Fluid dyamics discussion - someone educate me.....

[Brian_Bowers]

No... the M1 filter was new. 2 weeks ago I hit a chunk of concrete in the highway and that's when I noticed my pressure drop into the 30s. I was watching it closely for fear of a damaged filter or cracked oil pan. The fitler looked fine externally. But I was seeing high pressures in the 37-40 range.

So last weekend I changed the oil (the oil in the car was 11 months old) and put the M1 filter on. This resulted in the same 37-40 psi.

Then last night I put a new K&N on... so the M1 filter was never damaged at all, it's simply more restrictive than the K&N. The original K&N must have been jolted or jarred causing the original pressure drop at idle that sent me on this goose chase.

 

[jmac]

Now I understand

 

[440Magnum]

Originally Posted By: SuperBusa
Originally Posted By: BuickGN
I still have a hard time accepting that school of thought. I can see how 40% of the cooling may come from oil. But I have a few problems with the theory, maybe you can poke some holes in it.


The only way to make cooling worth while through removeing heat from the oil is to have an effective oil cooler. Just increasing the flow in an engine without an oil cooler isn't gonna do much to keep the temps down.


Yes and no... increasing oil spray to the bottom of the pistons (even without sprayer tubes- say by opening up the squirt holes in connecting rod big ends) will keep the undersides of the pistons cooler, even if it doesn't help OVERALL cooling. You can move heat away from a hot-spot with oil, even if you don't necessarily move it out of the engine itself with the oil. There are lots of areas inside the engine block where heat can flow from the oil TO the water jacket (the lifter valley and lower block skirt for example), so the heat removed from the undersides of the pistons eventually winds up going out the radiator even without an oil cooler.

 

[Gary Allan]

Originally Posted By: Brian_Bowers
Hold on... I think I may have just "gotten it". Are you guys saying that my oil pump is making enough pressure to always be in relief? That at idle the pump is putting out 52psi, but that by the time in goes down the oil galley, through the filter, and makes it to the presssure sensor it's dropped 12psi for the M1 filter and 2psi for the K&N?

(also posted this in my oil filter thread)


(mainly for others)


Suppose you had a 100psi relief limit (and the required disclaimer that your oil pump is of common efficiency - which is generally high) ..there would/could be NO alteration to flow. 100% of the sensible volume would be STILL reaching the sender/sensor as long as the pump is not seeing 100psi. Since you DID see alterations in pressure ..THERE HAD TO BE alterations in flow. For alterations in flow ..the flow had to be diverted to the relief.

Hence, to have a filter alter pressure readings below the filter ..the oil pump must be in relief.

There's not too much else to say about it.

Edit: This the point I keep trying to get most people to see (especially Soupahboosah as said by Jabba). The filter is virtually invisible under most sensible flows while the pump is NOT in relief. It's only in relief that a filter can show its comparative resistance in line. It is the relief act that makes it appear (actually revert to) a resistive state.

 

[BuickGN]

Originally Posted By: Gary Allan
Originally Posted By: Brian_Bowers
Hold on... I think I may have just "gotten it". Are you guys saying that my oil pump is making enough pressure to always be in relief? That at idle the pump is putting out 52psi, but that by the time in goes down the oil galley, through the filter, and makes it to the presssure sensor it's dropped 12psi for the M1 filter and 2psi for the K&N?

(also posted this in my oil filter thread)


(mainly for others)


Suppose you had a 100psi relief limit (and the required disclaimer that your oil pump is of common efficiency - which is generally high) ..there would/could be NO alteration to flow. 100% of the sensible volume would be STILL reaching the sender/sensor as long as the pump is not seeing 100psi. Since you DID see alterations in pressure ..THERE HAD TO BE alterations in flow. For alterations in flow ..the flow had to be diverted to the relief.

Hence, to have a filter alter pressure readings below the filter ..the oil pump must be in relief.

There's not too much else to say about it.

