# How to test opening PSI for oil filter bypass?

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#### Gary Allan

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Gary ... seriously - really, how does the oil flow through the filter/engine go down when the oil pump if in relief mode at 85 psi? I really want to hear a clear explanation of that. The amount of oil volume that goes down the filter/engine path is based on the inlet pressure (85 psi in your case) and the fixed resistance of the filter/engine path (assume oil viscosity constant as always).
In relief mode, that EXCESS oil volume is shunted back to the sump ... BUT, the flow volume associated at the relief pressure (say 85 psi) is still flowing down the filter/engine path just like it would if the pump was at 85 psi and NOT IN RELIEF mode. Get it? Maybe I'll have to draw you a diagram to help explain this. I know Chunky gets it.
I've stated so many times. There obviously is no residual here. YES the pump puts out ONE FLOW AT ONE SPEED. HOW IT IS DIVIDED BETWEEN THE ENGINE AND THE SHUNTED RELIEF CREATES THE PSID Oh ..are you FOR REAL? Seriously? Or is this just advanced chain jerk Here's how it happens. Maximum flow is processed through the engine. What cannot fit is shunted. As the flow transitions back to 100% engine, the pressure below the filter will RISE to MEET the pressure relief LIMIT since MORE FLOW IS BEING PROCESSED BY THE ENGINE ....AND THE PRESSURE SUPPLY IS PEAKED. PSID RETREATS DUE TO LESS FLOW SHUNTED ...MORE FLOW REALIZED THROUGH THE ENGINE ..and (at this moment) FLAT PRESSURE SUPPLIED. Easy enough to see ..if you're not a narcissist.

#### chunky

Thread starter
Well first off, let me say that this discussion has been quite entertaining so far. Here's a diagram to represent my view of the system. I - branch of circuit containing A and 1 II - branch of circuit containing B, 2, 3, and 4 P - pump A - oil pump relief valve (switch) B - oil filter bypass valve (switch) 1 - oil path through pump bypass 2 - oil filter media 3 - oil filter bypass 4 - oil path through engine In plain english, this represents the two possible paths oil can take after leaving the pump. Either through Branch I, the pump relief path, or branch II, the filter + engine path. Additionally, there's a switch on element 3 to represent the filter bypass route that is conditionally open. - Valves are modeled as switches followed by a resistive element for simplicity. In steady state (constant flow), the resistance of 1 and 3 is constant. However, keep in mind that with changing flow, the resistance of 1 and 3 would change based on conditions in order to satisfy loop constraints. Loop constraint meaning that the PSI drops around a loop must sum to zero. This must ALWAYS be true. - Assume we're only interested in steady state operation. If you can't understand it in steady state, then forget about transient behavior. - Switches close at some PSID, say 80psi for switch A and 13psi for switch B. For switch A, this regulates the PSID across the pump as a whole and also the PSID across branch II. However, switch B ONLY regulates PSID across element 2, the filter. Now, things that we KNOW. - Pump delivers FLOW. PSI is developed ONLY when the flow encounters elements that resist flow. Basically, no resistance to flow, no PSI. Thus if there is a measurable PSID across any element, that means that the element is resisting flow. - Pump flow rises linearly with engine RPM. No surprise since the pump is a positive displacement type. - A certain amount of FLOW at a fixed TEMPERATURE and VISCOSITY is required to generate 80PSI through branch II. After this FLOW volume is reached, switch A opens to divert any flow volume that would otherwise raise the pressure in any branch above 80PSI. This action defeats the rise of oil pressure with engine RPM, but note that it does not actually reduce the increase in flow output of the pump as RPM rises. - Similarly, a certain amount of FLOW at a fixed TEMPERATURE and VISCOSITY is required to generate 13PSID across the filter media (element 3). Once this flow is reached, switch B closes. Again, note that this defeats PSID rise across the filter element, but does not limit flow. - Fixed PSID across an element, with constant temp & viscosity oil, yields fixed flow across the element as long as the resistance of the element does not change. - If PSI measured at the junction of branches I and II is increasing, then so is flow. Things that I think are true, but feel free to debate. - Switches A and B are totally independent. Oil pump relief does not affect oil filter bypass. The only interaction is that the pump relief limits max flow through branch II. If the filter bypass PSI is properly selected for the hot operating temp & viscosity of the oil, then the bypass should never open once max flow (as limited by the relief) is achieved. However, if the pressure creeps up due to special conditions (relief becoming overwhelmed), then the bypass could open even when the pump is in relief. - Relief could be overpowered due to being undersized for the given flow rate (revving above stock redline), undersized for the given oil viscosity, just to name two possibilities. - When running a thicker oil, elevated pump relief is necessary to maintain the same flow rate. Thicker fluid = higher PSI for a given flow rate. - This added PSI could require a higher filter bypass to ensure bypass does not open at max engine speed. whew. I think that covers my take on everything so far. I should be able to get some PSID measurements across the filter soon enough. I don't know how I'd go about determining whether the pump relief is open or not because I'm clearly seeing the PSI creep up with RPM, although it's not rising as steeply as it does from 0-3000rpm. Anyhow, when I do take measurements, I'll be sure to record oil temps, pressures, and engine RPM so I can come up with some meaningful plots. Thanks for tuning in guys. :)

