Oil Pressure Question

[Z Licious]

Update:
Over the weekend I tried a couple of different filters on my 350Z to see if the oil pressures would move around.

Here is what I tested:
1. Bosch filter
2. STP Filter
3. FRAM

The STP and FRAM filter were both stock size (little baby filters) and the Bosch was oversized.

All filters performed nearly identical for oil pressures within say 5psi of each other. This then rules out that the increased oil pressure is from the filter itself.

I then tested the oil pressure with the BOSCH and STP filters versus ambient outside air temp:
1. Cold mornings: 40-50F -- oil pressure increased by 10spi (compared to hot days) even when the engine was fully hot.
2. Hot days were temp outside was 80-90F oil pressure reduced significantly.

This seems to indicate that the outside air temps have large effect on oil pressure whereas the filters have little effect.

So at this point I am happy running the Bosch filter. The increased oil pressure seems to be due to the oil itself as reported by several other people here and on Z car forums. The engine seems to like the synthetic oil as I get better gas mileage with it, but I have not done any UOA's as of yet.

 

[userfriendly]

LZ;
Boise eh? Home of the 6000 HP Caterpillar powered locomotives.

It looks like Nissan did their home work on this engine with the available oil pressure.
Others sould take note.
With that said, I'd bet that the engine could thrive on a less viscous engine oil such as an 0W30 or lighter, to get the flow as high as possible.
Running high oil pressure causes a parasitic HP loss, and by-passing oil instead of pumping it through the engine for the sake of a higher reading on the oil pressure guage is counter- productive.
The synthetic oil, as a mono-grade mineral could as well have, (lol) may improve the oil pumps efficiency, but we will have to leave that for the Good Will Hunters at MIT to prove...

 

[MolaKule]

Another issue could be gage nonlinearity. I.E., it reads extremely high when oil pressure is really only say 70 psi.

An external gage needs to be tapped in, IMO.

 

[John K]

I also think these oil pressures are really high. I had a 81 Rabbit Diesel that had an idiot light for oil pressure that had a habit of flashing when I drove through a puddle. I thought it was just an electrical problem, but was concerned enough to hook up a guage just to be sure. It pegged a 60# guage, and I had trouble finding a higher pressure guage. Put in a 100# guage I got from work, and it would peg it when the engine was cold. (I had visions of being sprayed with black oil!) If I remember correctly it would read about 60psi when warmed up. These engines were known to blow gaskets out of lesser filters. Seems to me some of the Japanese Chrysler products also had a problem blowing out some filters. FWIW.

 

[userfriendly]

Molakule got me thinkin'
The oil pressure at the opposite end of the engine from the oil pump, would be more important than the oil pressure feeding the engine.
For example, a Chev V8 engine feeds oil from the back of the engine to the front.
More often than not, bearing and engine failures on these engines start at the front of the engine, and work their way back.
Efforts to improve the flow AND pressure to the front of these engines should, I would think, help prevent engine failures.
The same would apply to the Nissan engine.
The oil pressure reading should be taken as far away from the oil pump as possible, but still from the high pressure oil gallery.
Now changes to the engine's oiling system, which includes all of the players such as the engine oil grade, oil pump, filter, external oil lines, and so on, can be changed and evaluated with out guesswork.
If a change of engine oil grade or brand of filter improved the pressure to the bearings furthest away from the oil pump, then I would guess that would be a change for the better.
Conversely, an increase in oil pressure at the pump from an increase in engine oil viscosity that dropped the oil pressure taken at other locations around the engine, may be viewed as a change for the worse, even though the oil pressure was seen to be higher, on the guage, located near or at the pump.

[ September 29, 2003, 09:18 PM: Message edited by: userfriendly ]