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Brian W. Neuschwander
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Message-ID: <3562E40D.4C2A@sjm.infi.net>
Date: Wed, 20 May 1998 07:09:17 -0700
From: Brian Neuschwander <bwnbcg@sjm.infi.net>
Reply-To: bwnbcg@sjm.infi.net
Organization: New Millennium Management
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To: James <james.carpenter@ukaea.org.uk>
Subject: Full Bed Pan
References: <98May20.120916gmt.66307@gateway.ukaea.org.uk>
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James-
Somewhere (can't remember now) there is a good article on just what
makes a ZS and SU work. The main principle is "constant depression"
over the jet. The rising needle via the dashpot is one control factor
for the mixture. The other is the amount of depression, based on air
volume and velocity. You will note the jet is at the narrowest passage
in the carb. The air velocity is the greatest. The depression is
therefore the least. (Depression being the opposite of compression).
It is this "constant depression" (as in the CD in the Stromberg CD150
etc) that draws the fuel from the jet. The venturi is in depression as
compared to the float bowl which is at atmosphere.
If you put the venturi in _com_pression, as with a forced induction
system, no fuel will come up through the jet, as air will be forced down
into the bowl, or more correctly drawn into the bowl, by the bowl being
at atmosphere. This will send fuel everywhere you don't want it. Kind
of like blowing bubbles in a full bed pan.
This is why there are few compression carburettors. It is a tought
situation to make work right. Most are on the intake end of the
induction system.
What I always wondered about is the explosive capability of the fuel/air
mixture in the intake and turbine. I will bet this compressed mixture
can make a backfire a hell of an event!
Some thoughts for the day.
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Brian W. Neuschwander
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