DENSO COMMON RAIL SYSTEM (CRS). SERVICE MANUAL (2007)

Operation Section

1-37

Pump Unit (Eccentric Cam, Ring Cam, Plunger)

• The eccentric cam is attached to the camshaft and the ring cam is installed on the eccentric cam. There are two plung-

ers at positions symmetrical above and below the ring cam.

Plunger A

Ring Cam

Camshaft

Feed Pump

Eccentric Cam

Plunger B

Q000845E

• Because the rotation of the camshaft makes the eccentric cam rotate eccentrically, the ring cam follows this and

moves up and down, and this moves the two plungers reciprocally. (The ring cam itself does not rotate.)

Eccentric Cam

Ring Cam

Camshaft

Q000846E

Operation Section

1-38

Delivery Valve

• The delivery valve for the HP3 has an integrated element and is made up of the check ball, spring, and holder. When

the pressure at the plunger exceeds the pressure in the rail, the check ball opens to discharge the fuel.

Check Ball

Element

Spring

Holder

Plunger

Q000847E

Fuel Temperature Sensor

• The fuel temperature sensor is installed on the fuel intake side and utilizes the characteristics of a thermistor in which

the electric resistance changes with the temperature in order to detect the fuel temperature.

Resistance - Temperature

Thermistor

Characteristic

Temperature

Q000848E

Operation Section

1-39

(4) Supply Pump Operation

Supply Pump Overall Fuel Flow

• The fuel is suctioned by the feed pump from the fuel tank and sent to the SCV. At this time, the regulating valve adjusts

the fuel pressure to below a certain level. The fuel sent from the feed pump has the required discharge quantity ad-

justed by the SCV, and enters the pump unit through the suction valve. The fuel pumped by the pump unit is pumped

through the delivery valve to the rail.

Inject

Rail

Suction Pressure

Feed Pressure

High Pressure

Suction Valve

Discharge Valve

Return Pressure

From Pump

Plunger

Return Spring

To Rail

Return

Combustion Overflow

Regulating Valve

Feed Pump

Filter

Fuel Intake Port

Camshaft

Suction

Fuel Filter

(With Priming Pump)

Fuel Tank

Q000849E

Operation Section

1-40

Operation

• The discharge quantity is controlled by SCV control, the same as for the HP2, however it differs from the HP2 in that

the valve opening is adjusted by duty ratio control.

• In the intake stroke, the spring makes the plunger follow the movement of the ring cam, so the plunger descends to-

gether with the ring cam. Thus, unlike the HP2, the plunger itself also suctions in fuel. When the suctioned fuel passes

through the SCV, the flow quantity is controlled to the required discharge quantity by the valve opening and enters

the pump main unit.

• The quantity of fuel adjusted by the SCV is pumped during the pumping stroke.

Suction Valve

Delivery Valve

Plunger A

Eccentric Cam

Ring Cam

SCV

Plunger B

Plunger A: End of Compression

Plunger A: Start of Suction

Plunger B: End of Suction

Plunger B: Start of Compression

Plunger A: Start of Compression

Plunger A: End of Suction

Plunger B: Start of Suction

Plunger B: End of Compression

QD0707E

Operation Section

1-41

3.4 HP4 Type

(1) Construction and Characteristics

• The HP4 basic supply pump construction is the same as for the HP3. The composition is also the same as the HP3,

being made up of the pump unit (eccentric cam, ring cam, plunger), the SCV (suction control valve), the fuel temper-

ature sensor, and the feed pump. The main difference is that there are three plungers.

• Because there are three plungers, they are positioned at intervals of 120? around the outside of the ring cam. In ad-

dition, the fuel delivery capacity is 1.5 times that of the HP3.

• The fuel discharge quantity is controlled by the SCV, the same as for the HP3.

SCV (Suction Control Valve)

Fuel Temperature Sensor

Delivery Valve

Feed Pump

Plunger

Suction Valve

Eccentric Cam

Q000850E

Operation Section

1-43

(3) Component Part Functions

Component Parts

Functions

Feed Pump

Draws fuel from the fuel tank and feeds it to the plunger.

Regulating Valve

Regulates the pressure of the fuel in the supply pump.

SCV (Suction Control Valve)

Controls the quantity of fuel that is fed to the plungers.

Eccentric Cam

Actuates the ring cam.

Pump Unit

Ring Cam

Actuates the plunger.