#### chunky

Thread starter
Originally Posted By: Gary Allan
I've stated so many times. There obviously is no residual here. YES the pump puts out ONE FLOW AT ONE SPEED.
Agreed.
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HOW IT IS DIVIDED BETWEEN THE ENGINE AND THE SHUNTED RELIEF CREATES THE PSID
Which PSID are you referring to here? The PSID across the pump relief and the filter + engine circuits MUST be equal. If you sum the pressure drops around any loops, they must add to zero. You cannot ignore this fact. It is a physical law. PSID across the pump relief must equal PSID of the filter + engine.
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Oh ..are you FOR REAL? Seriously? Or is this just advanced chain jerk Here's how it happens. Maximum flow is processed through the engine. What cannot fit is shunted.
I agree with that. To clarify explicitly, pump relief valve is open.
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As the flow transitions back to 100% engine,
meaning as the relief valve is closing
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the pressure below the filter will RISE to MEET the pressure relief LIMIT since
If by pressure below the filter you mean pressure between the pump & filter, then what you're saying cannot be. Pressure is purely an artifact of the flow encountering resistance. If pressure goes up, it means one of two things happened. Assume constant temp & viscosity. 1) resistance increased. 2) flow increased. As the relief closes, you should see no change in PSI below the filter.
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MORE FLOW IS BEING PROCESSED BY THE ENGINE ....AND THE PRESSURE SUPPLY IS PEAKED.
The engine cannot change its resistive properties. Not unless you have some system that draws oil pressure that can turn on and off, like VTEC or VTC.
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PSID RETREATS DUE TO LESS FLOW SHUNTED ...MORE FLOW REALIZED THROUGH THE ENGINE ..and (at this moment) FLAT PRESSURE SUPPLIED.
PSID retreats where? be specific. Across the filter? Across the bypass path? Across the engine? You simply cannot have more flow with less pressure unless the resistive properties have changed. The filter does not change properties. In most cases, the engine does not change flow properties. I think I see what you've missed in your observations. The reason why less flow is shunted is because the pump is producing less flow. It cannot be any other way. The relief opens to divert flow. As the relief closes, it means there is less flow that needs to be diverted. Period. Fullstop. End of story. The pump itself never transitions to anything other than a FLOW source. The pump relief allows it to take on some properties of a pressure source, but it's not a full functional transformation. The pump is and always will be a flow source. Less flow is shunted, that is very true, but it's not because the engine is suddenly less resistive to flow. It's because the pump is producing less input flow.
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Easy enough to see ..if you're not a narcissist.
LOL. I'll stay out of the personal stuff between you to. :p

#### SuperBusa

Originally Posted By: chunky
You simply cannot have more flow with less pressure unless the resistive properties have changed. The filter does not change properties. In most cases, the engine does not change flow properties. I think I see what you've missed in your observations. The reason why less flow is shunted is because the pump is producing less flow. It cannot be any other way. The relief opens to divert flow. As the relief closes, it means there is less flow that needs to be diverted. Period. Fullstop. End of story. The pump itself never transitions to anything other than a FLOW source. The pump relief allows it to take on some properties of a pressure source, but it's not a full functional transformation. The pump is and always will be a flow source. Less flow is shunted, that is very true, but it's not because the engine is suddenly less resistive to flow. It's because the pump is producing less input flow.
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Easy enough to see ..if you're not a narcissist.
LOL. I'll stay out of the personal stuff between you to. :p
Well, I just briefly scanned through all the new posts, but this caught my eye. Yes, that is exactly right. I don't think Gary realizes that the oil pumps output is ever changing with changing RPM ... AND the resistance to flow in the filter/engine circuit IS FIXED. What you have said above is the same thing I've said numerous times in these discussions. I think I'm going to draft up a chart showing how a positive displacement oil pump with a relief valve puts out flow so he can many realize is shortcomings in these discussions. When I find some time to burn, I'll also look at all the new info. From a brief glance, I think Chunky is on the same wavelength as me ... there's a reason for that ... it's called reality.

