What I am having a hard time emotionally accepting here is the brute
strength of the diaphragm spring required.
When one takes a carb apart one is not used to finding
an intake valve spring inside generating dozens of pounds
of force. What you usually find is a bunch of
little wimpy springs. That is the very amazing aspect
to this carb. When you think about it the intake manifold
negative pressure is a powerful force. Obviously it takes
several HP to pump the intake manifold down to several psi.
BTW If a way could be found to idle a gasoline engine with
a wide open throttle (like a diesel engine) the pumping loses
could be drastically reduced as would the idle fuel consumption.
The other thing that strikes me about this carb design
is its analog computer nature. It has infinite resolution.
None of this stair step analog to digital converter stuff.
If all works as it should the spring will stay deflected
at it's max deflection and the sum of the spring force (about 60 pounds)
and the intake manifold vacuum pneumatic force on the back side of
the diaphragm should equal the force on the front side of the
diaphragm due to fuel chamber pressure supplied by the high
pressure fuel pump. The forward spring force and the pneumatic
back force on the diaphragm remain in balance. As the intake manifold absolute
pressure increases reducing the pneumatic force on the back side of
the diaphragm the spring force increases.
For the diaphragm to remain stationary
the sum of the forces on both sides will be equal.
This is Newton's Third law of motion. I'll paraphrase.
For every action there is an equal and opposite reaction
for an object to remain stationary.
If the hydraulic pressure in the fuel chamber
becomes less due to fuel squirting out the main jets the
the diaphragm moves forward opening the needle
valve and the fuel pump replenishes the supply pushing
the diaphragm back in balance with the pneumatic and spring
force on the back side.
Stunningly simple. However Excedrin head ache number 400 to understand.
I am waiting to hear from someone where I am going wrong :)
Paul Lamar ...No rotor no motor.
Hi Paul,
I think your concept is correct. This same concept is used on
refrigeration expansion valves to modulate the flow of freon into the
evaporator ( that's where the ice cream lives). Google "Sporlan
expansion valve" and you'll see a cutaway pictorial view of the device.
The freon driving forces are different (suction vs pressure) as are the
controlling forces ( temperature is converted to pressure on a diaphragm
vs manifold pressure directly brought to a diaphragm), but the
principles are the same. Spring pressure plus supply force on one side
of the diaphragm, balanced by a variable pressure on the other side. The
diaphragm is physically attached to a pin and any inbalance of the
forces causes the diaphagm to move the pin toward or away from the pin's
seat ( the flow orifice), thus modulating the flow to maintain pressure
equalibrium. FWIW Dave M
Thanks Dave.
Paul Lamar
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