Smaller Oil Filters Less Efficient?

[ZeeOSix]

Originally Posted By: river_rat
Originally Posted By: Texan4Life
Doesn't oil velocity effect efficiency also? that is how fast the oil is flowing though the media.

Yes. Lower face velocity (more media) tends to more particles trapped.


A plus for running a larger filter to get more media area. And other benefits are traps more, holds more, flows better and has lower delta P. All plus factors.

 

[steve20]

I don't think the bypass design is the cause here (although it is a very interesting thought). I don't think you would ever get to >99% at any micron range if unfiltered oil was bypassing

 

[cp3]

Originally Posted By: steve20
I don't think the bypass design is the cause here (although it is a very interesting thought). I don't think you would ever get to >99% at any micron range if unfiltered oil was bypassing


That's a good argument. It would have to be a pretty small uniform leak to affect a difference in the 20 micron range but not the 40, wouldn't it?

 

[ZeeOSix]

Originally Posted By: cp3
Originally Posted By: steve20
I don't think the bypass design is the cause here (although it is a very interesting thought). I don't think you would ever get to >99% at any micron range if unfiltered oil was bypassing


That's a good argument. It would have to be a pretty small uniform leak to affect a difference in the 20 micron range but not the 40, wouldn't it?


If you have ever cut open a Purolator with this metal-to-metal bypass seal design you might also conclude that it may not seal perfectly. There is some delta P across the shut bypass valve at all times, and if the seal isn't perfect then there will be a small constant leak of dirty oil past the valve.

 

[cp3]

Oh, I'm not disagreeing. Just to Steve's point, would that leak be consistent enough to only leak <40microns?

 

[ZeeOSix]

Originally Posted By: cp3
Oh, I'm not disagreeing. Just to Steve's point, would that leak be consistent enough to only leak div>


The more the bypass valve leaks from a 100% perfect seal, a higher count of larger particles would get through. Maybe they only look at 5 to 40 micron particles, so anything much larger might just be ignored regardless of how many there are. I'm not familiar with the details of the ISO efficiency testing, but I'd assume not every size of particles are measured.

I just find it odd that the only spin-ons that Purolator makes with the 99.9% @ 40 microns have this style of metal-to-metal bypass valve.

If the bypass valve is not a factor in their reduced efficiency spec, then it must simply be due to their reduced media area. I can not believe that they would use an different media blend just for these 4 filters.

 

[ltslimjim]

So, how about theorizing something along the lines of:

...for some apps, a more 'restrictive' or 'highest available filtration AT the cost of "some" flow rate(when compared to the official OE's filter specs for said app)'...that such a filter 'may' allow for longer 'bypass' upon initial start up and high-RPM/high-load scenarios IF it is in fact more restrictive to the 'bypass' point while oil is thickest at start-up.

Of course, hot oil will flow more freely and there is less bypass scenarios(whether plausible or not depending on the app), but if the old 'filtration vs flow' holds weight for some apps would there be some possibility(?), therefore, that your overall oil is 'as clean' due to running through a 'less restrictive filter' when the 'more restrictive' may 'cause or allow for more often bypass operation(especially in start-up and and high load scenarios?)...

In other words, a less restrictive filter is filtering more often than a more restrictive filter IF the restrictive filter is in bypass mode more often during the operation of the vehicle/engine.

OR is it all in my head?

 

[river_rat]

Originally Posted By: ltslimjim
In other words, a less restrictive filter is filtering more often than a more restrictive filter IF the restrictive filter is in bypass mode more often during the operation of the vehicle/engine.

OR is it all in my head?

I think that's right. Even when the bypass opens though, most oil is going through the media unless the bypass opens all the way. There will be more passes for a particle, but it will likely get caught pretty soon as the bypass is opening at operating temperature only when the flow is high = more chances to get embedded in the media per minute.

 

[cp3]

Originally Posted By: ltslimjim

OR is it all in my head?

I don't know, you got me confused and opened the bypass in my head...

Does Purolator make any filters this size with no by-pass? If this is the reason it would make sense that a non-bypass filter, same size same media, should be more efficent.

 

[Ken2]

A bypass valve is essential. If the bypass isn't in the filter assembly, it will be very near by in the mount. Cold oil under high pressure will rip the filter media apart without the bypass.

 

[cp3]

Correct but would a filter built without a bypass, for an internally bypassed engine, have an efficiency rating effected by a leaky bypass?

 

[Eddie]

Just maybe the smaller can holds the same amount of media (area). In that case the only disadvantage is a few less ozs of oil. We have seen this before.Too much speculation without all the pertanent facts. Edy

 

[ZeeOSix]

Originally Posted By: cp3
Correct but would a filter built without a bypass, for an internally bypassed engine, have an efficiency rating effected by a leaky bypass?


A filter without a bypass valve has the potential to show a better efficiency on the test bench than one with a bypass valve that may leak slightly.

Of course, if the internal bypass valve in the engine block leaks, then the motor can't tell if that bypass valve was in the filter or in the engine block ... the result is the same; some unfiltered oil goes through the motor.

