Current Build for a customer 800HP

Dr. Performance Cummins 24V Turbo Diesel. I'll dig up some pics if you'd like. We did some really off the wall stuff with its cylinder head. It was years ago when I worked on it but it was very cool to see. Surprisingly, the cummins diesels have a better oiling system than we do for our VGs. They actually have a high speed oiling system from the factory.

 

The engine I done was also a 6B, we used an early Komatsu designated block as they have slightly different main supports due to construction only use coupled with an ISB 24V head that we basically milled a couple inches off each side to open it up and toallow use of a much better intake than the standard head allows.

I worked for cummins for almost 15 years, doing nothing but engine work for that amount of time, you learn a thing or 2.

Some of thier engines have good lube systems like the B and C series, as well as the K and later derivatives. The V, L, M and S have woefull lube systems, to the point of extremely early failure of pins in the S and mains in the L and M.

 

Ohh! Stuff I know stuff about

First things first...

Zed oil pumps (like all engine oil pumps) are positive displacement. You get a specified volume flow rate per revolution of the rotor/s, less hydraulic efficiency (leakage, which will increase at higher pressures and speeds, and volumetric efficiency.)

Pressure is the product of the resistance to the flow through the system. This resistance increases exponentially with a linear increase in flow. So as the flow goes through the discharge of the pump, through the galleries, through those itty bitty holes into the bearings, into the heads and everywhere else the friction of the oil flowing against everything creates the resistance to flow, or pressure.


Now if we improve the suction side of the pump by porting it, larger diameter strainer and pipework etc we will increase the efficiency of the pump. Less power is required to pumps the same volume flow as the total differential head is less than previously. The same goes for any improvement to the discharge and system side of the pump. You remove restrictions you can pump the same volume flow at a lower head and thus less power. Lower differential head will also improve any leakage and may improve the volumetric efficiency. Simple as right? Now if we continue this clever idea throughout the motor we can get the same volume flow at a reduced pressure.


Now...

Yep, correctomondo. How much of an improvement, I reckon an unmeasurable amount. Talking pump ONLY here...

Pressure is FIRST AND FOREMOST governed by the flow through the system. Only once the flow is so high that the pressure raises above the pressure relief valve spring pressure it is then regulated by the relief valve. You are correct in saying that the pump will flow more at the same pressure with less restrictions.

Assuming the pump speed is above that required to regulate system pressure via the pressure relief valve it WILL increase in flow at the same pressure and at that particular operating point. It will move the operating point to the right of the pump curve. Power required to run the pump will also decrease. At lower flows there will also be a drop in pressure.

You don't have to worry about that at all


This is easier with red writing!

Now all this stuff I don't know a whole lot about... I've done a bit with journal bearing lubrications, but only fixed speed industrial stuff like ocean freighters. The biggest issue is getting the right volume of oil to the bearing rather than the pressure it comes out at. The journal rotating within it's bearing creates enormous pressures that makes whatever the pump puts out look like pissing in the wind. The faster you spin it, the more oil comes out, so the more is required, to get more out you need a higher pressure to get a higher flow there. It's a vicious cycle Now how pressure impacts on the operation of the bearings I'm not sure and can't really comment, well not without going through my old Tribology notes and you'd have to pay me to do that

What do you mean by pin wheel? Are you referring to oil whirl?


Anyway it's bed time for me, I have to test a really big pump in the morning

 

Good information and noted. Pin wheeling may be the same terminology as oil whirl..im not sure but I do know the term of "pin wheeling" is exactly what the VG crankshafts are doing with the supplied oil with the cross drilled journals.

 

Thanks mate
I wasn't saying we should go reducing inlet size - seriously bad idea, just pointing out Nissan may have thought about the sizes of such things when they designed all this.
They had been making cars for over 50yrs by the time they got to the VG30DE, I would think they should have gathered up a few smart cookies in the design section by then.

Mind you not everything is perfect out of the factory due to $ etc but some things are pretty damn close.

 

you guys go deep. so good, such good solid information

 

Thanks chrispy, good explanation.

 

+1

Explained it very well. I actually managed to visualize it in my head as i read it. Kudos to you.

 

Immaculate and nice work. I hope it doesn't get an alloy engine pulley?

 

No sir, I sprung the $500 for an ATI Race Damper.

 

Very good and safe.