#### SuperBusa

Originally Posted By: chunky
Well first off, let me say that this discussion has been quite entertaining so far. Here's a diagram to represent my view of the system. I - branch of circuit containing A and 1 II - branch of circuit containing B, 2, 3, and 4 P - pump A - oil pump relief valve (switch) B - oil filter bypass valve (switch) 1 - oil path through pump bypass 2 - oil filter media 3 - oil filter bypass 4 - oil path through engine
Nice schematic of the oil system there Chunky. I'll try to whip up another chart that will show the RPM vs output of an ideal positive displacement pump, and show what happens to pump output flow then the relief valve kicks in.

#### SuperBusa

Originally Posted By: chunky
Originally Posted By: clueless Gary
the pressure below the filter will RISE to MEET the pressure relief LIMIT since
If by pressure below the filter you mean pressure between the pump & filter, then what you're saying cannot be. Pressure is purely an artifact of the flow encountering resistance. If pressure goes up, it means one of two things happened. Assume constant temp & viscosity. 1) resistance increased. 2) flow increased.
Exactly right. One caveat to mention is that IF the filter A is more restrictive to flow than filter B, then you WILL see less oil pressure between the filter and engine when the pump is in relief mode than if your were running filter B. When the pump is in relief mode, the pump's outlet pressure is (ideally) fixed to a constant value. So, if you run a more restrictive filter then there is a greater PSID across it which caused LESS engine oil pressure (the pressure BETWEEN the filter and engine). That was really for Gary, as it's clear you understand all of this. Bernoulli isn't wrong ... Gary is.
Originally Posted By: chunky
As the relief closes, you should see no change in PSI below the filter.
True ... as true until the pump starts going out of relief mode because as soon as the pump's output pressure drops anything below the relief pressure that means the pumps volume output has decreased. I think you mean (to clarify) that as long as the pump is IN RELIEF mode that the pressure between the filter and engine (the pressure gauge in most cars read at that point) will not change if viscosity is constant. That is true.

#### Gary Allan

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If by pressure below the filter you mean pressure between the pump & filter, then what you're saying cannot be. Pressure is purely an artifact of the flow encountering resistance. If pressure goes up, it means one of two things happened. Assume constant temp & viscosity. 1) resistance increased. 2) flow increased. As the relief closes, you should see no change in PSI below the filter.
Knock -knock, chunky ..the pressure is attenuated. This part keeps escaping your concession. You're stuck (kindly state) with your personal "the relief is not big enough) escalating evolution. Stop for the moment and think. You've conceded that the engine will be a static resistive element, correct? FREEZE THAT IMMUTABLE FACT and graft it in heraldry. Pretty PEL-EZ. 100psi at relief 25% flow shunted. Assume a 25psi bypass. 100psi to "ground" 75% of pump output through engine = 75psi ENGINE TO GROUND. 100psi to ground 80% of pump output through engine = 80psi ETG 100psi to ground 85% of pump output through engine = 85psi ETG 100psi to ground 95% of pump output through engine = 95psi ETG 100psi to ground 100% of pump output through engine= 98spi ETG The filter is seeing the difference. Just so Soupy doesn't say "how can it not go through the filter DOOD??" I'll do it pony style Same conditions 100 applied 25PSID 75 ETG 100 applied 20SPID 80 ETG 100 applied 15PSID 85 ETG 100 applied 10PSID 90 ETG 100 applied 5PSID 95 ETG 100 applied 2PSID 98 ETG As you can see, as MORE flow passed through the filter engine combo ..the supply stayed the same ..the engine approached supply as the flow became "undiverted". This can be at one static (but divided) flow rate where the inertia of the fluid gets up to speed ...or the viscosity decreased .. This is pathetically simple to see. The engine is what the engine is. The filter expresses the % of diverted flow in its PSID. The lower the diverted flow ..the higher the engine approached the ATTENUATED pressure. The closer the engine gets to that number the filter MUST RETREAT in "apparent" resistance ..so does it's "apparent" PSID. This is 100% independent of FLOW BASED PSID due to filter limits of throughput. That I would term impedance since it's a non-factor to a certain point in volume (frequency for something like a resonate circuit)

#### Gary Allan

Oh ..yeah ..since we're splitting hairs here. This is at ONE flow rate ...a fixed GPM (it doesn't have to be ..but just to stop the nitpicking objections). This is JUST to demonstrate where the vast galactic universal most frequent elevated PSID events occur in 99.44% of the known universe ....and nothing more. ..you may return to the stratosphere of ultra high volume discussion.

