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11 - 6
EXHAUST SYSTEM
TURBOCHARGER
DESCRIPTION
The boost pressure vacuum solenoid is located
under the air filter housing and is responsible for
turbo-charger boost pressure. It generates a control
vacuum in response to a PWM signal from the ECM.
Vacuum is achieved by mixing the system vacuum
(from the vacuum pump) with atmospheric pressure
to a certain degree. The resulting vacuum is sent to
the vacuum unit at the turbocharger (Fig. 4).
OPERATION
The vacuum solenoid receives 12V from the ECM.
The ECM controls the solenoid through a PWM sig-
nal. When the solenoid receives a signal it closes the
passage to atmospheric pressure. The subchamber is
no longer under atmospheric pressure, it's spring can
push the diaphragm and valve downwards; this
releases the VAC duct. Vacuum can now go from here
through the throttle hole, filters and out the connec-
tion to the turbocharger vacuum unit (Fig. 5).
1 - ENGINE
2 - BRAKE BOOSTER CHECK VALVE
3 - VACUUM PUMP
4 - TURBOCHARGER
Fig. 5 TURBOCHARGER VACUUM ROUTING
Fig. 4 CHARGE PRESSURE VACUUM TRANSDUCER
1 - CONNECTION TO TURBOCHARGER VACUUM UNIT
2 - VENT
3 - SUPPLY FROM VACUUM PUMP
5 - VACUUM SOLENOID
6 - VACUUM RESERVOIR
7 - ACCESSORY VACUUM JUNCTION
8 - FILTER
VA
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