oil pumps (not efi)

[Dave Williams]

-> WRONG.  Why the heck would it be called a high volume pump if it
-> didn't pump more volume per revolution?!?!?  If you carefully compare
-> the stock pump with a high volume pump, you will note the body of the
-> pump is longer, denoting longer gears in the pump, and thus more
-> swept area of the rotors. More area x same RPM = higher volume.  This
-> will equate to higher average oil pressure, all else being equal.
-> The only circumstance the oil pump recirculates is if the filter is
-> allowed to clog up, at which point there is a bypass valve in the
-> block which still allows oil to circulate, albeit unfiltered.

 For ordinary Ford and Chevy applications there is an internal bypass in
the actual pump casting itself.  A spring loaded plunger in the bypass
short-circuits the flow from the output to the input side of the pump
when design pressure is reached.

 With the same spring, both the standard and high volume pumps will flow
the same amount of oil at the same running pressure.  None of the "high
volume" ever makes it out of the pump.

 The only time you will ever see a difference between a standard and
high volume pump is when the standard pump can't meet its designed
pressure.  This happens at idle and very low RPM.  Past 1500 RPM or so
you're pumping far more oil than the engine needs.  A constant-volume
pump isn't the best choice for high RPM use, but it is mandatory if you
want to have oil pressure at low RPM.  Some true racing engines like the
old BRMs use centrifugal oil pumps which took far less power than
positive displacement pumps.  However, these engines never had to idle
for more than a few moments.

 The filter bypass valve you discussed has nothing to do with this.


====dave.williams at chaos.lrk.ar.us========================DoD#978=======
  can you help me...help me get out of this place?...slow sedation...
ain't my style, ain't my pace...giving me a number...NINE, SEVEN, EIGHT
==5.0 RX7 -> Tyrannosaurus RX! == SAE '82 == Denizens of Doom M/C '92==