Subaru Oil Pump Specs as Relates to Filter Bypass

[Gary Allan]

Quote:
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.


I disagree. It's only the exceptional engine that needs anything other than the generic bypass valve. That's why Wix offers 8-11 for the vast majority ..and Purolator offers 12-16. This is regardless (mostly) of the filter size or application. It is only the exceptional that requires anything other than generic.

 

[WagonBoss]

I've followed the discussion with great interest. Quite educational. Though I don't know that I can make practical sense of the information. I'd appreciate any discussion on the below questions.

If your choices for a filter were the current OEM replacement with the assumed correct BPV rating manufactured for Subaru by Honeywell, a Wix/Napa Gold 1356 (slightly longer and 8-11 psi BPV), or a Purolator PL14460 (a back-spec'd filter to pre-2005 and the original size and correct 23 PSID BPV rating when Purolator made Subaru filters, which would you choose?

The recommended oil is 5w-30. If one wanted to run a heavier 20w-50 or 15w-40 (perhaps towing or track duty in the summer) would you want a lower or same rating on the BPV?

 

[SuperBusa]

Originally Posted By: Gary Allan
Quote:
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.


I disagree. It's only the exceptional engine that needs anything other than the generic bypass valve. That's why Wix offers 8-11 for the vast majority ..and Purolator offers 12-16. This is regardless (mostly) of the filter size or application. It is only the exceptional that requires anything other than generic.


I’ve concluded you’ll look for anything to argue about. Re-read what I said ... it implies the same thing you said, that there are certainly filters that ARE different because of their intended application. If an “exceptional engine” needs anything “other than the generic bypass valve”, then it’s not the same as other filters, now is it?

Case in point ... Subaru with the 23 psi bypass valve ... it is NOT your “generic bypass valve”. Stop arguing about the same things you turn around and agree with ... it's a bad habit.

 

[SuperBusa]

Originally Posted By: WagonBoss

If your choices for a filter were the current OEM replacement with the assumed correct BPV rating manufactured for Subaru by Honeywell, a Wix/Napa Gold 1356 (slightly longer and 8-11 psi BPV), or a Purolator PL14460 (a back-spec'd filter to pre-2005 and the original size and correct 23 PSID BPV rating when Purolator made Subaru filters, which would you choose?


If it was my Subaru, I'd run the best filter that has the 23 psi bypass valve.

Originally Posted By: WagonBoss
The recommended oil is 5w-30. If one wanted to run a heavier 20w-50 or 15w-40 (perhaps towing or track duty in the summer) would you want a lower or same rating on the BPV?


You certainly wouldn't want a lower bypass valve setting with thicker oil ... that's going in the wrong direction. I'd say the 23 psi bypass would be OK with the heavier oil also. What choice do you have? ... none really, since there isn't a filter for your car that has a higher than 23 psi bypass valve.

 

[Gary Allan]

Originally Posted By: SuperBusa
Originally Posted By: Gary Allan
Quote:
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.


I disagree. It's only the exceptional engine that needs anything other than the generic bypass valve. That's why Wix offers 8-11 for the vast majority ..and Purolator offers 12-16. This is regardless (mostly) of the filter size or application. It is only the exceptional that requires anything other than generic.


I’ve concluded you’ll look for anything to argue about. Re-read what I said ... it implies the same thing you said, that there are certainly filters that ARE different because of their intended application. If an “exceptional engine” needs anything “other than the generic bypass valve”, then it’s not the same as other filters, now is it?

Case in point ... Subaru with the 23 psi bypass valve ... it is NOT your “generic bypass valve”. Stop arguing about the same things you turn around and agree with ... it's a bad habit.

..but that's not ALL you included in your assertion...

you tend to attempt to "slide" something in there as a universal truth ..when it's an exceptional one.

It's a bad habit you have

 

[Thingfish]

Originally Posted By: SuperBusa

What choice do you have? ... none really, since there isn't a filter for your car that has a higher than 23 psi bypass valve.


Unless you consider the Canton-Mecca design that has no pbv.

 

[unDummy]

4 pages of fun here.

You can debate flow, bypass pressure, relief pressure.... until the sun doesn't shine.

A filter will affect flow volume. This is why some engines make a little more noise or clatter with restrictive filters like Pureone or Toughgard. There is no excuse otherwise.

What is good is that page copied from the Subaru factory manuals. See the clearances and their tolerances. Depending on the pump, the accuracy of the springs..... you can have a decrease in oil volume. Every bit of resistance to flow will reduce the pumps ability to pump. Working with fixed rpm motor driven industrial lubrication pumps, one will learn what pump-slip is.

Your oil pump is like your engine. It has blowby like your engine. That is wasted pumpability. Slip can be increased by a worn out pump(which pumps a good volume with no resitance), and then pumps nothing when you put a load on it. Slip can be increased by a pump with wide tolerances and loose clearances. Slip can be increased by the load, whether the resistance caused by the fluid being too thick, or by the engine passages. EVERY nook/cranny in your lubrication system affects flow/pressure and that will affect the pump-slip directly.

