Toyota 3R-B 1969, Repair Manual

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5-8 F U E L S Y S T E M - Ca r bu re t or
and uniform distribution of the air-fuel mixture to the cylinders.
A s the engine revolution in c re a s e s , the air flow becom es strong enough to
o v e rc o m e the weight of the high speed valve weight, then the high speed valve
opens gradually, and starts the secondary fuel flow into operation.
L o w s p e e d
5. P o w e r system
5 0 0 —3 2 0 0 rpm O v e r 3 2 0 0 rpm
G1356
F i g . 5-7 High Speed V a lv e Operation G1357, G1358
Both systems just previously men­
tioned a r e designed to d eliver the
most economical air-fuel mixture .
H o w e v e r , at w id e-open throttle,
w h e re full engine p o w e r is d e ­
s ir e d , and in crea se of rich fuel
mixture is re qu ired . T o o b ta in th is
rich mixture, and the full engine
p o w e r , an additional device is in­
corporated in this c a rb u r e to r .
3 2
F i g . 5-8 P o w e r System
Y6715
A t light load when the manifold v a ­
cuum is high, the manifold vacuum
pulls up the p o w e r piston (1 ) to clo se the p o w e r valve ( 2 ) . A s the primary
throttle valve is opened fully, the manifold vacuum d rop s , and the p o w e r p is­
ton is pushed down by the spring tension which opens the p o w e r v a l v e . When
the p o w e r valve opens, the fuel
flo w s down being controlled through
the p o w e r jet ( 3 ) , and joints with
the fuel from the main jet. Thus
extra fuel can be discharged from
the main nozzle ( 5 ) .
6 . A c c e le r a t in g system
When the throttle va lve is suddenly
opened from the closed position,
a momentary out-of-balance con­
dition o c c u rs in the c a rb u r e to r .
T o obtain an immediate engine
t o V e n tu r i
f r o m F l o a t
C h a m b e r
F i g . 5-9 A c c ele ra tin g
System
G1737