CARBURETORS: STROMBERG
The amount of economizer action or change in the mixture depends
upon the difference in the air bleed opening with the needle
open and closed and this in turn is controlled by the size of
the economizer reducer.
When the economizer reducer is No. 52 or smaller, there will
be practically no economizer action.
When the economizer reducer is made as large as the main discharge
jet tip opening, which is the maximum size that should be used,
this will give the full economizer range possible.
When the Model "0" series were first introduced
in 1919,
the manifold design was not as far advanced as more recently, and
large economizer reducers were then used, giving a large range
of economizer action.
With the improved manifold design and hot-spot construction, less
economizer action is necessary, and smaller reducers have been
used.
A No. 42 economizer reducer in the 1" carburetors and No.
36 in the WI" and 1) " carburetors rep-resent a moderate
average.
Idling System
Idling system: For idling, the fuel is drawn from the outer space
around the main discharge jet and through a small hole in the
threaded body of the idling tube, this hole acting as the idle
metering orifice. In the sides of this tube, sometimes below
the level and sometimes at the level, are one or more small holes
which give an air bleed.
The idling tube channel terminates at the idling discharge jet,
whence it discharges into the carburetor barrel at the edge of
the throttle.
More air is admitted to the idling charge through the idling adjustment,
the air being taken by way of a hole (see Fig. 26) in the upper
part of the venturi tube.
The point of the idling adjustment needle is slightly offset from
the path of the idling tube, so that the stream of spray coming
up from the idling tube will not strike the needle shank and be
converted into larger drops.
The location of the idle discharge jet up or down in relation to
the position of the throttle-valve edge is very important, and
a variation of a few thousandths of an inch either way will perceptibly
change the low-speed mixture range of the carburetor.
Fig. 26. Showing how the fuel feed through the idle discharge jet
(IJ) is graduated by passage of the throttle edge across the jet.
As previously explained, there is a very high suction above the
throttle when the engine is idling and this suction does not change
very much from the time the engine is idling up to the time the
main jet comes in, which is perhaps 1.5 miles per hour.
If the idle were discharged in the space above the throttle valve,
the same amount of gasoline per minute would be fed, whether the
car were going two miles an hour or twelve miles an hour.
In order that the idling feed may increase as the throttle is opened,
although the suction above the throttle does not increase, the
construction shown in Fig. 26 is utilized.
The throttle is shown in a closed position corresponding to perhaps
two miles per hour, while the dotted line shows the position of
the throttle at about ten miles per hour.
The idle discharge jet (IJ) is made with a slot at the edge of
the throttle, so located that at the twomile-per-hour position
a considerable part of the slot is below the throttle and under
very little suction, while only a small part of the slot is above
the throttle and exposed to the high suction.
As the throttle opens, its edge travels downward on the slot so
that more of the slot is exposed to high suction and less to low
suction, and in this way the average suction, back of the slot
on the hole leading to the idling tube passage, is made to increase
as the throttle is opened.
If too little of the slot is above the throttle, at two miles per
hour, it will be necessary to screw the idling adjustment (IA)
almost down to its seat, which will result in the mixture being
richer than necessary at 10 to 20 miles per hour.
If too much of the slot shows above the throttle, it will be necessary
to take the idling adjustment screw almost all the way out to get
the proper mixture for low idling, and the mixture will then be
too lean at 12 to 17 miles per hour.
This leanness of mixture, besides showing an unsteady running at
these speeds, will cause the engine to be weak or misfire when
the throttle is opened from these speeds and may also cause the
engine to stumble or miss when the throttle is opened slightly
from a low idling position.
When this condition exists, it is necessary to try and average
up the idling adjustment so that the mixture will not be too lean
at 17 miles per hour and will not be too rich at a 5 miles per
hour idle.
Accelerating Well
Accelerating well: The need of an extra "shot," or accelerating
discharge of gasoline, when load is suddenly placed on the engine,
as the throttle is quickly opened, is well known.
The accelerating well system used on the Model "0" vertical
series of carburetors is the highest development in devices used
to perform this function. It operates each time the load is increased
on the engine, regardless of whether this is obtained by motion
of the throttle or increased road resistance.
Instead of discharging its whole supply while one cylinder is drawing,
as is the case at low speeds with devices of the syringe type,
the discharge from this type of accelerating well is measured by
the suction of the engine, so that each cylinder gets its share.
Since the accelerating chamber refills from the float chamber without
effect upon the action of the steady running fuel supply, it can
be made to refill quickly and handle a greater quantity of gasoline
than is practical with any devices which use the
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