[Land-speed] Dry Sump

Bryan Savage b.a.savage at wildblue.net
Tue Jan 6 22:00:22 MST 2009


Smokey did a lot of work on dry sump and windage control systems. He
even built a clear plastic oil pan about 3 feet deep. His justification for
dry sump was it could remove almost all of the air from the oil. Everything
else was just a side benifit.
You might check his writings.

Bryan

Ed Weldon wrote:
> Elon-- That friction you are measuring is mostly drag from the shaft seal, a
> little bearing friction and some friction from liquid shearing due to
> viscosity at the pumping temperature.  That will not increase a whole lot
> with speed; certainly not by a square function especially with racing motor
> oils at temperatures in the 180-200 degree range. At 80psi output roughly 90
> percent of the hp to pump the oil will be what goes into building the
> pressure.  The formula I gave in the other thread on hydraulic hybrids
> applies here.  Fluid power is psi x gpm /1714 = hp.  Divide that by about
> .85 (which factor allows for the inefficiency in the pump drive belts) and
> you'll get the horsepower use of the dry sump pressure pump stage.  As far
> as the scavenge pump stages are concerned they will be pumping the same
> amount only to a somewhat lower pressure.  If you know that pressure then
> use the same formula and reduce figure that dividing constant of 0.85 will
> be about 1.0 minus 0.08 x the number of scavenge stages (eg 0.76 for 3
> scavenge stages.)  Air entrained in the scavenge pump flow will not have a
> big effect on the total horsepower once the motor is up to speed and the pan
> has been "emptied" of residual oil that was there when the engine fired up.
> My numbers on this come from data I accumulated on the performance of small
> industrial gear pumps in my 1st job with Worthington pump 40 years ago. It's
> a subject I feel I'm fairly well versed in. (& I don't throw away very
> much).  For anyone really that interested in the minutia of the subject I
> will be glad to copy and forward (snail mail or email) what you may be
> interested in. (lots of charts and pump performance curves.)
> Still, if anyone out there has seen actual test stand performance on
> multistage dry sump pumps, especially horsepower readings from calibrated
> electric drives I'd love to look at it and use it to refine the constants in
> my abovementioned formulas.
> Ed


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