Foam filters and their Cotton Gauze cousins...
05-18-2005, 09:38 PM
#21
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Originally Posted by hotbox05
Yeah but will the scret weapon ever be carb approved? whats the estimated gain?
05-19-2005, 02:07 AM
#24
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actually I don't really have time to go into that much but those links.. well
a) they don't really match up
b) the first two are propaganda (the first link makes some claims which don't seem to bear out in the 3rd link's independant study). The second link doesn't seem to have much in the way of evidence.
c) realistically, yes if you used a thick enough piece of foam, obviously you would have better filtration and dirt capacity... but you are trading off air flow obviously.
Those links do show that foam MAY have the potential to be better. BUT, when it comes down to it it really seems to depend on design and basically what the engine and filter looks like.
But I am skeptical about the validity of all three pages (I'm not skeptical about the results of the independent study, but simply skeptical about how far the results can be applied).
I'll back up my statements based on the links themselves at some later post...
a) they don't really match up
b) the first two are propaganda (the first link makes some claims which don't seem to bear out in the 3rd link's independant study). The second link doesn't seem to have much in the way of evidence.
c) realistically, yes if you used a thick enough piece of foam, obviously you would have better filtration and dirt capacity... but you are trading off air flow obviously.
Those links do show that foam MAY have the potential to be better. BUT, when it comes down to it it really seems to depend on design and basically what the engine and filter looks like.
But I am skeptical about the validity of all three pages (I'm not skeptical about the results of the independent study, but simply skeptical about how far the results can be applied).
I'll back up my statements based on the links themselves at some later post...
05-21-2005, 05:47 AM
#26
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hey... post up the results of your test please... whenever it happens.. I dont know when the state college show is supposed to take place.
As promised this is my more detailed analysis of the articles presented in favor of foam filters:
Before I start however, I would just like the point out what the issue at hand is:
The issue isn't whether or not foam filters CAN provide better filtering, its whether foam filters can provide at LEAST the same amount of filtering as gauze filters while providing the same airflow.
Article 1: Amsoil page
I'm going to read between the lines here and say this statement more or less says.. that their foam filter won't provide the same amount or airflow.
The problem here is, this statement somewhat invalidates this article for comparing Foam vs. Gauze. Why? b/c we are not trying to determine if the foam AMSOIL filter is better b/c of the oil they use...
Again, we are presented with the same argument as before (our product doesn't provide as much airflow, but better filtering).
...and then they procede to contradict themselves in the very next sentence. Unless you read that as just "airflow capabilities" and not "superior airflow capabilities." My other problem with this statement is... well its simply not true. Well at least according to article 3 (the ISO 5011 comparison article)... Of all the filters tested, the AMSOIL filter reached maximum airflow restriction the fastest... meaning a shorter time than even the K&N... (the fifth chart down on the ISO 5011 article... lasted 20 minutes compared to 24 for the K&N)
I won't refute this, this may or may not be true.. shrug... but I will point out... they are once again conceding airflow.
Sure, I'm willing to believe that it IS.. the question is what is the trade-off? Airflow?
I'm going to nit pick a bit here and say... the numbers don't match up with the results shown in Article 3. In fact the AMSOIL filter is shown to have to LOWEST dirt capacity of all the filters (2nd chart in Article 3, the iso 5011 article). I'm not saying they're lying.. but different types of testing... and possibly different filters... Still though I see a lot of the page as a lot of marketing hype, and very little in the way of concrete evidence.
So in conclusion... this page basically told me:
Foam CAN filter better than gauze... but the trade-off is airflow.
Article 2: Trueflow page
I'm not going to quote anything here since there really isn't much they said. They claim better dirt filtering... but not necessarily better airflow. They claim "better airflow when dirty" but that could be a lot of things...
better airflow than a saturated gauze filter?
Anyhow this page is pure marketing... yes the filter is nice and thick.. but doesn't that just mean... worse airflow?
Anyhow that's all for today i'll talk about the third article some other time..
but my final point would be... all these filters are for large motors, i.e. trucks.... our poor 1.5L engines need all the help they can get... can they really afford to sacrifice airflow?
As promised this is my more detailed analysis of the articles presented in favor of foam filters:
Before I start however, I would just like the point out what the issue at hand is:
The issue isn't whether or not foam filters CAN provide better filtering, its whether foam filters can provide at LEAST the same amount of filtering as gauze filters while providing the same airflow.
Article 1: Amsoil page
This test comparison shows how oil-wetted gauze and paper air filters do not stop dirt particles as well as an AMSOIL Two-Stage foam filter does. Sure, they may flow air very well on a flowbench, dynomometer and in high performance applications, but what good is all the airflow if the filter isn't trapping and holding all the abrasive dirt particles?
Additionally, take a look at the oil used on the oil-wetted gauze filters. It is a lightweight viscosity spray oil. Put it between your index finger and your thumb and pull them apart and you'll see that very little happens. In contrast, try the same thing with AMSOIL Foam Air Filter Oil, which has a very high viscosity and when you pull your fingers apart the oil stretches because of it's extremely high tack properties. This is what you need on a filter to stop dirt dead in its tracks.
... why the air filter restriction gauge does not seem to move when using an oil wetted gauze air filter. The answer is that the oil wetted gauze has higher airflow capability due to larger holes in the filtering media and it apparently does not stop enough dirt particles to make the filter become restricted enough to make the restriction gauge move.
Same thing with the AMSOIL foam air filter: as it traps dirt, eventually it will cause the gauge to move, but it will take a longer period of time due to it's superior filtering and airflow capabilities.
So, you may then ask why do so many race cars use oil-wetted gauze filters? Our response is they are interested in airflow and horsepower. Racing engines get disassembled, inspected and re-built at least once a season and in many cases several times a season therefore dirt stopping ability is not the primary concern.
Our Conclusion is just as we stated previously: oiled foam is an excellent filtering media.
The AMSOIL 2-Stage Air Filter traps airborne dust with 99% efficiency; it holds an incredible 281 grams of contaminant (that's over half a pound); and it outlasts the competition. It performs two to four times longer than the others. That's why AMSOIL can confidently recommend a 25,000 mile/1-year service life. And the 2-Stage is actually re-usable, with proper cleaning and re-oiling.
So in conclusion... this page basically told me:
Foam CAN filter better than gauze... but the trade-off is airflow.
Article 2: Trueflow page
I'm not going to quote anything here since there really isn't much they said. They claim better dirt filtering... but not necessarily better airflow. They claim "better airflow when dirty" but that could be a lot of things...
better airflow than a saturated gauze filter?
Anyhow this page is pure marketing... yes the filter is nice and thick.. but doesn't that just mean... worse airflow?
Anyhow that's all for today i'll talk about the third article some other time..
but my final point would be... all these filters are for large motors, i.e. trucks.... our poor 1.5L engines need all the help they can get... can they really afford to sacrifice airflow?
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