I have a 69 Mustang with a built 428, when I start it up when it is cold it will hit a 100 psi. Does this mean my filter is in bypass mode when the oil pressure is so high? Just wondering if my oil is getting filtered when the engin is cold.
FLA1 Motorcraft filter & 100 psi oil pressure
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From my take on it, probably for a little bit. I'm of the belief that you're closest to, or in, bypass when the pump is in relief. If you're slammed up against 100psi and it takes a bit for it to settle down, you're surely developing PSID above normal.
Sure it's getting filtered ..just not 100% of it.
What are you running, 50 weight? What's your hot idle?
Sure it's getting filtered ..just not 100% of it.
What are you running, 50 weight? What's your hot idle?
Gary, I am under the impression that oil pressure by itself has nothing to do with filter bypass operation. It is only the "difference" in pressure between the dirty oil side of the filter and the clean oil side.
My pressure is about 25psi hot at idle and I'm running 10W30 with a high volume melling pump.
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You're absolutely correct. However when you're in pump relief (which you can be when your gauge is slammed up against the limit) you have two conditions that can surely add up to filter bypass. You have max PSI applied ..and reduced flow to the engine. The engine, with reduced flow, will have reduced PSI in backpressure. The filter will see MAX pressure. MAX pressure ..less "back pressure" (due to reduced flow) equals more PSID. Once the relief is closed ..100% of the net flow from the pump must pass through both the engine and the filter. The engine is a WAY bigger restriction then the filter. The filter is in proportion to the engine in pressure "drops" (elevations, actually) ..so doesn't (typically) amount to squat. Throw the pump in relief ..and the flow dynamics change radically. The oil no long just accellerates through the filter. It has other options for where it's going.
02, you're probably as thin as you can go for visc. Keep in mind whenever you're peaked out on the gauge, you're probably at reduced flow. The amount will be variable depending on the visc at the moment (oil temp). You may consider a couple of things. One would be synthetic to assure that you're as thin as possible at colder oil temps. Another is to install a heat exchanger to stabilize oil temps/visc.
This doesn't mean that you're necessarily seeing any problems from this. I have an HV pump on my wife's 4.0 jeep engine. The engine cannot consume the high volume. I peak out at 58lb (the pump's limit). To "fit" the entire range inside the flow capabilities of the pump, I have to use 5w-20 oil. Otherwise, I'm slammed up against the relief above 1200 rpms. I usually use a 5w-40 synthetic ..so my flow is 100% variable off idle depending on the visc at that time. Which probably means that my filter is at or near bypass more often then most.
(I'm almost done here)
As long as the majority of the time that you're operating you're not peaked out (max cold pressure) ..you're probably not getting naywhere near the bypass pressure in the filter.
Carry on...
I don't get it. If you have "max psi applied, and reduced flow to the engine"---why do you have reduced flow to the engine? Is the assumption that the oil is to thick to go through the filter, ie cold oil? If its reduced flow because it cann't exit the bearings, lifters etc. fast enough than that would create higher pressure not lower pressure. What am I missing? Are you suggesting that the pump relief is after the filter?
[ August 18, 2006, 07:05 PM: Message edited by: another Todd ]
[ August 18, 2006, 07:05 PM: Message edited by: another Todd ]
Gary Allen, have you given up on me?
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Okay ..keep in mind that this is a constructed theory due to my observations of PSID and reactions with before and after filter gauges and differential gauges. I can't articulate a viable, mathmatically supported, model to satisfy my BITOG internal peer review committee ..but if you attempt to see the rationale that I'm applying, you should be able to see the "intent" of my description here.
When the pump relief is closed, ALL the oil MUST go in a straight line through from the sump to the engine. It has no other choice. It goes down a pipe. Most of us are used to our garden hoses and water faucets and think "hmmm...more restriction ..less flow". Doesn't work that way with an oil pump. 5gpm is 5gpm. As long as that pressure limit is not reached ..that oil will SCREAM through whatever you put in its path. It has NO OTHER CHOICE. It's in a single conduit (until it hits the main oil gallery - but from the pump's view ..from the filter's view
So, you can easily visualize that the engine, with all its close clearances and mass size, is going to be a major resistance compared to the filter. (figuratively speaking) Miles of oil passages ..versus one small alleged choke.
