Subaru and 27psi bypass Filter selection

Originally Posted by Farnsworth
A further note, on Amazon the Puro Boss PBL14615 states compatible with Subaru. The 20-30 bypass is in line, likely the same as, a 27 psi stated as one number. If not wanting the OE that is what I would use or the Wix.

20-30 psi bypass, that is vague. Seems to me the Purolator can give a better spec than that.
 
Originally Posted by wdn
The Fram XG7317 has a bypass valve that opens at 13 PSI. That Fram filter does not meet the requirement. It open at half the designed pressure for a Subaru engine. When the bypass opens at just 13 PSI, the filter is 0% efficient.


Originally Posted by DudeNiceRide
I'd like to see some math behind the effect a pressure relief valve has on the overall efficiency of a filter combined with how good the filter itself actually performs.

What is worse?

A. The filter performs at 50% efficiency @ 20-micron for 99.9% of the time and 0% efficiency for 0.1% of the time when PRV is open.

B. The filter performs at 97% efficiency @ 20-micron for 99.8% of the time and 0% efficiency for 0.2% (twice as often) when PRV is open.

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The part in red is wrong - more misconceptions. When a bypass valve opens, only a fraction of the oil bypasses the media. So if 20% of the flow gets bypassed, the other 80% of the flow is still going through the media.

Also, the filters with lower set bypass valve specified for the Subarus may have less flow resistance than the Subaru OEM filter. The more flow restrictive an oil filter is, the higher the bypass valve needs to be set in order to prevent unwanted bypass events.
 
Originally Posted by Lubener
Originally Posted by Farnsworth
A further note, on Amazon the Puro Boss PBL14615 states compatible with Subaru. The 20-30 bypass is in line, likely the same as, a 27 psi stated as one number. If not wanting the OE that is what I would use or the Wix.

20-30 psi bypass, that is vague. Seems to me the Purolator can give a better spec than that.

That 20-30 is a better spec, the 27 is vague. Is the start of opening 27 or full open 27. Probably in the high middle somewhere is 27.
 
Originally Posted by wdn
Ignatius, Fram XG7317 does not meet the Subaru spec. Specs are specs. I don't know who appointed you the project historian for Bob, but a bunch of old threads are immaterial. In any case nobody is shooing me off this one. If you would care to identify some other aftermarket filters that do meet the spec, by Fram or others go ahead.

Today's topic is " Subaru and 27psi bypass Filter selection".


I appreciate your condescending remarks, perhaps you should realize that this very subject has been discussed ad nauseam over and over and over and over again and you have simply repeated the same bypass drivel that keeps getting regurgitated. If you need instructions on how to utilize the search function just ask.

Frankly speaking you might want to actually read through the thread as I clearly stated my recommendation for Wix/Napa Gold bypass spec friendly oil filters in my post that immediately preceeded your post where you spouted off the same tired nonsense about the Xg7317 that you are apparently ill informed about.

Just to clarify what those links I shared, that you dismissed, made reference to is the assessment that Fram utilizes a lower bypass spec because it is unnecessary as the XG7317 possesses a flow rate that negates the need for a higher bypass spec. The next time I feel the compulsion to share some common sense with you perhaps I need ask your permission.
 
The service manual for an 09 Legacy calls for the oil filter to open at 23.2 psi. It seems like Subaru calls for this spec on its newer models, as they've called for higher bypass numbers consistently in the past.
I too would love to know the rationale for this.
 
Pretty crazy how some have zero to little experience, yet take one number and proclaim it as gospel even in the face of data and relevant information. I agree, only a couple filters "meet" the 27psi bypass, but then again, it's only relevant when the filter in question is the original, OEM filter. If the flow rate of the media is such that the subject filter never reaches 13psid before the factory filter reaches 27psid, you're obviously talking out of the mouth you sit on, because the 13psid filter would offer complete filtration after the 27 was already in bypass.

OP, ignore the haters. Fram says the 7317 is the correct application for this engine, and if it wasn't, they'd have changed it by now since removing an application is cheaper than class-action lawsuits. So, use it if you want!
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Originally Posted by SubieRubyRoo
. . . you're obviously talking out of the mouth you sit on . . .


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Originally Posted by gathermewool
Originally Posted by geeman789
Let me summarize for you ...

For turbo's, the higher by-pass setting MIGHT matter, in a poorly maintained engine, where the turbo screen bolts MIGHT get clogged, if there were too many by-pass events with REALLY dirty oil and filter. MAYBE.

In a non-turbo engine, it won't make any difference.


That being said, the WIX 7055's are well built, and have the " correct " by-pass setting. They work, and you don't need to stress about the Subaru by-pass spec.



Huh!?

If the turbo screen clogs, it will increase ALL upstream pressure, meaning there won't be ANY appreciable change in differential pressure across the filter.

