Are you guys just doing this to get your post counts up?
Subaru Oil Pump Specs as Relates to Filter Bypass
- Thread starter LoneRanger
- Start date
- Status
- Joined
- Sep 28, 2002
- Messages
- 39,799
Well, now that you mention it
, I guess it is a by/co-product
Well, I have to get this message out immediately! After re-reading most of this thread and taking everything into consideration, it looks like I was completely wrong on all accounts!
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APRIL FOOLS !!!
I had to do an April Fools on someone today ... looked like a prefect opportunity.
Yes, I will look at the testing stuff and give my thoughts on it in the next day or two. Been really busy this week.
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I had to do an April Fools on someone today ... looked like a prefect opportunity.
Yes, I will look at the testing stuff and give my thoughts on it in the next day or two. Been really busy this week.
The guy at Wix Canada emailed me back (two emails actually posted below). The first email was sent to me after I emailed him the part # of the Subaru Canada dealer supplied filter. He seems to think it's a repainted FRAM ph3593a.
The second email was in response to my asking him if the dealer supplied filter could actually be made by FRAM but have a higher bypass filter setting (basically I asked if it could be a 3593 internally except for the bypass spring).
What do you all think are the chances that FRAM makes a filter specifically for Subaru that has the higher bypass? The Wix guy seemed to think that the FACTORY filter (which is not a FRAM as far as I can tell) might be 23psi, but the dealer filter would not be. Personally, I can't imagine FRAM making this one filter specifically for Subaru with the 23psi bypass setting but I could be wrong.
_____________________________
this is the subaru canada part number built by fram and it would be the equivalent to a ph3593a.
the valve setting on this filter is 12 psi which is what our filter would be set at as well.
which is the standard by the looks of things i have checked many other filter companys and have not found a filter with that high of a psi rating.
AFFINIA Group Canada, WIX Division
(519) 622-4545 *277
_____________________________________
The filter SCI530001 is the exact interchange to the 3593, valve setting and all.
it looks like the only way we would really be able to see that 23 psi setting would be to do a little research on the actual Original Equipment Manufacturer number.
Is there a number in your repair manual that you could give us and we could see what we find out about that filter?
We need the oem number in order to see the 23 psi valve setting
Thanks
AFFINIA Group Canada, WIX Division
(519) 622-4545 *277
The second email was in response to my asking him if the dealer supplied filter could actually be made by FRAM but have a higher bypass filter setting (basically I asked if it could be a 3593 internally except for the bypass spring).
What do you all think are the chances that FRAM makes a filter specifically for Subaru that has the higher bypass? The Wix guy seemed to think that the FACTORY filter (which is not a FRAM as far as I can tell) might be 23psi, but the dealer filter would not be. Personally, I can't imagine FRAM making this one filter specifically for Subaru with the 23psi bypass setting but I could be wrong.
_____________________________
this is the subaru canada part number built by fram and it would be the equivalent to a ph3593a.
the valve setting on this filter is 12 psi which is what our filter would be set at as well.
which is the standard by the looks of things i have checked many other filter companys and have not found a filter with that high of a psi rating.
AFFINIA Group Canada, WIX Division
(519) 622-4545 *277
_____________________________________
The filter SCI530001 is the exact interchange to the 3593, valve setting and all.
it looks like the only way we would really be able to see that 23 psi setting would be to do a little research on the actual Original Equipment Manufacturer number.
Is there a number in your repair manual that you could give us and we could see what we find out about that filter?
We need the oem number in order to see the 23 psi valve setting
Thanks
AFFINIA Group Canada, WIX Division
(519) 622-4545 *277
Last edited:
Jeez, no wonder I don't visit the filter forum that much.
Thanks for your work LoneRanger.
So as far as aftermarket filters go: 1) Purolator is very close to Subaru's spec and 2) Wix Canada is still researching it. Did I read that correctly? Or did I see a thread earlier saying there was a Wix fitment with 20 psi's? I did lots of skimming due to a spinning head.
Ed - Are you the running OEM FRAM in the LGT?
-Dennis
Amsoil EA on the FXT and down to two Tokyo Roki's for the RS and OB.
So as far as aftermarket filters go: 1) Purolator is very close to Subaru's spec and 2) Wix Canada is still researching it. Did I read that correctly? Or did I see a thread earlier saying there was a Wix fitment with 20 psi's? I did lots of skimming due to a spinning head.
Ed - Are you the running OEM FRAM in the LGT?
-Dennis
Amsoil EA on the FXT and down to two Tokyo Roki's for the RS and OB.
rcy: The blue Subaru filter is a repainted FRAM 9715 with the proper 23.3 by-pass spring pressure. I cut both apart just a couple of weeks ago.
bluesubie: No I'm not running the OEM FRAM. I have a stash of 13 of the Tokyo Roki filters. I'll probably go with the oversize PureOne when those are gone if Subaru is still using the FRAM filters at that point.
Ed
bluesubie: No I'm not running the OEM FRAM. I have a stash of 13 of the Tokyo Roki filters. I'll probably go with the oversize PureOne when those are gone if Subaru is still using the FRAM filters at that point.
Ed
The blue Subaru filter? Is that the one that comes on the cars from the factory? My stealership only has white ones - here in Canada, they seem to made by Honeywell/Fram, maybe a 3593, but I'm not sure if Fram makes the bypass setting higher to meet Subaru specs, or if it's just a 3593 painted white.
@rcy:
The blue Subaru/Fram filter is Subaru P/N 15208AA12A. Do yourself a favor and spend the money on EBay to find the black Tokyo Roki filters, Subaru P/N 15208AA100.
I'll warn you, though, that since the change to what the Subie community considers a junk Fram filter, the price of Tokyo Rokis is well above what they originally sold for.
Also, if your stealer is still selling you the white filter, that's OK if you're non-turbo or '05 and earlier turbo. The change to the 2.5L turbo for '06 and exhaust rerouting means the white filter is too close to the down pipe and can cook the oil from radiant heat, at least from Subaru's POV.
The blue Subaru/Fram filter is Subaru P/N 15208AA12A. Do yourself a favor and spend the money on EBay to find the black Tokyo Roki filters, Subaru P/N 15208AA100.
I'll warn you, though, that since the change to what the Subie community considers a junk Fram filter, the price of Tokyo Rokis is well above what they originally sold for.
Also, if your stealer is still selling you the white filter, that's OK if you're non-turbo or '05 and earlier turbo. The change to the 2.5L turbo for '06 and exhaust rerouting means the white filter is too close to the down pipe and can cook the oil from radiant heat, at least from Subaru's POV.
Well, I finally got a chance to look at this and respond like I said I would. I merged your two posts into one response.
Originally Posted By: Gary Allan
I used a Permacool sandwich adapter with the poppet relief welded shut. I then routed it to a dual Permacool filter mount where I used a block adapter on one of the filter mounts and a filter on the other. Hence pressure was read above and below the filter. This was routed to the two pressure gauges that you have seen. I later installed a 0-20 (or maybe 0-15, I had two - one stolen with the van) differential pressure gauge across the same setup.
The only time there was ever any appreciable PSID was during a relief event. That would be where the upstream reading attenuated (it always reached this pressure upon cold start) @ 82psi and the downstream side stopped at a lower level. Then the basement rose to (almost) meet the ceiling. This was always the case.