Now in series circuits ..the pressures are divided proportionally across the respective elements of the circuit. In my case, looking at a typical (warm) cold start without relief action, I see something like 80 psi post filter and 82 pre filter ...or 2 PSID. Nothing. The engine is WAY higher in resistance then the filter.
Now as the oil thins and the total pressure is reduced ...so does the PSID. The only exception is when the filter loads and increases its resistance. It changes, the engine does not. Hence you could get 2PSID min ..all the way up to the bypass limit if you left it in long enough (not likely for BITOG types ..but numb consumers that don't change their oil
So, can you agree with what I've said so far? If you had a positive displacement pump on your garden hose ..if you tried to put your thumb over the end ..the pressure would just build to what ever it had to and the flow would remain the same. This is how pressure washers work. When you close the trigger ..the "pump relief" opens and the pump is unloaded. It just recirculates the water. Otherwise, it doesn't care what nozzle you put on the end. Open pipe ...fine spray ..pinpoint tip ..whatever.
NOW ..when the relief is open ..this is no longer the case. The flow has an option NOT to go down the pipe/hose/oil passage ..it will choose the path of least resistance until it balances the two paths. This occurs at PEAK pressure (the pump's limit). So now we have PEAK pressure ..but, in regard to what goes to the engine, REDUCED FLOW ..just like your garden hose and your faucet. More restriction ..less flow. The engine and the relief port are now in competition in comparative resistance to flow.
Now do you recall how the engine generated a "back pressure"? It represented the lion's share of the pressure generation in the reading at the guage(s). That pressure was a result of a given flow through a given resistance. This will never change. Xvisc oil a Ygiven rate will result in Zpsi. Now, with the pump in relief, and the flow reduced (some of it is going through the pump relief), it will generate LESS pressure across it.
Example: 4gpm @ 100CST results in 80 psi from the engine. 3gpm will generate 60 psi from the engine.
Okay with that?
So, now we're at our peak pressure (let's say it's 82 psi), - keep in mind that there can be 82 with no relief action ..and 82 with near 100% relief action, ..and at REDUCED FLOW. So ..one side of the filter (engine side) sees 82 ...the other side of the filter sees 60 psi (pressure generated from 3 gpm through the engine) ..for a PSID of 22. Does that add up?
BUT WAIT!!! We typically have a bypass valve somewhere in the filter circuit that limits this PSID. Hence the flow to the engine will have a max reduction due to the relief of the oil pump (or loading). Let's say the bypass valve is 10 psid. Now the engine MUST see PEAK pressure - (minus) 10PSID ..or in this case ..72 psi ..and will have that resultant flow. The bypass limits the amount of flow that can be shunted to the relief by manipulating/annetuating the max PSID that the filter can produce.
If you have no bypass valve ..there is no limit to the resistance that the filter can elevate to in "apparent" resistance. The flow can be reduced to nothing (assume that the relief appears to be a very easy path compared to heading toward the engine) to the engine and the upside pressure will be limited only by the amount of oil that the relief port on the pump can bleed off ...until you breach the media.
So, relief closed ..filter equals next to nothing plus loading. Relief open ..whole different ball game. (reread the bold type disclaimer at the top)
Further qualifications: There is surely a "chicken and egg" situation here that you can run into with stuff like this and some Boolean states in circuits (AND NAND NOR OR - and their outputs). Looking at them, you have to assign them a given status. It's difficult to take snap shots of dynamic events.
[ August 20, 2006, 01:40 PM: Message edited by: Gary Allan ]
If you have room, use a bigger filter. Try the FL299! More media means more clean oil prior to bypassing.
Filter bypass means that any excess oil that can't make it through the media's restriction is bypassed. IMO, this is not something to worry about. The bypass isn't a perfect valve and probably leaks a fair amount regardless. I also don't see the pump's relief as a perfect valve.
Use a good oil(preferably synthetic) and if you are worried about filtration, install a bypass filter.
Filter bypass means that any excess oil that can't make it through the media's restriction is bypassed. IMO, this is not something to worry about. The bypass isn't a perfect valve and probably leaks a fair amount regardless. I also don't see the pump's relief as a perfect valve.
