Infiniti M35/M45 Y50. Manual - part 565

ENGINE CONTROL SYSTEM

EC-733

[VK45DE]

Multiport Fuel Injection (MFI) System

NBS0059J

INPUT/OUTPUT SIGNAL CHART

*1: This sensor is not used to control the engine system under normal conditions.
*2: This signal is sent to the ECM through CAN communication line.
*3: ECM determines the start signal status by the signals of engine speed and battery voltage.

SYSTEM DESCRIPTION

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 the crankshaft position sensor (POS), camshaft position
sensor (PHASE) and the mass air flow sensor.

VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION

In addition, the amount of fuel injected is compensated to improve engine performance under various operat-
ing conditions as listed below.
<Fuel increase>

●

During warm-up

●

When starting the engine

●

During acceleration

●

Hot-engine operation

●

When selector lever is changed from N to D

●

High-load, high-speed operation

●

During deceleration

●

During high engine speed operation

Sensor

Input Signal to ECM

ECM function

Actuator

Crankshaft position sensor (POS)

Engine speed*

Piston position

Fuel injection
& mixture ratio
control

Fuel injector

Camshaft position sensor (PHASE)

Mass air flow sensor

Amount of intake air

Engine coolant temperature sensor

Engine coolant temperature

Air fuel ratio (A/F) sensor 1

Density of oxygen in exhaust gas

Throttle position sensor

Throttle position

Accelerator pedal position sensor

Accelerator pedal position

Park/neutral position (PNP) switch

Gear position

Battery

Battery voltage*

Knock sensor

Engine knocking condition

Power steering pressure sensor

Power steering operation

Heated oxygen sensor 2*

Density of oxygen in exhaust gas

ABS actuator and electric unit (control unit)

VDC/TCS operation command*

Air conditioner switch

Air conditioner operation*

Wheel sensor

Vehicle speed*

EC-734

[VK45DE]

ENGINE CONTROL SYSTEM

MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)

The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst (manifold) can then better reduce CO, HC and NOx emissions. This system uses A/F
sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The ECM adjusts the
injection pulse width according to the sensor voltage signal. For more information about A/F sensor 1, refer to

EC-947, "DTC P0130, P0150 A/F SENSOR 1"

. This maintains the mixture ratio within the range of stoichio-

metric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three way catalyst (manifold). Even if the switching
characteristics of A/F sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal from heated
oxygen sensor 2.

Open Loop Control

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.

●

Deceleration and acceleration

●

High-load, high-speed operation

●

Malfunction of A/F sensor 1 or its circuit

●

Insufficient activation of A/F sensor 1 at low engine coolant temperature

●

High engine coolant temperature

●

During warm-up

●

After shifting from N to D

●

When starting the engine

MIXTURE RATIO SELF-LEARNING CONTROL

The mixture ratio feedback control system monitors the mixture ratio signal transmitted from A/F sensor 1.
This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to the theoret-
ical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as originally
designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes dur-
ing operation (i.e., fuel 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 A/F sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the the-
oretical 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.

PBIB3020E

ENGINE CONTROL SYSTEM

EC-735

[VK45DE]

FUEL INJECTION TIMING

Two types of systems are used.

Sequential Multiport Fuel Injection System

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

Fuel is injected simultaneously into all eight cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The eight fuel 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

Fuel to each cylinder is cut off during deceleration, operation of the engine at excessively high speeds or oper-
ation of the vehicle at excessively high speeds.

Electronic Ignition (EI) System

NBS0059K

INPUT/OUTPUT SIGNAL CHART

*1: This signal is sent to the ECM through CAN communication line.
*2: ECM determines the start signal status by the signals of engine speed and battery voltage.

SYSTEM DESCRIPTION

Firing order: 1 - 8 - 7 - 3 - 6 - 5 - 4 - 2
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.
The ECM receives information such as the injection pulse width and camshaft position sensor (PHASE) sig-
nal. Computing this information, ignition signals are transmitted to the power transistor.
During the following conditions, the ignition timing is revised by the ECM according to the other data stored in
the ECM.

●

At starting

●

During warm-up

●

At idle

●

At low battery voltage

PBIB0122E

Sensor

Input Signal to ECM

ECM function

Actuator

Crankshaft position sensor (POS)

Engine speed*

Piston position

Ignition timing
control

Power transistor

Camshaft position sensor (PHASE)

Mass air flow sensor

Amount of intake air

Engine coolant temperature sensor

Engine coolant temperature

Throttle position sensor

Throttle position

Accelerator pedal position sensor

Accelerator pedal position

Battery

Battery voltage*

Knock sensor

Engine knocking

Park/neutral position (PNP) switch

Gear position

Wheel sensor

Vehicle speed*

EC-736

[VK45DE]

ENGINE CONTROL SYSTEM

●

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.

Fuel Cut Control (At No Load and High Engine Speed)

NBS0059L

INPUT/OUTPUT SIGNAL CHART

*: This signal is sent to the ECM through CAN communication line.

SYSTEM DESCRIPTION

If the engine speed is above 1,400 rpm under no load (for example, the selector lever position is neutral and
engine speed is over 1,400 rpm) fuel will be cut off after some time. The exact time when the fuel is cut off var-
ies based on engine speed.
Fuel cut will be operated until the engine speed reaches 1,000 rpm, then fuel cut will be cancelled.

NOTE:
This function is different from deceleration control listed under Multiport Fuel Injection (MFI) System,

EC-733,

"Multiport Fuel Injection (MFI) System"

Sensor

Input Signal to ECM

ECM function

Actuator

Park/neutral position (PNP) switch

Neutral position

Fuel cut control

Fuel injector

Accelerator pedal position sensor