The oil filter is the 1st restriction that your pump sees. As the 1st restriction, it will affect every restriction downstream. And, the last circuit(valvetrain), might just feel that restriction and be poortly lubed.

Another slip example is your air powered tools. You can pump 100psi into that worn out impact wrench and get no work done(all slip/blowby = no torque). Give that impact wrench a shot of airtool oil and suddenly you can do work with low 30psi(compression=torque).

Your oil pump is no different.

The high PSI filter relief is simply to get more oil through the filter. Maybe some engynaire measured an increase in wear somewhere in the engine caused by unfiltered oil. German engines also tend to have higher PSI bypass valves. If you have an abundance in flow, then a little bit wasted on forcing more oil through the filter media to possibly reduce 'dirty' motor oil releated issues.

Don't assume your pump is perfect. Don't expect the pump's relief valve(or the filters bypass) to be a perfect poppit on/off switch. It probably leaks a little at idle and more as the pressure on it increases until it is open all the way(at its rating +/- whatever the tolerance is on that rating). Because your engine isn't perfect, what happens in the classroom doesn't always carry into the engine.

 

[Gary Allan]

While there are all those nuances and enclaves of truth in your statements, undummy, the vast majority don't experience any of them. Those who hear lingering start up rattle that is altered by filter choice ..are nothing in number compared to the millions of units that do not. While oil pumps are not perfect, most losses are minor and are taken for granted as non-influential for discussion's sake.

There are always exceptions. Exceptionally worn pump vanes/gears/rotors ..exceptionally high volumes ..and exceptionally high pressures. The only common theme to all of them is that they are exceptional.

I learned none of this in a classroom.

 

[bluesubie]

This response from SoA posted on nasioc is very interesting:

Quote:
Thank you for taking the time to contact us. We appreciate that you brought your concern with the oil filter we now offer for our vehicles. The prior oil filters did not meet the standards of Subaru. This is why our manufacturer diligently worked to redesign the oil filter so that it meets our standards. Subaru is not aware of any recurring concerns with our new oil filter...


I wonder if it's true or they didn't want to say they went cheaper?

-Dennis

 

[LoneRanger]

WHAT?! I cannot believe the black Tokyo Roki filter did not meet standards. I think that SOA response is smoke and mirrors covering up for, as you indicated, a bean counting decision to go cheaper on an OE part. The Tokyo Roki filter was a quality piece. I wish whoever corresponded with SOA would have sent them a photo of the new Honeywell blue filter and the Tokyo Roki filter side by side, cut open.

Over on Subaruforester.org, there is a vendor (a Subaru dealership) stocking a "Six Star" branded filter that looks quite similar to the black Tokyo Roki... I am trying to find out the BPV spec on it.

 

[SuperBusa]

Originally Posted By: unDummy

The high PSI filter relief is simply to get more oil through the filter.


What?! ... how can that be if Gary claims "all filters are the same".

Last time I checked, 23 was a different value than 8. I guess Gary's math is pretty strange when 23 = 8.

 

[LoneRanger]

My question:

Using your oil filter # 51365 on my 2009 Subaru Forester. I'm one of those filter geeks that cuts open filters to see how well made they are. Yours is well made. But I have one concern maybe you can put to rest. Bypass pressure for the 51365 is 11 psi according to tech specs on your website. I have since found out that Subaru OE filter bypass pressure is 23psi (!) Is it okay to run that much lower of a bypass pressure spec will the 51365 be in partial bypass most of the time? Or is the bypass rating more dependent on the flow rating of the filter itself and therefore my concern is baseless? Brand new car, just trying to make sure.

Wix response:

Thank you for your inquiry.
At three gallons per minute, the WIX 51365 will produce 2 pounds or less of differential pressure. Differential pressure is the measured pressure drop across the filter assembly. Therefore, the 51365 will have to trap and hold so much contamination that the differential pressure would increase over initial by approximately six times. Should this situation occur, the filter element would be completely plugged (regardless of brand). While it is accurate that a 23 PSID valve will not open until such time as the differential pressure drop meets or exceeds the valve spring force, this would not be an item of concern. Filters do not increase in differential pressure in a linear manner. Rather they gradually build in differential pressure until there is typically 15 % or so of the media's capacity remaining. At this point, the restriction curve rapidly increases and the filter quickly becomes plugged.
For more information on how the full flow filter bypass valve functions, as well as other information, we would encourage you to register and take the free on line E-Learning we have available at http://www.wixfilters.com.

 

[SuperBusa]

Originally Posted By: Gary Allan
Originally Posted By: SuperBusa
Originally Posted By: Gary Allan
Quote:
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.


I disagree. It's only the exceptional engine that needs anything other than the generic bypass valve. That's why Wix offers 8-11 for the vast majority ..and Purolator offers 12-16. This is regardless (mostly) of the filter size or application. It is only the exceptional that requires anything other than generic.


I’ve concluded you’ll look for anything to argue about. Re-read what I said ... it implies the same thing you said, that there are certainly filters that ARE different because of their intended application. If an “exceptional engine” needs anything “other than the generic bypass valve”, then it’s not the same as other filters, now is it?

