I don't know what's true anymore. I am now shaken to
the core! (Hey,that rhymed!) :) I believe Bernd's
experience,but also your logic,and I *think* they
conflict. But I am unsure.
Steve P.
--- jon@dakota-truck.net wrote:
>
> Terrible Tom <silvereightynine@aol.com> wrote:
> > Basic fundimentals review here...
>
> > The suction of multiple pistons pulling air in
> through open intake
> > valves is what keeps vacuum in the manifold.
>
>
> Yep!
>
>
> > The throttle blade is what will decrease the
> amount of vacuum (negative
> > air pressure) when the throttle is opened
>
>
> Yep! There are only two ways to decrease the
> amount of vacuum -
> allow/force more air to flow through the throttle
> body, or reduce the
> amount of air being pulled through the intake
> valves.
>
>
> > faster engine RPM with the throttle closed
> (accelerating and then
> > letting off the throttle) will cause more vacuum
> (higher values of
> > negative pressure)
>
>
> Yep!
>
>
> > Ok - all that said... I dont see how a restricted
> exhaust will have any
> > sort of effect on intake manifold vaccum?
>
>
> See my latest agonizing post in this thread for
> my thoughts on
> that process. :-)
>
>
> > I still think restricted exhaust would cause lower
> vacuum levels because
> > the engine has to fight and push the exhaust out -
> using more power and
> > choaking engine speed... less engine speed means
> the pistons are moving
> > slower and sucking air in slower meaning less
> vacuum in the manifold....
>
> > Right?
>
>
> I agree, that's a decent way to think about it.
> Or, you can
> probably simplify it even further if you wanted to
> and just think
> about the engine sucking in air and cramming it out
> the exhaust. If
> it can't force it out the exhaust, it is going to
> get backed up
> (pressurize) and can't suck more air in.
>
> Since an engine is basically a big pump, consider
> what would happen
> if you had a water pump. You've got the suction
> line down in a well
> or pond, and a garden hose attached to the outlet.
> If you put a kink
> in the garden hose, is that going to cause greater
> suction at the
> inlet? Most definitely not. :-) Neither will an
> engine with a
> "kinked" exhaust create more suction (vacuum) in the
> intake manifold.
>
> --
> -Jon-
>
> .- Jon Steiger -- jon@dakota-truck.net or
> jon@jonsteiger.com -.
> | '96 Kolb Firefly, '96 Suzuki Intruder,
> Miscellaneous Mopars |
> `--------------------------------
> http://www.jonsteiger.com --'
>
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