-- [ From: Bob Nogueira * EMC.Ver #2.10P ] --
-------- REPLY, Original message follows --------
>
> Subject: Vacuum
>
> Dirk asked:
>
> > The purpose of the vacuum advance is to get an earlier spark during
> > high vacuum conditions, but I cannot remember whether vacuum is
higher
> > during idle or at high rpm's. Anybody else who does?
> > I do recall stories about vacuum operated windshield wipers slowing
> > down when overtaking another car in the rain, which would indicate
> > lower vacuum during high rpm's.
>
And Denice Replied:
> There are two kinds of vacuum in a car: manifold and ported. Since
an
> internal combustion engine sucks air from the intake and shoves it
out
> the exhaust, the engine creates vacuum in the intake manifold and
pressure
And replied :)
more vacuum is created in the intake manifold. This is manifold
vacuum
> and it's highest (lowest pressure) at idle and lowest (nearer to the
> ambient air pressure) with the throttle wide open.
And replied :)
> Ported vacuum on the other hand is caused by air flowing through the
carb
OH SNIP>
AhAha Denice, Doe this mean that the vacuum to the advance unit is
ported vacuum ? If so it clears up a question I have had for a long
time
why would you want advanced spark at high vacuum ( closing throttle)
conditions. .
Bob Nogueira " Gee its nice to get my learning out of the way early
this year.'
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