 

[ltslimjim]

Originally Posted By: river_rat
Originally Posted By: ltslimjim
In other words, a less restrictive filter is filtering more often than a more restrictive filter IF the restrictive filter is in bypass mode more often during the operation of the vehicle/engine.

OR is it all in my head?

I think that's right. Even when the bypass opens though, most oil is going through the media unless the bypass opens all the way. There will be more passes for a particle, but it will likely get caught pretty soon as the bypass is opening at operating temperature only when the flow is high = more chances to get embedded in the media per minute.


...and of course, this isn't to generalize it.

By no means am I trying to make a grand blanket statement. I could just see some apps, perhaps with 'relatively' smaller filters for instance...a lot of the "EP" oil filters out there with the 'extra holding capacity', etc....

Is it 'just' for extra capacity that a 'more efficient' filter 'utilizes' a larger sized canister/more sqr media area(generally) and a sturdier canister to boot? ...OR could it also be that a much more 'efficient' media in a smaller canister(like those that generally favor flow > filtration) would be inadvisable for certain apps which have such filters(the smaller ones in PCMO apps)?

I have noted the original filter for the Honda in your study(excellent job btw)...generally they seemed to flow really well but had 'basic' filtration offered. So, would flow be more of an issue in an engine that needs to rev higher in order to reach it's peak torque/power output like the Civic I drive(not that it puts out much power lol)? All of the aftermarket filters seem to be larger to quite a bit larger.

 

[river_rat]

It's both really. All other things being equal, more media will hold more and be more efficient.
Honda filters are very small, and so the media is pretty porous. Same with Toyota OEM filters like the 90915-YZZD1 my truck spec's. That filter is not particularly small, but the media is relatively porous and the flow is great. Maybe Toyota and Honda engineers know something we don't about flow vs. filtration, but the way I see it, unless the oil pump relief valve is open, basically the same amout of oil goes through the filter per engine revolution regardless of media porosity. The only difference is that the finer media--for the same amount--will bypass less often. But it will still at least have the capability to catch smaller particles after a pass or several passes, whereas the porous media may never get them.
I have not seen a difference in oil pressure downstream from the filter of any type I've ever used, so I prefer the higher efficiency, (but not necessarily the highest one can buy) even though the bypass may open (at least partially) a little longer during warm-up or whatever.

My 2 cents worth.

 

[steve20]

I really am impressed with the leaking bypass idea, but
if the filter was > 99% efficient at 40 mics, and the cause was the leaky bypass, you would have to assume either:
the engine does not produce particles > 40 mics
or
all particles produced > 40 mics are caught in the media

I do not think either one of these above assumptions is reality

Steve

 

[ZeeOSix]

Originally Posted By: steve20
I really am impressed with the leaking bypass idea, but
if the filter was > 99% efficient at 40 mics, and the cause was the leaky bypass, you would have to assume either:
the engine does not produce particles > 40 mics
or
all particles produced > 40 mics are caught in the media

I do not think either one of these above assumptions is reality

Steve


The efficiency spec by the manufacture is determined on a test bench per ISO test standards. If a filter is rated at 99% @ 40 microns, that means it is also filtering anything bigger than 40 microns at 99%. There still might be larger than 40 micron particles getting through, but less than 1% by definition.

If a closed bypass valve is leaky enough to pass enough unfiltered oil to cause the particle count to go up, then it will hurt the efficiency measurement. Instead of being "99% @ 20u" with a leak tight valve, it could become "95% @ 20u" or "99% @ 40u" with a non-leak tight valve. Either the efficiency % has to go down at the same micron size, or the micron size has to go up at the same efficiency %.

 

[ltslimjim]

Originally Posted By: river_rat
It's both really. All other things being equal, more media will hold more and be more efficient.
Honda filters are very small, and so the media is pretty porous. Same with Toyota OEM filters like the 90915-YZZD1 my truck spec's. That filter is not particularly small, but the media is relatively porous and the flow is great. Maybe Toyota and Honda engineers know something we don't about flow vs. filtration, but the way I see it, unless the oil pump relief valve is open, basically the same amout of oil goes through the filter per engine revolution regardless of media porosity. The only difference is that the finer media--for the same amount--will bypass less often. But it will still at least have the capability to catch smaller particles after a pass or several passes, whereas the porous media may never get them.
I have not seen a difference in oil pressure downstream from the filter of any type I've ever used, so I prefer the higher efficiency, (but not necessarily the highest one can buy) even though the bypass may open (at least partially) a little longer during warm-up or whatever.

My 2 cents worth.


Thanks for sharing your opinion and preference. I had an interesting experience yesterday that I can't quite put my finger on. I'm posting about it in the mechanical and maintenance section.

 

[river_rat]

Originally Posted By: ltslimjim
Thanks for sharing your opinion and preference. I had an interesting experience yesterday that I can't quite put my finger on. I'm posting about it in the mechanical and maintenance section.

Cool. I'll look for it.