A loaded filter (9k) merely increased the level of PSID and elongated its duration upon startup ..but produced no substantial static PSID. That is, the 9k filter quickly retreated to 4PSID and then retreated even more as the oil warmed. @150F oil temp, running the rpms up into higher speeds (like the shifting point @ WOT but not achieved using WOT) produced a "surge" of PSID that retreated.
Nothing surprising here. Just as I’ve said many times, the max filter PSID and max engine oil pressure will always occur when the pump is in relief mode (under constant viscosity conditions as always). That is because when the pump is in relief mode, the max possible supply pressure is on the filter/engine flow path, and that will produce the max amount of oil flow at that instant in time. The corresponding filter PSID and engine oil pressure at that instant in time will be dependant on the volume & viscosity of the oil flowing through the system.
Of course if the engine PRM is decreased, and/or as the oil starts to warm up, then eventually the pump will go out of relief mode and the filter PSID and engine oil pressure will retreat (decrease) accordingly.
Originally Posted By: Gary Allan
I did see one event where the differential gauge reached the range of the normal Purolator bypass setting on the 9k loaded filter with 15w-40 oil @ 28F with overnight temps of the low 20's/high teens. The condition was brief ..like 30 sec.
Not surprising. Obviously with oil that viscous the pump was in relief mode supplying its max pressure. Even though the oil flow volume going to the filter/engine was much less, the high viscosity factor has a large influence on filter PSID and engine oil pressure. The filter was probably loaded enough to cause the flow’s volume & viscosity combo to create a PSID greater than the bypass setting. It’s also possible that the system was probably not fully pressurized initially upon startup for the first few seconds (up to 30 sec ?? – who knows) due to the oil being so viscous. This would cause an initial higher “in-rush” oil volume through the filter until the engine circuit was filled to produce the normal backpressure on the system which would then lessen the flow rate and filter’s PSID.
Originally Posted By: Gary Allan
With a new Pureone filter, the smallest one that they make in the 3/4-16 thread (or I could find, maybe) ..I thought the gauge was broken. I had to wonder if the blip that I thought I saw was a placebo effect, or some vibration from the engine on initial firing. It was that "unremarkable".
I’m assuming the same cold oil start-up conditions applied to this filter? If so, this doesn’t sound like a normal response. I would expect some noticeable/visible PSID at these cold startup conditions with any oil filter in the system. Maybe the gauge didn’t like the cold weather that day, or maybe the bypass valve was stuck open all the time. Hard to say.
Originally Posted By: Gary Allan
This would not be the situation with all engine/filter combo's. My 2.5 jeep resides at or near the relief level all the time. Depending on what visc oil I use, I would be in some state of elevated PSID based on visc (mostly) whenever off idle. Same with my wife's HV pump's 4.0. Both are slammed up against the relief most of the time. You have to use 20 grade in the 4.0 to "fit" all the volume through at full warm up ..with the 2.5, I THINK, I can manage to get into a decent range of flow within the relief limit. Throw in 5w-40 ..and neither will be out of relief. THEN the PSID will vary depending on visc. The higher PSID will retreat to a lower PSID.
A good reason to ensure the oil filter being used is matched to the vehicle in terms of flow resistance (ie, element size and flow vs PSID characteristics) and bypass valve setting. Just like the Subaru application (high volume oil pump!) this thread is focused on ... if you used a filter with a much lower bypass setting than specified, the filter could certainly be in bypass mode much more and much longer than really desired. I think we all have agreed to that conclusion.
Originally Posted By: Gary Allan
Here's a state that I think you've failed to consider (me too, for that matter). It will probably work with your basic rationale to this whole deal.
If a pump was in perpetual relief, all of your assumptions about filter resistance will be 100% valid (at least I think so). There you would/should have all of your pressure drops responding directly to volume. Cold oil, high PSID, hot oil ..low PSID ..but it would always vary with the volume through it ..high or low.
True ... there will always be a pressure drop across a device that is resistant to flow, and the associated pressure drop will be proportional to the flow volume and fluid viscosity.
Originally Posted By: Gary Allan
You would still have to figure some way of having the filter reduce it's relative resistance while still dropping the supply across both. I'm not sure (haven't thought it out too far), but I think you would have to see the engine side (on my two gauge setup) dip assuming that you don't exceed the oil pump's relief capacity. Both must add up to supply, so any increase in PSID must reduce the drop across the engine. It would be very odd to see.
I can't think straight at the moment, but I think that this too would require more flow being shunted to the relief.
If the pump is in relief mode and viscosity constant, then of course any increase in filter PSID (due to loading, etc) will cause a decrease in the engine oil pressure reading (sensor after the filter). Ideally, if more flow was shunted out the relief valve to the sump, then there should be a corresponding drop in both filter PSID and engine oil pressure after the relief valve has stabilized the flow conditions.
One thing never discussed yet is how does the flow resistance of the filter and engine chance with thermal effects. In other words, does the filter and engine flow resistance change as they heat up? It’s entirely possible that the engine’s flow path becomes less restrictive as all the parts heat up and expand (ie, bearing clearances increase), which could dynamically change the flow resistance ratio of the filter/engine circuit. I can’t really see how an oil filter’s flow resistance would decrease as it heated up, but if it did, due to the element material “opening up”, you would also think it’s filtering performance might also change some (become worse) with its temperature.
Originally Posted By: Gary Allan
I used a Permacool sandwich adapter with the poppet relief welded shut. I then routed it to a dual Permacool filter mount where I used a block adapter on one of the filter mounts and a filter on the other. Hence pressure was read above and below the filter. This was routed to the two pressure gauges that you have seen. I later installed a 0-20 (or maybe 0-15, I had two - one stolen with the van) differential pressure gauge across the same setup.
The only time there was ever any appreciable PSID was during a relief event. That would be where the upstream reading attenuated (it always reached this pressure upon cold start) @ 82psi and the downstream side stopped at a lower level. Then the basement rose to (almost) meet the ceiling. This was always the case.
A loaded filter (9k) merely increased the level of PSID and elongated its duration upon startup ..but produced no substantial static PSID. That is, the 9k filter quickly retreated to 4PSID and then retreated even more as the oil warmed. @150F oil temp, running the rpms up into higher speeds (like the shifting point @ WOT but not achieved using WOT) produced a "surge" of PSID that retreated.
Nothing surprising here. Just as I’ve said many times, the max filter PSID and max engine oil pressure will always occur when the pump is in relief mode (under constant viscosity conditions as always). That is because when the pump is in relief mode, the max possible supply pressure is on the filter/engine flow path, and that will produce the max amount of oil flow at that instant in time. The corresponding filter PSID and engine oil pressure at that instant in time will be dependant on the volume & viscosity of the oil flowing through the system.
Of course if the engine PRM is decreased, and/or as the oil starts to warm up, then eventually the pump will go out of relief mode and the filter PSID and engine oil pressure will retreat (decrease) accordingly.
Originally Posted By: Gary Allan
I did see one event where the differential gauge reached the range of the normal Purolator bypass setting on the 9k loaded filter with 15w-40 oil @ 28F with overnight temps of the low 20's/high teens. The condition was brief ..like 30 sec.
