Can someone explain Relief Valve Setting to me?

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The 13 PSI refers to the pressure differential across the filter, not the total oil pressure. When the oil is cold, the filter element is clogged, or the oil pump is moving more oil (high RPMs), the relief valve opens to prevent the can from being overpressurized and bursting.
 
It opens at 13 psi(+/-) DIFFERENTIAL, meaning there is 13psi MORE "buildup" in the outer filter can, than the simultaneous & instantaneous pressure at the filter OUTLET. Simply, the filter in this mode would be "throttling" the oil flow. COuld be caused by partially blocked filter media or a high oil pressure spike caused by a high RPM downshift and throttle blip.
 
Originally Posted By: ARCOgraphite
It opens at 13 psi(+/-) DIFFERENTIAL, meaning there is 13psi MORE "buildup" in the outer filter can, than the simultaneous & instantaneous pressure at the filter OUTLET. Simply, the filter in this mode would be "throttling" the oil flow. COuld be caused by partially blocked filter media or a high oil pressure spike caused by a high RPM downshift and throttle blip.


Or by pushing very cold (Therefore thick) oil through the filter media, before the engine warms up.
 
That's exactly what it means.

From what I understand, you want the same pressure on both sides of the filter. (Lets say A and B.) When the pressure of point A (inlet) becomes larger than the pressure at point B (outlet), the filter will go into bypass assuming it reaches 13 psi. This will keep the engine from being starved of oil. "Dirty" oil is better than no oil.

So many filters have bypass ratings at 9 psi through 13 psi.. Ideally you'd want a filter that has the exact settings as the OEM filter, but many here will argue a filter with say 9 psi and a filter with 13 psi will behave nearly identically and the filters will be interchangeable.

Using a filter that bypasses at say 35 psi on a vehicle who's OEM bypasses at say 12 psi would be asking for trouble though IMO.
 
Which factors do manufacturers consider when they spec the the PSI range for the valve to operate at?

Are there benefits to going higher or lower than recommended?
 
Originally Posted By: Olas
Which factors do manufacturers consider when they spec the the PSI range for the valve to operate at?

Are there benefits to going higher or lower than recommended?


Most manufacturers are in the 9-13 psi range.....The only serious outlier I am aware of is Subaru, which specs about 21 psi.

Only the engineer who specced it knows for certain how he/she arrived at the figure. No real advantage to lower or higher.

If you run oil of the proper grade, and change the oil and filter at reasonable intervals, plus avoid revving the engine to high RPM on cold starts, it is very possible to never nudge the bypass open. Which is what you really want. On the other hand, even unfiltered oil is better than no oil, if you are an engine bearing.
 
There are more advantages to a threaded end bypass than going with something different than the stock setting.
 
Originally Posted By: 4wheeldog
Most manufacturers are in the 9-13 psi range.....The only serious outlier I am aware of is Subaru, which specs about 21 psi.


Not to get all BITOG nitpicky on you, but (some) Audi's have about a 35 psi bypass setting. The OEM filter for my dads A4 is apparently equivalent to others that my Jeep takes, who's OEM bypass is around 12 psi. The M1-204 for my Jeep can be used on the Audi actually.
21.gif


I wouldnt dream of running that filter on my Jeep and I wouldnt dream of running my Jeeps filter on that Audi. The Audi would always be in bypass and my Jeep would be starved from oil.
 
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Originally Posted By: Rand
There are more advantages to a threaded end bypass than going with something different than the stock setting.


This i am unaware of. Can you elaborate?
 
It always bothers me when people talk about filter bypass setting as if it pertains to the car itself.... It doesn't. Filter bypass is based on the filter and it's design. Things like flow rate and media strength are what determine the bypass pressure. If it's set too high the media will be crushed. Has nothing to do with the car. Don't think too far into it. Different filters for the same car will have different bypass settings because each filter is a little bit different
 
Originally Posted By: SnowDrifter
It always bothers me when people talk about filter bypass setting as if it pertains to the car itself.... It doesn't. Filter bypass is based on the filter and it's design. Things like flow rate and media strength are what determine the bypass pressure. If it's set too high the media will be crushed. Has nothing to do with the car. Don't think too far into it. Different filters for the same car will have different bypass settings because each filter is a little bit different


Then why is it that a couple of car manufacturers (Subaru, and apparently, Audi) specify a relief setting way outside the norm? It ain't because the filters are built differently.....
 
Originally Posted By: dlundblad
Originally Posted By: Rand
There are more advantages to a threaded end bypass than going with something different than the stock setting.


This i am unaware of. Can you elaborate?


some people think threaded-end bypass is "better" because when the filter does go into bypass, the oil makes a quick turn and goes immediately back out of the filter without passing through the media or through the space around the media. Dome-end bypass valves make the oil flow around the outside of the filter element from the base end to the dome where it enters the byapss valve then goes right back out through the center tube without going through the media.

The belief is that a dome-end bypass could allow some trapped dirt to get swept off the filter surface and back into the engine. I don't believe this personally, because all the trapped stuff will be firmly pressed to the media because the differential pressure across the media will, by DEFINITION, be at the bypass pressure before the bypass valve opens. Its not going anywhere.
 
I propose that there IS junk (substantial particulate) settled at the dome on vertically mounted filters and the flow pattern change - in bypass - will surely wash some of that BIG stuff right into the mains. Streaking a main or rod bearing should be no biggie, but cars with stationary micro HLA in the valvetrain may be a different animal subject to these paranoia-driven ills.
 
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Originally Posted By: ARCOgraphite
I propose that there IS junk (substantial particulate) settled at the dome on vertically mounted filters and the flow pattern change - in bypass - will surely wash some of that BIG stuff right into the mains. Streaking a main or rod bearing should be no biggie, but cars with stationary micro HLA in the valvetrain may be a different animal subject to these paranoia-driven ills.


Not impossible... but I have opened a lot of filters and so far have *never* seen anything settled into the dome-end.
 
Originally Posted By: ARCOgraphite
I propose that there IS junk (substantial particulate) settled at the dome on vertically mounted filters and the flow pattern change - in bypass - will surely wash some of that BIG stuff right into the mains. Streaking a main or rod bearing should be no biggie, but cars with stationary micro HLA in the valvetrain may be a different animal subject to these paranoia-driven ills.


After seeing numerous cars go 300k miles or more using a dome end down, dome end bypass... in a cold winter city...

I conclude that it really makes no difference....

If it was a huge problem, filter makers wouldn't put it there...
 
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