Air Filter Flow vs. Filtration
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Air Filter Flow vs. Filtration
I read in the oil sticky, people reporting higher levels of silica in their oil tests using the K&N high flow filter. So basicly Ive been trying to decide if I want to leave my K&N air filter out. I pulled it yesterday and put in an OEM paper filter. I did notice a change in sound and throttle response. Its noticable, but by no means horrible (obviously). So today I'm searching for the best balance of filtration vs flow. I really dont like the idea of extra sand grinding away at my VQ. Here is the best article I have found so far. I would love to hear other peoples input, experiances, and recommendations.
**********************************************************
http://www.bobistheoilguy.com/airfilter/airtest1.htm
Air Filtration and Flow Test
As automotive enthusiasts, we are always looking for ways to increase the power output of our motors. Many aftermarket companies now manufacture and offer high performance air filters. Most all claim a power gain through increased airflow and some claim better filtration as well. In this test, many air filters will be compared. I personally have owned various makes of performance automobiles. This particular test is being conducted using a 1992 Mazda Miata with a bone stock engine (can't wait to modify it personally). I have many different turbocharger parts and components collected waiting to modify the Miata. The air filters tested include a Napa Gold, Amsoil two stage foam, Jackson Racing two stage foam, a Baldwin fiberous, a K&N, and a Mazda factory replacement.
The air filters will be mounted in the stock air box and filtration tested by placing a 2nd filter (after filter if you will) just before the airflow meter. A picture, as you will soon see, is worth a thousand words and shows this setup. A water manometer will be used to test pressure drop across each filter. Obviously the filters with lower pressure drop flow better, and have the potential to yield more power given the engine actually needs the airflow increase. The pressure drop across each filter will be measured in inches of H2O (water). The pressure drop will be from atmosphere using the stock Miata induction system to the air box just after the filter. 1 psi of pressure = 27.7 inches of water for reference.
I have a degree in mechanical engineering and am currently pursuing a master's in engineering management. I have been around the automobile all my life, and will be obtaining certification as an ASE certified mechanic this fall (for fun). My father worked in the automotive test industry my entire adolescent life. I've also spent much of my life at the race track, either racing as an amateur or with my father who was a crew chief for a stock car racer many years. He also was a crew chief at the 24 hours of Daytona and LeMans twice. I regret not being able to go to LeMans to this day. I'm a certified gage calibration technician, certified quality assurance inspector, certified as a refrigerant worker by the EPA, and work in the Navy as a mechanic in nuclear propulsion. I like to think I know a few things about machines including automobiles, but there is always something to learn.
I choose to conduct this test because of the conflicting information I see in advertisements and have read on the internet. Everyone claims that their filter flows the best, and removes the most dirt. If you think about it, flow and filtration ability are actually linked. A solid piece of metal would prevent any particles from entering the engine, but it wouldn't flow any air at all. On the other hand, the screen used on a window screen will flow well, but won't filter well at all. So if you think about it, the best flowing and best filtering is really contradictory in claim. I wanted to find out which filter really does filter the best, and which one really does flow the best. I have used almost every brand and type of air filter over the years including K&N. I had not used a foam filter until conducting this test. I have used every manner of off the shelf fiberous or paper filter.
There are basically four types of filtration materials currently in use for automobiles: paper or other fiberous (some appear much like fiberglass), foam, cotton gauze and stainless steel mesh. This test has used the first three, but not stainless steel mess. Steel mesh bathed in oil is some of the very first filtration materials ever used in an automotive application. There is a reason they were abandoned for paper in the '60s. I find it surprising that some aftermarket manufacturers are touting them now. In the links at the end, there is an interesting test of a stainless mesh filter.
The filters in this test were tested for both flow and filtration. The pressure drop across a filter is a good indication of its ability to rob the engine of needed airflow and hence power. Obviously the air filter with the least pressure drop is the highest performing. For the filtration test, I used a secondary filter after the filter being tested to catch any particles that passed through the first filter. The secondary filters were made by cutting apart an off the shelf Fram carburetor filter. The particles passing through the filter being tested leave a deposit on the secondary filter. The lightness or darkness on the secondary filter is an indication of how much dirt is getting through the filter being tested.
The differential pressure test was performed using a water manometer where one psi of pressure is equivalent to 27.7" of water. The differential pressure was measured between atmospheric and the pressure drop after the air filter in the stock airbox. The max pressure drop in this test was seen at only 7.0 inches of water or 0.25 psi. The factory airbox and piping with no filter yielded a pressure drop of 5.0 inches of water or 0.18 psi. That means that the worst filter in this test only caused a pressure drop of 0.07 psi. In my opinion, this means that if you are picking an air filter based on performance, you probably aren't doing your car any favors. For the record, the K&N was the best flowing filter. Of the 3 types of media tested, the cotton gauze type filters flow best. There are other brands besides K&N for sale, of which most are probably made by K&N for resellers. Foam air filters flowed marginally better than paper.
