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 22. FUEL INJECTION (FUEL SYSTEM STi) 02. Air Line
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W1860BE.book Page 3 Tuesday, January 28, 2003 11:01 PM
AIR LINE
FUEL INJECTION (FUEL SYSTEM)
2. Air Line
A: GENERAL
The air filtered by the air cleaner enters the throttle body where it is regulated in the volume by the
throttle valve and then enters the intake manifold. It is then distributed to each cylinder where the
air is mixed with fuel injected by the injector.
B: MANIFOLD ABSOLUTE PRESSURE SENSOR
The manifold absolute pressure sensor is attached to the top of the throttle body, and continuously
sends to the engine control module (ECM) voltage signals that are proportional to intake manifold
absolute pressures. The ECM controls the fuel injection and ignition timing based on the intake
manifold absolute pressure signals in addition to other signals from many sensors and other control
modules.
(1) (2)
(A)
(3) (B)
FU-00343
(1) Connector (A) Output voltage
(2) Terminal (B) Absolute pressure
(3) O-ring
FU(STi)-3
W1860BE.book Page 4 Tuesday, January 28, 2003 11:01 PM
AIR LINE
FUEL INJECTION (FUEL SYSTEM)
C: ELECTRONIC CONTROL THROTTLE SYSTEM
The electronic control throttle system consists of an accelerator pedal position sensor mounted
on the accelerator pedal, a throttle position sensor and a throttle motor mounted on the throttle body,
and the ECM which controls these components.
The movement of the accelerator pedal is converted into electrical signals by the accelerator ped-
al position sensor and sent to the ECM.
Based on these signals the ECM controls the throttle motor to open and close the throttle valve.
(3)
(4) (5)
(3)
(1)
(2)
(1)
FU-01069
(1) Throttle position sensor (4) Electronic control throttle relay
(2) Accelerator pedal position sensor (5) ECM
(3) Electronic control throttle assembly
FU(STi)-4
W1860BE.book Page 5 Tuesday, January 28, 2003 11:01 PM
AIR LINE
FUEL INJECTION (FUEL SYSTEM)
D: MASS AIR FLOW AND INTAKE AIR TEMPERATURE SENSOR
The mass air flow and the intake air temperature sensors are integrated into a single unit. The unit
is mounted on the air cleaner case and measures the amount as well as the temperature of the in-
take air.
The measured amount and temperature are converted into electrical signals and sent to the ECM.
The ECM uses these signals to control injection and ignition timing as well as the fuel injection
amount.
(1)
(2)
(3)
(A)
FU-00346
(1) Mass air flow and intake air temperature sensor (A) Air
(2) Mass air flow sensor
(3) Intake air temperature sensor
E: TUMBLE GENERATOR VALVE
A tumble generator valve is provided on each engine bank, between the intake manifold and in-
take air ports. The right bank tumble generator valve has butterfly valves for the #1 and #3 cylinders
and the left bank tumble generator valve has those for the #2 and #4 cylinders. The two butterfly
valves in each tumble generator valve are fitted on a single shaft that is driven by an actuator.
The tumble generator valves are controlled by the ECM according to the coolant temperature and
the time elapsed after start of the engine. When the engine is started, the butterfly valves are moved
to the closing ends. In this state, the intake air flows at very high speeds passing through narrowed
passages in the directions determined by the individual intake air ports in the cylinder head. This
creates tumbling air motions in the cylinders, which enables lean mixtures to be ignited and thus
harmful exhaust emissions to be reduced during engine start. The tumble generator valves are fully
open when the engine is operating at an ordinary driving speed, allowing intake air to flow without
being changed in direction and velocity.
FU(STi)-5
W1860BE.book Page 6 Tuesday, January 28, 2003 11:01 PM
AIR LINE
FUEL INJECTION (FUEL SYSTEM)
(3)
(1)
(2)
(A) (4) (B) (4)
(5) (6) (5) (6)
(3) (3)
(9) (9)
(7) (7)
(8) (8)
(10) (10)
FU-00998
(A) Activated
(B) Not activated
(1) Actuator (6) Tumble generating air passage
(2) Tumble generator valve position sensor (7) Intake main air passage
(3) Tumble generator housing (8) Piston
(4) Intake manifold (9) Injector
(5) Tumble generator valve (10) Cylinder Head
FU(STi)-6
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