Originally Posted By: ZeeOSix
So you think that Fram only puts in a ratio of 1 particle that is 20 microns and then puts in 99 particles that are 80 microns in size so the filter removes all the 80u particles so that only the 1% (all 20u particles) pass through? Then they can claim the "99% >20 microns".
Hummm ... boy, that's a pretty good stretch IMO. I'm betting the ISO test spec clearly stipulates exactly how the test dust needs to be mixed up and at what ratio of all sizes involved.
If you are saying the testers using ISO 4548-12 can play with the ratio of particle sizes as they see fit, then that is cheating from what the ISO test procedure would dictate. Is that what you are claiming here? I highly doubt the ISO test spec would allow such actions.
Not necessarily (I can't prove how Fram is counting just like we cant prove which test Wix is counting from).
I don't think Fram is using 1 20 micron particle and 99 80 micron particles. I would be more concerned if they are using the cumulative mass or volume of particles to determine the efficiency as then large particles would be weighted skewing things upward. For example of a particle with equal density, a single 20um particle is missed but a single 40um particle is captured, it might not be counted as 50% as it could be counted as mass or volume as easily as more than 60-70% from that application alone. I don't know if they are doing this, I kinda doubt it. But at the same time while I doubt Fram is doing this, I also kinda think that WIX is using ISO 4548... but neither can be proved one way or another.
Because ISO counts are very specific microns (and the dust link shows that particles can be made to exact sizes), then lets take the Mobil comparison with WIX in mind. Let's say that WIX uses the "greater than" definition too. It has:
We know there is at least a claim for:
95% at 20 (via WIX without documentation)
98.5% at 25 (via Mobil with ISO 4548)
So lets just take hypothetical for 30, 35, and 40 that reduce "missed" particles by 70% (which is the difference between 95% and 98.5%) for each 5 micron increase (this is conservative and simplified for demonstration), so:
98.95 @ 30
99.36 @ 35
99.49 @ 40
So, if we assume that all particles distributions are 1:1 the same with a simple count (not mass or volume), then WIX's capture rate is 99.07% for particles greater than 20um. Wait, whaaaa???? (My method: Efficiency % x 100 particles for each 5um increment size of 25-40 microns the divided by the total n of particles test). If you are curious about if I were to add 20 microns in, the result would be 98% at greater than and equal to 20um (note this is different than >20um).
This is what I mean when we do not know how Fram is counting or where they start counting from. We do not know where they slide within that >20um range to get that number. They could be counting in that >40um that I did not count for my example. I do know that >20 is not = 20.0001 and up as the standard does not use that distinction. Adding that > symbol opens a wide range of possibilities that Fram does not clear up.
