Bypass PSI specs

[ZeeOSix]

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.

I must have missed it, because I don't see anything the OP posted that talks about the oil pump pressure relief setting and how it might effect the filter bypass valve. The filter bypass valve doesn't care what the oil pressure is, it only cares what the delta-p is across the media. There could be 1 GPM of oil flow at 200 PSI of oil pressure and the delta-p across the media would be super low (like 1 PSI) and nowhere close to making the bypass valve open. Or there could be 15 GPM of flow at 20 PSI of oil pressure, and that would most likely cause the filter bypass valve to open (depending on the oil viscosity of course). Those are examples for illustration, not necessarily what any specific engine operates at.

Concur on your last sentence.

 

[Snagglefoot]

I must have missed it, because I don't see anything the OP posted that talks about the oil pump pressure relief setting and how it might effect the filter bypass valve. The filter bypass valve doesn't care what the oil pressure is, it only cares what the delta-p is across the media. There could be 1 GPM of oil flow at 200 PSI of oil pressure and the delta-p across the media would be super low (like 1 PSI) and nowhere close to making the bypass valve open. Or there could be 15 GPM of flow at 20 PSI of oil pressure, and that would most likely cause the filter bypass valve to open (depending on the oil viscosity of course). Those are examples for illustration, not necessarily what any specific engine operates at.

Concur on your last sentence.

And I concur with this as well. However, if an engine is redesigned and now uses a higher volume pump for any reason, a person should pay attention to what the OE recommended bypass pressure is. The redesign of the Chevy 5.3 LS engine in 2014 incorporated a higher rate variable pressure pump resulting in a redesigned filter with a higher bypass pressure. A person can ignore that if they want. Up to them.

 

[ZeeOSix]

And I concur with this as well. However, if an engine is redesigned and now uses a higher volume pump for any reason, a person should pay attention to what the OE recommended bypass pressure is. The redesign of the Chevy 5.3 LS engine in 2014 incorporated a higher rate variable pressure pump resulting in a redesigned filter with a higher bypass pressure. A person can ignore that if they want. Up to them.

Agree ... delta-p across the filter media is a function of oil flow volume (and viscosity of course), so yes if the oil pump is putting out more flow then the delta-p will be increased, and hence the bypass valve should also be increased if deemed by engineering not to be enough bypass setting headroom at the most extreme use conditions.

 

[4WD]

And I concur with this as well. However, if an engine is redesigned and now uses a higher volume pump for any reason, a person should pay attention to what the OE recommended bypass pressure is. The redesign of the Chevy 5.3 LS engine in 2014 incorporated a higher rate variable pressure pump resulting in a redesigned filter with a higher bypass pressure. A person can ignore that if they want. Up to them.

Yessir … my pressure can be very low sitting at a red light … and a few seconds later hit a high pressure … a few seconds later settle in at the cruising pressure in between

 

[garageman402]

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 oth

I must have missed it, because I don't see anything the OP posted that talks about the oil pump pressure relief setting and how it might effect the filter bypass valve. The filter bypass valve doesn't care what the oil pressure is, it only cares what the delta-p is across the media. There could be 1 GPM of oil flow at 200 PSI of oil pressure and the delta-p across the media would be super low (like 1 PSI) and nowhere close to making the bypass valve open. Or there could be 15 GPM of flow at 20 PSI of oil pressure, and that would most likely cause the filter bypass valve to open (depending on the oil viscosity of course). Those are examples for illustration, not necessarily what any specific engine operates at.

Concur on your last sentence.

I said it was in post #11, not the OP

 

[garageman402]

I must have missed it, because I don't see anything the OP posted that talks about the oil pump pressure relief setting and how it might effect the filter bypass valve. The filter bypass valve doesn't care what the oil pressure is, it only cares what the delta-p is across the media. There could be 1 GPM of oil flow at 200 PSI of oil pressure and the delta-p across the media would be super low (like 1 PSI) and nowhere close to making the bypass valve open. Or there could be 15 GPM of flow at 20 PSI of oil pressure, and that would most likely cause the filter bypass valve to open (depending on the oil viscosity of course). Those are examples for illustration, not necessarily what any specific engine operates at.

Concur on your last sentence.

Wait a minute, YOU posted #11, and you 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."

 

[ZeeOSix]

Wait a minute, YOU posted #11, and you 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."

Yes, I did say that - but the OP never mentioned anything about the pump pressure relief like you made it sound like in post #20. You said: "The poster suggested that if the filter bypass valve setting was higher than the oil pump pressure relief valve there would be problems."