The filtration test has been the cause of much argument and debate in some circles. Many contend that a color comparison (comparing shades of gray) is not scientific or appropriate. Again, this is a very low budget test, and there are other scientific analyses where color comparison is valid. In water chemistry a color comparison is often used to determine concentrations as low as parts per billion. Search for information on titrations (of which some are by color) or color comparators. In chemistry the color is compared to a known standard of specific ion concentration by color. If you have ever played with a fish tank chemistry sampling kit, then you have done color comparison yourself. In this air filter test, no attempt is made at determining actual concentration. A color comparison is used to determine real world filtration ability. Each test filter was used in the same car, on the same roads for 500 miles. The darker deposits indicate poorer filtration, and lighter ones better filtration. That said, both the cotton gauze type (K&N) and foam filters (Amsoil & Jackson Racing) showed the same levels of filtration. Both performed poorly compared to the fiberous or paper filters (Napa, Baldwin, and Mazda).
If you are interested in the filtration pictures or pressure test data, follow the links provided to my other pages. You will also find links to other tests, which I found interesting on the web. In the end, paper or fiberous filters do remove more particles from the air before they enter your engine. The cotton gauze filters indeed offer better airflow. You have to decide for yourself whether you value ever last ounce of power or filtration. I cannot, nor will I make this decision for you. I do know that on a relatively stock car with a properly sized air filter, you indeed have very little if any performance to gain by swapping filtration material.
Flow test:
http://www.bobistheoilguy.com/airfilter/airtest2.htm
Filtration test:
http://www.bobistheoilguy.com/airfilter/airtest3.htm
**********************************************************
http://www.bobistheoilguy.com/airfilter/airtest1.htm
Air Filtration and Flow Test
As automotive enthusiasts, we are always looking for ways to increase the power output of our motors. Many aftermarket companies now manufacture and offer high performance air filters. Most all claim a power gain through increased airflow and some claim better filtration as well. In this test, many air filters will be compared. I personally have owned various makes of performance automobiles. This particular test is being conducted using a 1992 Mazda Miata with a bone stock engine (can't wait to modify it personally). I have many different turbocharger parts and components collected waiting to modify the Miata. The air filters tested include a Napa Gold, Amsoil two stage foam, Jackson Racing two stage foam, a Baldwin fiberous, a K&N, and a Mazda factory replacement.
The air filters will be mounted in the stock air box and filtration tested by placing a 2nd filter (after filter if you will) just before the airflow meter. A picture, as you will soon see, is worth a thousand words and shows this setup. A water manometer will be used to test pressure drop across each filter. Obviously the filters with lower pressure drop flow better, and have the potential to yield more power given the engine actually needs the airflow increase. The pressure drop across each filter will be measured in inches of H2O (water). The pressure drop will be from atmosphere using the stock Miata induction system to the air box just after the filter. 1 psi of pressure = 27.7 inches of water for reference.
I have a degree in mechanical engineering and am currently pursuing a master's in engineering management. I have been around the automobile all my life, and will be obtaining certification as an ASE certified mechanic this fall (for fun). My father worked in the automotive test industry my entire adolescent life. I've also spent much of my life at the race track, either racing as an amateur or with my father who was a crew chief for a stock car racer many years. He also was a crew chief at the 24 hours of Daytona and LeMans twice. I regret not being able to go to LeMans to this day. I'm a certified gage calibration technician, certified quality assurance inspector, certified as a refrigerant worker by the EPA, and work in the Navy as a mechanic in nuclear propulsion. I like to think I know a few things about machines including automobiles, but there is always something to learn.
I choose to conduct this test because of the conflicting information I see in advertisements and have read on the internet. Everyone claims that their filter flows the best, and removes the most dirt. If you think about it, flow and filtration ability are actually linked. A solid piece of metal would prevent any particles from entering the engine, but it wouldn't flow any air at all. On the other hand, the screen used on a window screen will flow well, but won't filter well at all. So if you think about it, the best flowing and best filtering is really contradictory in claim. I wanted to find out which filter really does filter the best, and which one really does flow the best. I have used almost every brand and type of air filter over the years including K&N. I had not used a foam filter until conducting this test. I have used every manner of off the shelf fiberous or paper filter.