The dP across the filter is based on the flow rate of oil (engine/oil pump speed), the viscosity of the oil and the makeup of the filter.



Sure ...

Turbo screens get clogged when too much junk goes thru the filter ( or comes OUT of the filter ... ), goes into the oil circuit, and reaches the stupidly fine wire banjo bolt screens, clogging them up and restricting oil flow to the turbo. Which is bad.

The higher by-pass valve pressure DECREASES the number and duration of by-pass events, meaning there is less chance of filter debris getting washed off of the filter media and pushed thru the oil circuit.

This is another reason why some prefer a base end by-pass valve vs a dome end by-pass. Theoretically, IF the filter by-passes oil, a base end by-pass filter should minimize the possibility of any sludge / debris already caught in the pleats from getting washed out and pushed thru the by-pass valve. Maybe ...

Reasonably well maintained engines won't have this issue, because the oil never gets that used up and dirty, and the filter never builds up much junk. So when the filter does by-pass some oil, it's not really that dirty anyway ...

Again, on a non-turbo engine, maintained reasonably well, the oil filter by-pass pressure setting seems less critical. A lower by-pass setting MIGHT allow for more frequent and longer duration by-pass events, but given the oil and filter aren't really that dirty, nothing bad will happen. Obviously FEWER by-pass events are better, but letting some reasonably clean oil go thru unfiltered won't break stuff.

The oil filter by-pass valve is there to prevent a big pressure spike from tearing thru the filter media. It is better to allow some unfiltered oil thru and keep the filter media intact, instead of allow a pressure spike to destroy the media, allowing unfiltered oil thru 100 % of the time.

For those who don't know what a screened turbo bolt, or banjo bolt looks like, here is a pic ...

[Linked Image]
 
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Fram also specifies its lowest end filter the orange can of PH7317 for these same Subaru applications. What? It opens at 9-15 PSI. Do you attribute all of the wondrous properties of the Fram Extra Guard filter to the orange PH7317 too? No? Then why does Fram also recommend their lowest end filter that bypasses as low as 9 PSI, for this same high pressure, high volume Subaru engine? Never mind the hilarious straw man that the brand must be right or else the brand would be sued. That is just a dodge. Is the 9 PSI bypass valve recommended by Fram a sound choice? You sure place a lot of faith in Fram's fitment guide.


Again, show any Fram oil filter that meets the Subaru bypass spec, and you can keep the dumb veiled insults too while you're at it. Unimpressive. I am not saying there can be no Fram part number that meets the spec. There just might be one. However claiming that 13 PSI is dandy because the valve never opens is dubious. It is not limited to Fram either. In fact I would keep brand love out of this topic altogether. The spec that the Subaru drivetrain engineers spec'ed when they designed the engine applies to all aftermarket applications. The spec that whichever various vendors that bid for the OEM filter contract in various countries all had to meet. There are also at least two other aftermarket brands that meet it.
 
You have to understand that the poster is one of a long history of various user names that just comes on here to cause dissension and controversy. Many of the names have been banned in the past but of course new ones have been made.

Originally Posted by Ignatius
Originally Posted by wdn
Ignatius, Fram XG7317 does not meet the Subaru spec. Specs are specs. I don't know who appointed you the project historian for Bob, but a bunch of old threads are immaterial. In any case nobody is shooing me off this one. If you would care to identify some other aftermarket filters that do meet the spec, by Fram or others go ahead.

Today's topic is " Subaru and 27psi bypass Filter selection".
I appreciate your condescending remarks, perhaps you should realize that this very subject has been discussed ad nauseam over and over and over and over again and you have simply repeated the same bypass drivel that keeps getting regurgitated. If you need instructions on how to utilize the search function just ask.

Frankly speaking you might want to actually read through the thread as I clearly stated my recommendation for Wix/Napa Gold bypass spec friendly oil filters in my post that immediately preceeded your post where you spouted off the same tired nonsense about the Xg7317 that you are apparently ill informed about.

Just to clarify what those links I shared, that you dismissed, made reference to is the assessment that Fram utilizes a lower bypass spec because it is unnecessary as the XG7317 possesses a flow rate that negates the need for a higher bypass spec. The next time I feel the compulsion to share some common sense with you perhaps I need ask your permission.
 
It seems logical that the bypass is set by the filter maker from an internet poster engineer's standpoint like me. But the fly in the ointment here is Subaru tells Fram to use a higher bypass in the filters they order from them. Wonder what Subaru engineers are thinking, seems it isn't yet known. Actual question here.
 
FWIW, my shelf is full of Napa Gold 7055s, even though it's technically for the FA/FB and I only own EJs at this point. Main reasons: it lists the finest filtration of the filters that fit (dubious Wix specs, I know, but nominal is 15 micron, 99%@21 supposedly), is built like a tank with great construction on multiple C&Ps, and during the Farm & Fleet sale they're only $3.50 each. Try as I might, I still fall back into the 1 OCI per filter, so it's the most cost-effective for me. About the only thing I would change is I'd like a P-type gasket, just because.

