You better heed what this professor says. 
Motorcraft University
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- That is not technically "straight 30"
- That is not a 1969 Pickup.
- I cannot finish it.
A fourth thing that sometwo or three can never try: Positive displacement & the old showerhead...
Not one pressure / one flow throughout the engine, things get branched, can employ little balls and springs, experience temperature differences,.. The knee-jerk reaction of throwing in positive displacement should get treated. Time-to-lubrication is of interest, positive displacement less and less so along the way. Not one positive displacement unit on each point of lubrication, just one more conditioned reflex to revise.
The prof was further from disinformation than we are.
Not one pressure / one flow throughout the engine, things get branched, can employ little balls and springs, experience temperature differences,.. The knee-jerk reaction of throwing in positive displacement should get treated. Time-to-lubrication is of interest, positive displacement less and less so along the way. Not one positive displacement unit on each point of lubrication, just one more conditioned reflex to revise.
The prof was further from disinformation than we are.
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I always think along these lines when someone says "positive displacement". It's not one tube slap full of oil. It's many passages, scenarios, gravity fed areas, etc.
It's every oil gallery (regardless of size) that is flowing oil that is feed by the PD pump. The oil volume through all those galleries regardless of size (including those feeding the piston squirter oil jets) is flowing the same volume of oil vs engine RPM regardless of the oil viscosity as long as the pump is not in pressure relief. That's the main purpose of using a PD oil pump.
The "gravity fed" areas only become gravity fed after the oil volume in any supply gallery shoots out into the atmosphere, and then gravity and also splashing lubrication takes over. Piston oil squirters are going to exit the same oil volume (vs engine RPM) towards the pistons regardless of oil viscosity because they are supplied by the positive volume displacement oil pump.
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A single output getting divided guarantees nothing regarding individual branches and points of lubrication, cooling, actuation. Like a look at the water meter in the cellar tells nothing about the individual jets of a showerhead or equal supply for all showers in da house.
Neither quick nor equal lubrication are given from the positive displacement aspect. Regulators (mostly) keep pressures at their own location capped without ensuring same pressure at orifices, bearings or actuators; different pressure drops along parallel branches cause unequal distribution between branches, orifices etc. Paths of least resistance.
When more viscous oil takes thrice the time to arrive at some place this can be from combined effects, not open reliefs alone.
Neither quick nor equal lubrication are given from the positive displacement aspect. Regulators (mostly) keep pressures at their own location capped without ensuring same pressure at orifices, bearings or actuators; different pressure drops along parallel branches cause unequal distribution between branches, orifices etc. Paths of least resistance.
When more viscous oil takes thrice the time to arrive at some place this can be from combined effects, not open reliefs alone.
You do realize that the whole purpose of a PD oil pump is to ensure proper oil volume supply to parts regardless of the oil viscosity - assuming the pump is not in pressure relief.
Orifices flow oil based on the pressure difference across them, and with thicker oil the PD pump increases supply pressure in order to maintain the same volume of oil supply. That's why oil pressure goes up with thicker oil used in the same oiling system. So if thicker oil is in all the galleries and the PD is still moving the same volumetric rate (at X engine RPM), the pressure throughout the entire oiling system (all branches) is also going to increase - that's what PD pumps ensure. If the oiling system is designed right, all branches in the system will still be getting their designed share of the total volume leaving the pump, regardless of viscosity across the spectrum of oils used in engines.
If there's a separate "pressure regulator" buried down stream of the pump, then that's a different story. That regulator becomes a stand-along oil control device and isn't what I'm focused on.
blingo said:
Sure there are different pressure drops along all the individual branches of the oiling system. I'm not claiming that every branch has exactly the same oil flow volume going through it. When they are supplied by the oil pump, then their individual flows will be determined by the supply pressure to that circuit and their flow resistance. The sum of all the individual flows will equal the output volume of the pump.
A good analogy would be an electrical circuit of many different paths with different resistors (ie, galleries with different flow resistance), all supplied by the same power supply. Each circuit branch's current current flow will go up and down respectfully with voltage and current changes at the power supply. When the power supply is set to and hits a current limit, then that would be analogus to the pump hitting pressure relief.
How does more viscous oil take 3 times longer to arrive when it's being pushed through all the oil galleries by a positive volume displacement pump? If an oiling system was bone dry, and the pump all primed it would take some amount of time for oil to fill each branch of the oiling system. If you did that test with thin oil or thick oil, the time to fill each branch supplied by the pump is basically going to remain the same. That's the main purpose of using a PD pump in an engine.
It might take 3 times longer to arrive at some location by gravity or splash lubrication after leaving a supply gallery/circuit with more viscous oil, but it's not taking any longer to arrive through any PD pump supplied oil gallery.
I think you're believing an engine's oiling system is like the water system in your house. It's not.
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You have to accept the fact that the positive displacement aspect in that sense is not really that meaningful for anything but a first hop between pump outlet and a first bifurcation of some extent. Beyond that point the same total flow will have more and more options. Options per mile. Each and every molecule in there has primarily options everywhere.
How a more viscous oil would take three times as long to make it somewhere? Should be easy at cold starts. It could just take three times as long instead of four times as long, you know ;-)
Don't watch the pump, watch a remote point of lubrication at rather low temperatures and controlled rpm. Between the pump and where you are there's options and obstructions for wax and ice if you only will, even capillaries if you wish.
Not an actual simulation of start up and warming up (I'm not trying to quantify, data will be around with the professionals) but certainly a positive displacement pump as such not guaranteeing much (42min into the clip):
youtube.com/watch?v=dOyJaOdvswU#t=42m24s
How a more viscous oil would take three times as long to make it somewhere? Should be easy at cold starts. It could just take three times as long instead of four times as long, you know ;-)
Don't watch the pump, watch a remote point of lubrication at rather low temperatures and controlled rpm. Between the pump and where you are there's options and obstructions for wax and ice if you only will, even capillaries if you wish.