Not surprising. Obviously with oil that viscous the pump was in relief mode supplying its max pressure. Even though the oil flow volume going to the filter/engine was much less, the high viscosity factor has a large influence on filter PSID and engine oil pressure. The filter was probably loaded enough to cause the flow’s volume & viscosity combo to create a PSID greater than the bypass setting. It’s also possible that the system was probably not fully pressurized initially upon startup for the first few seconds (up to 30 sec ?? – who knows) due to the oil being so viscous. This would cause an initial higher “in-rush” oil volume through the filter until the engine circuit was filled to produce the normal backpressure on the system which would then lessen the flow rate and filter’s PSID.
Originally Posted By: Gary Allan
With a new Pureone filter, the smallest one that they make in the 3/4-16 thread (or I could find, maybe) ..I thought the gauge was broken. I had to wonder if the blip that I thought I saw was a placebo effect, or some vibration from the engine on initial firing. It was that "unremarkable".
I’m assuming the same cold oil start-up conditions applied to this filter? If so, this doesn’t sound like a normal response. I would expect some noticeable/visible PSID at these cold startup conditions with any oil filter in the system. Maybe the gauge didn’t like the cold weather that day, or maybe the bypass valve was stuck open all the time. Hard to say.
Originally Posted By: Gary Allan
This would not be the situation with all engine/filter combo's. My 2.5 jeep resides at or near the relief level all the time. Depending on what visc oil I use, I would be in some state of elevated PSID based on visc (mostly) whenever off idle. Same with my wife's HV pump's 4.0. Both are slammed up against the relief most of the time. You have to use 20 grade in the 4.0 to "fit" all the volume through at full warm up ..with the 2.5, I THINK, I can manage to get into a decent range of flow within the relief limit. Throw in 5w-40 ..and neither will be out of relief. THEN the PSID will vary depending on visc. The higher PSID will retreat to a lower PSID.
A good reason to ensure the oil filter being used is matched to the vehicle in terms of flow resistance (ie, element size and flow vs PSID characteristics) and bypass valve setting. Just like the Subaru application (high volume oil pump!) this thread is focused on ... if you used a filter with a much lower bypass setting than specified, the filter could certainly be in bypass mode much more and much longer than really desired. I think we all have agreed to that conclusion.
Originally Posted By: Gary Allan
Here's a state that I think you've failed to consider (me too, for that matter). It will probably work with your basic rationale to this whole deal.
If a pump was in perpetual relief, all of your assumptions about filter resistance will be 100% valid (at least I think so). There you would/should have all of your pressure drops responding directly to volume. Cold oil, high PSID, hot oil ..low PSID ..but it would always vary with the volume through it ..high or low.
True ... there will always be a pressure drop across a device that is resistant to flow, and the associated pressure drop will be proportional to the flow volume and fluid viscosity.
Originally Posted By: Gary Allan
You would still have to figure some way of having the filter reduce it's relative resistance while still dropping the supply across both. I'm not sure (haven't thought it out too far), but I think you would have to see the engine side (on my two gauge setup) dip assuming that you don't exceed the oil pump's relief capacity. Both must add up to supply, so any increase in PSID must reduce the drop across the engine. It would be very odd to see.
I can't think straight at the moment, but I think that this too would require more flow being shunted to the relief.
If the pump is in relief mode and viscosity constant, then of course any increase in filter PSID (due to loading, etc) will cause a decrease in the engine oil pressure reading (sensor after the filter). Ideally, if more flow was shunted out the relief valve to the sump, then there should be a corresponding drop in both filter PSID and engine oil pressure after the relief valve has stabilized the flow conditions.
One thing never discussed yet is how does the flow resistance of the filter and engine chance with thermal effects. In other words, does the filter and engine flow resistance change as they heat up? It’s entirely possible that the engine’s flow path becomes less restrictive as all the parts heat up and expand (ie, bearing clearances increase), which could dynamically change the flow resistance ratio of the filter/engine circuit. I can’t really see how an oil filter’s flow resistance would decrease as it heated up, but if it did, due to the element material “opening up”, you would also think it’s filtering performance might also change some (become worse) with its temperature.
- Joined
- Sep 28, 2002
- Messages
- 39,799
Here's where we differ. While you appear to agree on the conditions, the "cause" and the ending of the condition seem to "slide" a little
Quote:
Just as I’ve said many times, the max filter PSID and max engine oil pressure will always occur when the pump is in relief mode (under constant viscosity conditions as always).
Here we're in apparent agreement.
Quote:
That is because when the pump is in relief mode, the max possible supply pressure is on the filter/engine flow path, and that will produce the max amount of oil flow at that instant in time.
..and here we're mostly in agreement ..but we're creeping (I can feel it)
Quote:
The corresponding filter PSID and engine oil pressure at that instant in time will be dependant on the volume & viscosity of the oil flowing through the system.
Well .. here's what this statement doesn't resolve. As soon as the relief event is over ..with the same (near enough) viscosity and alleged filter resistance ..the PSID evaporates.
That's not apparent in that statement. It's PURELY because of the relief event that the filter presents so much resistance. The filter obviously doesn't change in any property from one state to the other ..nor does the viscosity (appreciably) ..so the applied physics must be altered. That is, the equation has to change to fit the apparent readings since the physical properties cannot (massage that to make sense).
This can also be the case where a stationary column of oil hasn't transitioned to a moving column of oil. The effects would appear the same.
The filter is exactly what it was. The oil (for the sake of discussion) was exactly what it was. The difference is the amount of oil shunted in relief. The more flow shunted, the more the apparent PSID. No shunted flow, no apparent (substantial) PSID (at sensible volumes).
Quote:
I’m assuming the same cold oil start-up conditions applied to this filter? If so, this doesn’t sound like a normal response. I would expect some noticeable/visible PSID at these cold startup conditions with any oil filter in the system. Maybe the gauge didn’t like the cold weather that day, or maybe the bypass valve was stuck open all the time. Hard to say.
Not quite as cold ..but run for weeks with no reaction. It was a transitional time of the year.
Relief events were rare with this engine. Start up pressure ALWAYS went to 82psi on a cold start. The difference would be how long 82 was maintained. The difference was about 2psi above:below.
Quote:
A good reason to ensure the oil filter being used is matched to the vehicle in terms of flow resistance (ie, element size and flow vs PSID characteristics) and bypass valve setting. Just like the Subaru application this thread is focused on ... if you used a filter with a much lower bypass setting than specified, the filter could certainly be in bypass mode much more and much longer than really desired. I think we all have agreed to that conclusion.
Here we're somewhat (and mostly) in agreement. The exception with the Subaru is that it's only due to its extreme volume where this would be a factor. The pressures that the engine produces are broad. That is, they aren't operating 24/7 at the relief level.
Quote:
One thing never discussed yet is how does the flow resistance of the filter and engine chance with thermal effects. In other words, does the filter and engine flow resistance change as they heat up? It’s entirely possible that the engine’s flow path becomes less restrictive as all the parts heat up and expand (ie, bearing clearances increase), which could dynamically change the flow resistance ratio of the filter/engine circuit. I can’t really see how an oil filter’s flow resistance would decrease as it heated up, but if it did, due to the element material “opening up”, you would also think it’s filtering performance might also change some (become worse) with its temperature.
Depending on how you're viewing it, the "apparent" resistance of the filter will be changed or unchanged with a decrease in viscosity. Out of relief you'll see virtually no PSID ..so it's mostly independent of visc and more a function of pressure limits. That is 85lb out of relief, next to nothing. 85lb in relief ..something.
