It takes about a minute for all the oil volume to go once through the oil pump or does one cycle around the engine. Not that the oil goes around the engine and takes it a minute to return. The oil pick up never runs out of oil because it's submerged at all times.
Hello,
but at a conservative 2000rpm which is what my engine warms up at..
O.K. I'm talking approximately. Plus cold engine usually runs at about 1,500 RPM, not 2K.
How and why in any of those scenarios the sump runs dry?
Also keep in mind that cold thick oil will make the pump cut back on output volume, so it's pumping less to the engine when in pressure relief at 1500 RPM compared to when it's not in relief at 1500 RPM. If the correct W rating is used, there should be no issues with lubrication at cold start-up ... that's the purpose of going by the W rating for the coldest expected start-up.
A spring loaded relief valve can't open enough and shunt every drop of oil in order to keep the output pressure exactly constant.
That's with 5W-30 at 200 deg F (it's noted at the bottom of the graph). With the oil much colder, the pump is going to cut back the output flow quite a bit, even at 1500 RPM.A spring loaded relief valve can't open enough and shunt every drop of oil in order to keep the output pressure exactly constant.
Here's some LS oil pump curves from Melling showing where the pump starts going into relief, and it still keeps increasing in output pressure and volume after the relief valve starts to open. There has been some detailed discussions of this in other threads.
Looks like an LS pump moves around 5 GPM at 1,500, which is 22 litres, so with a 5 litre sump, that's the entire sump volume 4.4 times.
The oil still needs to meet both the CCS and MRV spec in SAE J300 of the W rating to be labeled that W rating. If an oil meets the W rating, it meets the W rating. If one oil's W rating is much closer to the next lower W rating than another oil with the same W rating, then there might be a slight perceived difference in cranking and starting, but any specified W rated oil for the intended start-up temperature is going to perform without issue.
Its ability to clean pistons. I work in oil refining and am well aware of how tough it is to remove varnish and coked on deposits. Especially for an engine oil that cant use a ton of aromatics.
Thanks.
Less, which is a good thing because it takes longer for cold oil to return to the sump. So it's kind of a self balancing act, and why sumps don't get pumped dry on very cold start-ups if the right W rated oil is used.
Assuming it's on the relief, yes (which it probably would), but as we've seen my the videos of my SRT, it doesn't take long to come off the relief; each application is different
Right, but your assertion seemed to be that the sump overturn rate was much slower:
Japanese said:
That's going to depend on many factors:
Different engines will have different flow quantities through their gallery. Due to more or less restriction on that volume.
Yes, different engines will tolerate different volumes of oil at a given viscosity at a given pressure. My 6.4L definitely goes on the relief on a -11C cold start (a video of which I've shared here) but a bit warmer, and that doesn't happen, it gets close, but stays below relief pressure.
Some statements here don't take into account that the thinner the oil, more volume of it will flow through the same restriction, at the same set pressure - not being by-passed.Yes, different engines will tolerate different volumes of oil at a given viscosity at a given pressure. My 6.4L definitely goes on the relief on a -11C cold start (a video of which I've shared here) but a bit warmer, and that doesn't happen, it gets close, but stays below relief pressure.
We've previously discussed pump volume here:
As the Subi's have crazy oil pumps that move incredible volumes of oil.
The pump in my wife's 1500 moves:
5.7L HEMI pump:
500rpm: 1.90gpm
2,000RPM: 5.08gpm
The pump in my 6.4L is larger, so would move even more.
Yeah, if your relief pressure is 65psi, and, for the sake of this discussion, we'll assume it cracks at exactly 65psi, then as long as you are below that pressure, the volume of oil moved through the engine is the same, regardless of what oil is in the pan and what the temperature is. However, if 5W-30 puts you on the relief at say -5C, but 0W-20 doesn't put you on the relief until -15C, then from -5C down, the volume of 0W-20 moving through the engine is higher than the 5W-30 at the same RPM, because RPM and volume are decoupled with the 5W-30 with some of that oil being bypassed back to the feed side, to keep system pressure around relief pressure.
Yes, the size and length of the oil passages/galleries and all the components that get fed pressurized oil contributes to the overall flow restriction of the oiling system as seen by the oil pump. And the oil filter also contributes to that, but typically the oil filter is around 12-15 times less restrictive than the rest of the oiling system so it's pretty negligible. The journal bearings are one of the most flow restrictive components.
