Mitsubishi Pajero Pinin 1999, Workshop Manual

Page: 75 / 919

GDI ±
General Information
13A-3
GENERAL INFORMATION
The Gasoline Direct Injection System consists
of sensors which detect the engine conditions,
the engine-ECU which controls the system
based on signals from these sensors, and
actuators which operate under the control of
the engine-ECU. The engine-ECU carries out activities such as fuel injection control, idle
speed control and ignition timing control. In
addition, the engine-ECU is equipped with
several diagnosis modes which simplify
troubleshooting when a problem develops.
FUEL INJECTION CONTROL
The injector drive times and injector timing are
controlled so that the optimum air/fuel mixture
is supplied to the engine to correspond to the
continually-changing engine operation condi-
tions.
A single injector for each cylinder is mounted
at the cylinder head. The fuel is sent under
pressure from the fuel tank to the fuel pressure
regulator (low pressure) by the fuel pump (low
pressure). The pressure is regulated by the fuel
pressure regulator (low pressure) and the fuel
regulated is then sent to the fuel pump (high
pressure). The fuel under increased pressure
generated by the fuel pump (high pressure) is
then regulated by the fuel pressure regulator
(high pressure) and is then distributed to each
of the injectors via the delivery pipes. Fuel injection is normally carried out once for
each cylinder for every two rotations of the
crankshaft. The firing order is 1-3-4-2. This is
called sequential fuel injection.
When the engine is cold or under a severe load,
the ªopen-loopº control keeps the air/fuel ratio
at a richer than usual level to maintain
driveability. When the engine is under low or
medium loads, the air/fuel ratio becomes leaner
to reduce fuel consumption. When the engine
is running at medium or high loads after having
warmed up, the ªclosed-loopº control uses the
signal from the oxygen sensor to keep the
air/fuel ratio at the optimum theoretical level.
THROTTLE VALVE OPENING ANGLE CONTROL
This system controls throttle valve opening
angle electronically. The engine-ECU deter-
mines how deeply the accelerator pedal is
depressed by means of the accelerator position
sensor (APS). Then the engine-ECU sends a target value of the throttle valve opening angle
to the throttle valve controller. The throttle valve
control servo operates the throttle valve so that
it reaches the target opening angle.
IDLE SPEED CONTROL
This system maintains engine idle speed at a
predetermined condition by controlling the air
flow that passes through the throttle valve
according to engine idling condition and engine
loads at idling.
The engine-ECU operates the throttle valve
control servo so that engine speed is maintained within a map value. The map value is
predetermined according to engine coolant
temperature and air-conditioning load. In
addition, if the A/C switch is turned on or off
during
engine idling, the engine-ECU
compensates the engine speed by operating
the throttle valve control servo as necessary.
IGNITION TIMING CONTROL
The power transistor located in the ignition
primary circuit turns ON and OFF to control
the primary current flow to the ignition coil. This
controls the ignition timing in order to provide
the optimum ignition timing with respect to the
engine operating conditions. The ignition timing is determined by the engine-ECU from the
engine speed, intake air volume, engine coolant
temperature,
atmospheric pressure and
injection timing (intake stroke or compression
stroke).