Just who is "the poster" you are referring to if it's not the OP?

And that statement I made about the PD going into pressure relief holds true regardless of what's causing the oil pump to go into pressure relief. So what's the point you're trying to make?

 

[garageman402]

"The poster" I am referring to is you. In post #19, I stated: "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"". I had set the premise that I was referring to your post (#11) in my statements.

I was essentially agreeing with both of your subjects: (1) The oil pump pressure relief valve is going to be way higher than any filter bypass valve setting, and (2) "if" the filter bypass valve happened to be higher than the pressure relief valve in the pump it could cause decreased oil flow to the engine.

I would take (2) a step further and suggest there could be NO oil flow to the engine if the pump relief was lower than the bypass setting. In this hypothetical situation, lets say the filter bypass is 22, and the oil pump relief is 20. This situation is presuming the filter media is so plugged up that it is creating a 22psi differential, AND/OR the oil is so thick, that it is creating a 22psi differential across the media. Upon startup, the pressure throughout the system is zero. The oil pump starts sending oil the the filter, which is not allowing any flow until the system pressure attempts to reach 22psi. The pump relief is opening at 20psi, not allowing the 22psi differential to be reached, and the engine starves for oil.

I was giving the lowest oil pump relief pressure I could think of (35-40psi), to note that in all probability the oil pump relief is higher than the filter bypass setting.

I would expect lower oil pump relief pressures to be developed (if they haven't been already) to reduce engine load and increase fuel economy. Post #22 suggests this has already happened. We know that a PD oil pump has to have a relief, because if it didn't, the pressure theoretically would be infinite if the oiling system could not pass the entire volume of the pump output. This would either stall the engine or break something (oil pump drive shaft, stripped gears, etc). A pump trying to pass oil through with 80-100psi of back pressure will pass all the volume with enough released to keep the maximum pressure at 80-100. The pump is still fighting against this pressure and using energy to do it.

My suggestion in post #13 is based on the assumption that tighter tolerances, or more accurately, tighter clearances would cause the pump to bypass more oil through the relief valve, thereby reducing flow. As the engine wears, less oil is relieved so more flow is achieved. This is the increased flow I was referring to. You suggest that the oil pump relief valve almost never opens, I disagree with that.

If you have a pressure gauge, and you know for a fact that the pump relief is set at 100, and your gauge never gets over 80, then I would agree the relief valve never opens. That would tell me the pump is delivering maximum flow to the engine under current condition. There is no reserve. As the engine wears, pressure will surely drop. Some put higher viscosity oil in to "boost" the pressure, this will accomplish that, but flow will suffer if that gauge hits 100 in our hypothetical situation here, suggesting oil is now being relieved and flow is dropping. In real life, most vehicles do not have oil gauges, they have a light or a DIC message saying low oil pressure. Most of the time, we are guessing and assuming. If you have a gauge, on a very cold startup you can probably assume the relief valve is open. That is your reference point for opening pressure. If the gauge is pegged, you still don't know, but you can assume that when that gauge starts to drop the valve is closed.

I think most oil pressure sending units are BEFORE the filter, so an increase in pressure may suggest increased resistance through the filter up until the bypass opens. Once again flow will be the same, as the restriction will cause more pressure to be needed to push through the media. This of course assumes the relief valve is remaining closed. All of this is variable, depending on viscosity due to temperature or actual oil viscosity. You would have to have the oil at the same temp and vis to use pressure changes as a guide to filter restriction, once again, guessing and assuming......

 

[ZeeOSix]

"The poster" I am referring to is you. In post #19, I stated: "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"". I had set the premise that I was referring to your post (#11) in my statements.

I was essentially agreeing with both of your subjects: (1) The oil pump pressure relief valve is going to be way higher than any filter bypass valve setting, and (2) "if" the filter bypass valve happened to be higher than the pressure relief valve in the pump it could cause decreased oil flow to the engine.

You might want to clarify who you're actually responding to in your post, or better yet use the quote function and quote who you're responding to so there isn't any confusion. Anyway, there should be no engine that has a pump pressure relief set lower than the filter bypass valve - that wouldn't make any engineering sense. Like said before, every engine I've ever seen has a pump pressure relief set to 80+ PSI.