#### SuperBusa

Gary ... do you understand and agree with this simple graph? This graph shows how an ideal positive displacement oil pump operates with it's relief valve. In this chart, assume the oil viscosity is constant and the pump's relief valve is set to 80 psig. With this particular oil viscosity and temperature, let's say at 4000 RPM the pump output pressure is 80 psig and goes into relief mode. At that point, all excess oil volume above 6.0 gpm is shunted back to the sump above 4000 RPM. The MAX filter PSID and the MAX engine inlet oil pressure is seen at any RPM from 4000 RPM and above. Once the engine RPM falls below 4000 RPM, then (and only then) is the pump out of relief mode and the flow volume decreases with RPM. When the pump is out of relief mode then the filter PSID and the engine oil pressure goes up and down with engine RPM (anyone can see that on an engine oil press gauge). At 2000 RPM, the flow is half of what it is at 4000 RPM, and the filter PSID and engine oil pressure is less than what it was at 4000 RPM and above. If you don't agree with this, then you will never understand what's going on with the filter and engine flow and relative PSID across each.

#### Gary Allan

I don't necessarily disagree with it. What you're not doing is solving my equations or disproving them as stated. You're defaulting in this upper strata which is not where we're in conflict. I don't dispute that there will be a upper volume resistance to the filter. It is inconsequential for most sensible flows. You ONLY think up here. You refuse to see the other end of the spectrum since its in conflict with your impressions that are true at this end of things ..and ONLY this end of things. The filter is a very small resistance to flow for a wide range. Up until its (for lack of a better term) impedance kicks in, it's linear change in PSID is compressed to a very narrow range ..like that of a 6' pipe passing a low volume of fluid ..inches of W.C. up to maybe 2psid.

#### SuperBusa

Originally Posted By: Gary Allan
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If by pressure below the filter you mean pressure between the pump & filter, then what you're saying cannot be. Pressure is purely an artifact of the flow encountering resistance. If pressure goes up, it means one of two things happened. Assume constant temp & viscosity. 1) resistance increased. 2) flow increased. As the relief closes, you should see no change in PSI below the filter.
Knock -knock, chunky ..the pressure is attenuated. This part keeps escaping your concession. You're stuck (kindly state) with your personal "the relief is not big enough) escalating evolution. Stop for the moment and think. You've conceded that the engine will be a static resistive element, correct? FREEZE THAT IMMUTABLE FACT and graft it in heraldry. Pretty PEL-EZ.
Originally Posted By: Gary Allan
Oh ..yeah ..since we're splitting hairs here. This is at ONE flow rate ...a fixed GPM (it doesn't have to be ..but just to stop the nitpicking objections).
100psi at relief 25% flow shunted. Assume a 25psi bypass. 100psi to "ground" 75% of pump output through engine = 75psi ENGINE TO GROUND. 100psi to ground 80% of pump output through engine = 80psi ETG 100psi to ground 85% of pump output through engine = 85psi ETG 100psi to ground 95% of pump output through engine = 95psi ETG 100psi to ground 100% of pump output through engine= 98spi ETG
Well, for starters, if this example is for a fixed flow volume (gpm) as you have stated, then the ONLY way this could happen is IF this was seen in a very short time slice during dynamic (unstable) system operation. Under steady state engine RPM conditions (holding the RPM steady for 10+ seconds) and relatively slow engine RPM changes this will not happen. If what you are trying to describe above is something you saw on your van with the two pressure gauges, then what you saw was a dynamic unstable operation of the system as it was trying to balance itself back out. The pump’s relief valve opened due to a surge of oil volume from increasing engine RPM and then slowly closed as the system balanced itself out. I’m not arguing that dynamic surges can cause something like this to happen. I’m concentrating more on stead state operations here – keep that in mind. If the engine is held at a constant RPM – let’s say 5000 RPM in my pump chart above – then the flow rate going to the filer and engine circuit would be a constant 6.0 gpm … and also any time the engine was above 4000 RPM the flow volume would be 6.0 gpm. The PSID across the filter and the engine’s oil pressure (it’s PSID to sump “ground”) would also be the MAX possible for the oil viscosity at the moment in time. The filter PSID and engine oil pressure would NOT reduce until the engine RPM fell below 4000.
Originally Posted By: Gary Allan
The filter is seeing the difference. Just so Soupy doesn't say "how can it not go through the filter DOOD??" I'll do it pony style Same conditions 100 applied 25PSID 75 ETG 100 applied 20SPID 80 ETG 100 applied 15PSID 85 ETG 100 applied 10PSID 90 ETG 100 applied 5PSID 95 ETG 100 applied 2PSID 98 ETG As you can see, as MORE flow passed through the filter engine combo ..the supply stayed the same ..the engine approached supply as the flow became "undiverted". This can be at one static (but divided) flow rate where the inertia of the fluid gets up to speed ...or the viscosity decreased ..
What’s wrong with your thinking here is that if the pump is in relief at 100 psi like you have stated above, then the oil FLOW VOLUME IS CONSTANT … look at my pump chart. When the pump is in relief mode the output VOLUME IS FIXED TO A CONSTANT AMOUNT if the relief valve is doing it’s job effectively. How can the oil volume increase above the point of relief if the relief valve is doing it’s job 100% effectively? Remember we are dealing in IDEAL examples here to cut down on the complexity of this discussion. ONLY AFTER the pump goes OUT OF RELIEF then the volume going through the filter and engine MUST DECREASE. Look at the pump chart … it can’t magically work any differently. The only case would be if the relief valve is messed up or totally ineffective at high pump RPM during relief mode.
Originally Posted By: Gary Allan
This is pathetically simple to see. The engine is what the engine is. The filter expresses the % of diverted flow in its PSID. The lower the diverted flow ..the higher the engine approached the ATTENUATED pressure. The closer the engine gets to that number the filter MUST RETREAT in "apparent" resistance ..so does it's "apparent" PSID.
Apparently it’s not as simple as some think … but I maintain my stance that you’re missing the boat with the flow and pump relief operation characteristics. The filter is what the filter is too … think of it like a small added resistance to flow IN SERIES with the engine’s resistance to flow. The filter is really different … just less resistive, but resistive in a fixed manner just like the engine. The filter does not magically change it’s fixed flow resistance with time … just like the engine really doesn’t (for all practical purposes). The ONLY time the filter’s PSID “retreats” with constant viscosity oil is if the flow volume decreases. I’ve concluded were you’re messed up on this stuff. You saw the PSID across a filter “evaporate” or “reduce” at a constant engine RPM once and have come up with this explanation of what you thought you saw. What you probably saw was the oil pump going into relief mode for a short time -- either due to a volume surge and/or viscous oil – and then when the system stabilized after the surge and/or the oil become slightly less viscous as it warmed up some, the filter’s PSID naturally came down as it should.

