[Tom Vaught]

You can only pull the heat out of the bearing if you have proper oil flow clearances that allow the very hot oil to escape the bearing shell area. Possibly the extra oil feed passage allows removing extra heat at the main bearing and still supply proper oil flow to the rod bearings (and remove heat there too).

A Fluids Engineer (named Tom T) and I build a oil shell bearing rig one time for some bearing analysis work. Basically we rotated the rod journal without adding the reciprocating motion to the system. We were checking bearing speed vs oil pressure vs load on the rod.

We could load the rod with a pressure piston as the rod did not move (except in a vertical motion) and we could simulate actual rod loads.

We could control the actual pressure and flow to the bearings precisely.

We could monitor the bearing surface temperature as well as the oil discharge temperature leaking past the rod journal

And we could change the crank journal bearing speed.

So we finger-printed a bunch of different bearing designs, bearing clearances, oil flow rates, oil viscosity, and bearing speeds and loads.

In simple terms, for a small amount of bearing speed increase (say 500 rpm) the oil temperature and bearing temperatures go up dramatically every 500 rpm.

So cooling the bearing with proper oil flow is what makes the bearing survive

ps As far as the turbos adding heat to the oil, that is true. Vortech Superchargers add very little extra heat (only a .040" oil flow passage, (Like one extra lifter bore flow passage). But compared to Bearing Heat it is a very small addition.

When you fill the water jackets of a factory block (with fliier) you remove water cooling surface area so the water temp goes down but you increase the oil temp because the heat now has to be removed by the oil contact with the block surfaces. So the oil temp goes up. Doing this on a street engine causes the oil to now have to work even harder to remove heat at the bearings. So in reality at some point you really need an efficient oil cooling device to lower the oil temperature from the engine.

Tom Vaught