Use a good oil(preferably synthetic) and if you are worried about filtration, install a bypass filter.
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If you rewind to your original question, you asked about pressure differentials that the filter sees. That is the total content of what I just hammered out. I explained how those differentials occur as I see it.
The whole pump explation was to show you how, without pump relief, there should be very little differential under most circumstances. You asked for the $0.25 tour.
The whole pump explation was to show you how, without pump relief, there should be very little differential under most circumstances. You asked for the $0.25 tour.
Good post Gary so does this make sense, if you use a thicker oil than what is recomended, the relisf valve in the oil pump could open , resuting in the same oil psi but less flow. I know all engines are not designed the same, but could this be happening, and does the same psi with a thinner oil mean its flowing more oil ?
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It depends. If you peak out in psi at startup and stay at peak psi longer into warm up ...or are at peak psi unless you're idling ...probably. Your flow may be variable based on the visc at the moment.
Some engines appear setup this way ..even with spec'd oil.
In your older style domestic iron, the oil pump volume doen't appear to always match the relief limits. They may have a relief limit that limits the stress on the distributor drive ..while the vane area results in slamming up against it most of the time.
This is how my wife's 4.0 jeep engine reacted with an aftermarket high volume pump. The engine probably has a peak demand for 5 gpm of oil flow ..and I installed a 9 gpm (@3000 rpm, IIRC) pump. So it was slammed up against the relief nearly 24/7 off of idle. It was there with 40 weight ..it was there with 30 weight. It required 5w-20 to "fit" the entire flow into the engine without hitting the relief setting. I believe, after some education from my esteemed pals here, you reach a point in rpm where the oil is just as much "drawn through" by the laminar action of the bearings as it is pumped by the oil pump. You may just be "loading a hopper" so to speak ..while you reach a limit in psi just due to the resistance of the plumbing to the main oil gallery (and maybe include it). That is, I think this is the reason why we virtually never see a totally "progressive" psi reading over the full range of rpms. You're kinda getting deep into the cause and effect at that point, however ..and there's surely some variances and exceptions that will creep in (increased pumping losses due to reduced viscosity, etc.).
Let me add that if in fact the differentials were so high, so often, that bypass activity was routine (which I believe it was), that UOA showed no ill effects of any substance.
That is, 100% full flow filtration didn't seem to be a requirement for adaquate lubrication.
It will probably take a year before I get around to it ..but I hope to rig a differential gauge on my wife's engine and put in either 30 weight or 40 weight oil and do some real observations to assure that my observations on one engine, and yet to be proven opinions, are consistant on another.
The peer review committee here is pretty intense (a good thing)
Some engines appear setup this way ..even with spec'd oil.
This is how my wife's 4.0 jeep engine reacted with an aftermarket high volume pump. The engine probably has a peak demand for 5 gpm of oil flow ..and I installed a 9 gpm (@3000 rpm, IIRC) pump. So it was slammed up against the relief nearly 24/7 off of idle. It was there with 40 weight ..it was there with 30 weight. It required 5w-20 to "fit" the entire flow into the engine without hitting the relief setting. I believe, after some education from my esteemed pals here, you reach a point in rpm where the oil is just as much "drawn through" by the laminar action of the bearings as it is pumped by the oil pump. You may just be "loading a hopper" so to speak ..while you reach a limit in psi just due to the resistance of the plumbing to the main oil gallery (and maybe include it). That is, I think this is the reason why we virtually never see a totally "progressive" psi reading over the full range of rpms. You're kinda getting deep into the cause and effect at that point, however ..and there's surely some variances and exceptions that will creep in (increased pumping losses due to reduced viscosity, etc.).
Let me add that if in fact the differentials were so high, so often, that bypass activity was routine (which I believe it was), that UOA showed no ill effects of any substance.
That is, 100% full flow filtration didn't seem to be a requirement for adaquate lubrication.
It will probably take a year before I get around to it ..but I hope to rig a differential gauge on my wife's engine and put in either 30 weight or 40 weight oil and do some real observations to assure that my observations on one engine, and yet to be proven opinions, are consistant on another.
