Does 23psi bypass seem high?

[rcy]

Just curious. That's the psi setting for the bypass on the Subaru filter for a 2001 H6. I don't know who makes their filters, but the Wix filter recommended for this car only has a bypass setting of 8-11psi. How can there be such a difference between the two filters? What are the pros and cons of the higher setting vs the lower setting?

Thanks.

 

[Steve S]

I would guess Subaru likes the 23psi. engine mfgs also have higher bypass pressures.

 

[INDYMAC]

For engine safety reasons, I would have to assume that the filter media has incredibly high flow properties to allow for a 23psi differential setting. Maybe the engine oil bypass system picks up the slack?

 

[Gary Allan]

I'd say that it's a reinforced media to sustain the differential (maybe not). I'd say that it also has a high pressure relief setting on the oil pump.

Wix seems to think it can use the standard setting (which is odd for WIX if the application calls for an unusually high bypass setting - look up VW/Audi).

Interesting side note. When you try and seek H6 engines in the WIX filter finder, you get no 2001 options. When you hit the last H6 (3.6) you get 2008 model year. The 2.7 and 3.3 do not exist in 2001 as far as Wix is concerned.

 

[n8wvi]

Originally Posted By: Gary Allan
Interesting side note. When you try and seek H6 engines in the WIX filter finder, you get no 2001 options. When you hit the last H6 (3.6) you get 2008 model year. The 2.7 and 3.3 do not exist in 2001 as far as Wix is concerned.
The 2001 was a 3.0

Dave

 

[rcy]

Originally Posted By: Gary Allan
I'd say that it's a reinforced media to sustain the differential (maybe not). I'd say that it also has a high pressure relief setting on the oil pump.

Wix seems to think it can use the standard setting (which is odd for WIX if the application calls for an unusually high bypass setting - look up VW/Audi).

Interesting side note. When you try and seek H6 engines in the WIX filter finder, you get no 2001 options. When you hit the last H6 (3.6) you get 2008 model year. The 2.7 and 3.3 do not exist in 2001 as far as Wix is concerned.


If you do a search by vehicle instead - look under the Outback, because it's the only vehicle in 2001 that had the H6, you'll see filters listed for the H4 and the H6 (for some reason, Wix lists the 6 cyclinder as a V, but it is an H.

http://www.wixfilters.com/filterlookup/i...1&TempYear=2001

The pressure relief setting on the oil pump is 185 psi.

Next oil change (sometime in the fall probably), I'll cut open the Subaru filter and see what the inside looks like. I hope it's not a Fram painted white.

 

[Gary Allan]

Quote:
The pressure relief setting on the oil pump is 185 psi.


That would be one REALLY HIGH pressure limit for any engine. Are you sure it's not 85psi? You do have a fancy OCV (oil control valve) that runs your variable valve timing, but that should be independent of your oil pump relief setting.

 

[Shannow]

The Z63 (local parlance) for my BMW is set around 23psi.

Pulled it apart and found very standard looking internals.

Switched to Z9 (standard Ford)

 

[rcy]

Originally Posted By: Gary Allan
Quote:
The pressure relief setting on the oil pump is 185 psi.


That would be one REALLY HIGH pressure limit for any engine. Are you sure it's not 85psi? You do have a fancy OCV (oil control valve) that runs your variable valve timing, but that should be independent of your oil pump relief setting.


That's per the service manual.

http://www.ej207.com/files/Subaru%20Fact...T0203A11391.pdf


Interesting - I just noticed that there is 1 litre of oil left in the motor somewhere when doing an oil and filter change.

 

[Gary Allan]

Originally Posted By: rcy
Originally Posted By: Gary Allan
Quote:
The pressure relief setting on the oil pump is 185 psi.


That would be one REALLY HIGH pressure limit for any engine. Are you sure it's not 85psi? You do have a fancy OCV (oil control valve) that runs your variable valve timing, but that should be independent of your oil pump relief setting.


That's per the service manual.

http://www.ej207.com/files/Subaru%20Fact...T0203A11391.pdf


Interesting - I just noticed that there is 1 litre of oil left in the motor somewhere when doing an oil and filter change.



