oil filter flow percentage

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43,652
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'Stralia
Originally Posted By: QuadDriver
Originally Posted By: Shannow
BTW, I learned alright when I studied this stuff at University, and 20plus years as a practicing M.E., including lubricating oil systems.
If that is true, and I am not saying it isnt, why did you state with no ambiguity that I was wrong when I explained hydrodynamic lubrication and its requirements, only to stop when I provided 3 quotes re: Mr Reynolds proving what I had said? Are you seriously telling me that is the first time you heard it???
OK, please explain to this dumb Engineer what the Reynolds Number is in the oil filter of an operating engine, and how it applies to the bypass function of an oil filter. It's OK, drop back to first principals, so that I can follow you through the science. Which operating dimension do you apply the "D" to in Reynold's Number ?
 
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27,176
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PNW
QD - The filter's bypass valve is just a simple check valve. Do you understand the ultra simple operation of a check valve? http://en.wikipedia.org/wiki/Check_valve From the link: "Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position."
 
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742
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SW Missouri
QuadDriver: I say again, if you cannot provide references then what you have to say is only opinion, hearsay, or marketing fluff. I could not care less about what your "Honda friends" have to say, unless it is backed up by a verifiable reference. Your "Honda friends" have no more credence than you; which is to say, none. Give us verifiable references or what you say is just drivel and you are a troll.
 
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Sunny Florida
I am NOT calling anyone names, just offering some friendly advice via an old quote: "Never argue with a pig. It wastes your time... and it annoys the pig!" It doesn't sound as if anything is going to penetrate.
 
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713
Location
Pennsylvania
Originally Posted By: rslifkin
Quad - Let's look at it this way: Assume we have a filter with a bypass set at 10psi, and the oil pressure going into the filter is 50psi. The oil pressure coming out it 45 psi, meaning a drop of 5psi across the filter. While yes, there's 50psi pushing on the bypass trying to open it, there's also 45 psi of oil pressure, plus 10psi of spring pressure pushing on the other side keeping it closed. In the case of the filter flow charts, whether or not it has a bypass is irrelevant. All those charts tell us is how much pressure drop there is across the filter media. In other words, we can use that to determine whether a bypass valve added to the system would open or not. If you still think otherwise, then I can call you nothing but a moron or a troll.
ok, l;ets look at it this way, when the bypass is open, the pressure drop across the filter, as a whole is still in the 2-5psi range. but but but, the bypass opens at 8-12-15psi. how is this possible then? the bypass opens when the pressure differential betweeen the metal cage, and the bypass is at the rating. the output pressure is irrelevant.
 
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713
Location
Pennsylvania
Originally Posted By: Shannow
[Which operating dimension do you apply the "D" to in Reynold's Number ?
calculate the size in the can if the hydraulic diamter....4 times the area of the cylinder? or 4 tomes the area of the holes in the cylinder? I think it would an integral of all of the annular flows, broken up as small as you want it of course. and this is off the top of my head without having seen a formula for an oil filter.
 
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713
Location
Pennsylvania
[quote=Shannow][Where does this "instant" 40psi come from ? Surely a man of your advanced knowledge would understand that the resistance to flow in a hydraulic circuit (whether it be oil, air, water, boron moderated deionised water, or whatever) is the sum of the resistances in the flowpath, and a pump can't establish pressure until the entire flow path is established... and the filter is but part of the flow path... and the resistance across it is proportional to the flow rate squared... and that when the resistance times the flowrate squared reaches the DIFFERENTIAL pressure (inlet - outlet pressure), the bypass opens, preventing flow restriction to the whole circuit. However, the pump doesn't produce 40psi until the circuit is full, and providing a DP. I thought you were an eningeer? I can measure the oil pressure before the filter. easily. IT has to have some pressure to open the bypass valve no? befire ANY of the oil circuit is established. That sorta IS the purpose of the bypass valve when the oil is horribly cold no? It appears, from your posts that the concept of the pressure differential being measured across the soup can portion of the filter (described before) is lost on you. How can you respond then? IF there is no pressure differential between the insides of the soup can, and the outsides of the soup can (an nowhere else) then it wont work. NEVER. No matter how much puling you do.
 
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NC, United States
I'm an economist and there is the old George Bernard Shaw quote stating that "if you lay all the worlds economists end to end, they wouldn't reach a conclusion". There is an engineer corrollary here. If you lay all the world's engineers but one end to end, they would reach a conclusion.
 
