Bypass PSI specs

[SugarMouth]

I have two oil filters, both identical but the bypass valve psi is 12psi on one and the other is 22psi. The filter that the vehicle calls for recommends the filter with a 22psi bypass valve. Would any harm be done running a 12psi bypass valve?

My guess is the 12psi in a 22psi recommendation might hang open too often? Thoughts?

 

[ZeeOSix]

Are both oil filters specified in the look-up tool from the maker for that same vehicle?

 

[SugarMouth]

I found my answer.

 

[kschachn]

Tighter engine tolerances? Where is that “Tech Tip” from?

 

[ZeeOSix]

Tighter engine clearances and increased oil pressure has nothing to do with the filter's bypass valve setting.

 

[kschachn]

That “Tech Tip” looks to be anything but.

 

[SugarMouth]

Tighter engine clearances and increased oil pressure has nothing to do with the filter's bypass valve setting.

Ok, help me understand why filters have different psi ratings on the bypass valve.

 

[SugarMouth]

Tighter engine tolerances? Where is that “Tech Tip” from?

https://www.bobistheoilguy.com/forums/threads/pf48-pf63-pf64-question.266969/

 

[ZeeOSix]

Ok, help me understand why filters have different psi ratings on the bypass valve.

An oil filter bypass valve setting is based on: 1) Flow resistance of the media. 2) Anticipated oil viscosity used. 3) Anticipated media loading and increased delta-p of the media in use. 4) Maximum oil volume output of the oil pump.

That's why 10 different oil filter brands for the same exact engine will have some variance in the bypass valve setting. If Filter A has less flow resistance (ie, less delta-p at X GPM) compared to Filter B, then Filter A doesn't need to have the bypass valve set as high as Filter B.

 

[SugarMouth]

An oil filter bypass valve setting is based on: 1) Flow resistance of the media. 2) Anticipated oil viscosity used. 3) Anticipated media loading and increased delta-p of the media in use. 4) Maximum oil volume output of the oil pump.

That's why 10 different oil filter brands for the same exact engine will have some variance in the bypass valve setting. If Filter A has less flow resistance (ie, less delta-p at X GPM) compared to Filter B, then Filter A doesn't need to have the bypass valve set as high as Filter B.

So with my initial question would you run a filter with a 12psi valve on a vehicle asking for a 22psi valve?

 

[ZeeOSix]

So with my initial question would you run a filter with a 12psi valve on a vehicle asking for a 22psi valve?

That's why I asked if the filter with the 12 psi bypass valve was specified by the filter maker for your exact vehicle in their look-up tool. If so, then I would trust it more.

IMO, when GM increased the bypass valve setting on their AC Delco filters, other filter makers did the same thing because it was easier to do that then to try and explain why their filter didn't need a lower bypass valve setting.

If the filter media can take it, a higher bypass valve setting isn't hurting anything, UNLESS the filter gets too loaded up and then it will take more loading (and delta-p) to make the bypass valve open. Only bad thing that could happen in that scenario is if the oil pump goes into pressure relief before the filter goes into bypass could cause some decrease oil flow to the engine oiling system.

 

[SugarMouth]

That's why I asked if the filter with the 12 psi bypass valve was specified by the filter maker for your exact vehicle in their look-up tool. If so, then I would trust it more.

IMO, when GM increased the bypass valve setting on their AC Delco filters, other filter makers did the same thing because it was easier to do that then to try and explain why their filter didn't need a lower bypass valve setting.

If the filter media can take it, a higher bypass valve setting isn't hurting anything, UNLESS the filter gets too loaded up and then it will take more loading (and delta-p) to make the bypass valve open. Only bad thing that could happen in that scenario is if the oil pump goes into pressure relief before the filter goes into bypass could cause some decrease oil flow to the engine oiling system.

Ok thanks! I'll stick with 22psi (as recommended) and use the other filters hopefully elsewhere.

 

[garageman402]

I would think the tighter tolerances would result in less flow, thereby allowing some filter restriction to be negligible to flow rates. Older, looser tolerances would require higher flow, so a smaller amount of restriction would reduce the flow enough to cause problems. Strength of media and core would have to be higher, I would assume that is taken into consideration with the higher bypass pressure. The question of increased flow with wear also arises, so would you change out to the lower psi setting with age? Most bypass occurs at cold startup, so I would think the higher bypass setting would be better as long as the media and core can withstand the increased pressure as I stated earlier. Of course, a dirty filter filters better than a clean filter, so the higher bypass pressure would force oil through a dirtier filter longer.

I think most oil pump pressure relief settings are 40psi or higher (maybe 35?), so 22 is well below that.

 

[ZeeOSix]

I would think the tighter tolerances would result in less flow, thereby allowing some filter restriction to be negligible to flow rates. Older, looser tolerances would require higher flow, so a smaller amount of restriction would reduce the flow enough to cause problems. Strength of media and core would have to be higher, I would assume that is taken into consideration with the higher bypass pressure. The question of increased flow with wear also arises, so would you change out to the lower psi setting with age? Most bypass occurs at cold startup, so I would think the higher bypass setting would be better as long as the media and core can withstand the increased pressure as I stated earlier.

Are you talking wear of the engine? It really doesn't matter how worn the engine is ... the positive displacement oil pump puts out what it puts out vs the engine RPM regardless of how worn the engine is. The reason oil pressure goes down with worn bearings is because the flow resistance is less, and therefore the same PD output volume takes less pressure to push the same oil volume through the oiling system. Oil pressure goes up with a PD oil pump putting X volume aat Y RPM through a more restrictive (ie, tighter bearing clearances) oiling system.