#### SuperBusa

Originally Posted By: Gary Allan
I don't necessarily disagree with it. What you're not doing is solving my equations or disproving them as stated. You're defaulting in this upper strata which is not where we're in conflict. I don't dispute that there will be a upper volume resistance to the filter. It is inconsequential for most sensible flows. You ONLY think up here. You refuse to see the other end of the spectrum since its in conflict with your impressions that are true at this end of things ..and ONLY this end of things. The filter is a very small resistance to flow for a wide range. Up until its (for lack of a better term) impedance kicks in, it's linear change in PSID is compressed to a very narrow range ..like that of a 6' pipe passing a low volume of fluid ..inches of W.C. up to maybe 2psid.
We've been around and around on this stuff in multiple threads. The fact is, regardless of when and even if the oil pump goes into relief mode, the filter's PSID is only dependent on 3 things - oil viscosity, oil flow volume and filter media fixed resistance factor to flow. The oil filter could care less if the oil pump is in relief or not, because it's PSID will range between zero when the engine is off, to MAX when the pump is in relief. Of course, this is at stable constant oil viscosity, non-surge, stable flow conditions. Dynamic, surging unstable oil volume flow is a whole separate topic for discussion. So again, the bottom line boils down to: If an relatively restrictive oil filter with a low set bypass valve is used on a high volume pumped oil system with relatively viscous oil the it's entirely possible for that oil filer's bypass valve to open much more than desired while the engine is in the upper PRM range. REMEMBER, WE ARE TALKING SPECIFICALLY ABOUT THIS EXACT OPERATIONAL CONDITION (RACING ENGINES) IN THIS THREAD ... WE ARE NOT TALKING ABOUT YOUR 6 BANGER VAN WITH A 3 GPM MAX OUTPUT OIL PUMP GOING DOWN THE HIGHWAY AT 2000 RPM MAX.