That makes sense. In this case do you think the high volume pump is unnecessary??

 

[Gary Allan]

Originally Posted By: BuickGN
Originally Posted By: Gary Allan
Originally Posted By: Brian_Bowers
Hold on... I think I may have just "gotten it". Are you guys saying that my oil pump is making enough pressure to always be in relief? That at idle the pump is putting out 52psi, but that by the time in goes down the oil galley, through the filter, and makes it to the presssure sensor it's dropped 12psi for the M1 filter and 2psi for the K&N?

(also posted this in my oil filter thread)


(mainly for others)


Suppose you had a 100psi relief limit (and the required disclaimer that your oil pump is of common efficiency - which is generally high) ..there would/could be NO alteration to flow. 100% of the sensible volume would be STILL reaching the sender/sensor as long as the pump is not seeing 100psi. Since you DID see alterations in pressure ..THERE HAD TO BE alterations in flow. For alterations in flow ..the flow had to be diverted to the relief.

Hence, to have a filter alter pressure readings below the filter ..the oil pump must be in relief.

There's not too much else to say about it.

That makes sense. In this case do you think the high volume pump is unnecessary??


In his case, his filter will always have premature elevated PSID from the get go. He'll reach filter bypass sooner all the time.

The high volume pump, if accompanied with a high relief setting and perhaps lower visc oil, would result in high volume with extended filtration over his current setup.

It's a triangle of needs that are hard to perfectly setup over a broad range of operation.

He's obviously tolerant of 100psi+ pressures ..since he's seeing 80psi at the sender/sensor.

Regardless of the volume of the pump, I'd choose a relief setting that is closed for most of my sensible usage with the visc I'm using during that time.

 

[SuperBusa]

Originally Posted By: Gary Allan
Originally Posted By: Brian_Bowers
Hold on... I think I may have just "gotten it". Are you guys saying that my oil pump is making enough pressure to always be in relief? That at idle the pump is putting out 52psi, but that by the time in goes down the oil galley, through the filter, and makes it to the presssure sensor it's dropped 12psi for the M1 filter and 2psi for the K&N?

(also posted this in my oil filter thread)


(mainly for others)

Suppose you had a 100psi relief limit (and the required disclaimer that your oil pump is of common efficiency - which is generally high) ..there would/could be NO alteration to flow. 100% of the sensible volume would be STILL reaching the sender/sensor as long as the pump is not seeing 100psi. Since you DID see alterations in pressure ..THERE HAD TO BE alterations in flow. For alterations in flow ..the flow had to be diverted to the relief.

Hence, to have a filter alter pressure readings below the filter ..the oil pump must be in relief.

There's not too much else to say about it.

Edit: This the point I keep trying to get most people to see (especially Soupahboosah as said by Jabba). The filter is virtually invisible under most sensible flows while the pump is NOT in relief. It's only in relief that a filter can show its comparative resistance in line. It is the relief act that makes it appear (actually revert to) a resistive state.


OK ... I think I finally see why we mis-understand each other sometimes Gary. I don’t disagree with what you said above. You use the term “the filter is virtually invisible under most sensible flows while the pump is NOT in relief” ... and I’m realizing that in your mind that means that all the oil flow coming out of the pump is going through the filter/engine when the pump is not in relief mode. That part is true.

BUT ... your statement does not mean that the filter is “invisible” in terms of it producing resistance to flow and a corresponding PSID across it even when the oil pump is NOT in relief mode. Many times it seem like you make this argument where the filter has virtually no PSID unless the oil pump is in relief mode, but that is not true. The filter will always produce a PSID of some level depending on the oil viscosity, flow volume and filter’s resistance factor. And this is important to realize when looking at the filter's PSID and the bypass setting of the filter. As discussed before, it is entirely possible to cause a filter to go into bypass mode way before the pump goes into relief mode ... depending on the oil viscosity, flow volume and filter used.

