DYKE'S INSTRUCTION No. 88 (Supplement)
robbing the fuel flow from the main discharge jet and giving the
engine a temporarily lean mixture.
In order that this may not give an objectionable misfire, it is
necessary that the accelerating well space be not too large and
this in effect constitutes the limitation to the amount of accelerating
fuel discharge which can be used.
The tendency toward missing under these conditions is usually greatest
in warm summer weather, when the intake manifold is warm and relatively
dry, so that any diminution of fuel feed from the carburetor is
quickly felt by the cylinders.
Effects of too great accelerating charge: In both the vertical
and horizontal carburetors, the air-bleed passage from the economizer
is slightly below the fuel level, so that it entirely or partially
fills when the engine is idling, and if the throttle be opened
just the right amount, the whole contents of the cross drill channel
will be drawn into the engine as an accelerating charge.
In warm weather when the carburetor and intake system are so hot
that the gasoline vaporizes almost instantaneously, this extra
quantity of gasoline may be too much and give a charge so temporarily
rich that the engine misfires.
This has been overcome by using reducing plugs in these channels
which partly fill up the space (as, for example, Fig. 25, similarly,
extension plugs (P) (Fig. 33) have also been used in the cross-channel
of the accelerating well air bleed of the horizontal models.
The stumble, or flat spot (momentary lack of power) from too rich
an accelerating charge at this
Fig. 33. Showing how extension plugs (P) may be used in the horizontal
air-bleed channels to reduce the liquid space of the accelerating
well system.
small throttle opening is very similar to the stumble caused by
a too lean mixture on the idle range at 12 miles an hour.
The most definite distinction lies in the fact that if the stumble
is worse when the engine is cold, it is probably due to a lean
mixture just off the idle, due to improper location of the idle
discharge jet with reference to the throttle edge; while if the
stumble is worse as the engine gets warm, it is probably due to
a too great gasoline discharge from the accelerating well or from
the cross-channel passages.
STROMBERG MODELS "OA" AND "M" CARBURETORS
Model "OA" Carburetor No air bleeds are used in the idling
tithe, while the idle discharge jet, instead of being slotted as
in the Model "0" has a recessed round orifice.
The accelerating well is of the type used on the Models "OS" and "OC" and
two forms are commonly used; the "single" and the "compensating" (Figs.
37 and 3S). (See page 134 for adjustment of Model "-1" carburetor.)
The "single" accelerating well: This well differs from
the "compensating" well ic1 that it has a greater capacity
and also in that its effect is confined to low speeds; that is.
it is entirely empty at a comparatively low throttle position,
and is thus more violent in its action than the other type.
For commercial vehicles and trucks, this type of well is recommended,
with holes in the sides (beginning at the top) Nos. 60-58-57-57.
When more gasoline is needed for low-speed acceleration these same
parts may be used with holes Nos. 65-60-5S.
The Model "OA" is a simplified type of vertical carburetor
de-signed for package equipment (meaning for replacement purposes),
and uses a single venturi tube, the air-bleed economizer and the
accelerating well used and described for the Models "OC" and "OS" carburetors.
The action and adjustments are exactly the same as in the horizontal
models and the description and instructions given for them will
apply fully to the Model "OA."
Model "M" Carburetor
The Model "M" carburetor is a simplified form intended
for truck and heavy-duty service, although it has given very good
satisfaction on small four-cylinder engines in passenger car service.
To reduce the number of fuel passages, the emulsion columns for
the air-bleed jet is made concentric with (surrounds) the idling
tube and the fuel emulsion passes through a horizontal drill to
a groove around the small venturi, into which it discharges through
a number of small holes.
1 See footnote on page 1242 for meaning.
Fig. 35. Stromberg Model "Al" carburetor
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