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276
FIAT - 850 PASSENGER CARS
Fig. 432 • Carburetor viewed from the throttles control end.
22. Throttle stop screw. - 23. Throttles control lever. - 33. Idle
volume conlrol screw. - 43. Accelerator pump control lever. -
52. Choke throttle valve. - 55. Choke control lever. - 59. Primary
seclor relurn spring.
Fuel in the wells mixes with the air from the bleed
jets
(4)
issuing from the opening in the emulsion
tubes (14), then, past the discharge tubes (10), it is
advanced to the carburetion cone consisting of the
auxiliary Venturis (11) and the primary Venturis (12).
The secondary throat includes the super-feeder
device: the fuel from the bowl (17) is metered by
the calibrated bushing (3) and blends with the air
from the calibrated orifice (6).
During high speed operation with wide open
throttles, the mixture streaming past the passage
(7) and calibrated bushing (8) is drawn into the
secondary throat through the super-feeder nozzle (9).
Fig. 431 illustrates also the differential opening
device of throttle valves.
When the throttles control lever (23) is actuated,
the lug (29) of the sector attached solidly to the
primary shaft (24) at first rides free and the primary
throttle opens through a corresponding angle,
whereas the secondary throttle working on shaft
(27), remains closed.
Subsequently the lug (29) abuts against the lug
(28) of the idler lever (25) which will cause the
lever (26) to rotate the secondary shaft (27). until
both throttle valves are simultaneously wide open.
The primary throttle stop screw (22) is situated
on the idler lever (25).
While idling, the fuel is passaged from the pri-
mary well (IS, fig. 431) to the idling jet (31, fig. 435)
where it blends with the air from the calibrated
bushing.
Hence, through the idling feed passage
and orifice which can be adjusted by means of the
screw (33), fuel reaches the primary throat down-
stream of the throttle (35, fig. 433) where mixture
is also conveyed from the idle transfer port located
in exact relation to the primary throttle, thus enabl-
ing the engine to accelerate evenly from the idling
speed.
When the secondary throttle (13, fig. 431) is
opened, the fuel flows from the secondary well (15)
to the idling jet (31, fig. 435) where it blends with
the air from the calibrated bushing and eventually
17
JI
Fig. 433 _ Diagrammatic section views of Weber 30
ole
1 carburetor.
10. Discharge tube .• 35. Primary throttle valve. - 52. Choke throttle valve. - 53. Choke return spring. - 54. Choke control lever lug. -
55. Choke control lever. - 56. Primary throttle control lever rod. - 57. Primary throttle control lever.
A. Easy starting device (choke) In.• B. Easy starting device (choke) out.
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