Of course, a dirty filter filters better than a clean filter, so the higher bypass pressure would force oil through a dirtier filter longer.

Not always true with oil filtes, and could be more filters decrease in efficiency as they get loaded up. It's been discussed why many times. Oil filters do no behave like air filters due to the much higher delta-p across oil filters.

I think most oil pump pressure relief settings are 40psi or higher (maybe 35?), so 22 is well below that.

Automotive oil pumps have a pressure relief more in the neighborhood of 80 to 100 PSI.

 

[garageman402]

Are you talking wear of the engine? It really doesn't matter how worn the engine is ... the positive displacement oil pump puts out what it puts out vs the engine RPM regardless of how worn the engine is. The reason oil pressure goes down with worn bearings is because the flow resistance is less, and therefore the same PD output volume takes less pressure to push the same oil volume through the oiling system. Oil pressure goes up with a PD oil pump putting X volume aat Y RPM through a more restrictive (ie, tighter bearing clearances) oiling system.

You are forgetting the pressure relief valve in the oil pump. It is PD until that valve opens, now it is pressure regulated. Some of the Positively Displaced oil is going out the relief valve, so the engine is only getting what it needs. As bearings wear, and flow resistance is less, more will flow to the bearings, and less will flow out the pressure relief. A higher flow through the filter is what will result.

Not always true with oil filtes, and could be more filters decrease in efficiency as they get loaded up. It's been discussed why many times. Oil filters do no behave like air filters due to the much higher delta-p across oil filters.

I realized after I re-read this, that forcing oil through may dislodge already trapped particles, making matters worse.

Automotive oil pumps have a pressure relief more in the neighborhood of 80 to 100 PSI.

Some big diesel engines are 35 i think, but my point was, it would be way above 22

 

[ZeeOSix]

You are forgetting the pressure relief valve in the oil pump. It is PD until that valve opens, now it is pressure regulated. Some of the Positively Displaced oil is going out the relief valve, so the engine is only getting what it needs. As bearings wear, and flow resistance is less, more will flow to the bearings, and less will flow out the pressure relief. A higher flow through the filter is what will result.

I'm well aware that PD oil pumps have a pressure relief valve ... so I'm not forgetting it at all. My point was that the only time a more worn out engine will be taking more flow from the PD pump is IF the pump was always running in relief, and then wasn't as the engine wore out and the oiling system flow resistance went down.

Pretty much every motor I've ever seen never hits pump pressure relief pressure when the oil is at full operating temperature, even if the engine is at or very near redline. Therefore what I said above in post #14 holds true, and in that case the engine would be getting the same oil volume regardless of the level of engine wear because the oil pump wasn't ever running in relief even when new.

I realized after I re-read this, that forcing oil through may dislodge already trapped particles, making matters worse.

Exactly ... studies have been done that show as oil filters load up and the delta-p increases, already trapped particles can be dislodged from the media. Some filter media is better and retaining already captured particles compared to others.

Some big diesel engines are 35 i think, but my point was, it would be way above 22

Your comment of: "I think most oil pump pressure relief settings are 40psi or higher (maybe 35?), so 22 is well below that." ... makes it sound like you believe the oil filter bypass valve operates dependent on the PD pump's relief valve setting - ??.

Not sure what you're meaning, but the filter bypass valve only operates due to the level of delta-p across the media (a function of oil flow, media resistance/loading and oil viscosity). The PD pump pressure relief valve only operates based on the total pump output supply pressure to the oiling system and is a function of flow against oiling system resistance. The full flow filter in the system is typically only about 7-10% of the total oiling system flow resistance. The main flow resistance in the oiling system is mainly from all the journal bearings (crankshaft, piston, cam(s)).

 

[garageman402]

Your comment of: "I think most oil pump pressure relief settings are 40psi or higher (maybe 35?), so 22 is well below that." ... makes it sound like you believe the oil filter bypass valve operates dependent on the PD pump's relief valve setting - ??.

Negative. I was responding to a comment in post number 11, where it was stated: "Only bad thing that could happen in that scenario is if the oil pump goes into pressure relief before the filter goes into bypass could cause some decrease oil flow to the engine oiling system"

 

[Job]

You may want to look up your engine to see if it has a variable oil pump. It may be getting so sensitive the oe filter is the only really correct filter. Bypass valves have a setting but it's a range of pressures. Some bypass valves may open faster than others due to the spring design. It's all getting more complicated. Here is a search for gm variable ol pumps, there is a whole lot of information.

https://www.google.com/search?client=firefox-b-1-d&q=gm+variable+displacement+oil+pump

 

[ZeeOSix]

Negative. I was responding to a comment in post number 11, where it was stated: "Only bad thing that could happen in that scenario is if the oil pump goes into pressure relief before the filter goes into bypass could cause some decrease oil flow to the engine oiling system"

So what do you actually mean when you say: ""I think most oil pump pressure relief settings are 40psi or higher (maybe 35?), so 22 is well below that."

Can you give an example? You're talking about the pump pressure relief at 35~40 PSI and the filter bypass valve at 22 PSI. How do you see them interacting with each other?

 

[garageman402]

I was clarifying that the pump pressure relief valve would be way above the filter bypass pressure. The poster suggested that if the filter bypass valve setting was higher than the oil pump pressure relief valve there would be problems. I was giving a very low end possibility as an example.

They in no way interact with each other.