The oil pump produces a fixed volume tied to RPM. The output is a function of the total resistance to flow of the system which is just about fixed, plus the pop setting of the relief valve, also fixed.

 

So, if we do not include such things a viscosity changes, foaming, temperature changes, suction side losses and all of the things that cloud the issue,

and just look at the flow, we see that unless there has been a very small hose or gallery size selected, the hose or gallery diameter and volume has no affect at all on pump output, total resistance, or temperature. So the bigger the hoses, in effect the closer you get to a static system where pressure is uniform everywhere. The one effect of larger hoses we want is the lower velocity of the oil. Drag increases at the square of velocity, so a small increase in diameter reduces the velocity and drag and also the amount of heat the pump puts into the oil.

 

We are also adding some length of hose in excess of the stock system, with more remote filtering and ideal cooler locations and similar, so the larger hose diameter is of some benefit there.

 

Suppose we have a 200 foot long oil hose in 12" diameter, and another in 1/8" diameter. Both are pressurized with the same size pump turning the same RPM. We have pressure gages at the opposite end next to the relief valve with the pop pressure set at 80 PSI. We also have pressure gages at the pump end. Assume both volumes remain as at rest, what happens when we fire the pumps together?

 

The large diameter version, the pump builds to just above 80 PSI and the relieve valve pops at the far end about a second later holding the full 80 PSI in the tube, and dumping excess oil with gusto.

 

In the small diameter version, the pump builds up 150 PSI, and 3 seconds later the relief valve pops at 80 PSI, but just dribbles oil.

 

The larger system is a nearly static situation, while the smaller system is a very dynamic situation.

 

Lynn E. Hanover

 

No, I am not recommending 12" diameter oil hoses.

 

 

 

Kelly,

   I know you asked Lynn, but ...

Things to think about: the original oil system for the 13B was designed to support two 10mm (~3/8") oil paths - one to the main bearings and one to the pressure regulator in the rear (flywheel end) iron. Any volume of oil that exceeds the capacities of those paths will result in excessive oil pressure.  Going to an external pressure regulator will solve that problem, but to what purpose?  For any given pressure, going from a 3/8" line to 1/2" adds 77% to the volume being pumped; going to a -10 (5/8") nearly triples the oil flow; -12 (3/4") more than quadruples it - you end up pumping a lot of oil - thereby adding heat to it - then cooling it and returning it directly to the sump.

So, how much oil flow do you need for your turbo and re-drive?  As much as the engine itself?  I rather suspect that having larger than -10 up to the point where the oil supply splits to service the various components won't buy you any advantage except lower oil temps, and  that is actually doubtful.

Dale_R
COZY MkIV #0497