bypass and UOA

[GMorg]

Do bypass systems create the appearance of less wear? It seems that if the filter removes more suspended particles, then less contaminants would be seen in a UOA.

 

[Gary Allan]

I don't think so

. The machinery reads from the particle level up to, IIRC (always in question), 5um. That is, the majority of what is read is still there.

If it did effect UOA..then everyone with a bypass filter would have UOA that aligned itself with the PC between samples ...which they do not. You'll see a reduction in PC by about 1 or 2 levels (where the 1st particles are seen and continue the profile from there)...yet the markers aren't eliminated. They are reduced, if any, to a lesser degree.

That is, there is no direct relationship between PC and UOA indicators.

 

[LarryL]

If the oil in a system with a bypass is cleaner, is this cleaner oil better able to suspend particles.

 

[GMorg]

If metal containing particles of greater than 5 microns are resident in the bypass filter instead of the oil, then I don't see a way that they can be detected during analysis.

 

[JAG]

I agree. That's the big limitation of UOAs. Poopy on them yet so much faith is put in them as wear-ometers by the uninformed and I too was once guilty of that. Bypass filters are great despite what UOAs say about them. So are magnets - I use one inside the oil filter and one on the outside and they always catch a good deal of ferrous debris.

 

[Gary Allan]

quote:

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Originally posted by GMorg:
If metal containing particles of greater than 5 microns are resident in the bypass filter instead of the oil, then I don't see a way that they can be detected during analysis.

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That's what I'm trying to tell you. Whether they're in the oil or not ..they aren't detected. The machinery doesn't read much above 5um in size. So it doesn't matter where they are. What does matter is what is there due to them not knocking around and creating more particles ..or disintegrating and making more particles. This we can figure isn't THAT substantial in effect otherwise we would see radically different UOA with bypass equipped engines. What we DO see is radically cleaner oil.


I think that you can read this yourself on the Blackstone site. I asked Kristen if they filtered and/or digested their samples like our lab used to do with AA depending on if they wanted "free" elements or "total" elements. She replied that their process reads particles up to about 5um (again, IIRC). They don't digest them.

If they digested the samples in Nitric Acid before testing, then you would get results in proportion to the mass weighted average of what's in the oil. Fewer particles (of any size) would give you better UOA since ALL particles would be reduced to the particle size regardless of what their original size was. Any >5um particle would would impact the sample ...while in the normal UOA ..it wouldn't even be read.

This further supports the notion that the UOA tells far more about the oil then it can the engine's wear profile. It'll show you that you have a problem ..and someone like Terry can be a guru on interpretation due to his unique insight ..but a bypass is probably a radical upgrade in deposit control more then it is a wear reduction aid. It will, as we have repeatedly seen, extend the useful life of oil.

[ July 25, 2006, 11:49 AM: Message edited by: Gary Allan ]

 

[GMorg]

My understanding is that particles above a certain size are not fully "vaporized" and therefore elements that are in large particles are under-estimated. Under-estimated and not detected seem different to me. However, I think that I now understand your position.

 

[Gary Allan]

There could surely be that distinction, GMorg.