Most applications I’ve seen in store are just plain jane filters
Brand Ranks air filter test
- Thread starter KevinMalone
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Second test is live with performance filters:
The capacity results are a little misleading as unfiltered dust is getting through, which they acknowledge.
The capacity results are a little misleading as unfiltered dust is getting through, which they acknowledge.
The area under those curves are scary.
Air filters have a very low dP vs flow, and therefore become more efficient as they load up. They don't slough off captured debris like oil filters do because of their low dP vs flow.
Oil filters have a much higher relative dP vs flow, and therefore typically lose efficiency as they load up and slough off captured debris as the dP increases. Some are worse sloughers than others, depending on the media. High efficiency oil filters are low debris sloughers as they load up.
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dnewton3
Staff member
Way back in the day, our member Jim Allen visited a filter production and testing facility (it was either Parker or Fram IIRC). He learned that (as a generality) air filters will pass 90% of the total particulate in their lifetime in the first 10% of their lifecycle. Meaning that air filters most certainly do load-up and become more efficient in a desirable manner.
And, we can take a corollary story which exists beneath the headlines ... That changing one's air filter frequently will most certainly lead to more particulate ingestion because of the aforementioned loading cycle. The more "new" filters one installs, the more often you're in that first 10% of high-occurrence particulate pass. And air filtration is at least as important to engine wear control as any oil filter; some studies show that air filters actually are more important to wear control.
The moral of the story is to not change your air filter too often. You're probably doing more damage to the engine with frequent air filter changes that any worry about brand selection would ever create.
And, we can take a corollary story which exists beneath the headlines ... That changing one's air filter frequently will most certainly lead to more particulate ingestion because of the aforementioned loading cycle. The more "new" filters one installs, the more often you're in that first 10% of high-occurrence particulate pass. And air filtration is at least as important to engine wear control as any oil filter; some studies show that air filters actually are more important to wear control.
The moral of the story is to not change your air filter too often. You're probably doing more damage to the engine with frequent air filter changes that any worry about brand selection would ever create.
My biggest concern is finding an aftermarket air filter that fits correctly in my 18 Outback. Usually stick to OEM in this case.
The fit is very important! The Fram AF fit in my 19 Tacoma seems off.
Yep that's why I installed a filter minder.
I'll change the air filter when:
The foam rips (why I changed the last one)
The filter minder locks in a 12'' h2o reading at least twice
The air filter gets so dirty for so long it starts passing dirt to the inside of the intake.
Otherwise I'll inspect it for any of the above every 2,000 to 3,000 miles.
Lubrizol found that Performance Polymers, aka VIIs, helped reduce wear caused by the particles that get pass the air filter.
I'm not following this in a raw data sense. I'd like to see where this internet BITOG lore comes from.
It makes "sense" if you assume the filter media alone is not capable of stopping particulates from the intake, but needs to "load up" on dust, etc to actually become efficient in stopping foreign matter being taken into the engine. If that's the case, why don't they make the media more dense/more pleats/increase surface area/etc? I change my filters annually as that is around 15-20k on them with cleaning the air box, gasket contact area, etc. Am I destroying my engines by changing air filters "too much"? I am a cynic of this widely accepted "truth."
Depending on the air filter, they can still be pretty efficient when new, but the point is that they become more efficient as they load up. So if you used an air filter that wasn't real efficient when new, and changed it out way too often, then the engine would be subjected to more dirty air over time vs either using a filter with a higher starting efficient and/or not changing the air filter so often and instead changing it when it really needs to be changed due to it being excessively loaded and starting to effect the dP vs flow.
Thanks for this. Again, it makes sense. It’s just difficult for me to wrap my smooth brain around a dirty filter being better at filtering particulates when it’s already got particulates occupying part of the filter media.
Could this logic be applied to other (oil, etc) filters?
As mentioned in post 44, air filters get more efficient with loading, but oil filters get less efficient with loading. The dP vs flow across an air filter's media is very minor compared to the dP vs flow across an oil filter's media - therefore it's easier for an air filter to retain already captured debris. Some oil filters lose a lot of efficiency as they load up and the dP across the media increases. Therefore the media can't retain all of the captured debris, and the dP across the media makes some already captured debris slough off the media and go down stream. Testing of the real time efficiency of air and oil filters as they load up show this to be true.
In their test, a real time particle counter is recording the number of particles getting through as the filter loads up with time. You can see that after it peaks out, the number of particles getting through decreases as it continues to load up. I don't know what the time scale is (the x-axis), but the filter is loading up more and more after the peak with time (as the x-axis goes right), and the efficiency is getting better - ie, less particles are getting through the filter. The slight up tick in particles from the beginning to the peak may be from the media letting more debris through until it gets to a certain point of loading, then the already captured debris actually helps the filter become more efficient as some larger media pores start getting closed from debris loading.
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One thing I noticed in the BR air filter testing video is that during the holding capacity test, they just counted the number of 5 gram dust dumps they put through the test apparatus. You can see through the clear plexiglass window on the dirty side of the filter that lots of dust clings to the inside of the box. Could also be some is just laying on the floor and in the corners and that never gets trapped in the filter.
If I was designing this test, I'd make it so the dirty side of the filter is pointing up so the dirty filter could be carefully removed after the test without spilling any captured debris. Weigh the clean filter before testing on a very accurate gram scale, and then weigh it again after the test to determine how many grams of dust was actually in the filter.
If I was designing this test, I'd make it so the dirty side of the filter is pointing up so the dirty filter could be carefully removed after the test without spilling any captured debris. Weigh the clean filter before testing on a very accurate gram scale, and then weigh it again after the test to determine how many grams of dust was actually in the filter.
Here's an interesting paper. More data that shows used air filters are more efficient than new filters. You can download the whole article PDF in the link below:
https://www.researchgate.net/public...ating_Tests_for_Automotive_Engine_Air_Filters
Snips from the paper in the link.
https://www.researchgate.net/public...ating_Tests_for_Automotive_Engine_Air_Filters
Snips from the paper in the link.
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Thanks for the article. Even if it's from 2001, I'd imagine air filter media hasn't had huge strides compared to engine oils, etc during the past 23 years. Looks like cellulose media fared the best and as you mentioned, the newer media of any type was not able to capture the dust as well as the older, exposed filters.
Cool, I got a Walmart Fram AF in my truck
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The whole "90% of particulate passing through the filter occurs within the first 10% of it's service" situation is why I switched to OEM air filters for my Honda. They come lightly oiled to trap that particulate before the filter is sufficiently loaded. I'm not sure why oiled filters aren't more popular.