10CST fluid flows much easier through a filter than 140CST fluid. The same as it requires less "power" to push it through the engine. Again, it's not an issue at most sensible flow rates and the difference is (probably) measured in inches of water column. The turnstile that you think is slowing you up is nothing when the traffic jam is all the way to the exit. An engine is always a traffic jam to the exit. Out of relief, you can't be "slowed up" in a fully enveloped engine. You can just move easier (at whatever flow rate that is at the moment). The fluid will just accelerate or decelerate with the relative size of the conduit that it's transitioning to.
Quote:
Just as I’ve said many times, the max filter PSID and max engine oil pressure will always occur when the pump is in relief mode (under constant viscosity conditions as always).
Here we're in apparent agreement.
Quote:
That is because when the pump is in relief mode, the max possible supply pressure is on the filter/engine flow path, and that will produce the max amount of oil flow at that instant in time.
..and here we're mostly in agreement ..but we're creeping (I can feel it)
Quote:
The corresponding filter PSID and engine oil pressure at that instant in time will be dependant on the volume & viscosity of the oil flowing through the system.
Well .. here's what this statement doesn't resolve. As soon as the relief event is over ..with the same (near enough) viscosity and alleged filter resistance ..the PSID evaporates.
That's not apparent in that statement. It's PURELY because of the relief event that the filter presents so much resistance. The filter obviously doesn't change in any property from one state to the other ..nor does the viscosity (appreciably) ..so the applied physics must be altered. That is, the equation has to change to fit the apparent readings since the physical properties cannot (massage that to make sense).
This can also be the case where a stationary column of oil hasn't transitioned to a moving column of oil. The effects would appear the same.
The filter is exactly what it was. The oil (for the sake of discussion) was exactly what it was. The difference is the amount of oil shunted in relief. The more flow shunted, the more the apparent PSID. No shunted flow, no apparent (substantial) PSID (at sensible volumes).
Quote:
I’m assuming the same cold oil start-up conditions applied to this filter? If so, this doesn’t sound like a normal response. I would expect some noticeable/visible PSID at these cold startup conditions with any oil filter in the system. Maybe the gauge didn’t like the cold weather that day, or maybe the bypass valve was stuck open all the time. Hard to say.
Not quite as cold ..but run for weeks with no reaction. It was a transitional time of the year.
Relief events were rare with this engine. Start up pressure ALWAYS went to 82psi on a cold start. The difference would be how long 82 was maintained. The difference was about 2psi above:below.
Quote:
A good reason to ensure the oil filter being used is matched to the vehicle in terms of flow resistance (ie, element size and flow vs PSID characteristics) and bypass valve setting. Just like the Subaru application this thread is focused on ... if you used a filter with a much lower bypass setting than specified, the filter could certainly be in bypass mode much more and much longer than really desired. I think we all have agreed to that conclusion.
Here we're somewhat (and mostly) in agreement. The exception with the Subaru is that it's only due to its extreme volume where this would be a factor. The pressures that the engine produces are broad. That is, they aren't operating 24/7 at the relief level.
Quote:
One thing never discussed yet is how does the flow resistance of the filter and engine chance with thermal effects. In other words, does the filter and engine flow resistance change as they heat up? It’s entirely possible that the engine’s flow path becomes less restrictive as all the parts heat up and expand (ie, bearing clearances increase), which could dynamically change the flow resistance ratio of the filter/engine circuit. I can’t really see how an oil filter’s flow resistance would decrease as it heated up, but if it did, due to the element material “opening up”, you would also think it’s filtering performance might also change some (become worse) with its temperature.
Depending on how you're viewing it, the "apparent" resistance of the filter will be changed or unchanged with a decrease in viscosity. Out of relief you'll see virtually no PSID ..so it's mostly independent of visc and more a function of pressure limits. That is 85lb out of relief, next to nothing. 85lb in relief ..something.
10CST fluid flows much easier through a filter than 140CST fluid. The same as it requires less "power" to push it through the engine. Again, it's not an issue at most sensible flow rates and the difference is (probably) measured in inches of water column. The turnstile that you think is slowing you up is nothing when the traffic jam is all the way to the exit. An engine is always a traffic jam to the exit. Out of relief, you can't be "slowed up" in a fully enveloped engine. You can just move easier (at whatever flow rate that is at the moment). The fluid will just accelerate or decelerate with the relative size of the conduit that it's transitioning to.
What I am having a problem wrapping my mind around is that if the filters we use have a maximum flow rate of 9 gpm, and the Subaru can deliver up to almost 17 gpm ( 12mm rotors ), wouldn't the filter ALWAYS be in bypass if is was only 8-11 psid? And making the bypass stiffer, would force it to flow through the element instead of bypassing it?
Bear with me, there are much sharper knives in the drawer....
Fwiw, next time I have a block here, I am interested to measure the oil galleys..
Bear with me, there are much sharper knives in the drawer....
Fwiw, next time I have a block here, I am interested to measure the oil galleys..
- Joined
- Sep 28, 2002
- Messages
- 39,799
Quote:
What I am having a problem wrapping my mind around is that if the filters we use have a maximum flow rate of 9 gpm, and the Subaru can deliver up to almost 17 gpm ( 12mm rotors ), wouldn't the filter ALWAYS be in bypass if is was only 8-11 psid?
No. It would only be in bypass, due to volume, somewhere above 9-11 gpm (or wherever the filter itself became a factor). It could become a factor of measurable merit at 6 or 7. I've personally never seen it in most routine driving ..which would include some WOT to the shifting point on my 3.0 Mitsubishi ..which would sensibly be somewhere in the 5000rpm+ range.
Quote:
And making the bypass stiffer, would force it to flow through the element instead of bypassing it?
Yes.
At some point in volume, the media is going to look like a solid piece of cardboard. Just up the volume to 50gpm.
..but how many times does anyone push that much oil through the engine?
This may surely be a requirement of that little pesky screen for the turbo, but it is more likely needed to filter more during the startup process, which you dwell at every time you turn it on, rather than the 6000 rpm level which you dwell at very little. It would also work well at that level of operation.
You're going to have a high(er) differential across the filter every time you start it up due to being in relief far more often then you're going to have an elevated differential due to volume. That is, unless you live in AZ or NV or some other open space place where you can literally drive hours at some high speed.
You may or may not be in bypass at every startup ..but you'll be at some elevated PSID every time you're in relief. If we accept that the turbo owner's gauge is somewhat accurate, the PSID will vary depending on the visc of the oil at that starting temp, and how fast the engine is operated before it is reduced in visc enough to "fit" full volume (whatever the pump is putting out= at THAT time)through the engine.
What I am having a problem wrapping my mind around is that if the filters we use have a maximum flow rate of 9 gpm, and the Subaru can deliver up to almost 17 gpm ( 12mm rotors ), wouldn't the filter ALWAYS be in bypass if is was only 8-11 psid?
No. It would only be in bypass, due to volume, somewhere above 9-11 gpm (or wherever the filter itself became a factor). It could become a factor of measurable merit at 6 or 7. I've personally never seen it in most routine driving ..which would include some WOT to the shifting point on my 3.0 Mitsubishi ..which would sensibly be somewhere in the 5000rpm+ range.
Quote:
And making the bypass stiffer, would force it to flow through the element instead of bypassing it?
Yes.
At some point in volume, the media is going to look like a solid piece of cardboard. Just up the volume to 50gpm.
..but how many times does anyone push that much oil through the engine?