Looks like someone at Subaru didn't proof read the pdf file ..that's if my conversion chart is correct. http://www.sciencemadesimple.net/pressure.php
588 kilopascal (kPa) is equal to 85.28 psi

That's a pretty decent ceiling with a 23lb bypass filter setting. Now if you had a 40psi relief setting, then you could lose over half your flow due to filter resistance when in relief. Out of relief, the filter doesn't amount to much resistance at all.


..but it is interesting that it caches 1.1 quarts of oil somewhere in there.

 

[rcy]

OK...well that makes more sense then. Unless of course, they made the mistake in the other direction...hahaha.

Thanks for figuring that out.

 

[Gary Allan]

Originally Posted By: Shannow
The Z63 (local parlance) for my BMW is set around 23psi.

Pulled it apart and found very standard looking internals.

Switched to Z9 (standard Ford)


I really never got the Euro high bypass valve thing to reason well in my head. Now the thing can surely open in rapid transitions where physics trumps mechanisms..but so?

I see no reason not to use a standard Ford filter

rcy: Now you have something to tell those on some Subbie board

 

[SubLGT]

Subaru also specifies a 23 psi opening pressure for the filter bypass in the 2.5L turbo motor in the 2005 Legacy. The oil pump relief valve is set at 85 psi. On my first start of the day, in the morning, I see an oil pressure of around 90-95 psi at idle.

Subaru also sets the oil pressure warning light at 2 psi. IMO this is too low to give adequate warning of impending doom.

 

[Gary Allan]

Quote:
On my first start of the day, in the morning, I see an oil pressure of around 90-95 psi at idle.


Are you using spec'd grade oil?

 

[SubLGT]

Originally Posted By: Gary Allan
Quote:
On my first start of the day, in the morning, I see an oil pressure of around 90-95 psi at idle.


Are you using spec'd grade oil?


Yes, 5W30 or 10W30. Once the oil is warmed up, idle oil pressure is around 20 psi.

 

[SubLGT]

Originally Posted By: Gary Allan
..................but it is interesting that it caches 1.1 quarts of oil somewhere in there.


Sounds in line for a 6 cyl Subaru motor. The 4 cyl turbo motor holds back 0.7 quart during an oil change.

 

[Gary Allan]

Originally Posted By: SubLGT
Originally Posted By: Gary Allan
Quote:
On my first start of the day, in the morning, I see an oil pressure of around 90-95 psi at idle.


Are you using spec'd grade oil?


Yes, 5W30 or 10W30. Once the oil is warmed up, idle oil pressure is around 20 psi.


Naturally, temp is a component here, but right off the bat your filter is seeing between 5-10 PSID at startup. Does it peak even higher as you move down the road cold? I'd suspect that it retreats rather quickly as the fluid starts moving more freely.

 

[SubLGT]

Originally Posted By: Gary Allan
..........Does it peak even higher as you move down the road cold? I'd suspect that it retreats rather quickly as the fluid starts moving more freely.


On a 20 degF winter morning, the oil pressure will max out at 105-110 psi during the first minute or two of driving, with Pennzoil Platinum 5W30. Based on what I have read on the Subaru forums, this is typical behavior for the 2.5L turbo motor

 

[SubLGT]

Originally Posted By: Gary Allan
.........Naturally, temp is a component here, but right off the bat your filter is seeing between 5-10 PSID at startup..........


I am currently using the EaO12 filter, which has a 8-11 psi bypass setting. Terry Dyson has informed me that based on UOA he sees no indication that this filter has been going into excessive bypass.

 

[Gary Allan]

As long as you're below relief, there's little chance of bypassing. The differential is the greatest when the flows are the most unlike each other. Your oil pump is producing an output. Some of that is not going to the engine. The "back pressure" produced on the engine side of the media is a product of the flow at that viscosity. The pressure on the upper side of the media is whatever the pump's limit pressure is (or greater).

Now in advanced loading, it will take longer to reach the negligible PSID that you'll see at full warm up ...but as long as you're below relief level, it's very hard to open the bypass valve. Now if you're flat shifting @ 7000 rpm and the oil has to change velocity faster than possible, the relief and the bypass provide "slack".

Bypass frequency has more to do with the span between your floor and ceiling on pressures. The broader the span ..the less likely it is to occur. If normal operating pressure is only slightly below the relief level, it will occur more often ..or at least have more opportunity to be in use.