There are basically four types of filtration materials currently in use for automobiles: paper or other fiberous (some appear much like fiberglass), foam, cotton gauze and stainless steel mesh. This test has used the first three, but not stainless steel mess. Steel mesh bathed in oil is some of the very first filtration materials ever used in an automotive application. There is a reason they were abandoned for paper in the '60s. I find it surprising that some aftermarket manufacturers are touting them now. In the links at the end, there is an interesting test of a stainless mesh filter.
The filters in this test were tested for both flow and filtration. The pressure drop across a filter is a good indication of its ability to rob the engine of needed airflow and hence power. Obviously the air filter with the least pressure drop is the highest performing. For the filtration test, I used a secondary filter after the filter being tested to catch any particles that passed through the first filter. The secondary filters were made by cutting apart an off the shelf Fram carburetor filter. The particles passing through the filter being tested leave a deposit on the secondary filter. The lightness or darkness on the secondary filter is an indication of how much dirt is getting through the filter being tested.
The differential pressure test was performed using a water manometer where one psi of pressure is equivalent to 27.7" of water. The differential pressure was measured between atmospheric and the pressure drop after the air filter in the stock airbox. The max pressure drop in this test was seen at only 7.0 inches of water or 0.25 psi. The factory airbox and piping with no filter yielded a pressure drop of 5.0 inches of water or 0.18 psi. That means that the worst filter in this test only caused a pressure drop of 0.07 psi. In my opinion, this means that if you are picking an air filter based on performance, you probably aren't doing your car any favors. For the record, the K&N was the best flowing filter. Of the 3 types of media tested, the cotton gauze type filters flow best. There are other brands besides K&N for sale, of which most are probably made by K&N for resellers. Foam air filters flowed marginally better than paper.
The filtration test has been the cause of much argument and debate in some circles. Many contend that a color comparison (comparing shades of gray) is not scientific or appropriate. Again, this is a very low budget test, and there are other scientific analyses where color comparison is valid. In water chemistry a color comparison is often used to determine concentrations as low as parts per billion. Search for information on titrations (of which some are by color) or color comparators. In chemistry the color is compared to a known standard of specific ion concentration by color. If you have ever played with a fish tank chemistry sampling kit, then you have done color comparison yourself. In this air filter test, no attempt is made at determining actual concentration. A color comparison is used to determine real world filtration ability. Each test filter was used in the same car, on the same roads for 500 miles. The darker deposits indicate poorer filtration, and lighter ones better filtration. That said, both the cotton gauze type (K&N) and foam filters (Amsoil & Jackson Racing) showed the same levels of filtration. Both performed poorly compared to the fiberous or paper filters (Napa, Baldwin, and Mazda).
If you are interested in the filtration pictures or pressure test data, follow the links provided to my other pages. You will also find links to other tests, which I found interesting on the web. In the end, paper or fiberous filters do remove more particles from the air before they enter your engine. The cotton gauze filters indeed offer better airflow. You have to decide for yourself whether you value ever last ounce of power or filtration. I cannot, nor will I make this decision for you. I do know that on a relatively stock car with a properly sized air filter, you indeed have very little if any performance to gain by swapping filtration material.
Flow test:
http://www.bobistheoilguy.com/airfilter/airtest2.htm
Filtration test:
http://www.bobistheoilguy.com/airfilter/airtest3.htm
Last edited by WhiteNoiz; Oct 13, 2008 at 09:44 AM. Reason: to make it moar better.
I remember reading this back when I was driving miatas. great writeup he did. Only thing I would have preferred would have been 3-4 papers for each filter...I have issue with taking one result as hard fact....too many variances for my liking.
He also refers to the Amsoil filter as a foam filter which needs to be serviced, but according to Amsoil you don't service them, you trash em....well I guess if blowing them out with compressed air is servicing....
7/8 of the way down the page
http://www.amsoil.com/storefront/eaa.aspx
I'm not sure if this is a recent change for amsoil...since that was written a cpl yrs back
He also refers to the Amsoil filter as a foam filter which needs to be serviced, but according to Amsoil you don't service them, you trash em....well I guess if blowing them out with compressed air is servicing....
7/8 of the way down the page
http://www.amsoil.com/storefront/eaa.aspx
I'm not sure if this is a recent change for amsoil...since that was written a cpl yrs back
Last edited by WTX350Z; Oct 13, 2008 at 10:20 AM.
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Yea, duplication would have been nice. Good write up for some engineer with some spare time. I guess doing each one 3-4 times would = a huge PITA for no $$. So I can understand why he didn't.
I dont know much about amsoil products. So I really dont have much of a comment there.
