Originally Posted by dnewton3
Originally Posted by A310
From this UOA I learned that:
... Contrary to popular belief, you can't filter out the wear metals with a bypass filter, they will continue to increase over time. The only reason that the wear metals have started to decrease on this engine is due to the 2000-2500 miles bypass filter changes.
I am going to disagree here.
A typical cellulose or syn media filter has no ability (none whatsoever) to discern what it captures or passes in terms of wear metals. I catches stuff based on size, not composition. If we assume that your assertion is fair ( let's say the media is absolute at 2um; anything that size and larger is caught by this filter set-up), then ANY PARTICLE presented to the media will be caught if large enough (2um+). Because wear particles come in all sizes, there is not only a presumption, but nearly an assurance, that while the filter does reduce damaging abrasive particle load, it also removes the evidence of wear wear as well. Since a UOA using typical spectral analysis can see stuff from sub-micron up to around 5um in size, then the BP element you're using most certainly is removing evidence of wear that would exist between 2-5um in size. In short, PCs can see size but not composition, whereas UOAs can see composition but not size. It is completely unfair to attribute the ability of one to another, and therefore we cannot reasonably make assertions such as what you did; that the BP element somehow is not reducing the PC of wear metals in the range of 2-5um.
As a quick, off the cuff, example, the data would be affected thusly:
- anything smaller than 2um will be seen by the UOA (wear metals, silica, etc), but not stopped by the BP element
- between 2um and 5um, stuff still can be seen by the UOA, but the percentage present is altered by the capture ratio of the BP element
- anything larger than 5um cannot be seen by the UOA, but still will be stopped by the media
You cannot accurately state that "
Contrary to popular belief, you can't filter out the wear metals with a bypass filter ..." That is absurd. Your statement that "
they will continue to increase over time" is correct, but that is because the particles
below 2um are still accumulating in the sump and therefore the count goes up in the UOA. Some of the wear evidence is lost to the BP filter. In fact, even a typical FF filter will remove metal particles, but because that typical FF filter is absolute around 20um or so, there's no way a UOA would know any difference.
Your logic is flawed.
Thanks for the reply,
I agree with you 100%. I'm referring to the wear metals that are in the UOA, not the particle count. It never even occurred to me that one would think I was talking about the particle count. I shall make myself clearer in the future.
I'm running bypass filters on three vehicles and am well aware of what they will and will not filter.