Case in point ... Subaru with the 23 psi bypass valve ... it is NOT your “generic bypass valve”. Stop arguing about the same things you turn around and agree with ... it's a bad habit.

..but that's not ALL you included in your assertion...

you tend to attempt to "slide" something in there as a universal truth ..when it's an exceptional one.

It's a bad habit you have

You're really getting hopeless. Looks like you've been demoted to deputy status with one bullet in your shirt pocket (if ya know what I mean

).

 

[SuperBusa]

Originally Posted By: LoneRanger


Wix response:

Thank you for your inquiry.
At three gallons per minute, the WIX 51365 will produce 2 pounds or less of differential pressure. Differential pressure is the measured pressure drop across the filter assembly. Therefore, the 51365 will have to trap and hold so much contamination that the differential pressure would increase over initial by approximately six times. Should this situation occur, the filter element would be completely plugged (regardless of brand). While it is accurate that a 23 PSID valve will not open until such time as the differential pressure drop meets or exceeds the valve spring force, this would not be an item of concern. Filters do not increase in differential pressure in a linear manner. Rather they gradually build in differential pressure until there is typically 15 % or so of the media's capacity remaining. At this point, the restriction curve rapidly increases and the filter quickly becomes plugged.
For more information on how the full flow filter bypass valve functions, as well as other information, we would encourage you to register and take the free on line E-Learning we have available at http://www.wixfilters.com.


The problem I see in the response from WIX is that they are only talking about the PSID due to filter loading with time - and I think are assuming flow conditions with oil at full operating temps. They never talk about the increased PSID during cold start and engine warm-up transitional time with increased engine RPMs.

I'd email WIX back and pose those specific running conditions to see how he responds knowing their filter has a much lower bypass setting than the Subaru spec. There's no doubt that when the oil is nice and hot that 8~11 psi bypass would probably be OK ... but what about with cold thick oil at startup and during engine warm-up. That has been the focus of this whole discussion from page one.

 

[SuperBusa]

Originally Posted By: LoneRanger
Wix response:

Thank you for your inquiry.
At three gallons per minute, the WIX 51365 will produce 2 pounds or less of differential pressure. Differential pressure is the measured pressure drop across the filter assembly.


To add ... if what WIX said above is true with hot oil (say 5w-30 @ 200 F), and if the Subaru's oil pump is actually putting out 12 gpm at high RPM with the same hot oil, then the PSID across the filter is going to much higher than 2 psi, leaving less margin for loading etc, before bypass mode is reached. IMO, WIX needs to address the fact that the Subaru has a high volume oil system, and if their 8~11 psi bypass filter will suffice in all extremes of operating conditions (including loading factors). What do they really have to say about these conditions?

 

[Gary Allan]

Quote:
What do they really have to say about these conditions?



I too would protest this egregious assault upon all the standards of sensible filtration self governess!!!



Psst! and I'd also ask them about cold start situations where the PSID will always be elevated due to low ..but relatively higher, volumes and the immutable conditions that will be present far more often.

 

[SuperBusa]

Originally Posted By: Gary Allan
Quote:
What do they really have to say about these conditions?


I too would protest this egregious assault upon all the standards of sensible filtration self governess!!!

Psst! and I'd also ask them about cold start situations where the PSID will always be elevated due to low ..but relatively higher, volumes and the immutable conditions that will be present far more often.

Ya mean like what I already said? Seems you're falling a little behind.

Originally Posted By: SuperBusa

I'd email WIX back and pose those specific running conditions to see how he responds knowing their filter has a much lower bypass setting than the Subaru spec. There's no doubt that when the oil is nice and hot that 8~11 psi bypass would probably be OK ... but what about with cold thick oil at startup and during engine warm-up. That has been the focus of this whole discussion from page one.

 

[Gary Allan]

But you seem to default to that 12gpm thing. You know, the operational mode that no one really exists at for any length of time. Where's your chart (yes, I know where it is)?

JH: 20!

 

[SuperBusa]

Originally Posted By: Gary Allan
But you seem to default to that 12gpm thing. You know, the operational mode that no one really exists at for any length of time. Where's your chart (yes, I know where it is)?

JH: 20!


There is no doubt that a HV oil system will have a bearing on the oil filter's design requirements; like the bypass setting which is the focus here ... even at full oil temperature at high RPM (yeah, some people do actually rev their engines near redline at times

). As said above ... even WIX understands that flow volume has a bearing on PSID. And why wouldn't they ... they actually design filters - what a concept.

You seem to forget the focus of this thread at times. Looks like straw grasping is about the only thing you have left to fall back on.

"JH: 20!" ... must be the brain cell filtering beta ratio for the 20 micron nerve synapse gat rating performance while you're wearing the tin foil hat.

 

[Gary Allan]

Well, keep in mind that volume is like viscosity. Any volume is low or high volume at some point in the process from zero to peak. Isn't a standard volume pump, on average the same as midspan in a HV pump (somewhere in there). It's just indexed at a lower engine speed ..which doesn't really mean much in that snap shot.

SB ..let's not get too far into our little tango here. I'm sure that Helen will be more than happy to end this permanently for both of us.

John Henry: "20!"