Oil filter flow test thread

[GMGuy]

I'm trying to find the oil filter flow test thread that BobisTheOilGuy was writing, comparing various oil filters on a home-made test jig.

Searching is turning up nothing, my bookmark is for the old board and 404. Anybody have a current link or able to find the thread?

Alex.

 

[Steve S]

I remember the testing . It really doesnt prove much. The only time to worry about flow is if you have an all out race engine.

 

[MarkC]

Gary did something like that a while back, maybe ask him.

 

[Gary Allan]

I'll find it. I found flaw in Bob's methodology in that he applied a give pressure ..and measured the differential.


Bob used room temp fluid (I think 30 weight) and drove an oil pump with an electric motor. He then ran the oil pump into a remote mount that was plumbed, in one manner or another, into an engine.

He would run the pump up to some level ..and then read the differential over two gauges.

The hole there is that he regulated the upper pressure. If he had instead regulated the lower pressure, assuming temp was comparable, he would have almost assured a stable volume since the engine would have been a somewhat fixed element.

If he had done that, no upper level pressure would have exceeded the bypass setting for any given filter. He could then have turned down the lower pressure to below all bypass thresholds (lowest common denominator) and showed how all filters compared at ONE flow rate while not in bypass.

 

[SuperBusa]

Here's an interesting oil filter flow test IMO.

http://www.peterverdonedesigns.com/oilfiltertest.htm

This link [ http://www.geocities.com/rfpxj/Oil_Filter_Experiment.pdf ] inside the link above was really intesting and had test measurement numbers ... but the link if broken now.

Here's a flow vs. PSID chart with oil at a constant viscosity for various filters that was published by AC Delco. I think this chart is the PSID you would see if there was no by-pass valve - in other words, they did the flow test just on the element cartridge, not the filter assy.

 

[SuperBusa]

Originally Posted By: Gary Allan
I'll find it. I found flaw in Bob's methodology in that he applied a give pressure ..and measured the differential.

Bob used room temp fluid (I think 30 weight) and drove an oil pump with an electric motor. He then ran the oil pump into a remote mount that was plumbed, in one manner or another, into an engine.

He would run the pump up to some level ..and then read the differential over two gauges.


Doing the test that way would only tell you which filters would be more restrictive on that particular engine, and not really give a true "Flow vs. PSID" chart (like in previous post) for all the filters in the test.

Since the engine was a fixed resistance, and he was swapping out and testing different filters in the system while using a constant input pressure (say it was 80 psi) and a constant oil viscosity, then it would be like comparing different filter PSIDs with an oil pump in pressure relief mode at 80 psi with constant viscosity oil.

Since the engine is a fixed flow resistance, then the flow rate going through the filter/engine flow path would only change dependent on the relative flow resistance of each filter put in series with the engine. So, lets say filter A is more restrictive than filter B. In his test, he would see a larger PSID across filter A and he would also see a corresponding lower engine input pressure (pressure between filter and engine circuit). He would not know what the actual oil volume flow rate was unless he had a flow meter in the test setup. With Filter B, the total oil flow volume decreased through the filter/engine compared to using Filter A. Assume the pump can supply any required flow for the pressure/resistance circuit it is supplying.

Examples:
Filter A (more restrictive than Filter B)
Filter Inlet P = 80
Filter Outlet P = 72
Filter PSID = 8
Engine Inlet P = 72
Sump P = 0

Filter B
Filter Inlet P = 80
Filter Outlet P = 76
Filter PSID = 4
Engine inlet P = 76
Sump P = 0
Note - Flow volume increased some amount due to Filter B being less restrictive.


Note that if there was no filter, the engine inlet pressure would be equal to the pump's outlet pressure (80 psi). If the filter was super restrictive ... say a 25 PSID, then the engine's inlet pressure would only be 55 psi with an 80 psi pump pressure.

Originally Posted By: Gary Allan
The hole there is that he regulated the upper pressure. If he had instead regulated the lower pressure, assuming temp was comparable, he would have almost assured a stable volume since the engine would have been a somewhat fixed element.

If he had done that, no upper level pressure would have exceeded the bypass setting for any given filter. He could then have turned down the lower pressure to below all bypass thresholds (lowest common denominator) and showed how all filters compared at ONE flow rate while not in bypass.


Yep ... if the inlet pressure to the engine was controlled then that would mean the flow rate would be the same through the filter/engine regardless of which filter was used. It would also mean that the pump's output pressure would have to be increased when using a more restrictive filter (a higher PSID) in order to achieve the same engine inlet pressure.

Quote:
If he had done that, no upper level pressure would have exceeded the bypass setting for any given filter.


Actually, the only thing that determines if the filter's bypass valve opens or not is the PSID across the filter. The filter's inlet pressure could be very high and not produce a very high PSID if the flow rate is low due high flow resistance of the engine circuit. Of course, if the filter PSID is at or above the rated bypass setting of the filter, then it's real likely the bypass is open to some degree.

 

[Gary Allan]

Quote:
Actually, the only thing that determines if the filter's bypass valve opens or not is the PSID across the filter. The filter's inlet pressure could be very high and not produce a very high PSID if the flow rate is low due high flow resistance of the engine circuit. Of course, if the filter PSID is at or above the rated bypass setting of the filter, then it's real likely the bypass is open to some degree.



Well, for that to happen, in most cases, the pump itself has to be in relief. What Bob would have found is very little difference in PSID until the oil pump was in relief ..then it would attenuate at the bypass setting. We're naturally talking clean filters here.