When the oil pump is NOT in relief mode, the filter is still a resistor to flow and has a PSID dependant on the factors mentioned above. When the pump is NOT in relief, and if the filter is really restrictive (high PSID) then it just causes the pump’s output pressure to increase in order to get the same volume through it, which in turn causes the pump’s output pressure to run closer to the relief pressure.

 

[440Magnum]

Originally Posted By: SuperBusa


BUT ... your statement does not mean that the filter is “invisible” in terms of it producing resistance to flow and a corresponding PSID across it when the oil pump is NOT in relief mode. Many times it seem like you make this argument where the filter has no PSID unless the oil pump is in relief mode, but that is not true. The filter will always produce a PSID of some level depending on the oil viscosity, flow volume and filter’s resistance factor.

When the oil pump is NOT in relief mode, the filter is still a resistor to flow and has a PSID. If the filter’s PSID is high, then it just causes the pump’s output pressure to increase in order to get the same volume through it, which in turn causes the pump’s output pressure to run closer to the relief pressure.


Couple of things occur to me.

1) the filter ALWAYS has some pressure drop across it. Whether this shows up as an engine oil pressure drop or not depends on several factors. One, if the engine pressure regulator valve (aka "relief valve" is downstream of the pump and upstream of the oil filter, the PSID of the filter will always be directly reflected in engine oil pressure. If the regulator valve is downtstream of the filter, then the PSID of the filter is invisible to the engine oil pressure. The *pump* just produces a correspondingly higher pressure to get oil through the filter, and puts a correspondingly higher load on the engine.

2) Most of the discussion in the thread so far assumes an ideal positive displacement pump. Engine oil pumps, whether gear type or gerotor type, are positive displacement but they aren't ideal. There's always some leakage past the gerotor tips or the gear teeth, and there is also leakage past the rotor or gear sides and the housing. Its a small effect, but it becomes more noticeable at lower RPM because the leakage is pretty much independent of RPM, but the pump output is directly proportional to RPM. Its also more noticeable as the oil pump itself gets worn (and remember the oil pump tends to wear a little faster than other things because it pumps unfiltered oil). So the fixed leakage is a bigger percentage of the total flow at low RPM. Furthermore, the added PSID of a filter will, at least theoretically, increase the internal leakage in the pump, which will *slightly* reduce volume flow. Again most noticeable at low RPM

 

[Gary Allan]

Quote:
Many times it seem like you make this argument where the filter has virtually no PSID unless the oil pump is in relief mode


And I stand by this assertion. I've observed it with my own eyes. If our friend with the Honda ever gets below relief with his 50 weight oil, and isn't @ 9000rpm ..he'll see it too.


Quote:
but that is not true.


It is more than it is not.

Try pouring any oil through a filter ...ANY filter. Compared to a funnel it's HIGHLY restrictive. That restrictive property is next to nothing when a much more highly restrictive element trumps it. Out of relief, the engine is way bigger. When the relief is open, the flow sees two paths ..the highly resistive filter and the highly resistive relief. The relative resistance of the filter is based on the amount of shunted flow versus realized flow ..up to the limits of the bypass valve.

Now, YES, when you approach higher levels of flow (that very few people will ever see) the filter itself, being a bunch of orifices, will produce PSID on its own.

TRUST ME. If there was any truth to linear models of PSID ..then every filter out there would be in perpetual bypass at highway speeds. That PSID is COMPRESSED due to the series nature of the single, non-divergent, flow.

Our OP is always in relief (his hot idle is above his alleged relief setting WAY downstream) ..hence he will always be at SOME elevated PSID.

If he threw in whatever oil was necessary to get below the relief at idle ..the M1 and the K&N would not alter the pressure at the sender/sensor.

Relief results in (higher) PSID. It's next to nothing outside of relief at all sensible flow rates.