I like the Ultra and have no doubt it's likely the finest-filtering non-bypass filter available, and I use the ones I have, but I waste them since only twice have I gone 2+ OCIs on them. Fram Ultras are also the only filter that's ever left the gasket on the filter mount, even though I install them using exactly the same routine. However, since OP's filter is on top of the engine, there is little risk here so that's why I still stand by the XG. It's what I installed on my mom's '18 Forester the last time.
 
If valve issues were showing up in warranty, the many brands would change it. But it doesn't. So they don't.

And how does one prove the lower-opening PRV tanked an engine as long as said lower-opening PRV was functioning properly (i.e. didn't starve engine of oil and didn't fall apart)?? Again, where's the data? An oil filter is one of HUNDREDS of failure modes of an engine. But it just so happens to be one that [1] the OEM automotive engineer can't control and [2] is typically a cheap fix to get vehicles to squeak on past warranty mileage, so always prioritizes it as public enemy #1.
 
Crazy thought - but maybe Subaru specs a different filter media.

If Frams aftermarket media flow better than the requested spec from the manufacturer it makes complete sense that Fram would set the bypass lower on their aftermarket products while still meet Ming the same flow requirements as the OEM.
 
It makes a lot of sense Subaru may specify a more restrictive media in order to raise the bypass to 27. Rather than use Fram's bypass choice and their regular media.
 
What media is more restrictive than the most efficient media? AFAIK Fram Ultra has that title with its efficiency rating.

Also, the bypass is really determined by the media and construction in the filter....so why would an engine manufacturer specify such....is that even true? Or does it just happen to be the case with their own filter?
 
Originally Posted by tundraotto
What media is more restrictive than the most efficient media? AFAIK Fram Ultra has that title with its efficiency rating.


Just because a filter is efficient doesn't mean it's also flow restrictive. That's the beauty of full synthetic media.

Another miconception to add to the list.
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Originally Posted by geeman789
Originally Posted by gathermewool
Originally Posted by geeman789
Let me summarize for you ...

For turbo's, the higher by-pass setting MIGHT matter, in a poorly maintained engine, where the turbo screen bolts MIGHT get clogged, if there were too many by-pass events with REALLY dirty oil and filter. MAYBE.

In a non-turbo engine, it won't make any difference.


That being said, the WIX 7055's are well built, and have the " correct " by-pass setting. They work, and you don't need to stress about the Subaru by-pass spec.



Huh!?

If the turbo screen clogs, it will increase ALL upstream pressure, meaning there won't be ANY appreciable change in differential pressure across the filter.

The dP across the filter is based on the flow rate of oil (engine/oil pump speed), the viscosity of the oil and the makeup of the filter.



Sure ...

Turbo screens get clogged when too much junk goes thru the filter ( or comes OUT of the filter ... ), goes into the oil circuit, and reaches the stupidly fine wire banjo bolt screens, clogging them up and restricting oil flow to the turbo. Which is bad.

The higher by-pass valve pressure DECREASES the number and duration of by-pass events, meaning there is less chance of filter debris getting washed off of the filter media and pushed thru the oil circuit.

This is another reason why some prefer a base end by-pass valve vs a dome end by-pass. Theoretically, IF the filter by-passes oil, a base end by-pass filter should minimize the possibility of any sludge / debris already caught in the pleats from getting washed out and pushed thru the by-pass valve. Maybe ...

Reasonably well maintained engines won't have this issue, because the oil never gets that used up and dirty, and the filter never builds up much junk. So when the filter does by-pass some oil, it's not really that dirty anyway ...

Again, on a non-turbo engine, maintained reasonably well, the oil filter by-pass pressure setting seems less critical. A lower by-pass setting MIGHT allow for more frequent and longer duration by-pass events, but given the oil and filter aren't really that dirty, nothing bad will happen. Obviously FEWER by-pass events are better, but letting some reasonably clean oil go thru unfiltered won't break stuff.

The oil filter by-pass valve is there to prevent a big pressure spike from tearing thru the filter media. It is better to allow some unfiltered oil thru and keep the filter media intact, instead of allow a pressure spike to destroy the media, allowing unfiltered oil thru 100 % of the time.

For those who don't know what a screened turbo bolt, or banjo bolt looks like, here is a pic ...





Sorry for the late response. I understand your logic now and agree with everything you posted above.

I don't believe any modern turbo Subaru still utilizes a banjo-bolt screen at the turbo oil inlet. IIRC, and based on a response by bluesubie on NASIOC to a question I asked on the subject, I believe my '08 STI was one of the first turbo Subies to come WITHOUT any turbo supply line screen-type filter (aka banjo-bolt screen).
 
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