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Rochester, NY
Originally Posted By: QuadDriver
I can measure the oil pressure before the filter. easily. IT has to have some pressure to open the bypass valve no? befire ANY of the oil circuit is established. That sorta IS the purpose of the bypass valve when the oil is horribly cold no?
Quad - Nobody said there was NO pressure immediately on startup (the filter alone could certainly provide enough resistance to open the bypass with cold enough oil, which would get you to about 15psi at the pump output). However, the gauge won't show a full 40+ psi until the entire system has filled with oil and is providing resistance. Once this happens, you would likely be seeing a difference in pressure of slightly greater than the oil bypass rating if you compared the filter inlet PSI to the outlet PSI. Once the oil warms up sufficiently that the filter media provides less of a restriction than the bypass, the pressure difference will fall below the bypass rating, indicating the bypass to have closed. As an example of how non-restrictive most filter media is, I took a spare Magnefine sitting around in the garage and blew through it. As a human, I couldn't generate enough flow through the filter to feel ANY increase in resistance compared to an empty tube of equal length. While yes, air is far less viscous than oil, it still makes the point that the filter media is a heck of a lot less restrictive than plexiglass!
 
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27,176
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PNW
Originally Posted By: QuadDriver
Originally Posted By: rslifkin
Quad - Let's look at it this way: Assume we have a filter with a bypass set at 10psi, and the oil pressure going into the filter is 50psi. The oil pressure coming out it 45 psi, meaning a drop of 5psi across the filter. While yes, there's 50psi pushing on the bypass trying to open it, there's also 45 psi of oil pressure, plus 10psi of spring pressure pushing on the other side keeping it closed. In the case of the filter flow charts, whether or not it has a bypass is irrelevant. All those charts tell us is how much pressure drop there is across the filter media. In other words, we can use that to determine whether a bypass valve added to the system would open or not. If you still think otherwise, then I can call you nothing but a moron or a troll.
ok, lets look at it this way, when the bypass is open, the pressure drop across the filter, as a whole is still in the 2-5psi range. but but but, the bypass opens at 8-12-15psi. how is this possible then? the bypass opens when the pressure differential betweeen the metal cage, and the bypass is at the rating. the output pressure is irrelevant.
rfliskin has is right ... QuadDriver has it completely wrong. This why: In order for a simple check valve - which is exactly what the bypass valve in an oil filter is - there needs to be a differential pressure across it. In this case let's say it's 12 psi. So it will take a 12 psi pressure difference between the outside surface of the filter media and the inside surface of the media (ie, at the "metal cage"). The pressure difference is simply across the media surface as the oil flows through it - which is also the pressure difference across the bypass valve. QD - have you ever cut open an oil filter. Have you every seen a cross-section view of one on the internet and have understood how the oil flows through it? When the bypass valve opens at 12 psi, then the pressure across the filter "as a whole" is also 12 psi. It is NOT 2~5 psi like you think. I really don't understand why you can't grasph this super simple concept. ???
 
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Originally Posted By: QuadDriver
I can measure the oil pressure before the filter. easily. IT has to have some pressure to open the bypass valve no? befire ANY of the oil circuit is established.
Here's something that will blow your mind. It could be possible to have pressure on the inlet side of a filter at 200 PSI, and the pressure on the outlet side of the filter at 195 PSI (hint: that's a 5 PSI difference) ... and the filter's bypass vavle set to 12 PSI will NOT be open. Can you believe that? Most everyone here will.
 
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43,652
Location
'Stralia
Originally Posted By: QuadDriver
It appears, from your posts that the concept of the pressure differential being measured across the soup can portion of the filter (described before) is lost on you.
LOL.... DIFFERENTIAL PRESSURE =PRESSURE IN - PRESSURE OUT Regardless of the absolutes of those pressures. I've only said it like a half dozen times in the thread, and you keep telling me that I'm wrong.
 
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4,564
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If Quad wants to prove some things to himself rather than relying on inaccurate heresay, all he needs to do is hook up a differential pressure gauge, or two gauges one before and one after the oil filter, and watch. The relief valve will NOT open unless the DP exceeds it's preset limit. That's simple physics. How often it actually does open, is not generally found in the info I have seen. We have had some discussions on that but AFAIK, nobody has produced any test data the shows an average frequency. The recent Fram info published hinted that the relief valve may open thousands of times momentarily over the fitler's lifetime... certainly they claim to build towards that possibility by using a robust valve. I can run two gauge now on my setup (though not permanently YET) and for a test, I hooked up a second gauge temporarily. On starting my truck, I'd see a momentary blip of about 15 psi (this is 10W30 oil). Otherwise, it stayed pretty stable at about 3-5 psi, lower at low rpm and higher at higher rpms (up to about 2500). I'd see some momentary movement (7-8 psi) on a hard throttle blip acceleration from low idle (especially with cold oil), and considerably less movement with any change of speed, but it would rapidly stabilize in any case. I believe the relief pressure listed for my P/N of P1 filter is 8-16 psi, so theoretically, it may be opening momentarily on those cold starts. I suppose I will later permanently install a second oil pressure gauge and sender, because I now have an extra port on the clean side of the filter. It will be interesting to monitor this going down the road.
 
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