I wish the objections were brought up when he was doing this. It would have been real easy for him to alter his premise for determining whether a filter is free flowing or not. Those figures are for comparative purposes only.

That is, a filter that sports 10PSID @ 10 gpm with 150SUS fluid is more "free flowing" than one that sports 6 PSID under the same conditions. It makes little difference if you're talking about an engine with 6 gallons max oil pump potential @ 5500 rpm. If you're not in relief, then the flow is going to occur and impact the PSID across the engine to an equal amount ..up to the true impedance of the filter itself ..which very few ever challenge.

 

[SuperBusa]

Assuming you keep oil viscosity constant and the filter/engine flow resistance constant, and you have a pump relief pressure of say 80 psi ... then IF the filter's bypass valve is going to open at all, it will open sometime before or just at the pumps' pressure relief setting. If the filter's bypass valve isn't open by the time the pump hits relief mode, then it's never going to open at that particular oil viscosity.

Once the pump is in pressure relief, you can not increase oil flow volume down the filter/engine flow path any more than it already is at the pump's relief pressure ... of course, assuming the pump's relief valve is 100% effective at regulating the pressure right at it's setting (of 80 psi in this case).

 

[Gary Allan]

Quote:
If the filter's bypass valve isn't open by the time the pump hits relief mode, then it's never going to open at that particular oil viscosity.


Aren't you missing a qualification here, Soupy??

 

[SuperBusa]

Originally Posted By: Gary Allan
Quote:
If the filter's bypass valve isn't open by the time the pump hits relief mode, then it's never going to open at that particular oil viscosity.


Aren't you missing a qualification here, Soupy??

Nope ... you tell me what "qualifications" you think are missing. That statement is 100% true. All the qualifications were explained in the original post (go re-read it) - which really says it all. Of course, I'm not talking about crazy pressure/volume surges going on, or pump relief valves that are messed up or designed incorrectly so the pump's output pressure isn't controlled well. I'm talking about controlled stead-state flow scenarios. Remember my ideal PP pump performance curve?

If the pump's relief valve is working correctly, and the pump's output pressure is controlled to a fixed value at the point the relief valve kicks in ... AND IF the filter is every going to go into bypass mode with that oil viscosity at the point in time, then it will go into bypass mode before the pump goes into pressure relief mode - or possibly right at the exact point of relief. If the filter doesn't hit bypass by the time the pump hits relief mode, then the filter never going to go into bypass at any engine RPM with that viscosity of oil. It's that simple.

Once the pump hits relief pressure (with a constant viscosity), then that is the point of highest flow to the filter, and the highest PSID for that particular viscosity. If the filter is not in some level of bypass by the time it the pump hits pressure relief, then the filter will never go into bypass with that viscosity oil .... [NOTE - not counting insane surges, which actually caused flow volume spikes, which in turn cause PSID spikes, which in turn cause bypass valve opening spikes.

]

 

[Gary Allan]

Quote:
AND IF the filter is every going to go into bypass mode with that oil viscosity at the point in time, then it will go into bypass mode before the pump goes into bypass mode, or possibly right at the point of relief.


...but I recall DISTINCTLY you saying that the two mechanisms have nothing to do with each other. Go back and look.

..are you saying that you were in error ..or ...perhaps ..you've gone home and gotten rid of the death sticks and rethought your life

Quote:
Of course, I'm not talking about crazy pressure/volume surges going on, or pump relief valves that are messed up or designed incorrectly so the pump's output pressure isn't controlled well.


You're the only one I've ever heard mention those things. I can't for the life of me think of where you have observed such things. Then again, I don't think you've ever observed any of this at all, correct?

 

[SuperBusa]

Originally Posted By: Gary Allan
Quote:
AND IF the filter is every going to go into bypass mode with that oil viscosity at the point in time, then it will go into bypass mode before the pump goes into bypass mode, or possibly right at the point of relief.


...but I recall DISTINCTLY you saying that the two mechanisms have nothing to do with each other. Go back and look.

..are you saying that you were in error ..or ...perhaps ..you've gone home and gotten rid of the death sticks and rethought your life

The pump's relief valve operates independently of the filter's bypass valve, and vica-versa ... that's what I mean.

Now, it's true that IF you modified the oil pump's relief valve so it kept the pump's output pressure to say 125 psi max instead of say the original setting of 80 psi max ... THEN it's possible that mod could cause the filter to now go into bypass mode when it originally didn't when hit with 80 psi. Do you know why? - because of increased flow volume and increased filter PSID due to higher pressure (125 vs 80 psi) on the fixed resistance filter/engine flow path. And if the filter did go into bypass with the higher relief pressure of 125 psi (and particular viscosity), then it would do it at some point before or right at the time the pump goes into relief mode. Again, if the filter didn't go into bypass mode with a max regulated pressure of 125 psi, then it would never go into bypass with that viscosity of oil, on that particular engine at any RPM between idle and redline. You would have to increase the flow even more to get an even larger PSID to get the bypass valve to operate. Get the pattern?


Originally Posted By: Gary Allan
Quote:
Of course, I'm not talking about crazy pressure/volume surges going on, or pump relief valves that are messed up or designed incorrectly so the pump's output pressure isn't controlled well.


You're the only one I've ever heard mention those things. I can't for the life of me think of where you have observed such things. Then again, I don't think you've ever observed any of this at all, correct?


Those are just special "qualifications" for your benefit ... just so there is no confusion, grasshopper.