I guess the big thing that stood out is that all the non-paper filters didn't filter as many particles out of the air, which is supported by the oil tests on this site.
I also read while doing this research that the high flow filters filter better after use, as the holes fill up. Same with the paper filter, but the drawback is that the paper filter becomes more restrictive when dirty.
I'm wondering how much damage the extra silica does before, and if, the oil filter catches it first. I imagine, the extra debris would do its damage, and then get filtered out (hopefully) before doing damage over and over. Although, the oil test would not support that theory.
I dont know much about amsoil products. So I really dont have much of a comment there.
I guess the big thing that stood out is that all the non-paper filters didn't filter as many particles out of the air, which is supported by the oil tests on this site.
I also read while doing this research that the high flow filters filter better after use, as the holes fill up. Same with the paper filter, but the drawback is that the paper filter becomes more restrictive when dirty.
I'm wondering how much damage the extra silica does before, and if, the oil filter catches it first. I imagine, the extra debris would do its damage, and then get filtered out (hopefully) before doing damage over and over. Although, the oil test would not support that theory.
Not bashing his test, as it does show that paper filters better, foam/cotton flows better...
I guess the big thing that stood out is that all the non-paper filters didn't filter as many particles out of the air, which is supported by the oil tests on this site.
I also read while doing this research that the high flow filters filter better after use, as the holes fill up. Same with the paper filter, but the drawback is that the paper filter becomes more restrictive when dirty.
I also read while doing this research that the high flow filters filter better after use, as the holes fill up. Same with the paper filter, but the drawback is that the paper filter becomes more restrictive when dirty.
I'm wondering how much damage the extra silica does before, and if, the oil filter catches it first. I imagine, the extra debris would do its damage, and then get filtered out (hopefully) before doing damage over and over. Although, the oil test would not support that theory.
Last edited by WTX350Z; Oct 13, 2008 at 12:41 PM.
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I have been using Amsoil paper EaAU on the last 2 UOA's submitted to Terry Dyson of dysonanalysis which were also commented by Resolute (Will) on his thread VQ Oil Analysis and Info (on a previous UOA).
Switching over to a paper filter on my NISMO CAI (which is basically a K&N type oil cotton AIR filter) have improved the silicon numbers immensely. The UOA chart below has three UOA readings and shows the silicon dropping after I switched to paper, right after the reading of "48", then it dropped to 25 and recently to 20.
The paper air filter has been good to me. If it helps, my location is Northern Calif and the area (Sacramento) does NOT get as windy or dusty as the southern central valley.
My UOA and silicon readings.
https://my350z.com/forum/6268916-post611.html
Switching over to a paper filter on my NISMO CAI (which is basically a K&N type oil cotton AIR filter) have improved the silicon numbers immensely. The UOA chart below has three UOA readings and shows the silicon dropping after I switched to paper, right after the reading of "48", then it dropped to 25 and recently to 20.
The paper air filter has been good to me. If it helps, my location is Northern Calif and the area (Sacramento) does NOT get as windy or dusty as the southern central valley.
My UOA and silicon readings.
https://my350z.com/forum/6268916-post611.html
I have been using Amsoil paper EaAU on the last 2 UOA's submitted to Terry Dyson of dysonanalysis which were also commented by Resolute (Will) on his thread VQ Oil Analysis and Info (on a previous UOA).
Switching over to a paper filter on my NISMO CAI (which is basically a K&N type oil cotton AIR filter) have improved the silicon numbers immensely. The UOA chart below has three UOA readings and shows the silicon dropping after I switched to paper, right after the reading of "48", then it dropped to 25 and recently to 20.
The paper air filter has been good to me. If it helps, my location is Northern Calif and the area (Sacramento) does NOT get as windy or dusty as the southern central valley.
My UOA and silicon readings.
https://my350z.com/forum/6268916-post611.html
Switching over to a paper filter on my NISMO CAI (which is basically a K&N type oil cotton AIR filter) have improved the silicon numbers immensely. The UOA chart below has three UOA readings and shows the silicon dropping after I switched to paper, right after the reading of "48", then it dropped to 25 and recently to 20.
The paper air filter has been good to me. If it helps, my location is Northern Calif and the area (Sacramento) does NOT get as windy or dusty as the southern central valley.
My UOA and silicon readings.
https://my350z.com/forum/6268916-post611.html
This brings up a possibly retarded question.
is the filter allowing silicon to enter? or is the filter "producing" (for lack of a better term) the silicon?
It certainly appears that flow and filtration are inverse principles...if you want one, you give up a little on the other....which makes sense, but it sucks.
