N does the filtering, (sorry he didn't write a paper on it), you - did nothing, nothing at all - all you have to show is a lot of opinion.
David is a living legend when it comes to those things, while you are (no offense) just a random guy on the internet - so guess where my trust is?
Track record is everything.
If the pulse of the the intake charge was critical to the operation of an oiled cotton filter, the media type and density would have to be tuned to the application.
The number of cylinders, the number of filters, whether or not the engine is forced induction - each filter would have to be tuned to all of these scenarios and more.
Instead, the same media is used in every application, across multiple brands. Even my helicopters have oiled cotton media.
Agreed. I think there is a lot of imagination going on with the whole “pulse” thing, all of which is trying to somehow justify and substantiate superiority but with zero actual facts.
Yes; if the theory of "pulse" had any basis in reality, we'd see LOWER silicon results on UOAs with oiled filters, correct? Not the ubiquitous higher silicon on every UOA that the owner admits to having a K&N on?
Cleaning and re oiling them is also a PITA.
I would much rather toss out a paper filter and replace it in seconds.
I would much rather toss out a paper filter and replace it in seconds.
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