Tim,
Steve and Stu have given already given you the long and short of it, so
probably no real need to flog this subject any further. I would only add
that the reason for the pressure drop along the flow path are the effects
of fluid friction (with the internal surfaces), which causes the pressure
drop when there is flow instead of a static condition. There are a lot of
analogies between fluid flow and electrical current, and you can think of
the various elements in the cooling loop in terms of various size resistors
across which there is a pressure drop in the case of fluid flow, or voltage
drop in the electrical analogy. However, I'm more often using this analogy
to explain electrical behavior in terms of fluid behavior, so this reversed
logic may not be very helpful unless you are already familiar with the
basics of electricity - like V = IR (Ohm's Law) for example.
To expand on this subject just a little, consider the case of the two usual
aftermarket oil pump choices - high volume or high pressure. Which are you
going to pick? Melling used to have two models, the high volume one having
the bigger gear rotor. As far as I could tell, both the "high pressure" and
"high volume" relief valves were set a the same pressure (ca. 65-70 psig).
As long as your engine is nice and tight, the smaller "high pressure" pump
is fine. But, if you set the clearances loose, then the pressure the "high
pressure" pump can maintain falls off more quickly than the larger "high
volume" pump. What should also be obvious is that if they are both
producing the same pressure (which I believe they do), then the flow is the
same and the pressure at the bearings, etc. is also the same for both
pumps. And, in any case, when the flow of oil is great enough so the "high
pressure" pump can't keep up, the pressure where it counts, at the
bearings, is then greater with the "high volume" pump. This is just a long
way of saying what Tom Hall mentioned a while back - always buy a high
volume oil pump.
Well, TTFN guys,
Bob
At 02:05 PM 11/11/99 -0600, Ronak, TP (Timothy) wrote:
>Bob, Steve, Theo, and Listers,
>Maybe some of you engineering types can helpout.
>
>At least I did not say a dirty word like ... GM or anything.
>Regards,
>Tim Ronak
Robert L. Palmer
Univ. of Calif., San Diego
Department of AMES
rpalmer@ucsd.edu
rpalmer@cts.com
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