Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Subaru Impreza 2001-2002.2004-2007 Approved Subaru Impreza 2004 WRX STi 08. MECHANISM AND FUNCTION 14. INTAKE (INDUCTION) 02. Turbocharger System
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W1860BE.book Page 3 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
2. Turbocharger System
A: GENERAL
The turbocharger system consists of a water-cooled turbocharger, air-cooled intercooler, waste-
gate control solenoid valve, etc.
The turbine rotated by exhaust gas pressure rotates the compressor.
As a result, the intake air is compressed by the compressor before it is delivered to the intake
manifold.
This turbocharger system controls the supercharging pressure according to changes in the atmo-
spheric pressure. Even at a high altitude, therefore, the system offers stable performance without
being affected by variations in atmospheric pressure.
IN(H4DOTC)-3
W1860BE.book Page 4 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
(12)
(1) (8)
(7)
(2)
(11)
(3)
(13)
(15)
(9)
(14)
(4)
(10)
(5)
(6)
IN-00046
(1) Manifold absolute pressure sensor (9) Wastegate controller
(2) Crankshaft position sensor (10) Wastegate control solenoid valve
(3) Camshaft position sensor (11) Air bypass valve
(4) Throttle position sensor (12) Intercooler
(5) Engine coolant temperature sensor (13) Throttle body
(6) Mass air flow and intake air temperature sensor (14) Intake manifold
(7) Wastegate valve (15) ECM
(8) Turbocharger unit
IN(H4DOTC)-4
W1860BE.book Page 5 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
B: TURBOCHARGER UNIT
The turbocharger is water-cooled. It utilizes a wastegate valve to adjust its supercharging pressure
to an optimum level. The turbine is housed in a lightweight, thin-wall, heat-resistant casting. The
compressor housing is made of thin-wall, aluminum alloy casting. The shaft for turbine and com-
pressor is supported by a full-floating metal bearing system.
(E)
(1)
(B)
(G)
(3)
(C)
(F)
(D)
(2)
(A) IN-00047
(1) Wastegate controller (A) Lubricating oil outlet (E) Lubricating oil inlet
(2) Compressor housing (B) Exhaust gas outlet (F) Air inlet
(3) Turbine housing (C) Air outlet port (G) Wastegate valve operation pres-
sure
(D) Engine coolant inlet
IN(H4DOTC)-5
W1860BE.book Page 6 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
C: LUBRICATION OF TURBOCHARGER
The turbocharger is lubricated by engine oil branched out from the oil pump. To cope with very high
speed of the turbocharger turbine and the compressor shaft which may reach a maximum of several
hundred thousands of rpm, full-floating type bearings are used which can form adequate oil films
on their inside and outside during running.
Further the oil supplied to the turbocharger also plays a role of cooling the turbine so that heat from
exhaust gas does not transmitted to the bearings.
(1)
(2)
(3)
(4)
IN-00048
(1) Compressor housing (3) Turbine housing
(2) Turbine wheel (4) Compressor impeller
D: COOLING OF TURBOCHARGER
The turbocharger unit is cooled by engine coolant, which enhances the reliability and durability of
the unit. The engine coolant from the coolant drain hose located under the cylinder head is led by
a pipe to the coolant passage provided in the turbocharger bearing housing. After cooling the bear-
ing housing, the engine coolant is led into the coolant filler tank through a pipe.
IN(H4DOTC)-6
W1860BE.book Page 7 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
E: WASTEGATE CONTROL SOLENOID VALVE
The wastegate control solenoid valve switches the intake air pressure passages to the wastegate
controller in response to signals from the ECM. When the solenoid valve is closed, the intake air
pressure upstream of the turbocharger unit is applied to the wastegate controller. When the sole-
noid valve is opened, the intake air pressure downstream of the turbocharger unit (supercharged air
pressure) is applied to the wastegate controller.
(1)
IN-00055
(1) Coil
IN(H4DOTC)-7
W1860BE.book Page 8 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
F: REGULATION OF SUPERCHARGING PRESSURE
1. BASIC FUNCTION OF THE WASTEGATE VALVE
When the engine speed increases as the throttle valve opens, the amount of exhaust gas increases.
This increases the speed of the turbine (approx. 20,000 to 150,000 rpm), the supercharging pres-
sure and the engine output.
If the resultant supercharging pressure is extremely high, however, it may cause knocking and an
excessively high thermal load on such engine components as pistons. In the worst case, the engine
may be damaged or broken. To prevent this, the wastegate valve and its controller are provided. By
sensing the supercharging pressure, the wastegate valve controller controls the operation of the
wastegate valve to maintain the supercharging pressure below a predetermined level.
(1)
(2)
(3)
IN-00049
(1) Wastegate valve
(2) Turbocharger
(3) Wastegate valve controller
IN(H4DOTC)-8
W1860BE.book Page 9 Tuesday, January 28, 2003 11:01 PM
TURBOCHARGER SYSTEM
INTAKE (INDUCTION)
While the supercharging pressure is lower than the predetermined level, the wastegate valve is
closed so that entire exhaust gas is directed to the turbine.
IN-00050
When the supercharging pressure reaches the predetermined level, the wastegate controller lets
the supercharging pressure press the diaphragm. This causes the wastegate valve to open through
a linkage. With the wastegate valve open, part of the exhaust gas is allowed to flow into the exhaust
gas pipe that bypasses the passage to the turbine.
This decreases the exhaust gas pressure that rotates the turbine and keeps the supercharging
pressure constant.
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