Nissan Primera P11. Instruction — part 116
Multiport Fuel Injection (MFI) System
DESCRIPTION
NCEC0014
Input/Output Signal Chart
NCEC0014S01
Sensor
Input Signal to ECM
ECM func-
tion
Actuator
Crankshaft position sensor (POS)
Engine speed and piston position
Fuel injec-
tion & mix-
ture ratio
control
Injector
Camshaft position sensor (PHASE)
Cylinder number
Mass air flow sensor
Amount of intake air
Engine coolant temperature sensor
Engine coolant temperature
Heated oxygen sensor 1 (front)
Density of oxygen in exhaust gas
Throttle position sensor
Throttle position
Throttle valve idle position
PNP switch
Gear position
Vehicle speed sensor or ABS actuator and
electric unit (control unit)
Vehicle speed
Ignition switch
Start signal
Air conditioner switch
Air conditioner operation
Knock sensor
Engine knocking condition
Electrical load
Electrical load signal
Battery
Battery voltage
Power steering oil pressure switch
Power steering operation
Heated oxygen sensor 2 (rear)*
Density of oxygen in exhaust gas
* Under normal conditions, this sensor is not for engine control operation.
Basic Multiport Fuel Injection System
NCEC0014S02
The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of
time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the
ECM memory. The program value is preset by engine operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from both the camshaft position sensor and the mass air
flow sensor.
Various Fuel Injection Increase/Decrease Compensation
NCEC0014S03
In addition, the amount of fuel injected is compensated to improve engine performance under various oper-
ating conditions as listed below.
<Fuel increase>
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During warm-up
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When starting the engine
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During acceleration
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Hot-engine operation
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High-load, high-speed operation
<Fuel decrease>
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During deceleration
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During high engine speed operation
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During high vehicle speed operation (M/T models)
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Extremely high engine coolant temperature
ENGINE AND EMISSION BASIC CONTROL
SYSTEM DESCRIPTION
QG16
I
18DE
Multiport Fuel Injection (MFI) System
EC-21
Mixture Ratio Feedback Control (Closed loop control)
NCEC0014S04
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission con-
trol. The three way catalyst can then better reduce CO, HC and NOx emissions. This system uses a heated
oxygen sensor 1 (front) in the exhaust manifold to monitor if the engine operation is rich or lean. The ECM
adjusts the injection pulse width according to the sensor voltage signal. For more information about the heated
oxygen sensor 1 (front), refer to EC-QG-132. This maintains the mixture ratio within the range of stoichiomet-
ric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 (rear) is located downstream of the three way catalyst. Even if the switching char-
acteristics of the heated oxygen sensor 1 (front) shift, the air-fuel ratio is controlled to stoichiometric by the
signal from the heated oxygen sensor 2 (rear).
Open Loop Control
NCEC0014S05
The open loop system condition refers to when the ECM detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
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Deceleration and acceleration
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High-load, high-speed operation
I
Malfunction of heated oxygen sensor 1 (front) or its circuit
I
Insufficient activation of heated oxygen sensor 1 (front) at low engine coolant temperature
I
High engine coolant temperature
I
During warm-up
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When starting the engine
Mixture Ratio Self-learning Control
NCEC0014S06
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from the heated oxy-
gen sensor 1 (front). This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio
as close to the theoretical mixture ratio as possible. However, the basic mixture ratio is not necessarily con-
trolled as originally designed. Both manufacturing differences (i.e., mass air flow sensor hot film) and charac-
teristic changes during operation (i.e., injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This
is then computed in terms of “injection pulse duration” to automatically compensate for the difference between
the two ratios.
“Fuel trim” refers to the feedback compensation value compared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical
value. The signal from the heated oxygen sensor 1 (front) indicates whether the mixture ratio is RICH or LEAN
compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is
rich, and an increase in fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation carried out long-term to compensate for continual deviation
of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences,
wear over time and changes in the usage environment.
SEF336WA
ENGINE AND EMISSION BASIC CONTROL
SYSTEM DESCRIPTION
QG16
I
18DE
Multiport Fuel Injection (MFI) System (Cont’d)
EC-22
Fuel Injection Timing
NCEC0014S07
Two types of systems are used.
Sequential Multiport Fuel Injection System
NCEC0014S0701
Fuel is injected into each cylinder during each engine cycle according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport Fuel Injection System
NCEC0014S0702
Fuel is injected simultaneously into all four cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The four injectors will then receive the signals two times for each engine cycle.
This system is used when the engine is being started and/or if the fail-safe system (CPU) is operating.
Fuel Shut-off
NCEC0014S08
Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds.
Electronic Ignition (EI) System
DESCRIPTION
NCEC0015
Input/Output Signal Chart
NCEC0015S01
Sensor
Input Signal to ECM
ECM func-
tion
Actuator
Crankshaft position sensor (POS)
Engine speed and piston position
Ignition tim-
ing control
Power transistor
Camshaft position sensor (PHASE)
Cylinder number
Mass air flow sensor
Amount of intake air
Engine coolant temperature sensor
Engine coolant temperature
Throttle position sensor
Throttle position
Throttle valve idle position
Vehicle speed sensor or ABS actuator and
electric unit (control unit)
Vehicle speed
Ignition switch
Start signal
Knock sensor
Engine knocking
PNP switch
Gear position
Battery
Battery voltage
SEF337W
ENGINE AND EMISSION BASIC CONTROL
SYSTEM DESCRIPTION
QG16
I
18DE
Multiport Fuel Injection (MFI) System (Cont’d)
EC-23
System Description
NCEC0015S02
The ignition timing is controlled by the ECM to maintain the best air-fuel ratio for every running condition of
the engine. The ignition timing data is stored in the ECM. This data forms the map shown above.
The ECM receives information such as the injection pulse width, crankshaft position sensor signal and cam-
shaft position sensor signal. Computing this information, ignition signals are transmitted to the power transis-
tor.
e.g.,
N: 1,800 rpm, Tp: 1.50 msec
A°BTDC
During the following conditions, the ignition timing is revised by the ECM according to the other data stored
in the ECM.
I
At starting
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During warm-up
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At idle
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During acceleration
The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not
operate under normal driving conditions.
If engine knocking occurs, the knock sensor monitors the condition. The signal is transmitted to the ECM. The
ECM retards the ignition timing to eliminate the knocking condition.
Air Conditioning Cut Control
DESCRIPTION
NCEC0016
Input/Output Signal Chart
NCEC0016S01
Sensor
Input Signal to ECM
ECM func-
tion
Actuator
Air conditioner switch
Air conditioner “ON” signal
Air condi-
tioner cut
control
Air conditioner relay
Throttle position sensor
Throttle valve opening angle
Crankshaft position sensor (POS)
Engine speed
Engine coolant temperature sensor
Engine coolant temperature
Ignition switch
Start signal
Refrigerant pressure sensor
Refrigerant pressure
Vehicle speed sensor or ABS actuator and
electric unit (control unit)
Vehicle speed
Power steering oil pressure switch
Power steering operation
System Description
NCEC0016S02
This system improves engine operation when the air conditioner is used.
Under the following conditions, the air conditioner is turned off.
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When the accelerator pedal is fully depressed.
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When cranking the engine.
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At high engine speeds.
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When the engine coolant temperature becomes excessively high.
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When operating power steering during low engine speed or low vehicle speed.
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When engine speed is excessively low.
SEF742M
ENGINE AND EMISSION BASIC CONTROL
SYSTEM DESCRIPTION
QG16
I
18DE
Electronic Ignition (EI) System (Cont’d)
EC-24
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