This may surely be a requirement of that little pesky screen for the turbo, but it is more likely needed to filter more during the startup process, which you dwell at every time you turn it on, rather than the 6000 rpm level which you dwell at very little. It would also work well at that level of operation.
You're going to have a high(er) differential across the filter every time you start it up due to being in relief far more often then you're going to have an elevated differential due to volume. That is, unless you live in AZ or NV or some other open space place where you can literally drive hours at some high speed.
You may or may not be in bypass at every startup ..but you'll be at some elevated PSID every time you're in relief. If we accept that the turbo owner's gauge is somewhat accurate, the PSID will vary depending on the visc of the oil at that starting temp, and how fast the engine is operated before it is reduced in visc enough to "fit" full volume (whatever the pump is putting out= at THAT time)through the engine.
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- Sep 28, 2002
- Messages
- 39,799
It's a very difficult thing to articulate. You, more or less, have to observe it and back construct the reasons from the apparent results. I'm sure some engineer somewhere knows exactly how to state this, but may not be able to in a way we can understand. I can see the effects, but can't fully articulate the theoretical mechanisms employed to satisfy some ..this includes myself. I'm sure there are tons of things you've figured out the cause and effect relationship on ..but can't "get there" in true definition. So, you do the best you can to describe how you came to your conclusions and leave the absolute finer details to someone who can.
A filter is not an easy thing for oil, at any visc, to pass through. Surely if one compares it to just pouring it out of a bottle. It's only when there's a much more restrictive element downstream of it does it get reduced to "also ran". This is unique to flow dictated scenarios. It's not like water faucets or electrical outlets or garden hoses.
It's like a pressure washer. You put in a smaller nozzle, the water travels faster at the same volume. If you had a 2" hose ..or one slightly smaller, the nozzle would still be the one element that's bringing the pump up to the (near) 2500psi (or whatever) level where it's operating at. If water didn't have the VI that it does, you would see your water stream go limp ..the pressure you developed would tank..but the volume would remain the same. You could put a filter of whatever restrictive property you please in line (assuming that you used one that could withstand 2500 psi) and the flow wouldn't even see it.
A filter is not an easy thing for oil, at any visc, to pass through. Surely if one compares it to just pouring it out of a bottle. It's only when there's a much more restrictive element downstream of it does it get reduced to "also ran". This is unique to flow dictated scenarios. It's not like water faucets or electrical outlets or garden hoses.
It's like a pressure washer. You put in a smaller nozzle, the water travels faster at the same volume. If you had a 2" hose ..or one slightly smaller, the nozzle would still be the one element that's bringing the pump up to the (near) 2500psi (or whatever) level where it's operating at. If water didn't have the VI that it does, you would see your water stream go limp ..the pressure you developed would tank..but the volume would remain the same. You could put a filter of whatever restrictive property you please in line (assuming that you used one that could withstand 2500 psi) and the flow wouldn't even see it.
Originally Posted By: SuperBusa
I agree that it seems like a HUGE (and unbelievable) amount of oil volume output from the oil pump. It very well could be a typo, but who can prove it? I don’t think my garden hose even flows at 12 gpm.
I have no doubt the pump will free flow that much...it probably will flow that much, and more (since that is most likely a "minimum" specification. But the engine (or more specifically engine clearances) is the restriction. You could have a pump that is capable of free flowing 50,000GPM, but if you are trying to force it through a 1/4" diameter hole, it won't/can't flow anywhere near its rated flow. That's because the restriction is the factor regulating the flow rate.
Another point is the fact the filter is pressurized. You would need to have a 8-11psi drop across the filter media in order to have the bypass open. That would imply the filter media is really being restrictive by itself correct?? Would a fresh filter be that restrictive (at normal operating temperatures)??
Just some food for thought...
I agree that it seems like a HUGE (and unbelievable) amount of oil volume output from the oil pump. It very well could be a typo, but who can prove it? I don’t think my garden hose even flows at 12 gpm.
I have no doubt the pump will free flow that much...it probably will flow that much, and more (since that is most likely a "minimum" specification. But the engine (or more specifically engine clearances) is the restriction. You could have a pump that is capable of free flowing 50,000GPM, but if you are trying to force it through a 1/4" diameter hole, it won't/can't flow anywhere near its rated flow. That's because the restriction is the factor regulating the flow rate.
Another point is the fact the filter is pressurized. You would need to have a 8-11psi drop across the filter media in order to have the bypass open. That would imply the filter media is really being restrictive by itself correct?? Would a fresh filter be that restrictive (at normal operating temperatures)??
Just some food for thought...
Originally Posted By: Gary Allan
It's a very difficult thing to articulate. You, more or less, have to observe it and back construct the reasons from the apparent results. I'm sure some engineer somewhere knows exactly how to state this, but may not be able to in a way we can understand. I can see the effects, but can't fully articulate the theoretical mechanisms employed to satisfy some ..this includes myself. I'm sure there are tons of things you've figured out the cause and effect relationship on ..but can't "get there" in true definition. So, you do the best you can to describe how you came to your conclusions and leave the absolute finer details to someone who can.
A filter is not an easy thing for oil, at any visc, to pass through. Surely if one compares it to just pouring it out of a bottle. It's only when there's a much more restrictive element downstream of it does it get reduced to "also ran". This is unique to flow dictated scenarios. It's not like water faucets or electrical outlets or garden hoses.
It's like a pressure washer. You put in a smaller nozzle, the water travels faster at the same volume. If you had a 2" hose ..or one slightly smaller, the nozzle would still be the one element that's bringing the pump up to the (near) 2500psi (or whatever) level where it's operating at. If water didn't have the VI that it does, you would see your water stream go limp ..the pressure you developed would tank..but the volume would remain the same. You could put a filter of whatever restrictive property you please in line (assuming that you used one that could withstand 2500 psi) and the flow wouldn't even see it.
In your model, you indicate the pressure washer nozzle is the filter; however the restriction is internal in the engine, downstream of the filter.
So the filter would be somewhere along the supply hose in your example and the engine would be the restriction/nozzle...while there may be a huge pressure differential at the engine/nozzle, there is potentially very little across the filter itself...
Make sense?
It's a very difficult thing to articulate. You, more or less, have to observe it and back construct the reasons from the apparent results. I'm sure some engineer somewhere knows exactly how to state this, but may not be able to in a way we can understand. I can see the effects, but can't fully articulate the theoretical mechanisms employed to satisfy some ..this includes myself. I'm sure there are tons of things you've figured out the cause and effect relationship on ..but can't "get there" in true definition. So, you do the best you can to describe how you came to your conclusions and leave the absolute finer details to someone who can.
A filter is not an easy thing for oil, at any visc, to pass through. Surely if one compares it to just pouring it out of a bottle. It's only when there's a much more restrictive element downstream of it does it get reduced to "also ran". This is unique to flow dictated scenarios. It's not like water faucets or electrical outlets or garden hoses.
It's like a pressure washer. You put in a smaller nozzle, the water travels faster at the same volume. If you had a 2" hose ..or one slightly smaller, the nozzle would still be the one element that's bringing the pump up to the (near) 2500psi (or whatever) level where it's operating at. If water didn't have the VI that it does, you would see your water stream go limp ..the pressure you developed would tank..but the volume would remain the same. You could put a filter of whatever restrictive property you please in line (assuming that you used one that could withstand 2500 psi) and the flow wouldn't even see it.
