1990 MITSUBISHI ECLIPSE oil

-
14-34FUEL SYSTEM - Fuel Injection Control
TDC sensorAir flow sensor
I
Reading of input signal1
I ,,
uOperation mode decisionOperation mode decision data
I rBasic valve opening time data
Enginecontrol unitInjector activation time control
Injector activation pulse generationControl factor data of
engine coolant temperature,
intake air temperature and
barometric pressure, etc.
Injector1
6FUO766Needle valveFilter
Connector
Solenoid coil
Plunger
-4
INJECTOR,
The injection nozzle spray opening area is constant and the fuelinjection pressure is also constant; therefore, the injection
quantity is determined by the amount of time that the solenoid
coil is energized.
.

14-36FUEL SYSTEM- Fuel lniection Control
SFUOSlS
RESISTOR The resistor functions to regulate the current flowing in the
co,.of the injector.
Because the injector must respond instantly to fuel-injection
signals, the number of windings of the coil is reduced in order
to facilitate current rise when the current is flowing in the coil.
By doing so, the resistance of the injector coil becomes smaller
and a greater amount of current can flow, with the result that
the calorific value of the injector coil becomes greater, and
1overheating occurs.
For this reason, for turbocharger-equipped models (which have
low resistance of the injector coil), a resistor is provided
between the power supply (+) and the injector in order to
regulate the amount of current flowing in the coil.
FUEL INJECTION TIMING (INJECTOR AC-
TIVATION TIMING)
The fuel injection timing in multipoint fuel injection
has two modes, sequential and simultaneous. In
sequential injection, fuel is injected into each
cyl-inder sequentially throughout the entire normaloperating range including idling; in simultaneous
injection, fuel is injected simultaneously into all
cylinders during starting and acceleration.
Sequential Injection
r
No. 1cylinder
TDC sensor signal
Crank angle
sensor signal
No. 1 cylinder
No. 3 cylinder
No. 4 cylinder
No. 2 cylinder
In sequential injection, the’ injectors are activated foreach cylinder on the combustion stroke of the
piston. The No. 1 cylinder TDC signal is the
refer-
ence signal for sequential injection. The signal
represents the compression stroke in the No.
1cylinder and, with that timing as a reference, fuel isinjected into the cylinders in the order of
No.2,No.
1, No.3, and No.4. The injection for each
cylinder is synchronized with the crank angle
sen-sor’s 5” BTDC signal. Fuel is injected in each
cylinder once for every two revolutions of the
crankshaft.
-

14-42
FUEL SYSTEM- Fuel Injection Control
4
Fz.or.c
4:0/
E
{!*760 (301Barometric pressure
mmHg (in.Hg) 6Fuo9z
c
Timet
6FUO279Drivecurrent
0: bri
F2JJ’ ipe; II
I+-JValve opening timi16240:
E‘C
F
.-
is
3
3:\Battery voltage
V162406
80 (176)Coolant temperature
“C (“F)162401HIGH ALTITUDE COMPENSATION
A change in barometric pressure, which may be caused by
change in altitude, alters the intake air density, resulting in an
improper air-fuel ratio. To compensate this deviation, the
amount of fuel injected is controlled; i.e., the amount of fuel
injected is decreased to compensate for the lower intake air
density caused by the decreased barometric pressure, or the
higher altitude.
CONTROL FOR FUEL ENRICHMENT DURING ACCELERA-
TIONDuring acceleration at low and middle loads, fuel supply rate is
increased to improve acceleration performance.
FUEL DECREASE CONTROL DURING DECELERATION
During deceleration, fuel supply rate is decreased to improve
fuel economy.
BATTERY VOLTAGE COMPENSATION
As described earlier in “INJECTOR”, the needle valve of the
injector is pulled to the fully open position when current flow-
through the solenoid coil. This means that there is a time I;
between the time when the current starts flowing and when
the needle valve starts opening. This time lag is called the dead
time.
The dead time varies with different battery conditions:: the
lower the battery voltage, the longer the dead time.
Since the injector activation duration depends on the intake air
volume and other factors, a longer dead time means a shorter
activation duration, or a smaller amount of fuel injected. This
results in an improper air-fuel ratio. At such times, the solenoid
coil is energized for a longer period of time depending on the
current battery voltage to correct the valve opening time, thus
ensuring that the optimum amount of fuel is injected.
Fuel Injection Control at Starting
When the engine is cranked, the map value preset according to
the engine coolant temperature is used as the basic injector
activation duration, to which the high altitude compensation is
applied..