 

[SuperBusa]

Originally Posted By: 440Magnum
Originally Posted By: SuperBusa


BUT ... your statement does not mean that the filter is “invisible” in terms of it producing resistance to flow and a corresponding PSID across it when the oil pump is NOT in relief mode. Many times it seem like you make this argument where the filter has no PSID unless the oil pump is in relief mode, but that is not true. The filter will always produce a PSID of some level depending on the oil viscosity, flow volume and filter’s resistance factor.

When the oil pump is NOT in relief mode, the filter is still a resistor to flow and has a PSID. If the filter’s PSID is high, then it just causes the pump’s output pressure to increase in order to get the same volume through it, which in turn causes the pump’s output pressure to run closer to the relief pressure.


Couple of things occur to me.

1) the filter ALWAYS has some pressure drop across it.


True .. based on 3 factors (that I repeat over and over) ... oil viscosity, flow volume and the fixed resistance factor of the filter assy.


Quote:
Whether this shows up as an engine oil pressure drop or not depends on several factors. One, if the engine pressure regulator valve (aka "relief valve" is downstream of the pump and upstream of the oil filter, the PSID of the filter will always be directly reflected in engine oil pressure.


AFAIK, the pressure relief valve is ALWAYS between the pump output and oil filter. Its purpose is to regulate the input pressure to the filter/engine circuit.

The engine’s oil pressure reading (sensor between the filter and engine input) will only be effected by the filter’s PSID if the oil pump is in relief mode. When the pump is NOT in relief mode then ALL of the pump’s output volume is going down the filter/engine circuit. If 5 gpm of 200 deg F 5w-30 Mobil 1 oil takes 60 psi at the inlet of the engine to be pushed through the engine, then that means anytime there is 5 gpm of this oil (same temp/viscosity) going through the engine then you will see 60 psi on the oil pressure gauge. It really doesn’t matter what pump or releif valve setup up stream is causing the 5 gpm to move down the engine ...it could be 3 monkeys cranking 55 gallon drum pumps plumbed in parallel as long as they can produce 60 psi at the engine's inlet point.

Quote:
If the regulator valve is downtstream of the filter, then the PSID of the filter is invisible to the engine oil pressure. The *pump* just produces a correspondingly higher pressure to get oil through the filter, and puts a correspondingly higher load on the engine.


I’ve never seen any engine design where the pressure regulator is AFTER the filter. If that was the case, then the oil filter would have to withstand even larger absolute oil pressures and more pressure spikes/pulsations.

Your statement “The *pump* just produces a correspondingly higher pressure to get oil through the filter, and puts a correspondingly higher load on the engine.” ... is actually what happens with the oil pump output pressure (with relief valve after the pump) when it’s not in relief mode and a more restrictive filter is used. If a more restrictive filter is used it causes the pump to work harder to put that same volume (pump NOT in relief) through a higher resistance. This means the pump’s output pressure MUST increase to achieve putting the same volume through a higher resistance.

Quote:
Most of the discussion in the thread so far assumes an ideal positive displacement pump. Engine oil pumps, whether gear type or gerotor type, are positive displacement but they aren't ideal. There's always some leakage past the gerotor tips or the gear teeth, and there is also leakage past the rotor or gear sides and the housing. Its a small effect, but it becomes more noticeable at lower RPM because the leakage is pretty much independent of RPM, but the pump output is directly proportional to RPM. Its also more noticeable as the oil pump itself gets worn (and remember the oil pump tends to wear a little faster than other things because it pumps unfiltered oil). So the fixed leakage is a bigger percentage of the total flow at low RPM.


Yes, the pump “leakage” or inefficacies would cause the pump output volume to be less than an idea 100% efficient positive displacement pump.

If that is the case, then the pump’s flow volume would be reduced if not in relief mode, which would in turn reduce the filter PSID and the engine’s oil pressure. Realize that the engine oil pressure you see on the oil gauge is the total PSID across the engine. If an oil pump was so ineffective at idle you would also see a lower engine oil pressure at idle, as compared to a 100% tight pump at idle under the same conditions.