In your model, you indicate the pressure washer nozzle is the filter; however the restriction is internal in the engine, downstream of the filter.
So the filter would be somewhere along the supply hose in your example and the engine would be the restriction/nozzle...while there may be a huge pressure differential at the engine/nozzle, there is potentially very little across the filter itself...
Make sense?
- Joined
- Sep 28, 2002
- Messages
- 39,799
Quote:
In your model, you indicate the pressure washer nozzle is the filter;
No ..I'm offering that the nozzle is the engine ..and that the hose, and anything that you would likely put in line, is the filter ...accounting for very little in most modes of operation.
Quote:
So the filter would be somewhere along the supply hose in your example and the engine would be the restriction/nozzle...while there may be a huge pressure differential at the engine/nozzle, there is potentially very little across the filter itself...
Exactly.
Quote:
Make sense?
Has to me since I installed those gauges and observed them for many months ..many moons ago
Getting others to accept that for most people that there is no "free flowing" or "tight" filter is another story. For most of us, the filter is invisible.
In your model, you indicate the pressure washer nozzle is the filter;
No ..I'm offering that the nozzle is the engine ..and that the hose, and anything that you would likely put in line, is the filter ...accounting for very little in most modes of operation.
Quote:
So the filter would be somewhere along the supply hose in your example and the engine would be the restriction/nozzle...while there may be a huge pressure differential at the engine/nozzle, there is potentially very little across the filter itself...
Exactly.
Quote:
Make sense?
Has to me since I installed those gauges and observed them for many months ..many moons ago
Getting others to accept that for most people that there is no "free flowing" or "tight" filter is another story. For most of us, the filter is invisible.
Originally Posted By: Gary Allan
Here's where we differ. While you appear to agree on the conditions, the "cause" and the ending of the condition seem to "slide" a little
Quote:
Just as I’ve said many times, the max filter PSID and max engine oil pressure will always occur when the pump is in relief mode (under constant viscosity conditions as always).
Here we're in apparent agreement.
Amazing
Originally Posted By: Gary Allan
Quote:
That is because when the pump is in relief mode, the max possible supply pressure is on the filter/engine flow path, and that will produce the max amount of oil flow at that instant in time.
..and here we're mostly in agreement ..but we're creeping (I can feel it)
It’s a true statement as written – can’t argue the truth; no “creeping” here. So far so good.
Originally Posted By: Gary Allan
Quote:
The corresponding filter PSID and engine oil pressure at that instant in time will be dependant on the volume & viscosity of the oil flowing through the system.
Well .. here's what this statement doesn't resolve. As soon as the relief event is over ..with the same (near enough) viscosity and alleged filter resistance ..the PSID evaporates.
That's not apparent in that statement. It's PURELY because of the relief event that the filter presents so much resistance. The filter obviously doesn't change in any property from one state to the other ..nor does the viscosity (appreciably) ..so the applied physics must be altered. That is, the equation has to change to fit the apparent readings since the physical properties cannot (massage that to make sense).
Keep in mind that in order for the pump to go out of relief mode that means one or both of two things must happen: a) the oil viscosity is becoming much less, and/or b) the engine RPM has decreased enough to significantly reduce the pump’s output volume. When both things are happening at once, very dynamic conditions can occur.
If the viscosity is becoming so thin enough that the pump goes out of relief mode, then the filter PSID will also drop accordingly. If the engine RPM decreases, the flow volume also goes down and the filter’s PSID will also drop accordingly. I don’t think you are seeing anything “magical” with your limited experimental observations.
Keep in mind that these relationships between flow, pressure and oil viscosity are not linear, and as such you could see some drastic differences in filter PSID between conditions where the pump is in relief and not in relief.
Originally Posted By: Gary Allan
The filter is exactly what it was. The oil (for the sake of discussion) was exactly what it was. The difference is the amount of oil shunted in relief. The more flow shunted, the more the apparent PSID. No shunted flow, no apparent (substantial) PSID (at sensible volumes).
I think you are veering off track some here. For the pump to go out of relief mode, there has to be a reason for it to happen. Like I said above, it can be either: a) the oil viscosity is becoming much less, and/or b) the engine RPM has decreased enough to significantly reduce the pump’s output volume.
If the pump goes out of relief mode with the engine at a constant RPM, then the oil is not “exactly what it was” ... it is becoming thinner – otherwise the pump would not go out of relief mode.
The filter PSID is higher when the pump is in relief mode with cold oil because the combination of the lower flow volume with a higher oil viscosity creates a larger PSID then when the pump is out of relief and the combination of higher flow volume with a lower oil viscosity.
Low flow volume + high viscosity can cause more PSID than high flow volume + low viscosity. You must realize that both of these parameters are the sole cause of pressure drop. This is why you see less PSID when out of pump relief, even though the flow volume is much higher. The viscosity is probably a stronger factor than flow volume on the observed PSID.
Originally Posted By: Gary Allan
Quote:
I’m assuming the same cold oil start-up conditions applied to this filter? If so, this doesn’t sound like a normal response. I would expect some noticeable/visible PSID at these cold startup conditions with any oil filter in the system. Maybe the gauge didn’t like the cold weather that day, or maybe the bypass valve was stuck open all the time. Hard to say.
Not quite as cold ..but run for weeks with no reaction. It was a transitional time of the year.
Relief events were rare with this engine. Start up pressure ALWAYS went to 82psi on a cold start. The difference would be how long 82 was maintained. The difference was about 2psi above:below.
My take is that this engine’s oil pump probably doesn’t put out very much oil volume and/or the engine’s flow path is pretty restrictive thereby significantly reducing the flow volume through the filter/engine when the pump was in relief mode with cold oil. If the cold oil flow volume is very low, then of course you won’t see much filter PSID even though the oil pump is in relief at 82 psi. Just because you have high oil pressure doesn’t always mean there will be lots of flow volume – it all depends on the flow resistance of engine. Even though the oil was cold and viscous, the volume was probably so low going through the filter/engine path at this point in time that the filter PSID was also low. Plus you said the filter was a brand new (PureOne) and would have been as free flowing as possible at the time. Without having an actual flow meter in the test, you really have no idea what the actual flow volume is ... and the flow volume is a major factor in the filter PSID you will see on your delta P gauge. Without an actual flow meter you don’t see the whole story to fit all the pieces together. I really see nothing that you have seen with your gauges that can’t be explained.
This again goes full circle with regard to the oil filters used on HV oil pumps like the Subaru’s. If and engine’s flow path is relatively free flowing (ie, less restrictive than most cars), then a HV oil pump will be able to force a lot higher oil volume of cold oil through the circuit. And if the oil filter doesn’t have the bypass valve set high enough, then there will definitely be more frequent and longer bypass events as a result – especially during engine cold and warm-up run time. This is exactly why Subaru has specified a 23 psi filter bypass.
Originally Posted By: Gary Allan
Quote:
A good reason to ensure the oil filter being used is matched to the vehicle in terms of flow resistance (ie, element size and flow vs PSID characteristics) and bypass valve setting. Just like the Subaru application this thread is focused on ... if you used a filter with a much lower bypass setting than specified, the filter could certainly be in bypass mode much more and much longer than really desired. I think we all have agreed to that conclusion.
Here we're somewhat (and mostly) in agreement. The exception with the Subaru is that it's only due to its extreme volume where this would be a factor. The pressures that the engine produces are broad. That is, they aren't operating 24/7 at the relief level.