The peer review committee here is pretty intense (a good thing)
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Sure, but this is also typical conditions that cause pump relief. In my observations, excessive loading of the filter would be required to reach bypass conditions without pump relief also occurring at the same time.
Exactly. You can't achieve too much PSID because of the bypass valve. The bypass valve is to protect the engine from starvation in pump relief events..the bypass valve setting is to protect the media.
I used a dual remote Permacool remote adapter. Put a engine side adapter where one filter would be for temp and one pressure take off ..and used one of the end ports for the other pressure tap. I could do it with one of those sandwhich taps and the OEM sender port as well, I suppose
I reversed the orientation of the filters when I added a temp sensor and moved one of the pressure taps.
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I think I see your confusion. You're not alone.
Let's chaulk our intial startup issues with the pump to "inertia" (just as a suggestive explanation). Heavy fluid at rest ..that desires to stay at rest. Don't confuse this with "truth" ..but merely a tool to allow you to view the example in a given manner. It may very well be true ..but let's not dwell on it now.
Okay ..so your pump has a column of stationary jelly to push ..heck, with enough mass ..it could be water and the stuff doesn't want to move. The pump sees a transient spike of pressure ..the relief opens ..reducing flow to the filter and the engine at the max pressure that the system can see ..the pump shunts flow ..the upside of the filter sees the peak pressure ...the engine developes it's pressure ..and if there was no bypass valve in the filter or block ..the PSID would be the difference.
You may want to review my comments in this thread.
Here's what happens when your pump is in relief and you have no bypass valve
Let's chaulk our intial startup issues with the pump to "inertia" (just as a suggestive explanation). Heavy fluid at rest ..that desires to stay at rest. Don't confuse this with "truth" ..but merely a tool to allow you to view the example in a given manner. It may very well be true ..but let's not dwell on it now.
Okay ..so your pump has a column of stationary jelly to push ..heck, with enough mass ..it could be water and the stuff doesn't want to move. The pump sees a transient spike of pressure ..the relief opens ..reducing flow to the filter and the engine at the max pressure that the system can see ..the pump shunts flow ..the upside of the filter sees the peak pressure ...the engine developes it's pressure ..and if there was no bypass valve in the filter or block ..the PSID would be the difference.
You may want to review my comments in this thread.
Here's what happens when your pump is in relief and you have no bypass valve
The bypass valve setting is to protect the media, TRUE.
For those following this thread, I want to make sure you understand the difference between the two valves Gary and I are discussing here.
First we have an oil pump "relief" valve. It relieves excessive pressure in the oil system, and is usually part of or near the oil pump. Its setting is like Gary said, usually at the highest pressure you ever see on your gauge, because beyond that it would be relieving the "excess". Usually it is set in the neighborhood of 65-85psi, in Garys case 82psi. Oil pressure in your system should never exceed that setting. This valve protects the filter and pump from over pressurization among other things. Signs of a stuck closed relief valve would be excessively high oil pressure, and oil filter ballooning/rupture, or leaks. A stuck open relief valve would cause very low or no oil pressure at normal operating temps when the oil is thinnest.
Second we have the Oil Filter "BYPASS" valve. Often located in the filter but sometimes (GM) located in the engine block. This valve protects the engine from oil starvation when the oil cannot flow through the filter media fast enough, due to filter loading (plugging up) or thick oil, or more flow than filter can handle. USUALLY these valve are set around 8-16 psi(some are higher, some lower)but it's not important for this discussion. For this, let's just say the filter bypass valve is set at 10psi. This 10 psi is "diferential pressure. "Oil pressure has no real effect on it", it only opens when the difference in pressure between the two sides of the filter media is greater than 10psi. Obviously the oil pump side of the filter has the higher pressure. When you have 80 psi oil pressure on the pump side and 71psi on the engine side of the media the bypass valve remains closed and all oil goes through the media. The "difference" is only 9psi. If the engine side drops more than 10 psi than the pump side then the bypass valve opens to maintain 10 psi differential maximum. If your filter plugged up the bypass would be wide open all the time.
