It can be either way, you send enough to protect at all range and since you can control how much to send you can use a thinner oil. Or you reduce the flow even more and use a thicker oil, either way it comes out the same.
0w-8 in the new non US Yaris hybrid
- Thread starter JavierH19
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It can be either way, you send enough to protect at all range and since you can control how much to send you can use a thinner oil. Or you reduce the flow even more and use a thicker oil, either way it comes out the same.
Re: the bolded part in quote above. The variable volume oil pumps are still PD oil pumps, so if all things are constant they will be moving the same volume regardless of what the oil viscosity is. If you use a lower viscosity in a variable volume oil pump, the oil pressure will be less. The only way it wouldn't be is if the oiling system used an oil pressure sensor as active pressure feedback to the pump, and the pump controlled output volume and pressure proportionally, but I don't think that's how they work - they aren't that sophisticated. Most are simply two-stage - ie, either low or high output based on engine RPM and pressure relieve valve is either open or closed from what I've seen.
Oil pressure doesn't ensure lubrication, but adequate oil volume does. Journal bearings don't rely and survive solely on oil pressure (the oil pressure doesn't add any significant hydrodynamic wedge inside the bearings), they survive only if enough oil volume is supplied to them, and that is also true with all lubricated engine components.
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They are not all things constant, the design I saw move the impeller toward and away from the housing to control the flow which means the volume. So now they don't need to worry about the worst case scenario on both extreme with the same volume per engine rev. The flow can now be adjusted to be good enough for every rpm on its own.
Can they design it to use the same 0w20 oil? Sure, but why do that when they realize they can now use a thinner oil and adjust the flow to save even more energy?
So, do not use the 0w8 in your good ole fashion PD oil pump.
stricter emission requirements are root cause. they are literally chasing every gram of co2.in 2013, psa engines (stellantis) lowsaps oil norms were hths 2,6...
now they are >2,9 and with small bump in saps too...
(guess why)i don´t feel comfortably below 3,5 hths, seeing the 0w8 almost got stroke...
Are the impeller vanes moved proportionally through a range as a function of oil pressure sensor down stream? Or are the movable vanes either in one position or the other? I've seen other variable volume PD pumps where there's simply a secondary pump bypass valve that is open at low RPM and closed at higher RPM to give more flow above a certain engine RPM. The former design would be way more complicated than the latter. Not all variable displacement oil pumps are designed the same.
Like said earlier ... as long as you can get an adequate volume (regardless of how much pressure that takes) to moving parts, then lubrication will be fine. You could absolutely use 0W-8 in a good ol' fashion PD pump because the supplied volume would be adequate, but the viscosity/HTHS/MOFT of the oil itself may not be adequate.
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The impeller "vanes" or blandes slide in and out of the center hub and along the housing of the pump. The center hub can slide to one side of the housing to create a bigger or smaller volume sweep between the inlet and outlet of the pump per rotation. It is not an external bypass valve design, although a variable bypass design would work as well (although not really saving you a lot of energy, as you still need to pump the worst case scenario volume and then just bypass and slosh around wasting all the flow.
Agree about them able to use 0w8 regardless of pump type, just that they probably know it is optimal for constant volume per rpm pump to use 0w20 after some calculation and simulation. I'm sure they come to 0w16 and 0w8 for this new pump after calculation and simulation too. Whatever works, and they found what works for them.
Looks like that is a totally mechanically controlled variable PD oil pump (not an electrical actuated system based on oil pressure sensor feedback, etc). As engine RPM increases and causes the oil outlet pressure to increase, the small cavity with a feed hole near the compression spring pressurizes more and more, and compresses the spring more which moves the control ring CCW and causes the volume output to decrease.The impeller "vanes" or blandes slide in and out of the center hub and along the housing of the pump. The center hub can slide to one side of the housing to create a bigger or smaller volume sweep between the inlet and outlet of the pump per rotation. It is not an external bypass valve design, although a variable bypass design would work as well (although not really saving you a lot of energy, as you still need to pump the worst case scenario volume and then just bypass and slosh around wasting all the flow.
Agree about them able to use 0w8 regardless of pump type, just that they probably know it is optimal for constant volume per rpm pump to use 0w20 after some calculation and simulation. I'm sure they come to 0w16 and 0w8 for this new pump after calculation and simulation too. Whatever works, and they found what works for them.
At idle and low RPM the pump would be putting out max volume possible for that RPM. It only starts cutting back output volume at higher RPM when the oil pressure increases significantly. That is typically the downfall of an old fashioned PD pump - it puts out way more than needed oil volume at higher RPM. This variable volume pump design would also cut back volume flow if the oil was thicker or during a cold start-up, which would cause more pressure on the control spring. I'm sure the pump must also have a separate pressure relief valve somewhere that's not shown in the photo.
Yeah, good stuff. So I guess 0w8 is not too thin for this design on a hybrid and 0w16 is not too thin for a regular car?
An oil pump like that design will actually pump a little more volume at higher RPM with thinner oil than with a thicker oil. If a pump designed like that was designed for a car specifying 0W-8 then the engineers would design the control spring to provide an adequate oil volume over the entire engine RPM range while trying to minimize the parasitic oil pumping losses.
When factoring in an engine with a variable volume oil pump, it would be wise to understand how the pump performs if different viscosity oils are used. But I'd bet that even if someone used a thicker oil, the pump will still provide adequate lubrication since it does so with cold thick 0W-8 oil. Even cold 0W-8 is many times thicker than even a xW-50 oil at operating temperature.
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You fit right in here....................
Half the BITOG community (many with engineering backgrounds) would have said to use thicker oil before Ford engineers decided to.
Was there something I didn't understand correctly?
first of all, they have to obey rules...use thicker oil before Ford engineers decided to.
really simple because: new cars which does not comply with latest emission standards, you can´t sell.
this is what happened few years ago here, when euro6b was coming to end..
dealerships moved all new cars to car bazaars.
then you bought unused car from bazaar instead. 1st owner was the bazaar, you were 2nd owner.
simple trick, because new emission rules don´t apply for 2nd hand cars.
Yes-,many with armchair degrees.Half the BITOG community (many with engineering backgrounds) would have said to use thicker oil before Ford engineers decided to.
The property of 0W-8 oil is actually really good for what it is made for. https://www.sae.org/publications/technical-papers/content/2020-01-1423/preview/
molybdenum dithiocarbamate MoDTC friction modifier and really good base oil are needed.
molybdenum dithiocarbamate MoDTC friction modifier and really good base oil are needed.
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0W-40, 0W-30, 0W-20, 0W-16, 0W-8... I wonder how long it will be before we see 0W-0 ?
We use 5 centistoke oils in gas turbine engines and their associated gearboxes. The oil really is water thin and lubricates everything perfectly. However, we do not have timing chains, plain bearings and camshaft driven high pressure fuel pumps. We have gears, ball+roller bearings and carbon/labyrinth seals. The difference between automotive and aeronautical components is quite simply, money. Those funds are used to design components that last.
The idea that 0W-8 oil is sufficient for conventional chains, is absolutely incorrect. Chains last longest with 30+ viscosity oils. We can, and do design plain bearings to hold up well with thin oils. However, automotive manufacturers continue to use parts designed decades ago, without the upgrades necessary for ultra long life. This may be why many companies are moving to wet belts.
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I have both FCA and GM VO’s - they pretty much behave as two stage pumps - very clear to see when the ECM makes the change - the Jeep looks more dramatic with a digital output - but both spike sharply when “shifted“ …
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