[Diy_efi] crankcase vacuum control

[Dave Dahlgren]

Theoretically there are no pumping losses I can see that involve the pressure of
the crankcase or vacuum either. For every piston going down there is one going
up. The volume ought to be the same in all positions. That is until you start
the engine up and have some ring leakage. Then you have oil aeration and should
be concerned about the delta-p across the rings as that is how they seal. If the
air suspended in the oil is at a higher pressure than the crankcase, the vacuum
pump will pull the air out of the oil reducing the volume it displaces and will
then reduce crank windage and the splash lubrication to a certain degree as
well.(Think vacuum packing machines) It will also increase the delta-p across
the rings  and make the oil rings more efficient as well scraping oil off the
cylinder walls, the compression rings will seal slightly better also.. It makes
things better from what I have seen but 40 hp might be quite a reach for
estimated improvement on a well sealed up engine. Seems to work better at
elevated rpm as well I would not expect much effect at 3500 rpm but 8500 is a
whole different ball game. I have also seen that like nitrous you can have too
much as well and start burning up parts from lack of lube oil unless you start
fooling with jets to spray oil on some parts like piston pins and cam followers
in a push rod engine.
Dave Dahlgren
Engine Management Systems

Adam Wade wrote:
> 
> --- Jack Vines <jackv at ambassadorprograms.org> wrote:
> 
> > You can pick up 30-40hp on a strong engine through
> > reduced pumping losses.  The pistons don't have to
> > compress the crankcase atmosphere on their way down.
> 
> But they have to fight the vacuum on the way back up.
> 
> Frankly, I have never bought this as a source of
> power, and there has yet to be a scientific
> explanation that "washes", IME.  I'd love to hear one,
> but this ain't it, I don't think.
> 
> > The most important factor for turbos is it keeps the
> > oil out of the combustion chamber and thus helps
> > prevent detonation under high boost.
> 
> How does oil get into the combustion chamber?  Through
> the airbox?  That can be eliminated with a simple
> crankcase vent filter, and elimination of the hose
> between crankcase and airbox.
> 
> =====
> | Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
> |   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
> | "It was like an emergency ward after a great catastrophe; it  |
> |   didn't matter what race or class the victims belonged to.   |
> |  They were all given the same miracle drug, which was coffee. |
> |   The catastrophe in this case, of course, was that the sun   |
> |     had come up again."                    -Kurt Vonnegut     |
> 
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