Interesting note on the Bypass valve located inside filters. In the past they were always located in the bottom of the filter and you could see the valve down in there. Lately, some filter manufactures have begun to put them just below the threads of the filter. I think this is a much better design because when the valve is bypassing it does not wash across the media before going to your engine unfiltered. The style with the bypass valve in the bottom of the can could actually reintroduce contaminants that were previously held on the outer layer of the filter. Purolator says that doesn't happen, but I bet in the future they will change to this newer style valve under the threads.
I forgot something on the Bypass valve. A stuck closed bypass valve will most likely result in collapsed center tube inside filter and ripped filter media. A stuck open bypass valve will result in unfiltered oil circulating through your engine.
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Todd, you're arguing from I don't know where
If you can offer any empirical or documented authoritative source to substaniate your assertions ..by all means ..produce them.
You're dancing around stuff that I've observed with my own eyes. I didn't just pull it out of my behind.
I've watch every weight of all under all temperatures ..in every event (there were thousands) the two guages may have rose fast ..they may have rose slow ..but they moved in tandem with nearly undetectable delay between them. The ONLY tiem that there was a substantial differential ..they still ramped up as a pair. The difference was that the pump side continued to climb and the engine side stopped at a lower level. This was a very breif transition. It was so cold and the oil so heavy that I wasn't even able to attain the peak observed pressure of 82 PSI.
Pulling out of my memory:
77:70
In this case, the viscosity was so high ..and so much flow was shunted that the point of reading realized lower then peak psi. That is, the lines themselves became a more substantial part in the equation.
As it transitioned ..the lower (engine side) pushed the pump side as it "met" it ..and it resumed its normalized state of 82:80 ..and then decayed as the oil warmed.
Gary, in following the link you gave me you posted the following with pictures. Pictures didn't copy. Here is what is wrong with your theory. When you increase the amount of oil "shunted to the relief" you state there is reduced flow--presumably because more oil is now flowing out the relief. This is incorrect because you have to increase RPM to increase flow, the engine will see the exact same flow, the extra flow from the positive displacement pump turning faster will get dumped out the relief valve. Otherwise, what "caused" more oil to be shunted to the relief valve?
The heirarchy of "circles" is PUMP, filter, engine. I did not draw the relief circuit = which effectively is a parallel variable resistance. This will allow you to see this as a simple series circuit in a variable flow/regulated pressure situation. All three of these images must add up to 100psi. The split is a function of the constant pressure ..and the reduced pressure drop across the engine at the reduced flow rate.
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No go to 10% flow shunted to the relief. We'll still see 100psi ..but at reduced flow.
Note the pressure drop changes over the individual elements.
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Now at 50% flow shunted:
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So ..all they had to do is hit the relief valve and have it shunt a good % of the flow to the suction side/sump ..and the differential would go sky high with, perhaps, NO FLOW
This is why Pete C. insists that the bypass is there to protect the engine. If the PSID was limited to 15PSID ..then the engine would have to receive more flow at 100 psi applied. Now the bypass SETTING is there to protect the MEDIA. It was not easy to make this distinction.
[ June 15, 2006, 01:51 PM: Message edited by: Gary Allan ] Posts: 10063 | From: Pottstown, PA
The heirarchy of "circles" is PUMP, filter, engine. I did not draw the relief circuit = which effectively is a parallel variable resistance. This will allow you to see this as a simple series circuit in a variable flow/regulated pressure situation. All three of these images must add up to 100psi. The split is a function of the constant pressure ..and the reduced pressure drop across the engine at the reduced flow rate.
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No go to 10% flow shunted to the relief. We'll still see 100psi ..but at reduced flow.
Note the pressure drop changes over the individual elements.
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Now at 50% flow shunted:
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So ..all they had to do is hit the relief valve and have it shunt a good % of the flow to the suction side/sump ..and the differential would go sky high with, perhaps, NO FLOW
This is why Pete C. insists that the bypass is there to protect the engine. If the PSID was limited to 15PSID ..then the engine would have to receive more flow at 100 psi applied. Now the bypass SETTING is there to protect the MEDIA. It was not easy to make this distinction.
[ June 15, 2006, 01:51 PM: Message edited by: Gary Allan ] Posts: 10063 | From: Pottstown, PA
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