Quote:
Furthermore, the added PSID of a filter will, at least theoretically, increase the internal leakage in the pump, which will *slightly* reduce volume flow. Again most noticeable at low RPM.


By the time the filter PSID is that high the pump is probably already in relief mode (shunting lots of volume back to the sump), so it really wouldn’t matter at that point because the pressure and pump output volume going to the filter/engine is maxed out at the regulated point.

 

[Gary Allan]

Quote:
If that is the case, then the pump’s flow volume would be reduced, which would in turn reduce the filter PSID



This is the comical (sorta) part. If the filter is causing MORE flow to be shunted ..it's PSID (effectively its indicated resistance) MUST BE HIGHER not lower

Really guys ..this is a done deal. Really.

 

[SuperBusa]

Originally Posted By: Gary Allan
Quote:
Many times it seem like you make this argument where the filter has virtually no PSID unless the oil pump is in relief mode


And I stand by this assertion. I've observed it with my own eyes. If our friend with the Honda ever gets below relief with his 50 weight oil, and isn't @ 9000rpm ..he'll see it too.


I think what you saw was a non-stable condition and you have mis-interpreted it. I’ve lost track of some of the details of your test (I have to admit), so maybe you should start a brand new tread with the details and maybe we can get to the bottom of this debate.

Originally Posted By: Gary Allan
Quote:
but that is not true.


It is more than it is not.

Try pouring any oil through a filter ...ANY filter. Compared to a funnel it's HIGHLY restrictive. That restrictive property is next to nothing when a much more highly restrictive element trumps it.


Whoa ... you just admitted above that a filter element is (quote) “HIGHLY restrictive”. Yes, it has a fixed restriction factor ... obviously. Let’s not compare the restrictiveness of the filter to the engine for example. But, if you recall some of our past conversations, some engines might flow better (ie, be less restrictive) than others. And some filters are obviously more restrictive than others. What happens when you put a very restrictive filter on a very free flowing (Subaru) engine? You can see that the restriction ratio of the filter/engine can vary.

Originally Posted By: Gary Allan
Out of relief, the engine is way bigger.


This is where you are messed up. It doesn’t matter if you’re out of relief or not ... the filter still has a PSID and the engine still has a PSID. The resistance factor of the filter and engine do not change ... they are FIXED / CONSTANT.

When the pump is “out of relief” (ie, NOT in relief), then ALL the oil volume must go through the filter and engine. That flow causes some PSID across the filter, and that flow causes some PSID across the engine. If the pump output needs to be 80 psi to push the entire pump’s volume through the filter/engine circuit (NONE going to sump via relief valve), then there might be 6 PSID across the filter, which means the engine oil pressure sensor after the filter will see 80 – 8 = 72 psi. Dude, there IS some level of pressure drop across the filter of some level anytime there is flow through it. Increase viscosity, keep volume constant = more PSID. Increase volume, keep viscosity constant = more PSID. Increase both viscosity and volume = even more PSID than the first two senarios.



Originally Posted By: Gary Allan
When the relief is open, the flow sees two paths ..the highly resistive filter and the highly resistive relief. The relative resistance of the filter is based on the amount of shunted flow versus realized flow ..up to the limits of the bypass valve.


The filter doesn’t care how much flow is shunted to the sump. All it cares about is how much pressure is on its inlet. When the pump is in relief mode the pump’s output pressure is at the max regulated pressure ... anyone can see that. This means the flow volume going through the filter is at the max for the viscosity or oil used, and that means the filter’s PSID is at the max for these conditions. As I’ve always said in the past, the filter’s PSID and the engine’s oil pressure reading will always be max when the pump is in relief mode.

Originally Posted By: Gary Allan
Now, YES, when you approach higher levels of flow (that very few people will ever see) the filter itself, being a bunch of orifices, will produce PSID on its own.


