Cummins new replacement oil pumps.

[Mattman]

I have read where the new style oil pump is said to deliver more volume but at a lower pressure. Is that even possible?

The oil pressure is the measure of resistance for the flow of oil thru the engine.

So the resistance to flow is not going to change. The only change is the oil pumps.

How can you move more volume of oil thru the same restrictions but at a lower pressure?? I can't get that idea thru my head. In my way of thinking the pressure should increase because you have more flow with the new style pump trying to get thru the same restrictions as before.

Example. We unload tank trailers with air pressure. 20psi of air trailer is empty in one hour. 30psi of air trailer is empty in 45 minutes. The higher the pressure the more volume there is.

Tell me what I am missing??

[Rawze]

The actual TSB reads as follows...

Quote:Reason for Change

A new cast iron lubricating oil pump, Part Number 5532492, was released to replace an existing aluminum lubricating oil pump, Part Number 3687527, and cast iron lubricating oil pump Part Number 3687528, for some 15L engines. New Part Number 5532492 has different flow characteristics that do not affect lubricating oil system function, but can result in different oil pressure values than expected. Part Number 5532492 does not use shims to set gear lash like existing lubricating oil pump Part Numbers 3687528 and 3687527.

All it really says is that the new pump does not need shimms any more (easier to install ) and that is has slightly different flow characteristics ( likely due to different the gearing arrangement to help accommodate the 'no-more-shimms' mod ). <- nowhere does it say that it is supposed to have higher volumes, nor claims of overall lower engine pressures that I could find. But It DOES have different flow characteristics.

(speculation) ...
I can see it being different due to it now circulating oil back to the intake of the pump when the regulator valve opens, rather than it being dumped into the oil pan( hence the plug instead of the carter-pin at the one end) ... and due to the different gear ratios it runs on. It is obvious that the pump itself turns slower, but has a larger internal size. - This makes for a different flow characteristics for certain, but not necessarily guarantees it has a higher rate.

(more speculation) ...
- This overall would mean it has likely less aeration of the engine oil, (possibly) easier to install, but more likely a lot cheaper to have cast (lower mfg. cost), as it is iron now and not aluminum.

-- It also seems to be that 'no more having to shimm it and lower mfg. costs) is at the new cost of a high possibility of gear whine, which people have already complained about.

here is some related experiences and info posted on the forum recently: http://rawze.com/forums/showthread.php?t...3#pid52633

Just my thoughts any ways. I am thinking that some salesman or parts person, or some other person made claims about more flow and lower pressures ... not any sort of official document.