jjandascog

'So....then where is the oil pressure guage coming in to play here? How can there not be an pressure? That makes no sense whatsoever'

It comes into play by telling you the resistance that the oil sees downstream of the sensor (not upstream), like I said the clearance between the bearing and journals creates resistance therefore you read a pressure (which is just a force across and area). You can use this pressure to help determine the health of the internals of the engine. Yes in our case there is a suction that brings oil into the oil pump but in other systems ones that I have designed and used, there is no suction and the inlet on the pump (there are reasons you want a pump system like this). I have a fueling system that runs a 150GPM but has 0 psi on the system but it is a closed loop system (unless you get to the molecular level but I am an engineer not a scientist).

A positive displacement pump is used b/c there needs to be pressure for the journals 'float' in the bearings, in order for that to happen you need some force i.e. pressure.

"what do you think moves the oil? "hopes and dreams" ?
oil doesnt natually just flow up from the oil pan, pressure pushes it up there."

I guess I was getting to deep into hydraulic system, should have just stuck with the ones generally used in a car engine.

So in a car engine there is a differential pressure that gets oil into the pump from the pan on the low side and the gears create flow of the oil through the oil system and the restrictions down stream create the pressure. the clearence between the gears and housing determins the max pressure the pump can produce.

pcs

closed loop fluid systems are beyond the scope of this topic and irrelevant to cars since the oil,fuel, and cooling systems are vented to the atmosphere. you are correct that the pressure gauge reads the resistance to the flow of oil in the system and it can be used to determine the overall health of the engine.
a centrifugal pump can also be used to create pressure in a system for journal float but the discharge pressure is based on the speed of the impeller and if one was used powered by the engine crank it probably wouldnt be able to provide sufficcent pressure for proper system operation when the engine was idling and still provide enough flow at max engine speed. since u are an engineering and work with hydraulic systems im sure u have seen or used pump curves and know that a pos dis pump will maintain a specified output press. regardless of its speed hence be able to maintain bearing float regardless if the engine is idling or a redline.
wow, this topic has quickly digressed from what we where talking about originally =)

jjandascog

HAHA, yes this thread has gotten way off topic and I will take the blame. As you stated a postive displacement pump will deliver its pressure no mater what the RPM (to a point) of the pump hence the flow is not a factor in the pressure (at the discharge) it can deliver. I guess that is what I was trying to say about the article when it mentions that flow is what lubercated the engine parts.

The fuel system on some cars is a closed loop system, but then the thread to super way off topic

And yes the main reason that a centrifugal pump is not used in the oiling system it for the reason you stated. Centrifugal pumps are better when flow rate is desired over a certian pressure like in the water pump in our cooling systems.

I am schedualed to test out in Yuma at the end of Septemper, hopefull it will be lower that 100 degrees then. Were do you work out in Yuma?