#### Gary Allan

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Well, for starters, if this example is for a fixed flow volume (gpm) as you have stated, then the ONLY way this could happen is IF this was seen in a very short time slice during dynamic (unstable) system operation.
So? ..and this alters my assertion in what way? I've only stated that this is the highest incidence of elevated PSID. I specifically excluded the conditions that you fall back on in arguing with me. GRANTED under the narrow confines of your arguments.
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The fact is, regardless of when and even if the oil pump goes into relief mode, the filter's PSID is only dependent on 3 things - oil viscosity, oil flow volume and filter media fixed resistance factor to flow.
This is not true. We'll wait for our friend's observations if he bothers. Maybe you won't believe his methodology either.
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REMEMBER, WE ARE TALKING SPECIFICALLY ABOUT THIS EXACT OPERATIONAL CONDITION (RACING ENGINES) IN THIS THREAD ... WE ARE NOT TALKING ABOUT YOUR 6 BANGER VAN WITH A 3 GPM MAX OUTPUT OIL PUMP GOING DOWN THE HIGHWAY AT 2000 RPM MAX.
Remember, I don't dispute your assertions within the limited confines of your conditions. You, however, are disputing mine with ONLY your constructed scenario. You can't effectively dispute my assertions as I've presented the. Soupy. Hundreds of people are watching this thread. Many subscribe to false notions of "highly restrictive" and "free flowing" concepts on filters. Most are NOT racing. The filter is invisible for 99 and 44/100'ths % of normal operations and bypass activity, outside of severe loading, is totally related to pump relief action at cold start. You're preaching to a much broader crowd then just racers. You're leading them into false beliefs by ignoring these characteristics that they will most encounter in their ownership and form their opinions of these matters. ..but have fun.

#### SuperBusa

Originally Posted By: Gary Allan
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Well, for starters, if this example is for a fixed flow volume (gpm) as you have stated, then the ONLY way this could happen is IF this was seen in a very short time slice during dynamic (unstable) system operation.
So? ..and this alters my assertion in what way? I've only stated that this is the highest incidence of elevated PSID. I specifically excluded the conditions that you fall back on in arguing with me. GRANTED under the narrow confines of your arguments.
It alters your assertions like I described in the original post I replied to. You are claiming that the filter’s PSID magically “evaporates” or “retreats” to nearly nothing while the oil pump remains in relief mode. Like I said earlier, the ONLY way this could happen is if you are seeing a large surge of oil volume being forced down the filter/engine circuit before the pump’s relief valve can compensate and react to the volume surge change. Once the surge has balanced, then the flow will decrease through the filter (because the relief is doing its job correctly) and cause the filter PSID to decrease. This is probably what you have observed in your "tests" … since the vehicle you were using probably has a low volume oil pump, and once the system rebalanced after the surge, the flow settled down to a small volume even while the pump was in relief mode. Heck, for all we know the pressure relief valve on your van could be malfunctioning and sticky with sludge buildup, causing it to be very lazy to react to changes in pump output pressure and volume. Now if you did the same test on a high volume oil pumped system, and held the RPM high and steady for quite awhile then you would see much higher PSID than “a psi or a few inches of water”. Again, the filter PSID all depends on oil viscosity, the pump’s volume vs. RPM characteristics and the filter/engine flow circuit's fixed flow resistance – I really don’t know how many times I have to qualify this with you.
Originally Posted By: Gary Allan
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The fact is, regardless of when and even if the oil pump goes into relief mode, the filter's PSID is only dependent on 3 things - oil viscosity, oil flow volume and filter media fixed resistance factor to flow.
This is not true. We'll wait for our friend's observations if he bothers. Maybe you won't believe his methodology either.
Yes, my statement is entirely true under STEADY STATE CONDITIONS. But, if you start talking about surging oil pressures/volumes then things need to be explained a little differently. The fact is, even when the oil pressure and volume surges you will still see corresponding filter PSID and engine oil pressures (if you had a very fast acting pressure gauge) … and corresponding reactions from the pump’s relief valve and the filter’s bypass valve. I hope Chunky does his filter PSID measurement under track (and other) conditions. Based on what he’s said about his system, I’d venture to say that the filter’s PSID will be close to or at the filter’s bypass setting while at high RPM with hot oil. If the PSID he measures is equal to the bypass setting, then it would be safe to say the filter is in some level of bypass mode.
Originally Posted By: Gary Allan
Remember, I don't dispute your assertions within the limited confines of your conditions. You, however, are disputing mine with ONLY your constructed scenario. You can't effectively dispute my assertions as I've presented them.
Sure I did dispute your assertions … you are basing all your understanding of a complete oiling system under the pretense of some surging and dynamic conditions with two pressure gauges across a filter to measure the filter’s PSID. That’s fine, because what you saw may very well be the “surge effect” … but don’t let that make you think that the oiling system reacts that way when there is more steady state, non-surging flow going on - even when the pump is in relief mode (see my pump graph). They are TWO DIFFERENT scenarios.
Originally Posted By: Gary Allan
Soupy. Hundreds of people are watching this thread. Many subscribe to false notions of "highly restrictive" and "free flowing" concepts on filters. Most are NOT racing. The filter is invisible for 99 and 44/100'ths % of normal operations and bypass activity, outside of severe loading, is totally related to pump relief action at cold start.
I agree we are specifically talking about “outside the normal operating conditions” of the majority oil filters on the public roads … except for maybe a hard driven street Subaru with a 12 gpm oiling system running an 8 psi bypass filter instead of the specified 23 psi filter by Subaru. The fact still remains, that if an inadequate filter (or very dirty/loaded up filter) is used on a particular vehicle, and that vehicle is pushed hard, that the filter’s bypass may very well be opening much more than if the right filter was used for the right conditions, or if the vehicle is driven like a granny going to church.
Originally Posted By: Gary Allan
You're preaching to a much broader crowd then just racers. You're leading them into false beliefs by ignoring these characteristics that they will most encounter in their ownership and form their opinions of these matters. ..but have fun.
Ummm … if the readers of this thread can’t understand the dozens of explanations and “qualifications” these discussions revolve around, then they probably aren’t interested anyway. Hopefully, they can read and comprehend better than some people can. Now it's Chunky's turn.

