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Still concerned about oil pump so tested mine.

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J

John_Progess

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I rigged up a very simple test stand using my vice, piping, oil supply sump, existing oil pump and discharge pressure gauge. I made a mandrel to drive the oil pump gear using my 1/2" drill. The drill turns about 1725 rpm and at this speed the pump was putting out 65 lbs. As I closed the discharge valve a little (should not totally block the discharge of a positive displacement pump) it went up to 80 lbs. Is there any reason to suspect that this pump will not work in the car? Thanks and have a good day!

John
 
This may be overkill, but you could heat the oil up to 180 degrees or so and see what kind of pressure you get, not sure how hot engine oil gets in actual operation--I don't know that I would bother doing this, I think you have proven that the pump seems to be doing well, but if you are so inclined...I have had cars where the pressure drops dramitically as they warm up, don't know if this is because of the pump or pressure created by the bearing clearances or a combination of both.

Greg
 
glemon said:
This may be overkill, but you could heat the oil up to 180 degrees or so and see what kind of pressure you get, not sure how hot engine oil gets in actual operation--I don't know that I would bother doing this, I think you have proven that the pump seems to be doing well, but if you are so inclined...I have had cars where the pressure drops dramitically as they warm up, don't know if this is because of the pump or pressure created by the bearing clearances or a combination of both.

Greg
Click to expand...
Both of my BMWs have oil temperature gauges, and they normally run around 200-210 degrees once fully warmed up. I've had the gray car reading as high as 260 degrees during a (100 degree ambient day, at) Evolution Challenge autocross school. That's a little hotter than I would've liked, but 4-5 years later, the engine still purrs.

It's not the oil getting hot (or thinning out) that causes the drop in oil pressure; as the metal heats up, the running clearances are greater. A drastic oil pressure difference between hot & cold running is probably excess wear on the rockershaft and bushes. Crankshaft main & rod bearings won't "spread" enough to cause a big oil pressure swing.
 
What Randy said!

Smokey Yunick did a study on oil degradation and temperatures(now this was for his race engines, but principle still applies). When the oil temperature got above 230 degrees fahrenheit(non-synthetic oil) the oil usable life, degradation of the polymers was four hours. Smokey found that you needed 190 degrees for proper lube, no more than 230 for maximum protection...
 
Anthony7777,
Based on the diameters of the gears, I figured that if I turned the pump at 1725 rpm, the cam would have been turning about 1500 rpm and the crank would be turning 750 rpm. Is my thinking correct?

John
 
I am not sure I am buying into this idea that oil temp does not affect pressure.

Oil does thin as it heats, I get higher pressure with 20w50 than 5W-30.

I get much higher pressure if I start my car on a really cold day.

Am I missing something?

Maybe clearances change as well, but the oil temp and viscosity make a difference.
 
also, don't clearances get tighter as an engine warms up, that is why valves can stick in their guides if not enough clearance as the engine heats up.

Rings must have a gap to allow for expansion, rod knocks can go away as motor heats up, etc.
 
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