Plunger

Moves reciprocally to draw and compress fuel.

Suction Valve

Prevents reverse flow of compressed fuel into the SCV.

Delivery Valve

Prevents reverse flow from the rail of the fuel pumped from the plunger.

Fuel Temperature Sensor

Detects the fuel temperature.

• The HP4 supply pump component parts and functions are basically the same as for the HP3. The explanations below

only cover those points on which the HP4 differs from the HP3. For other parts, see the appropriate item in the expla-

nation of the HP3.

Pump Unit (Eccentric Cam, Ring Cam, Plunger)

• A triangular ring cam is installed on the eccentric cam on the drive shaft, and three plungers are installed to the ring

cam at intervals of 120°.

Plunger

Camshaft

Eccentric Cam

Ring Cam

Q000851E

Operation Section

1-45

(4) Supply Pump Operation

Supply Pump Overall Fuel Flow

• The fuel is suctioned by the feed pump from the fuel tank and sent to the SCV. At this time, the regulating valve adjusts

the fuel pressure to below a certain level. The fuel sent from the feed pump has the required discharge quantity ad-

justed by the SCV, and enters the pump unit through the suction valve. The fuel pumped by the pump unit is pumped

through the delivery valve to the rail.

Feed Pump from Fuel Tank (Suction)

SCV from Feed Pump (Low Pressure)

Pump Unit from SCV (Low-Pressure Adjustment Complete)

From Pump Unit to Rail (High Pressure)

SCV

Camshaft

To Rail

From Fuel

Tank

Feed Pump

Ring Cam

Plunger

Delivery Valve

Suction Valve

Q000853E

Operation

• The discharge quantity is controlled by the SCV. As with the HP3, the valve opening is adjusted by duty ratio control.

The only difference from the HP3 is the shape of the pump unit. Operation and control are basically the same. For

details on operation and control, see the explanation of the HP3.

Operation Section

1-46

4. RAIL DESCCRIPTION

4.1 Rail Functions and Composition

z The function of the rail is to distribute fuel pressurized by the supply pump to each cylinder injector.

z The shape of the rail depends on the model and the component parts vary accordingly.

z The component parts are the rail pressure sensor (Pc sensor), pressure limiter, and for some models a flow damper and

pressure discharge valve.

Pressure Limiter

Rail

Flow Damper

Rail Pressure Sensor (Pc Sensor)

Pressure Discharge Valve

Rail

Pressure Limiter

Rail Pressure Sensor (Pc Sensor)

Q000854E

4.2 Component Part Construction and Operation

Component Parts

Functions

Rail

Stores pressurized fuel that has been pumped from the supply pump and distrib-

utes the fuel to each cylinder injector.

Pressure Limiter

Opens the valve to release pressure if the pressure in the rail becomes abnormally

high.

Rail Pressure Sensor (Pc Sensor)

Detects the fuel pressure in the rail.

Flow Damper

Reduces the pressure pulsations of fuel in the rail. If fuel flows out excessively, the

damper closes the fuel passage to prevent further flow of fuel. Mostly used with

engines for large vehicles.

Pressure Discharge Valve

Controls the fuel pressure in the rail. Mostly used with engines for passenger cars.

Operation Section

1-47

(1) Pressure Limiter

• The pressure limiter opens to release the pressure if abnormally high pressure is generated. If pressure within the rail

becomes abnormally high, the pressure limiter operates (opens). It resumes operation (closes) after the pressure falls

to a certain level. Fuel released by the pressure limiter returns to the fuel tank.

< NOTE >

The operating pressures for the pressure limiter depend on the vehicle model and are approximately 140-230MPa for

the valve opening pressure, and approximately 30-50MPa for the valve closing pressure.

Leak

(To Fuel Tank)

Pressure Limiter

Abnormally High Pressure

Valve Open

Valve Close

Return

Rail Pressure

Q000855E

(2)

Rail Pressure Sensor (Pc Sensor)

•

The rail pressure sensor (Pc sensor) is installed on the rail. It detects the fuel pressure in the rail and sends a signal

to the engine ECU. This is a semi-conductor sensor that uses the piezo-electric effect of the electrical resistance vary-

ing when pressure is applied to a silicon element.

Output

Common Rail

Sensor Wiring Diagram

Voltage -

Pressure Characteristic

Vout

Vcc=5V

Vcc

+5V

Vout

ECU

GND

GND Vout Vcc

Rail Pressure

Q000856E

•

There are also rail pressure sensors that have dual systems to provide a backup in case of breakdown. The output

voltage is offset.

