Toyota COMPUTER-CONTROLLED SYSTEM - Page 133

OTHER CONTROL SYSTEMS - ACI S
OPERATIO N
1 Low and medium speeds (below set speed )
The ECU turns the VSV on when the engine is
running at low to medium speeds . Therefore, the
vacuum (supplied by the vacuum tank) causes
the actuator to close the air control valves fully .
By closing the air control valves, the same effect
as lengthening the intake manifold is obtained .
This improves intake efficiency in the low- and
medium-speed ranges .
Thro tt
le valve Air contro l
No
. 1 air intake valve
( closed)
chamber
1-Z No
. 2 ai r
a~
intak e
chambe r
OHP 8 7
2 High speed (above set speed )
When the engine speed rises above the
predetermined speed, the ECU turns the VSV off
and the atmospheric air acts directly upon the
actuator . Therefore, the spring damper causes
the actuator to open the air control valves fully .
By opening the air control valves, the same
effect as shortening the intake manifold is
obtained . This shifts the peak intake efficiency
to the high engine speed range, improving
output in the high-speed range .
OHP 87
1
23