[Diy_efi] crankcase vacuum control

[Mike]

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Aerodynamics - Adam,

moving air back and forth around the crankcase at high
speed chews up power, vacuum helps up to a point until
the energy to maintain the vacuum becomes too high, better
to attend to aerodynamics inside the crankcase and get as
much vacuum as *practical*...

Of course if it aint broke, dont fix it ;)

rgds

mike




At 09:02 AM 4/27/03 -0700, you wrote:
>
>--- Jack Vines <jackv at ambassadorprograms.org> wrote:
>
>> The crankcase pumping losses are real when a
>> crankcase has positive pressure, which can happen,
>> especially on a high-boost, high-rpm turbo
>> engine.
>
>Again, I find that very hard to believe, since for
>every cylinder going down, you have one going up, so
>there is a net effect on the bottoms of the pistons of
>zero.
>
>I can believe the ring sealing issue, and I can
>believe the aerated oil issue for parts that might
>have windage issues with the oil (spray- or
>plash-lubed parts, crankshaft).
>
>> That is why dry-sump systems have as many as 4-5
>> scavenge stages and only one pressure stage.
>
>Well, there are a lot of reasons for that in most
>cases, including mutiple oil pickup points, as was
>described by a gracious race engine tuner last night
>
>> It becomes a vacuum pump and maintains a vacuum
>> in all parts of the engine.
>
>ITYM "crankcase".
>
>
>In any case, I have yet to see it make any difference
>on the dyno with newer high-performance motorcycles,
>and I fond the "40-50 horsepower" claim a bit hard to
>swallow without back-to-back dyno runs with no other
>differences on an eddy current dyno

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