Saab 95 1967, Руководство по обслуживанию

Страница: 114 / 610

Booster system
To provide additional power at high engine speeds and
under heavy loads, there are two different systems which
supply additional fuel to the engine.
One of the systems operates in the primary stage and is
actuated by the vacuum in a recess in the throttle valve
section. When there is a high vacuum in the suction pipe.
3 piston in the upper section of the carburetor is drawn
upwards. When the vacuum drops below a certain limit
owing to the wider throttle opening, a piston spring over-
comes the vacuum and forces the piston rod against the
needle valve, whereupon the valve opens. This permits ad-
ditional fuel to flow from the float chamber to the main
system of the primary stage.
The other booster system operates in the secondary stage
and is actuated by the vacuum in the upper part of the
carburetor throat. The system comes into operation when
the air velocity — and thus the vacuum in this part of the
throat — has become so high that fuel is drawn up from
the float chamber through a calibrated ascending pipe.
Vacuum valve (PVS-valve)
A thermo-regulated vacuum (positive vacuum supply)
valve is located in the coolant pipe from the engine. The
VACUUM CONTROL, DISTRIBUTOR
1. Carburetor
2. Vacuum valve
3. Distributor
function of this valve is to regulate the vacuum in the
vacuum control unit of the distributor when the engine
is hot and idling. This will increase the ignition timing,
thereby reducing the temperature of the engine.
When the temperature of the coolant is below about 215°F
(10400), the vacuum signal is regulated by the vacuum re-
cess in the primary stage of the carburetor.
In the event of the temperature of the coolant rising, the
passage from the primary recess is closed, and the distri.
butor will receive a vacuum signal from a recess in the
secondary stage instead. This signal is stronger since the
recess here is below the throttle valve, which implies an
increase in the setting of the ignition timing.
Throttle valve damper (Dash-pot valve)
A mechanical damping device is provided to ensure satis-
factory combustion during engine overrun. The damper
retards the return of the throttle valve from high engine
speed to idling speed.
TH ROTTLE VALVE DAMPER