GENERAL INFORMATION
MULTIPORT FUEL INJECTION (MPI) <4A9>
13A-2
GENERAL INFORMATION
M1131000102741
The Multipoint Fuel Injection System consists of sen-
sors which detect the engine conditions, the
engine-ECU <M/T> or engine-CVT-ECU <CVT>
which controls the system based on signals from
these sensors, and actuators which operate under
the control of the engine-ECU <M/T> or
engine-CVT-ECU <CVT>. The engine-ECU <M/T>
or engine-CVT-ECU <CVT> carries out activities
such as fuel injection control, idle speed control and
ignition timing control. In addition, the engine-ECU
<M/T> or engine-CVT-ECU <CVT> is equipped with
several diagnosis modes which simplify trouble-
shooting when a problem develops.
FUEL INJECTION CONTROL
The injector drive times and injection timing are con-
trolled so that the optimum air/fuel mixture is sup-
plied to the engine to correspond to the
continually-changing engine operation conditions.
A single injector is mounted at the intake port of each
cylinder. Fuel is sent under pressure from the fuel
tank by the fuel pump, with the pressure being regu-
lated by the fuel pressure regulator. The fuel thus
regulated is distributed to each of the injectors.
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. The engine-ECU <M/T> or
engine-CVT-ECU <CVT> provides a richer air/fuel
mixture by carrying out "open-loop" control when the
engine is cold or operating under high load condi-
tions in order to maintain engine performance. In
addition, when the engine is warm or operating under
normal conditions, the engine-ECU <M/T> or
engine-CVT-ECU <CVT> controls the air/fuel mixture
by using the oxygen sensor signal to carry out
"closed-loop" control in order to obtain the theoretical
air/fuel mixture ratio that provides the maximum
cleaning performance from the three way catalyst.
THROTTLE VALVE OPENING CONTROL
This system electrically controls the opening of the
throttle valve. The engine-ECU <M/T> or
engine-CVT-ECU <CVT> detects the amount of
travel of the accelerator pedal via the accelerator
pedal position sensor, and controls the actuation of
the throttle valve control servo, which is mounted on
the throttle body, in order to attain the target throttle
valve opening that has been predetermined in
accordance with driving conditions.
IDLE SPEED CONTROL
The idle speed is kept at the optimum speed by con-
trolling the amount of air that passes through the
throttle valve in accordance with changes in idling
conditions and engine load during idling.
The engine-ECU <M/T> or engine-CVT-ECU <CVT>
drives the throttle valve control servo to keep the
engine running at the pre-set idle target speed in
accordance with the engine coolant temperature and
A/C and other electrical load. In addition, when the
air conditioning switch is turned off and on while the
engine is idling, the throttle valve control servo
adjusts the throttle valve passes through air amount
according to the engine load conditions to avoid fluc-
tuations in the engine speed.
IGNITION TIMING CONTROL
The power transistor located in the ignition primary
circuit turns ON and OFF to control the primary cur-
rent 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
<M/T> or engine-CVT-ECU <CVT> from the engine
speed, intake air volume, engine coolant tempera-
ture and atmospheric pressure.
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