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No, the silica is not coming from the filter, and there is no way it could produce it, physicly impossible. Silica is the most abundant mineral on the earths crust. So its in the air, not being filtered out before it goes into the motor.
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Well according to the flow test, it had the best flow, so it must be good for that.
vs. the filtration, it does not seem to be that good. You can see the visible increase of particles caught by the secondary filter (vs paper), and the increase of silica is shown in ZeeForces' oil analysis.
vs. the filtration, it does not seem to be that good. You can see the visible increase of particles caught by the secondary filter (vs paper), and the increase of silica is shown in ZeeForces' oil analysis.
Well according to the flow test, it had the best flow, so it must be good for that.
vs. the filtration, it does not seem to be that good. You can see the visible increase of particles caught by the secondary filter (vs paper), and the increase of silica is shown in ZeeForces' oil analysis.
vs. the filtration, it does not seem to be that good. You can see the visible increase of particles caught by the secondary filter (vs paper), and the increase of silica is shown in ZeeForces' oil analysis.
No question is a stupid question right?
No, the silica is not coming from the filter, and there is no way it could produce it, physicly impossible. Silica is the most abundant mineral on the earths crust. So its in the air, not being filtered out before it goes into the motor.
No, the silica is not coming from the filter, and there is no way it could produce it, physicly impossible. Silica is the most abundant mineral on the earths crust. So its in the air, not being filtered out before it goes into the motor.
I figured it had to be from dirt and such. but figured I'd ask since a lot of this stuff is beyond my understanding. I'm a suspension guy.....I comprehend all that nonsense....but these elements in oil, are beyond my simple mind.
All I know is I run Amsoil drop in - its paper, its supposed to last a long time. and its not oiled...I liked the sound...looks like I got lucky this time.
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Thought it was the 2nd most abundant?
I figured it had to be from dirt and such. but figured I'd ask since a lot of this stuff is beyond my understanding. I'm a suspension guy.....I comprehend all that nonsense....but these elements in oil, are beyond my simple mind.
All I know is I run Amsoil drop in - its paper, its supposed to last a long time. and its not oiled...I liked the sound...looks like I got lucky this time.
I figured it had to be from dirt and such. but figured I'd ask since a lot of this stuff is beyond my understanding. I'm a suspension guy.....I comprehend all that nonsense....but these elements in oil, are beyond my simple mind.
All I know is I run Amsoil drop in - its paper, its supposed to last a long time. and its not oiled...I liked the sound...looks like I got lucky this time.
How is the sound compared to a high flow filter? One thing is certain, paper doesn't flow as well, and the extra flow is what creates the extra sound. (good example is the MD spacer). The sound, and throttle response (aka flow) was better with my K&N, filtration, apparently not so much.
My quest now is to find the filter with the best balance of filtration, and flow. Which leads me to my question. Are all paper filters the same?
Off to do some research...
Last edited by WhiteNoiz; Oct 14, 2008 at 08:57 AM.
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Filter Performance
Take a look at the R2C Performance Filter site. It will answer many of your questions regarding efficiency and high flow. No oil, no gauze, no cleaners and no high restriction synthetics.
www.r2cperformance.com
www.r2cperformance.com
Last edited by Dynamicperf; Oct 14, 2008 at 09:20 AM. Reason: grammar
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Take a look at the R2C Performance Filter site. It will answer many of your questions regarding efficiency and high flow. No oil, no gauze, no cleaners and no high restriction synthetics.
www.r2cperformance.com
www.r2cperformance.com
Are you saying that if your questioned, you dont back it up?
Lastly, you work for this company.
I consider (IMO) your post discredited until I see test results, or some sort of proof. (no offense)
**edit:
also I dont like the fact that if I do go with that companies filter, I will be forced to buy their intake. (unless I have a short-ram already, and I'm not a fan of heat soak) They could come back with the design arguement. Lets see some test results.
Last edited by WhiteNoiz; Oct 14, 2008 at 09:51 AM.
The Amsoil drop in increased the sound made just like the K&Ns....based on my prev. cars which I had K&N drop-in filters in the change in sound is the same from OE to Amsoil vs OE to K&N. I'm pretty confident that the Amsoil is a great compromise...but I have no real data to back it up. Its louder than stock, so that's something...less restriction as you stated is likely.
Last edited by WTX350Z; Oct 14, 2008 at 10:21 AM.
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I can't upload xls files here to display test results. If you know how to add xls files, let me know. Send an e-mail address by PM and I'll send the restriction/dust test documents if .xls isn't compatible. I've worked with these poeple on the military side.