The filter ALWAYS produces some level of PSID on its own ... always. As said above, for any system the maximum flow volume and pressure to the filter/engine will occur during pump relief mode. You get max flow volume at max pump output pressure ... always! So, you get max filter PSID and max engine oil pressure ... if you can never see or realize this then you will never understand what’s really going on.

Originally Posted By: Gary Allan
TRUST ME. If there was any truth to linear models of PSID ..then every filter out there would be in perpetual bypass at highway speeds. That PSID is COMPRESSED due to the series nature of the single, non-divergent, flow.


It’s not really linear (but pretty close) ... the PSID falls off some with increased flow volume. See the AC Delco “PSID vs. Flow” graph. Why do you think there is a PSID shown on that graph with very little flow volume?

Originally Posted By: Gary Allan
Our OP is always in relief (his hot idle is above his alleged relief setting WAY downstream) ..hence he will always be at SOME elevated PSID.


Agreed ... that’s because his HV oil pump is basically performing at idle like a normal pump would perform at high RPM.

Originally Posted By: Gary Allan
If he threw in whatever oil was necessary to get below the relief at idle ..the M1 and the K&N would not alter the pressure at the sender/sensor.


True ... at least we see that the same.

Originally Posted By: Gary Allan
Relief results in (higher) PSID. It's next to nothing outside of relief at all sensible flow rates.


Don’t agree here ... this seems to be the point we always get hung up on. Let me ask you this – what do you think a filter’s PSID is just a hair before the pump goes into relief mode? What do you think the pump output volume is just a hair before it goes into relief mode? (Ans – just a hair less than the max it could ever produce, and that means a hair less than the max filter PSID and engine oil pressure will ever be seen at this point).

 

[SuperBusa]

Originally Posted By: Gary Allan
Quote:
If that is the case, then the pump’s flow volume would be reduced, which would in turn reduce the filter PSID


This is the comical (sorta) part. If the filter is causing MORE flow to be shunted ..it's PSID (effectively its indicated resistance) MUST BE HIGHER not lower

Now don't be taking things out of context and without the original qualifiers. Go back and re-read where you got this snippet - 3 posts above this one. I was talking about oil pump leakage ... I was NOT talking or insinuating that the filter PSID was causing more oil to be shunted. You are not comprehending or keeping up very well.

But even as the snippet statement is stated above, it's true. Anytime you reduce flow volume through a fixed flow resistor you will reduce the pressure drop across it. I really don't see why you don't grasp this simple fluid dynamics fact. I'm sure plenty of other people reading this thread know that if you have a constant viscosity oil, and reduce the flow volume through a fixed resistance filter that you will also reduce the pressure drop (PSID) across the filter. Can't you see that? ... if not, why?

Originally Posted By: Gary Allan
Really guys ..this is a done deal. Really.

... Sorry, you're not even close to being "done". Straw grasping phase is near.

 

[Gary Allan]

Think about it. Under your assumed rules, a filter would be in elevated PSID the entire sensible flow ..all the time.

Even WIX told one poster that it would be about 2PSID at highway speeds. Even that didn't convince you.

You see the elevated PSID that he's experiencing in relief. You see that if he wasn't that his pressure downstream would be unaltered (probably).

Yet you insist that this static 10 psid difference represents some baseline for some linear progressive model. No way.

Under your belief, every filter would be in bypass 24/7/365

I've shown you the simple way to view it. I'll do it for the audience that never made it down to filters

100 pressure relief limit
20 psi bypass setting

cold oil of no distinct visc = who cares ..just so that the pump goes into enough relief to max out the filter's resistance as viewed from the pump. Imagine an infinite sized relief port so that 100 psi will never be exceded

100:20:80 - 82% flow to filter:engine
Fluid gets either lower in visc ..easier to move ..whatever
100:18:82 - 84% of flow to through filter:engine
100:15:85 ..how can this freaking be? More flow to the engine ..and less across the filter - what the ach? 87% flow through filter:engine
100:12:88 90% flow through filter:engine
100:10:90 92% flow thought filter:engine
100:8:92 94% flow through filter:engine
100:2:98 100% flow through fitler:engine

98:2:96 100% flow through engine

..and all the way up to when the filter itself produces resistance at high volume.