Agreed ... see above. Of course the filter won’t be in bypass 100% of the time when the oil is nice and hot, even if the filter had an 8~11 psi bypass. I have qualified the statement many times in the past in this thread that it would mostly be a potential problem only during engine cold starts and warm-up run times.
Originally Posted By: Gary Allan
Quote:
One thing never discussed yet is how does the flow resistance of the filter and engine chance with thermal effects. In other words, does the filter and engine flow resistance change as they heat up? It’s entirely possible that the engine’s flow path becomes less restrictive as all the parts heat up and expand (ie, bearing clearances increase), which could dynamically change the flow resistance ratio of the filter/engine circuit. I can’t really see how an oil filter’s flow resistance would decrease as it heated up, but if it did, due to the element material “opening up”, you would also think it’s filtering performance might also change some (become worse) with its temperature.
Depending on how you're viewing it, the "apparent" resistance of the filter will be changed or unchanged with a decrease in viscosity. Out of relief you'll see virtually no PSID ..so it's mostly independent of visc and more a function of pressure limits. That is 85lb out of relief, next to nothing. 85lb in relief ..something.
10CST fluid flows much easier through a filter than 140CST fluid. The same as it requires less "power" to push it through the engine. Again, it's not an issue at most sensible flow rates and the difference is (probably) measured in inches of water column. The turnstile that you think is slowing you up is nothing when the traffic jam is all the way to the exit. An engine is always a traffic jam to the exit. Out of relief, you can't be "slowed up" in a fully enveloped engine. You can just move easier (at whatever flow rate that is at the moment). The fluid will just accelerate or decelerate with the relative size of the conduit that it's transitioning to.
See previous response above about the effect of the volume + viscosity parameter combination on the effect of pressure drop. It’s not a linear relationship, and once the pump is out of relief mode there can certainly be a drastic fall off of PSID as compared to relief mode. I’ve never argued any differently, and if you could looked at the actual flow and viscosity measurements during all of these conditions you’d see it all correlates. There is still a filter PSID (no matter how small) and an engine pressure drop from supply to sump. The fact is if you increased the flow volume without changing anything else in the system, you will see increased pressure drops. If you increased the oil viscosity without changing anything else, you will see increased pressure drops. If you change both at once you will see the effects of both, and which ever factor is stronger will determine the actual pressure drop.
It’s the combination of these two factors that will determine the actual pressure drops you see. Not all engines are the same and not all filters are the same; therefore it’s possible that a particular filter on a particular engine could certainly be cause for concern. Prime example – putting a relatively restrictive filler with a low bypass valve setting on a high flow volume engine system like the Subaru’s will cause the filter to behave differently than it if was put on a 1975 6-banger Econoline Van with a low flow volume oiling system.
I’ve stayed true to this fact from day one ... regardless of the convoluted discussions we have had on this subject. Obviously, we’ve both dug deeper into these discussions and have probably filleted in more ways than one.
Here's where we differ. While you appear to agree on the conditions, the "cause" and the ending of the condition seem to "slide" a little
Quote:
Just as I’ve said many times, the max filter PSID and max engine oil pressure will always occur when the pump is in relief mode (under constant viscosity conditions as always).
Here we're in apparent agreement.
Amazing
Originally Posted By: Gary Allan
Quote:
That is because when the pump is in relief mode, the max possible supply pressure is on the filter/engine flow path, and that will produce the max amount of oil flow at that instant in time.
..and here we're mostly in agreement ..but we're creeping (I can feel it)
It’s a true statement as written – can’t argue the truth; no “creeping” here. So far so good.
Originally Posted By: Gary Allan
Quote:
The corresponding filter PSID and engine oil pressure at that instant in time will be dependant on the volume & viscosity of the oil flowing through the system.
Well .. here's what this statement doesn't resolve. As soon as the relief event is over ..with the same (near enough) viscosity and alleged filter resistance ..the PSID evaporates.
That's not apparent in that statement. It's PURELY because of the relief event that the filter presents so much resistance. The filter obviously doesn't change in any property from one state to the other ..nor does the viscosity (appreciably) ..so the applied physics must be altered. That is, the equation has to change to fit the apparent readings since the physical properties cannot (massage that to make sense).
Keep in mind that in order for the pump to go out of relief mode that means one or both of two things must happen: a) the oil viscosity is becoming much less, and/or b) the engine RPM has decreased enough to significantly reduce the pump’s output volume. When both things are happening at once, very dynamic conditions can occur.
If the viscosity is becoming so thin enough that the pump goes out of relief mode, then the filter PSID will also drop accordingly. If the engine RPM decreases, the flow volume also goes down and the filter’s PSID will also drop accordingly. I don’t think you are seeing anything “magical” with your limited experimental observations.
Keep in mind that these relationships between flow, pressure and oil viscosity are not linear, and as such you could see some drastic differences in filter PSID between conditions where the pump is in relief and not in relief.
Originally Posted By: Gary Allan
The filter is exactly what it was. The oil (for the sake of discussion) was exactly what it was. The difference is the amount of oil shunted in relief. The more flow shunted, the more the apparent PSID. No shunted flow, no apparent (substantial) PSID (at sensible volumes).
I think you are veering off track some here. For the pump to go out of relief mode, there has to be a reason for it to happen. Like I said above, it can be either: a) the oil viscosity is becoming much less, and/or b) the engine RPM has decreased enough to significantly reduce the pump’s output volume.
If the pump goes out of relief mode with the engine at a constant RPM, then the oil is not “exactly what it was” ... it is becoming thinner – otherwise the pump would not go out of relief mode.
The filter PSID is higher when the pump is in relief mode with cold oil because the combination of the lower flow volume with a higher oil viscosity creates a larger PSID then when the pump is out of relief and the combination of higher flow volume with a lower oil viscosity.
Low flow volume + high viscosity can cause more PSID than high flow volume + low viscosity. You must realize that both of these parameters are the sole cause of pressure drop. This is why you see less PSID when out of pump relief, even though the flow volume is much higher. The viscosity is probably a stronger factor than flow volume on the observed PSID.
Originally Posted By: Gary Allan
Quote:
I’m assuming the same cold oil start-up conditions applied to this filter? If so, this doesn’t sound like a normal response. I would expect some noticeable/visible PSID at these cold startup conditions with any oil filter in the system. Maybe the gauge didn’t like the cold weather that day, or maybe the bypass valve was stuck open all the time. Hard to say.
Not quite as cold ..but run for weeks with no reaction. It was a transitional time of the year.
Relief events were rare with this engine. Start up pressure ALWAYS went to 82psi on a cold start. The difference would be how long 82 was maintained. The difference was about 2psi above:below.
My take is that this engine’s oil pump probably doesn’t put out very much oil volume and/or the engine’s flow path is pretty restrictive thereby significantly reducing the flow volume through the filter/engine when the pump was in relief mode with cold oil. If the cold oil flow volume is very low, then of course you won’t see much filter PSID even though the oil pump is in relief at 82 psi. Just because you have high oil pressure doesn’t always mean there will be lots of flow volume – it all depends on the flow resistance of engine. Even though the oil was cold and viscous, the volume was probably so low going through the filter/engine path at this point in time that the filter PSID was also low. Plus you said the filter was a brand new (PureOne) and would have been as free flowing as possible at the time. Without having an actual flow meter in the test, you really have no idea what the actual flow volume is ... and the flow volume is a major factor in the filter PSID you will see on your delta P gauge. Without an actual flow meter you don’t see the whole story to fit all the pieces together. I really see nothing that you have seen with your gauges that can’t be explained.