I would take (2) a step further and suggest there could be NO oil flow to the engine if the pump relief was lower than the bypass setting. In this hypothetical situation, lets say the filter bypass is 22, and the oil pump relief is 20. This situation is presuming the filter media is so plugged up that it is creating a 22psi differential, AND/OR the oil is so thick, that it is creating a 22psi differential across the media. Upon startup, the pressure throughout the system is zero. The oil pump starts sending oil the the filter, which is not allowing any flow until the system pressure attempts to reach 22psi. The pump relief is opening at 20psi, not allowing the 22psi differential to be reached, and the engine starves for oil.

That situation won't ever happen because oil pump relief valves are never set lower than the filter bypass valve - if they are, it's a total engineering fail. Assuming that oil pump pressure relief valves are set lower than filter bypass valves has just made the conversation convoluted and non-realistic.

I think most oil pressure sending units are BEFORE the filter, so an increase in pressure may suggest increased resistance through the filter up until the bypass opens. Once again flow will be the same, as the restriction will cause more pressure to be needed to push through the media. This of course assumes the relief valve is remaining closed. All of this is variable, depending on viscosity due to temperature or actual oil viscosity. You would have to have the oil at the same temp and vis to use pressure changes as a guide to filter restriction, once again, guessing and assuming......

Every vehicle I've seen has the oil pressure sensor after the oil filter, so in that case a more restrictive oil filter will not be seen as a change in oil pressure, except only if the pump is in pressure relief. If you research it, you would be looking long and hard to find any factory vehicle with the oil pressure sensor placed before the oil filter. The only time a more restrictive oil filter (when the oil pressure sensor is after the filter) effects oil pressure and can be seen on an oil pressure gauge is when the oil pump goes into pressure relief. If the sensor was before the filter, then yes I agree you'd see a change in pressure if the filter became more or less restrictive - but the sensor is after the filter on every vehicles I've ever seen or researched.

 

[garageman402]

You might want to clarify who you're actually responding to in your post, or better yet use the quote function and quote who you're responding to so there isn't any confusion. Anyway, there should be no engine that has a pump pressure relief set lower than the filter bypass valve - that wouldn't make any engineering sense. Like said before, every engine I've ever seen has a pump pressure relief set to 80+ PSI.

I hit the reply arrow at the bottom of your post, but it doesn't quote, my mistake. I see I have to highlight what I want to quote, then hit the reply balloon in that highlight.

That situation won't ever happen because oil pump relief valves are never set lower than the filter bypass valve - if they are, it's a total engineering fail. Assuming that oil pump pressure relief valves are set lower than filter bypass valves has just made the conversation convoluted and non-realistic.

Actually you initiated this assumption in post #11

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.

Above quote from you in post #11

Every vehicle I've seen has the oil pressure sensor after the oil filter, so in that case a more restrictive oil filter will not be seen as a change in oil pressure, except only if the pump is in pressure relief. If you research it, you would be looking long and hard to find any factory vehicle with the oil pressure sensor placed before the oil filter. The only time a more restrictive oil filter (when the oil pressure sensor is after the filter) effects oil pressure and can be seen on an oil pressure gauge is when the oil pump goes into pressure relief. If the sensor was before the filter, then yes I agree you'd see a change in pressure if the filter became more or less restrictive - but the sensor is after the filter on every vehicles I've ever seen or researched.

I remember seeing a sender mounted right on the filter mounting base, but I can't remember what vehicle. I'll research this more, thanks.

 

[ZeeOSix]

Actually you initiated this assumption in post #11

Here's what I said in post #11.
"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."

Let me clarify the context of my point in post #11, specifically the 2nd sentence. The first sentence if pretty self explanatory.

First off, the pump's pressure relief valve and the oil filter's bypass valve are not connected functionally, meaning one doesn't actually cause the other to operate. The filter's bypass valve operates solely on the delta-p developed across the media, and at any given point in time the delta-p across the media is based on: 1) the oil flow volume, 2) the oil viscosity and 3) the flow resistance of the media, which can change as it loads up with debris. The maximum delta-p across the media will be with thick oil and high oil flow (ie, high engine RPM), and a loaded oil filter. It's a point that is rarely obtainable, and typically in short term on a street car. Regardless, it can happen given the right conditions.

What I'm saying is if an oil pump pressure relief valve is set to 80 PSI (for example), and a filter bypass valve is set to 22 PSI, it could be possible that the oil pump would hit pressure relief before the filter hit bypass. It would of course depend on the volumetric output of the pump and the delta-p vs flow curve of the oil filter. It would also depend on the engine oiling system's delta pressure vs PD output flow curve. In other words, some engines will build more oil pressure than others given the same oil flow volume, depending on the overall oiling system design. So if an engine produced and built-up oil pressure quickly with a relatively small change in oil volume flow coming out the PD pump, and the filter had a high bypass valve setting, then it could be possible that the pump's pressure relief valve would open before the filter bypass valve opened under those rare high delta-p conditions. On the other hand, If the filter bypass valve was set lower (12 PSI for example), then the filter bypass would most likely open before the pump hit pressure relief, and therefore no oil volume would be lost going to the engine.