Now later, after the fluid is EVEN MORE THIN we're supposed to see even HIGHER PSID?

Or are we supposed to see

50:20:30
35:20:15

Really ..nope. Dog won't hunt.

Now SURE ..into a zero pressure model ..higher flow will produce supply across it. No argument. But with a higher restriction down stream, that PSID will retreat and be a much lower parallel tracking resistance of the engine.

You can't achieve the PSID levels that you show in your chart. it would have the total pressure attenuating flow at the relief level.

 

[SuperBusa]

Originally Posted By: SuperBusa
Originally Posted By: Gary Allan
TRUST ME. If there was any truth to linear models of PSID ..then every filter out there would be in perpetual bypass at highway speeds. That PSID is COMPRESSED due to the series nature of the single, non-divergent, flow.


It’s not really linear (but pretty close) ... the PSID falls off some with increased flow volume. See the AC Delco “PSID vs. Flow” graph. Why do you think there is a PSID shown on that graph with very little flow volume?


Here's the graph. As you can see, anytime there is flow volume there is PSID. The higher the flow volume, the higher the PSID -this example is with constant oil viscosity (and rather thick, see temperature). If you had a constant flow volume and then increase the viscosity, you would also see increase PSID. Flow volume and viscosity are the two factors determining the PSID across the FIXED resistance of the filter element.

 

[Gary Allan]

Okay ..chop the chart off at a bypass level and amplify it for an engine that is at least 10X in relative resistance.

That chart is useless in process.

 

[SuperBusa]

Originally Posted By: Gary Allan
Think about it. Under your assumed rules, a filter would be in elevated PSID the entire sensible flow ..all the time.


I'm NOT saying that. The PSID INCREASES WITH INCREASED FLOW ... look at the graph above !

Originally Posted By: Gary Allan
Even WIX told one poster that it would be about 2PSID at highway speeds. Even that didn't convince you.


Yeah, no surprise there. That was with hot oil (very thin), and most likely with a low volume / low pressure relief valved oil pump seen on Grandma's 6 banger.

Originally Posted By: Gary Allan
You see the elevated PSID that he's experiencing in relief. You see that if he wasn't that his pressure downstream would be unaltered (probably).


Yeah, nothing surprising there. As I keep saying, when the pump is in relief is when you will have the MAX filter PSID and MAX engine oil pressure. If he wasn't in relief, that means the FLOW VOLUME coming out of the pump has reduced ... which will also reduce the filter PSID and engine oil pressure. As the pump's volume decreases more and more when not in relief mode, then the filter and engine pressure drops also have to decrease. It's simple to see.

Originally Posted By: Gary Allan
Yet you insist that this static 10 psid difference represents some baseline for some linear progressive model. No way.


Straw grasping ... don't know where you're coming up with this conclusion.

Originally Posted By: Gary Allan
Under your belief, every filter would be in bypass 24/7/365.


I never claim anything like that - more grasping and twisting. The only time a filter would might be in bypass with hot oil is if the pump was HV and the engine was also free flowing. Remember the Subaru thread? If you put a filter with a 8-10 psi bypass valve on an engine that called for a 23 psi bypass filter and flowed 12 gpm, then you'd probably push that 8-10 psi filter into bypass quite often.

I'll address the rest of this post later ... stay tuned.

 

[SuperBusa]

Originally Posted By: Gary Allan
Okay ..chop the chart off at a bypass level and amplify it for an engine that is at least 10X in relative resistance.


That graph is meant to show the restriction of the filtering media ... obviously the bypass valves in those filters is not operating. Maybe they used a filter model in each brand that didn't even have a built in bypass valve (ie, GM application).