Vout/Vcc

E2S PR2 VCS

+5V

Vcc=5V

VCS

ECU

PR2

ECU

Sensors

E2S

VC PR E2

Rail Pressure

Q000857E

Operation Section

1-48

(3) Flow Damper

• The flow damper reduces the pressure pulsations of the fuel in the pressurized pipe and supplies fuel to the injectors

at a stabilized pressure. The flow damper also presents abnormal discharge of fuel by shutting off the fuel passage

in the event of excess fuel discharge, for example due to fuel leaking from an injection pipe or injector. Some flow

dampers combine a piston and ball, and some have only a piston.

Type Combining Piston and Ball

Piston-Only Type

Piston

Ball

Piston

Seat

Spring

Q000858E

Operation of Piston-and-Ball Type

- When a pressure pulse occurs in a high-pressure pipe, the resistance of it passing through the orifice disrupts the

balance between the rail side and injector side pressures, so the piston and ball move to the injector side, absorbing

the pressure pulse. With normal pressure pulses, since the rail side and injector side pressures are soon balanced,

the piston and ball are pushed back to the rail side by the spring. If there is an abnormal discharge, for example

due to an injector side fuel leak, the amount of fuel passing through the orifice cannot be balanced out and the pis-

ton presses the ball against the seat, so the passage for fuel to the injector is shut off.

· During Pressure Pulse Absorption

· Fuel Cut-Off

Piston

Ball

Spring

Seat

Q000859E

Operation of Piston-Only Type

- The piston contacts the seat directly and the piston shuts off the fuel passage directly. Operation is the same as for

the piston-and-ball type.

· During Pressure Pulse Absorption

· Fuel Cut-Off

Piston

Seat

Spring

Q000860E

Operation Section

1-49

(4) Pressure Discharge Valve

• The pressure discharge valve controls the fuel pressure in the rail. When rail fuel pressure exceeds the target injection

pressure, or when the engine ECU judges that rail fuel pressure exceeds the target value, the pressure discharge

valve solenoid coil is energized. This opens the pressure discharge valve passage, allowing fuel to leak back to the

fuel tank, and reducing rail fuel pressure to the target pressure.

Solenoid Coil

Pressure Discharge Valve

Rail

Operating

ECU

To Fuel tank

Q000861E

Operation Section

1-50

5. INJECTOR DESCRIPTION

5.1 General Description

z The injector injects the pressurized fuel in the rail into the engine combustion chamber at the optimal injection timing,

injection quantity, injection rate, and injection pattern, in accordance with signals from the ECU.

z Injection is controlled using a TWV (Two-Way Valve) and orifice. The TWV controls the pressure in the control chamber

to control the start and end of injection. The orifice controls the injection rate by restraining the speed at which the nozzle

opens.

z The command piston opens and closes the valve by transmitting the control chamber pressure to the nozzle needle.

z When the nozzle needle valve is open, the nozzle atomizes the fuel and injects it.

z There are three types of injectors: the X1, X2, and G2.

TWV

Rail Pressure Sensor

Orifice

ECU

Control Chamber Portion

Rail

Command Piston

Nozzle Needle

Supply Pump

Nozzle

Q000862E

Operation Section

1-51

5.2 Injector Construction and Features

z The injector consists of a nozzle similar to the conventional "nozzle & nozzle holder", an orifice that controls the injection

rate, the command piston, and a TWV (two-way solenoid valve). The basic construction is the same for the X1, X2, and

G2 types.

(1) X1 Type

• Precision control is attained through electronic control of the injection. The TWV comprises two valves: the inner valve

(fixed) and the outer valve (movable).

Solenoid

TWV

Inner Valve

Outer Valve

Command Piston

Nozzle

Orifice 1

Orifice 2

Q000863E

Operation Section

1-53

(3) G2 Type

• To ensure high pressure, the G2 type has improved pressure strength, sealing performance and pressure wear re-

sistance. It also has improved high-speed operability, enabling higher-precision injection control and multi-injection.

To Fuel Tank

Connector

Solenoid Valve

From Rail

Command Piston

Nozzle Spring

Pressure Pin

Nozzle Needle

Seat

Leak Passage

Q000865E

< NOTE >

Multi-injection means that for the purpose of reducing exhaust gas emissions and noise, the main injection is accom-

plished with one to five injections of fuel without changing the injection quantity.