Not an actual simulation of start up and warming up (I'm not trying to quantify, data will be around with the professionals) but certainly a positive displacement pump as such not guaranteeing much (42min into the clip):
youtube.com/watch?v=dOyJaOdvswU#t=42m24s
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Extremely cold start up conditions...
With a oil that w rating is at its extreme end... Say a 10w at say -13°f.... Then yeah it could take awhile to get up to the top end of a motor.
But a 5w at -13°f... It would get there with no real delay.
With a oil that w rating is at its extreme end... Say a 10w at say -13°f.... Then yeah it could take awhile to get up to the top end of a motor.
But a 5w at -13°f... It would get there with no real delay.
If the pumpability of the oil doesn't degrade due to viscosity - ie, the pump intake can ingest and flow the same oil volume regardless of the viscosity, and the oil pump is always fully primed - then the pump will flow the same volume vs RPM. When the discussion starts going down the super cold/super viscous start-up temperature focus, then it's a whole different story.
When the oil is so cold that the pumpability into the pump is compromised, then sure it would take longer to distribute throughout the oling system because the pumping performance of the PD is compromised. But that is not the opeatiing coditions I'm talking about, and not what I'm addressing in the posts above. If blingo is just focusing on that (as a strawman argument), it's way outside of the relm of the discussion at hand in the Motorcraft video in post #1.
When the oil is so cold that the pumpability into the pump is compromised, then sure it would take longer to distribute throughout the oling system because the pumping performance of the PD is compromised. But that is not the opeatiing coditions I'm talking about, and not what I'm addressing in the posts above. If blingo is just focusing on that (as a strawman argument), it's way outside of the relm of the discussion at hand in the Motorcraft video in post #1.
I'm not "just focusing on that". Of course we need not talk about times, the Motorcraft professor didn't talk about times when trying to be graphic. Still viscosity is resistance to flow and while he probably need not be informed about PD by us, we need to grasp what positive displacement means and what it doesn't mean.
PD does not mean that flow through a gallery were unimpeded by viscosity. That's not in positive displacement, never was. Oil has choices instead of one pressure / one flow figure or fixed flow ratios throughout an engine. ...things get branched, can employ little balls and springs, experience temperature differences,.. The knee-jerk reaction of throwing in positive displacement should get treated. Time-to-lubrication is of interest, positive displacement less and less so along the way. Not one positive displacement unit on each point of lubrication, just one more conditioned reflex to revise.
The prof was further from disinformation than we are.
PD does not mean that flow through a gallery were unimpeded by viscosity. That's not in positive displacement, never was. Oil has choices instead of one pressure / one flow figure or fixed flow ratios throughout an engine. ...things get branched, can employ little balls and springs, experience temperature differences,.. The knee-jerk reaction of throwing in positive displacement should get treated. Time-to-lubrication is of interest, positive displacement less and less so along the way. Not one positive displacement unit on each point of lubrication, just one more conditioned reflex to revise.
The prof was further from disinformation than we are.
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You do realize that with a PD pump, the outlet oil pressure will increase in order to put the same volume through the oiling system. That is probably the point that most people don't grasp, and therefore form misconceptions about engine oiling systems.
As I explained earlier, each "flow branch" will flow what it does depending on the flow resistance of each branch, and the oil pressure feeding each branch (the electrical circuit analogy). If the inlet pressure (ie, pump output pressure) to the system increases because the engine RPM goes up, then the flow in every branch will also increase (assuming viscosity remains constant). And if the oil pressure goes up at a constant RPM due to thicker oil, the PD is still going to flow that same volume at that RPM as long as the oil is pumpable from the sump and each oiling branch is still going to flow its percentage of the total flow volume coming out of the pump. No oiling system branch is going to be oil starved if the system is designed correctly to supply the minimum volume required for adequate lubrication and the oil if 100% pumpable.
It doesn't matter if there are multiple oil branches in the system ... they will still get their relative flow amount percentage of the total volume coming out of the PD pump.
Based on his comment about piston oil squirters, I'll have to disagree.
I am not arguing with you.............
Just stating what could happen..... In a different circumstance... Like running a w rated oil at very, very cold conditions.
That's all...... I was just making that single point.
I agree with you on all the other technical details.
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With a positive displacement oiling system, if there is a small restricted oil gallery that feeds off a main supply gallery, then the oil volume going into the start of that small, long gallery is the same as the flow going out at the gallery's exit to the atmosphere. What goes in comes out ... that's the whole premise of a PD oiling system. It does not behave like a water system inside your house (which is not PD pump fed).
Like said before, if the oil in the sump is 100% pumpable regardless of temperature, and the pump is fully primed and the entire system was bone dry, it would take the same amount of time to fill each respective oil gallery regardless of the oil viscosity. In other words, oil gallery "branch A" would fill completely and exit oil into the atmosphere (ie, 0 gauge pressure) in basically the same time if fill times for "branch A" were compared with different viscosities. That's the whole purpose of a PD oiling system, to ensure the same oil supply volume goes down each respective oiling gallery "branch" regardless of viscosity - as long as the pump is not in pressure relief, of course.
Yes, I know ... but wanted to clarify that a super cold operating condition is not the focus of the discussion. There seems to be a belief that a different viscosity is going to change the volume of oil to parts in the oiling system that is being supplied by a PD oil pump running at the same RPM. The only time that the oil volume is cut back is in a few rare circumstances - ie, when the oil is not 100% pumpable from the sump due to super cold temperatures, and when the pump is in pressure relief.
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That's " Pure Ford Magic"
Keep a pair of walking shoes in the trunk.
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