[Diy_efi] Venturi effect crankcase breather

[Dave Dahlgren]

Has anyone ever seen something get vacuum packed?? The air is at a higher
pressure than the crankcase so the bubbles come to the surface and out the pipe
through the scavenge stage of a dry sump pump perhaps?? If the oil is forcefully
folded over and compressed slightly wouldn't the air in the oil be at a higher
pressure than the crankcase?? If that were true and it seems logical then the
lower the pressure in the crankcase the faster the air comes out of the oil..
Dave

clay0052 wrote:
<Major snip>
 3)Entrained air. This is what most people are referring to
> when they're are talking about aeration. This will effect the ability of
> the oil to support a load (along with cavitation, too). Typically entrained
> air is from oil being whipped around or thrown into itself. Take a quart of
> oil and pour it into the beaker and you will see some air being entrained,
> even as you pour it.
> 
> Dropping the viscosity and/or surface tension is the largest factor in
> getting the air out of the oil. Lowering crankcase pressure will help some,
> but is not a big deal. There were some SAE papers on WW2 dry sump tanks
> that I read (1945 I believe) and they were trying to keep the oil as hot as
> absolutely possible going into the tank to allow the bubbles to rise to the
> top and leave the oil, as quickly as possible.
> 
> So, I think if you tried raising the crankcase pressure you would end up
> dissolving more entrained air. Later on in the oil flow pathway, a drop in
> pressure would reduce the saturation point, and release that air back into
> the oil as entrained air.
> 
> Mark
> 
> On 9 Jul 2003, Ne14RoxCJ at aol.com wrote:
> > In a message dated 7/8/03 11:56:41 PM Central Daylight Time,
> > espresso_doppio at yahoo.com writes:
> >
> >
> > > lowering the pressure will only egxacerbate this
> > > problem.
> >
> > So how come the engineers have found otherwise?
> > Doesn't make sense to me.  You're saying the exact
> > opposite of the research I've seen.
> >
> >
> >
> > My visualization of this involves my coil-over Sway-Away shocks with
> their
> > remote reservoirs. To reduce oil areation, we apply 120-150 psi of
> nitrogen
> > to
> > the piston of the reservoir. This places the oil under that same
> pressure. If
> >
> > oil areation were solved by a vacuum, then all of those desert racers,
> > monster
> > trucks, rock-crawlers, indy-cars, etc. have got it severely wrong. I'm
> not
> > convinced that I should pull a vacuum on my shock reserviors (as if it
> were
> > even
> > possible). My classes in fluid dynamics taught me this, but it helps to
> have
> > actual applications to SEE the relationship. Feel free to cut into ANY
> shock
> > absorber to prove this, but use extreme care since there WILL be a very
> > high-pressure stream of oil squirting you in the eye. Hope this is
> helpful.
> >
> > Beau
> >
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> >
> 
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