Originally Posted By: Gary Allan
That chart is uses in process.


Say what ? ... "useless" is what you meant? Actually it isn't useless, as it shows how a typical filter's PSID is a function of flow volume ... and volume is what you are trying to move through the oiling system. Look at the title of the graph ... "Resistance to Flow".

 

[Gary Allan]

No correction, it shows the PSID across media with zero back pressure at volume.

Put a filer ..any filter at any volume with no restriction for an outlet ..and you'll see supply across the filter.

Those figures are only useful in comparison to each other. They don't mean squat in line/in process ..except perhaps in relief.

 

[SuperBusa]

Originally Posted By: Gary Allan


I've shown you the simple way to view it. I'll do it for the audience that never made it down to filters

100 pressure relief limit
20 psi bypass setting

cold oil of no distinct visc = who cares ..just so that the pump goes into enough relief to max out the filter's resistance as viewed from the pump. Imagine an infinite sized relief port so that 100 psi will never be exceded

100:20:80 - 82% flow to filter:engine
Fluid gets either lower in visc ..easier to move ..whatever
100:18:82 - 84% of flow to through filter:engine
100:15:85 ..how can this freaking be? More flow to the engine ..and less across the filter - what the ach? 87% flow through filter:engine
100:12:88 90% flow through filter:engine
100:10:90 92% flow thought filter:engine
100:8:92 94% flow through filter:engine
100:2:98 100% flow through fitler:engine

98:2:96 100% flow through engine

..and all the way up to when the filter itself produces resistance at high volume.


Whoa ... wait a minute. You say above “Fluid gets either lower in visc... easier to move .. whatever”. Every time I talk about this stuff I’m qualifying that the viscosity is CONSTANT. Of COURSE if the viscosity goes down (oil becomes THINNER) then the filter’s PSID will reduce. If the pump max pressure output is always 100 psi, and the oil viscosity is always becoming less with time, then yes the filter’s PSID will reduce significantly. Even though the flow volume is increasing as the viscosity goes down while keeping the pressure at 100 psi, this means the bigger influence on PSID is the viscosity and not the flow volume of the oil. So what’s your point?

Do an example where the oil viscosity is constant, and you slowly increase the oil flow volume (engine RPM) from idle to oil pump relief pressure (and RPM beyond relief) and see what you see. I know the answer already.

Originally Posted By: Gary Allan

Now later, after the fluid is EVEN MORE THIN we're supposed to see even HIGHER PSID?

Or are we supposed to see

50:20:30
35:20:15

Really ..nope. Dog won't hunt.


NO ... you are all screwed up! Of course as the oil gets hot and thin the filter PSID and the engine oil pressure will decrease. I’ve never argued otherwise. I don’t know how many times I’ve qualified all the examples and discussions I’ve put on this board, but obviously you have missed the point(s) I’ve tried to make.

Look at this WITH A CONSTANT OIL VISCOSITY. When you throw in a changing oil viscosity it changes things. I fully understand that the filter’s PSID and the engine’s oil pressure reading will decrease significantly when the viscosity reduces. I see it happen every day on my oil pressure gauge.

Originally Posted By: Gary Allan

Now SURE ..into a zero pressure model ..higher flow will produce supply across it. No argument. But with a higher restriction down stream, that PSID will retreat and be a much lower parallel tracking resistance of the engine.


Agreed ... if you make the engine the huge resistor, then the flow will be choked down because of it, and that in turn will make the filter PSID small. But make the engine free flowing, and you’ve now increased the flow through the filter and also increased the filter’s PSID.

Originally Posted By: Gary Allan

You can't achieve the PSID levels that you show in your chart. it would have the total pressure attenuating flow at the relief level.


Keep in mind that the chart from AC Delco is probably showing the relative PSID of all those filters when NOT on an engine. It’s just a marketing tool to compare filter flow resistance baring no other factors – like engine circuit resistance, etc.

We are getting close to the “going in circles” phase.