#### chunky

Thread starter
I haven't read everything in the thread yet, but I will later today. I just spent some time cutting open two filters & taking some notes & measurements. I'm sure you all have seen filters cut open, so that's not new. However, since my interest is in the bypass function, I thought I'd take some measurements to see what it takes for the bypass to open. I have a used Bosch 3312 filter for the Honda S2000 f20c/f22c motor. I have been looking for a suitable oversize application and found that the Porsche 968 uses the same thread pattern, has a similar case diameter, but is significantly longer. The 968 filter also had a higher bypass valve rating. I sacrificed a new filter to see if it would be suitable for my use. Here are the two filters cut open. Bosch on top. As you can see, the Porsche filter is much longer. However, looking inside the filter, there is this oddly placed valve right near the center outlet of the filter that seems to be a restrictor of some sort. The Bosch filter does not have this. Looking into the center hole, you can see the perforated center column and the bypass valve at the end. So it seems I won't be able to use the 968 filter as an oversize application. Oh well. At this point, I figured I would see what kind of force it takes to open the bypass valve on the Bosch. I grabbed some weight plates from my home gym and a Phillips head screwdriver with a fat handle. Going in 2.5lb increments, I added weight to the screwdriver, of which the point was positioned directly on the center of the valve, until the bypass valve started to open, then kept adding weight until the valve was fully open. weight | Bosch | Purolator 2.5lb | closed | closed 5.0lb | just open | closed 7.5lb | fully open | just open 10.0lb | fully open | 3/4 open Then I took a simple diameter measurement of the visible size of the bypass valve. Bosch | Purolator 0.4965" | 0.490" Then calculating area Bosch | Purolator 0.194in^2 | 0.189in^2 Then calculating the force over area for the "just open" valve state. Bosch | Purolator 25.8PSI | 39.7PSI I don't have hard info for the Bosch filter, but the Purolator filter is rated as 25-35PSI. Also, since I was going in very coarse weight increments, there is a ton of error. In addition, "just open" is not a very scientific qualifier. If I were to re-do the test, I would put a small amount of very light oil on the bypass valve & repeat the test adding weight in fine increments, maybe by adding sand into a container, until the valve just opens, as indicated by the oil running through the edge of the bypass valve. I could alternatively use a fine feeler gauge, 0.005" is the smallest I have I think, to set a consistent standard for "just open." So, it's actually relatively straightforward to calculate when the bypass valve is just open b/c the exposed area of the valve is easy to measure. Other states of the bypass valve would be hard to measure accurately because the exposed area of the valve changes once it opens even slightly. I'll probably try to make a more accurate measurement for the Bosch filter and see how it compares to the rating Bosch gives me whenever the respond to my inquiry. :p