That's all that one sentence is implying. Bottom line is the higher the filter bypass valve is set, the more likely it is (given the right conditions) that the pump could hit pressure relief before the filter hits bypass. It depends on a lot of factors, but my comment was implying that it could happen.

 

[garageman402]

What I'm saying is if an oil pump pressure relief valve is set to 80 PSI (for example), and a filter bypass valve is set to 22 PSI, it could be possible that the oil pump would hit pressure relief before the filter hit bypass. It would of course depend on the volumetric output of the pump and the delta-p vs flow curve of the oil filter. It would also depend on the engine oiling system's delta pressure vs PD output flow curve. In other words, some engines will build more oil pressure than others given the same oil flow volume, depending on the overall oiling system design. So if an engine produced and built-up oil pressure quickly with a relatively small change in oil volume flow coming out the PD pump, and the filter had a high bypass valve setting, then it could be possible that the pump's pressure relief valve would open before the filter bypass valve opened under those rare high delta-p conditions. On the other hand, If the filter bypass valve was set lower (12 PSI for example), then the filter bypass would most likely open before the pump hit pressure relief, and therefore no oil volume would be lost going to the engine.

I see your point now, thanks for clarifying. The extra pressure needed to open the filter bypass valve might be enough to push the pressure relief valve open, thereby losing oil volume.

 

[bullwinkle]

Or, if your oil pump is worn enough that it can't maintain oil pressure above the filter bypass PSI, there's a chance that a plugged filter might cause oil starvation. The 6.0 LS in the Express in my sig has somewhat low oil pressure, probably because Hertz & its' other PO couldn't seem to use Dexos oil in it, so ~20 PSI at hot idle in drive is about all she's got.

 

[2016 Outback]

This is what GM says.

 

[garageman402]

The 6.0 LS in the Express in my sig has somewhat low oil pressure, probably because Hertz & its' other PO couldn't seem to use Dexos oil in it, so ~20 PSI at hot idle in drive is about all she's got.

I think those engines have lower oil pressure than we are expecting. The 2020 Express chassis in my signature has low oil pressure too. We got it last month, new, but driven to CA from IN, so it had 2300 (+/-) miles on it. I assume it has factory fill. Of course, the first thing I did was change the oil. The RV is considered a 2021, but the chassis is actually a 2020 (build date 12/19), so 1 year old oil. I filled the filter up to the top, which is easy to install, as it mounts vertically. I cranked over in flood clear mode to bring up the pressure. Seemed like I cranked it a long time, pressure never showed on the gauge. After starting it seemed to take a long time to start showing pressure. I plan to change it again after the next short trip (12 mi) and back (24 mi total) to the dealer next month, I will crank a little longer and check the actual time for pressure to register.

Edit: Sorry, I didn't see that your Express is 2011, before the GM bulletin's year coverage. Maybe my 2020 is completely different?

 

[garageman402]

This is what GM says.

Interesting. The oil filter I replaced, which I assume was from the factory, was a PF-48 (not 'e'). I replaced it with the larger size Purolator One PL22500. When I do the second oil change I referred to in the last post, I am installing a Boss PBL 22500. I believe they both have the 22psi bypass.

 

[ZeeOSix]

Edit: Sorry, I didn't see that your Express is 2011, before the GM bulletin's year coverage. Maybe my 2020 is completely different?

Not sure when GM started using the variable volume oil pump, but that could certainly make oil pressure different than the old traditional oil pumps.

 

[4WD]

Not sure when GM started using the variable volume oil pump, but that could certainly make oil pressure different than the old traditional oil pumps.

My first was a 2013 4 banger … think the V8’s got them in 2014 … my first in V8’s were 2017/2018 …
Pretty common in various brands now like my V6 Jeep. … kinda snuck in like electric power steering did …

 

[garageman402]

Not sure when GM started using the variable volume oil pump, but that could certainly make oil pressure different than the old traditional oil pumps.

So cranking the engine in “flood clear” mode won’t bring up oil pressure? How long should I crank (if at all) to prime the system after an oil change before starting it? Computer controlled throttle is brutal on startup, I like to get all the air out.