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.
Really, why is that?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.
Engines don't have a constant suction like test benches, engines pulse.Really, why is that?
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.Wet "gauze" filters like K&N are depended on those pulses - no pulsing = no filtering.
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.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.
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.I would think the air flow rate may have some impact on the measured efficiency as that may cause some captured debris "sloughing off", but nobody would know for sure without some controlled experimentation to show how. I'd suspect the design of the media has a big factor there, and filters that test lower efficiency are 1) letting particles through, and 2) probably sloughing off some already captured debris too. Filters that test higher in efficiency are doing 1) and 2) to a lesser degree.
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.
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.
Not that I know, but here is an explanation from one of the most respected living engine builders.
If you can do data logging off an engine that uses a MAF sensor, you can do those comparisons.I'd like to see how a K&N air filter would do if they made one with 1.5 and 2 times the number of cotton fabric layers (6 and 8 instead of 4 ?). How would the dP vs flow and the efficiency change?
Well you don't have to be an engineer or scientist, to do such a test, but actually he is an engineer.Engine builder ... not an engineer or scientist.
What he's saying is all "theory" with no controlled testing to prove the claim.
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.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?
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.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.
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.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.
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?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.