- __..--
14-44FUEL SYSTEM- Idle Speed Control
IDLE SPEED CONTROL
RlUU*I,GENERAL DESCRIPTION
If the load changes while idling, the idle speed
control servo is activated according to the preset
control logic to control the air flow that bypasses thethrottle valve, thus maintaining the optimum idle
speed.Fast idle air valve
Idle speed
control servo
Cooiar
To intakemanifoldFrom air
cleanerSpeed
adjustrng screwInhibitor switch
Ignition switch
Coolant temperature sensorThrottle position sensor
Crank angle sensorVehicle speed sensor
Air conditioner switch
Barometric pressure sensor
Power steering oil
pressure switch
Intake air te.mperature sensorIdle position switchIgnition timing adjustment
terminalSelfdiagnosisIdata trans-
mission switching terminal
6FUO796
Input signal reading
-3I9Control modedecision
II
41*
Target speed dataIdle speed control---cIdle speed
feedback controlservo position- Target position data
control
Idle speed controlIdle speed control
servo dnve pulse-Drive pulse setting
Drive pulse setting-servo drive pulse
setting data

3-d__- .
FUEL SYSTEM
-Idle Speed Control14-45IDLE SPEED CONTROL SERVO
L
PtntleThrottle bodv
Idle speed control
servo
Extend
7 -IMagnet rotordoil
/Stepper motor
6FUO799The idle speed control servo, consisting of a
steptype motor and pintle, is mounted on the throttle
body. As the motor operates, the pintie extends or
retracts to control the bypass air flow.
The step type motor, or stepper motor, is a motor
that rotates a fixed angle when an electric
Pulse is
rpplied.The rotor of the stepper motor used here rotates
15degrees whenever a pulse is applied.
The pintle meshes with the lead screw on the
magnet rotor shaft, as shown in the above
illustra-tion. When the rotor rotates in the direction of the
outlined arrow, the lead screw causes the pintle t0
retract towards the interior of the motor. When the
rotor rotates in the direction of the solid arrow, the
pintle extends.

.
14-46FUEL SYSTEM- Idle Speed Control
The rotor rotates in either direction by angular step increments
corresponding to the number of pulses coming from the en
?control unit, causing the pintle to extend or retract. As
pintle retracts or extends, the gap it forms between the
sea:changes, controlling the bypass air flow. The relationship
between the pintle extension or retraction movement and
bypass air flow rate is as shown at the left.
Number of pulse
7F UW(Control relay
@iI---
unit
Battery power is supplied first to the control relay,
then to the idle speed control servo coil, then to theservo activation signal to turn the power transistor
engine control unit.on and thus forms the coil grounding circuit. As the
The engine control unit uses the idle speed controlcoils are sequentially energized, the magnet rotor of
the idle speed control servo is caused to rotate.

FUEL SYSTEM- Idle Speed Control14-47Operating Principles of Stepper Motor
Stator ICoil Al and
A2 e
Stator II
Fig. A7FUO43Fig. B6FUO519The stepper motor construction is as shown in Fig.
A. Its operating principles are explained below, with
reference to the schematic Fig.
8.STEP “0”
Engine controlunitPower
Coil B 1Coil
B2
I6FU0520
- Stator IStator
II
U
LdStep o 1 23When coils Al and
Bl are energized the upperhalves of stators I and
II are N poles and their lower
halves are
S poles. Thus, their N poles and S polesattract the
S poles and N poles of rotor magnets.
respectively, and the rotor is held stationary.

14-48STEP
“1”
FUEL SYSTEM - Idle Speed Control
Engine control unitPowerSUPPlYI IStepper motor
Stator I
Stator II
I6FUO522When coil
A2 is energized instead of coil Al, the
lower half of stator I becomes an
N pole. This
means that the
N pole is moved one step to the
right compared to the condition in Step 0. As aresult, the
S pole of the rotor is attracted to the Npole of the stator and the rotor moves, or rotates,
one step to the right.
STEP
“2”
Engine control unitPower
=JPPb
1 IStepper motor
Stator IStator II
mI6FU0524w3Step o 1 2
6FUO525When coil
B2 is energized instead of coil Bl, the
lower half of stator II becomes and
N pole. This
means that the
N pole is moved one step to the
right compared to the condition in Step 1. Thus, as
in step 1, the rotor rotates one step to the right.
Each time a different pair of coils energized as
shown above, the rotor rotates one step.When the coil energizing sequence is as Al, B!
3
Bl, A2 -) A2. B2 + B2. Al + Al, Bl . . . . the I*rotates clockwise.
When coil pairs are energized in the reverse
sequence, namely in the order
Bl, Al + Al, B2 -)
B2, A2 --) A2, Bl 3 Bl, Al . . . . the rotor rotates
counterclockwise.