This again goes full circle with regard to the oil filters used on HV oil pumps like the Subaru’s. If and engine’s flow path is relatively free flowing (ie, less restrictive than most cars), then a HV oil pump will be able to force a lot higher oil volume of cold oil through the circuit. And if the oil filter doesn’t have the bypass valve set high enough, then there will definitely be more frequent and longer bypass events as a result – especially during engine cold and warm-up run time. This is exactly why Subaru has specified a 23 psi filter bypass.
Originally Posted By: Gary Allan
Quote:
A good reason to ensure the oil filter being used is matched to the vehicle in terms of flow resistance (ie, element size and flow vs PSID characteristics) and bypass valve setting. Just like the Subaru application this thread is focused on ... if you used a filter with a much lower bypass setting than specified, the filter could certainly be in bypass mode much more and much longer than really desired. I think we all have agreed to that conclusion.
Here we're somewhat (and mostly) in agreement. The exception with the Subaru is that it's only due to its extreme volume where this would be a factor. The pressures that the engine produces are broad. That is, they aren't operating 24/7 at the relief level.
Agreed ... see above. Of course the filter won’t be in bypass 100% of the time when the oil is nice and hot, even if the filter had an 8~11 psi bypass. I have qualified the statement many times in the past in this thread that it would mostly be a potential problem only during engine cold starts and warm-up run times.
Originally Posted By: Gary Allan
Quote:
One thing never discussed yet is how does the flow resistance of the filter and engine chance with thermal effects. In other words, does the filter and engine flow resistance change as they heat up? It’s entirely possible that the engine’s flow path becomes less restrictive as all the parts heat up and expand (ie, bearing clearances increase), which could dynamically change the flow resistance ratio of the filter/engine circuit. I can’t really see how an oil filter’s flow resistance would decrease as it heated up, but if it did, due to the element material “opening up”, you would also think it’s filtering performance might also change some (become worse) with its temperature.
Depending on how you're viewing it, the "apparent" resistance of the filter will be changed or unchanged with a decrease in viscosity. Out of relief you'll see virtually no PSID ..so it's mostly independent of visc and more a function of pressure limits. That is 85lb out of relief, next to nothing. 85lb in relief ..something.
10CST fluid flows much easier through a filter than 140CST fluid. The same as it requires less "power" to push it through the engine. Again, it's not an issue at most sensible flow rates and the difference is (probably) measured in inches of water column. The turnstile that you think is slowing you up is nothing when the traffic jam is all the way to the exit. An engine is always a traffic jam to the exit. Out of relief, you can't be "slowed up" in a fully enveloped engine. You can just move easier (at whatever flow rate that is at the moment). The fluid will just accelerate or decelerate with the relative size of the conduit that it's transitioning to.
See previous response above about the effect of the volume + viscosity parameter combination on the effect of pressure drop. It’s not a linear relationship, and once the pump is out of relief mode there can certainly be a drastic fall off of PSID as compared to relief mode. I’ve never argued any differently, and if you could looked at the actual flow and viscosity measurements during all of these conditions you’d see it all correlates. There is still a filter PSID (no matter how small) and an engine pressure drop from supply to sump. The fact is if you increased the flow volume without changing anything else in the system, you will see increased pressure drops. If you increased the oil viscosity without changing anything else, you will see increased pressure drops. If you change both at once you will see the effects of both, and which ever factor is stronger will determine the actual pressure drop.
It’s the combination of these two factors that will determine the actual pressure drops you see. Not all engines are the same and not all filters are the same; therefore it’s possible that a particular filter on a particular engine could certainly be cause for concern. Prime example – putting a relatively restrictive filler with a low bypass valve setting on a high flow volume engine system like the Subaru’s will cause the filter to behave differently than it if was put on a 1975 6-banger Econoline Van with a low flow volume oiling system.
I’ve stayed true to this fact from day one ... regardless of the convoluted discussions we have had on this subject. Obviously, we’ve both dug deeper into these discussions and have probably filleted in more ways than one.
Originally Posted By: deeter16317
Originally Posted By: SuperBusa
I agree that it seems like a HUGE (and unbelievable) amount of oil volume output from the oil pump. It very well could be a typo, but who can prove it? I don’t think my garden hose even flows at 12 gpm.
I have no doubt the pump will free flow that much...it probably will flow that much, and more (since that is most likely a "minimum" specification. But the engine (or more specifically engine clearances) is the restriction. You could have a pump that is capable of free flowing 50,000GPM, but if you are trying to force it through a 1/4" diameter hole, it won't/can't flow anywhere near its rated flow. That's because the restriction is the factor regulating the flow rate.
Keep in mind that those Subaru oil pump flow specs are listed at a specific engine RPM, oil temp (ie, viscosity) and pressure. This tells me that the pump is flowing into some kind of resistance (same as the engine's?? - who knows?), not open output flow.
Originally Posted By: deeter16317
Another point is the fact the filter is pressurized. You would need to have a 8-11psi drop across the filter media in order to have the bypass open. That would imply the filter media is really being restrictive by itself correct?? Would a fresh filter be that restrictive (at normal operating temperatures)??
Just some food for thought...
Yes, of course the filter is being restrictive by itself ... just like this graph shows for example.
How much flow restriction depends on the design of the element for the most part - and of course the PSID across the filter is dependant on the oil's viscosity and flow volume going through it. If the element is small and uses very restrictive media, then it will be much more restrictive than if it was large and had free flowing media. Not all filters are equal ... but most are probably pretty close because the filter designers (if they know what they are doing) should take flow vs PSID (and bypass valve setting) into prime consideration for each application - ideally speaking of course.
Originally Posted By: SuperBusa
I agree that it seems like a HUGE (and unbelievable) amount of oil volume output from the oil pump. It very well could be a typo, but who can prove it? I don’t think my garden hose even flows at 12 gpm.
I have no doubt the pump will free flow that much...it probably will flow that much, and more (since that is most likely a "minimum" specification. But the engine (or more specifically engine clearances) is the restriction. You could have a pump that is capable of free flowing 50,000GPM, but if you are trying to force it through a 1/4" diameter hole, it won't/can't flow anywhere near its rated flow. That's because the restriction is the factor regulating the flow rate.
Keep in mind that those Subaru oil pump flow specs are listed at a specific engine RPM, oil temp (ie, viscosity) and pressure. This tells me that the pump is flowing into some kind of resistance (same as the engine's?? - who knows?), not open output flow.
Originally Posted By: deeter16317
Another point is the fact the filter is pressurized. You would need to have a 8-11psi drop across the filter media in order to have the bypass open. That would imply the filter media is really being restrictive by itself correct?? Would a fresh filter be that restrictive (at normal operating temperatures)??
Just some food for thought...
Yes, of course the filter is being restrictive by itself ... just like this graph shows for example.
How much flow restriction depends on the design of the element for the most part - and of course the PSID across the filter is dependant on the oil's viscosity and flow volume going through it. If the element is small and uses very restrictive media, then it will be much more restrictive than if it was large and had free flowing media. Not all filters are equal ... but most are probably pretty close because the filter designers (if they know what they are doing) should take flow vs PSID (and bypass valve setting) into prime consideration for each application - ideally speaking of course.
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