#### SuperBusa

Interesting stuff. Looks like your bypass opening analysis might be a little off if you got 39.7 psi for "just opening" value for the Porsche filter that is rated at 25-35 psi by the manufacture. There 25-35 psi spec probably means it just starts to open at 25 psi and is fully open at 35 psi. The bypass valve is not a fully closed or fully open "digital" mechanism since it is spring loaded mechanism using a constant spring constant. So, what this means is the filter's PSID has to get all the way up to 35 psi before the bypass valve goes fully open. You were referring to the Porsche filter as the "Purolator" ... is it a Purolator filter made for Porsche OEM brand?
Originally Posted By: chunky
As you can see, the Porsche filter is much longer. However, looking inside the filter, there is this oddly placed valve right near the center outlet of the filter that seems to be a restrictor of some sort.
Yes, that certainly does look like a flow restrictor inside the center tube ... very strange. I'm wondering if the oiling system on that Porsche engine does not use a full flow oil filtering system, but rather just filters a portion of the total oil flow that goes to the engine. That doesn't sound very high tech, as that would be like having the filter in bypass all the time, but I can't see them putting a flow restrictor in the oil filter to control the total oil flow going into the engine.

#### chunky

Thread starter
Originally Posted By: SuperBusa
Interesting stuff. Looks like your bypass opening analysis might be a little off if you got 39.7 psi for "just opening" value for the Porsche filter that is rated at 25-35 psi by the manufacture. There 25-35 psi spec probably means it just starts to open at 25 psi and is fully open at 35 psi. The bypass valve is not a fully closed or fully open "digital" mechanism since it is spring loaded mechanism using a constant spring constant. So, what this means is the filter's PSID has to get all the way up to 35 psi before the bypass valve goes fully open. You were referring to the Porsche filter as the "Purolator" ... is it a Purolator filter made for Porsche OEM brand?
Originally Posted By: chunky
As you can see, the Porsche filter is much longer. However, looking inside the filter, there is this oddly placed valve right near the center outlet of the filter that seems to be a restrictor of some sort.
Yes, that certainly does look like a flow restrictor inside the center tube ... very strange. I'm wondering if the oiling system on that Porsche engine does not use a full flow oil filtering system, but rather just filters a portion of the total oil flow that goes to the engine. That doesn't sound very high tech, as that would be like having the filter in bypass all the time, but I can't see them putting a flow restrictor in the oil filter to control the total oil flow going into the engine.
Agreed, the bypass is not a discrete on/off thing. My measurements today were EXTREMELY rough. The numbers I came up with are much higher than they would be as "just open" means that it was the first 2.5lb increment that produced some visible gap. The actual opening threshold weight would be somewhere between the last "closed" weight and the first "just open" weight. The visible gap was not measured. Same goes for half open and fully open. Fully open happened when the valve reached its mechanical limit. It's a Purolator L30165. It's for a Porsche 968 motor, all model years. I looked it up using the model year 1995. There is also a Bosch Premium filter for this car, but I can't find it locally and I'm afraid it will have the same weird spring loaded choke valve on the outlet so I'm not sure I want to order one from online to find out. Plus, using regular maintenance parts that can't be found locally is a huge pain in the [censored]. I always prefer to use routine maintenance parts I can pick up locally.

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#### Gary Allan

Quote:
there is this oddly placed valve right near the center outlet of the filter that seems to be a restrictor of some sort.
Does it move? Some filters (very few and no domestics that I'm aware of) have an ADFV. One Oz outfit featured them. It would essentially keep the filter from draining in either direction. Gut the media and see what it looks from from the interior view.

#### chunky

Thread starter
Originally Posted By: Gary Allan
Quote:
there is this oddly placed valve right near the center outlet of the filter that seems to be a restrictor of some sort.
Does it move? Some filters (very few and no domestics that I'm aware of) have an ADFV. One Oz outfit featured them. It would essentially keep the filter from draining in either direction. Gut the media and see what it looks from from the interior view.
It's a spring loaded valve. I cut the filter in half and it takes almost no force to open the valve. It's still a bit of a concern for me as the valve appears to bottleneck flow a good bit. Whether it's more restrictive to flow than the engine, I couldn't tell ya. However, I'd rather use a filter that's more similar in construction to the OEM Honda filter construction.

#### Gary Allan

I doubt that it trumps the ID of the threaded nipple that the whole filter attaches to the engine with. Orifices ..or "short transitional passages" don't effect flow like pipes do ..at least in most situations. That's how Permacool gets to use a dinky little poppet bypass valve to regulate 2psid across a cooler circuit when fitting a brick wall bypass filter. Rarely does a 1/64 hole need to be drilled through the partition to allow full flow with only 2psid across the ports. The oil just (cough-cough) accelerates. Naturally, there are limits to everything for throughput.

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