Originally Posted By: used_0il
I think, therefore I believe (unqualified!), the point Shannow is repeatedly trying to
make is, and this is not a quote;
"Try and get your thinking away from oil pumps, oil pressure and forget about by-pass for once."
If the concern is lubricating "hydrodynamic" bearings, according to Shannow, I believe his point
is; ensure a supply or reservoir of oil. The self-pumping action of the bearing will
be enough to replace the side leakage. Hydrodynamic bearings are not lubricated by
forcing oil through them.
Now, (the light goes on) a non-Newtonian lubricant's ability to temporary shear may
actually help this self-pumping action.
This self-pumping action can be easily visualized in the elliptical rotation that
is found at the big end of an engine's connecting rod.
As rpm is increased, the bearing pumps more oil.
If the oil is colder, the leakage is less.
Spot on the former, and very close, but for the action of pumping in a bearing.
The Pressure Distribution around a journal is as depicted here.
If you introduce oil in the area of "pmin", there is a suction, that can be 3-4psi, and once primied the bearing can be self sustaining, no oil pressure applied...Engine manufacturers often use a grooved main top shell to move the effective low pressure xone closer to the oil feed hole at TDC.
Then as the oil is dragged around the journal, it's pressure is increased due to hydrodynamics, and some is forced out the sides (side leakage)...That's the pumping action at work. Drawing in at low pressure, and squeezing out in the high pressure zones (couple hundred PSI in the loaded area, pump pressure is doing bupkis about getting the oil into the "wedge")
The bearing will only draw from the reservoir (pressurised gallery in an engine) sufficient oil to replace that lost to side leakage...when it doesn't take it all, that builds pressure in the galleries...you are not "pushing" oil through the bearings, the bearings are drawing what they need.
Some of the oil is obviously retained, and does a couple of tours of duty in the bearing before being the bit that leaks out the side.
The stuff leaking out the side is typically 15-30C higher than the supply temperature, and some of the oil within the bearing, around the journals and shells quite some higher (*)...the engine has done work to spin the journals in a film of oil (like a chinese wrist burn for a bad analogy), and it is this effect that people chase when installing low viscosity oils.