Example : Pattern with Five Injections

Main Injection

Pilot Injection Pre-Injection

After-Injection Post-Injection

Time

Q000866E

Operation Section

1-54

5.3 Injector Operation

z The injector controls injection through the fuel pressure in the control chamber. The TWV executes leak control of the

fuel in the control chamber to control the fuel pressure within the control chamber. The TWV varies with the injector type.

Non-Injection

• When the TWV is not energized, the TWV shuts off the leak passage from the control chamber, so the fuel pressure

in the control chamber and the fuel pressure applied to the nozzle needle are both the same rail pressure. The nozzle

needle thus closes due to the difference between the pressure-bearing surface area of the command piston and the

force of the nozzle spring, and fuel is not injected. For the X1 type, the leak passage from the control chamber is shut

off by the outer valve being pressed against the seat by the force of the spring, and the fuel pressure within the outer

valve. For the X2/G2 types, the control chamber outlet orifice is closed directly by the force of the spring.

Injection

• When TWV energization starts, the TWV valve is pulled up, opening the leak passage from the control chamber.

When this leak passage opens, the fuel in the control chamber leaks out and the pressure drops. Because of the drop

in pressure within the control chamber, the pressure on the nozzle needle overcomes the force pressing down, the

nozzle needle is pushed up, and injection starts. When fuel leaks from the control chamber, the flow quantity is re-

stricted by the orifice, so the nozzle opens gradually. The injection rate rises as the nozzle opens. As current continues

to be applied to the TWV, the nozzle needle eventually reaches the maximum amount of lift, which results in the max-

imum injection rate. Excess fuel is returned to the fuel tank through the path shown.

End of Injection

• When TWV energization ends, the valve descends, closing the leak passage from the control chamber. When the

leak passage closes, the fuel pressure within the control chamber instantly returns to the rail pressure, the nozzle

closes suddenly, and injection stops.

X2 · G2

Leak Passage

To Fuel Tank

Solenoid

TWV

Inner

Actuating

Valve

Actuating

Current

Outer Valve

TWV

Rail

Leak

Outlet Orifice

Passage

Control

Outlet Orifice

Control

Chamber

Inlet Orifice

Pressure

Command

Piston

Injection Rate

Nozzle

Non-Injection

Injection

End of Injection

Q000867E

Operation Section

1-55

5.4 Injector Actuation Circuit

z In order to improve injector responsiveness, the actuation voltage has been changed to high voltage, speeding up both

solenoid magnetization and the response of the TWV. The EDU or the charge circuit in the ECU raises the respective

battery voltage to approximately 110V, which is supplied to the injector by signal from the ECU to actuate the injector.

EDU Actuation

EDU

Constant

Amperage Circuit

Charging Circuit

High Voltage

Injector

Generation Circuit

INJ#1 (No.1 Cylinder)

Actuating Current

IJt

INJ#2 (No.3 Cylinder)

ECU

INJ#3 (No.4 Cylinder)

IJf

Control

Circuit

INJ#4 (No.2 Cylinder)

ECU Direct Actuation

ECU

Common 2

Constant

Amperage Circuit

Common 1

Constant

Amperage Circuit

Injector

High Voltage Generation Circuit

2WV#1 (No.1 Cylinder)

Actuating Current

2WV#2 (No.5 Cylinder)

2WV#3 (No.3 Cylinder)

2WV#4 (No.6 Cylinder)

2WV#5 (No.2 Cylinder)

2WV#6 (No.4 Cylinder)

Q000868E

Operation Section

1-56

5.5 Other Injector Component Parts

(1) Hollow Screw with Damper

• The hollow screw with damper enhances injection quantity accuracy, by reducing the back-pressure pulsations (pres-

sure fluctuations) of the leak fuel. In addition, it minimizes the back-pressure dependence (the effect of the pressure

in the leak pipe changing the injection quantity even though the injection command is the same) of the fuel in the leak

pipe.

Hollow Screw with Damper

O-ring

Damper

O-ring

To Fuel tank

Q000869E

(2) Connector with Correction Resistor

• The connector with correction resistor has a built-in correction resistor in the connector section to minimize injection

quantity variation among the cylinders.

Correction Resistor Terminal

Solenoid Terminal

Q000870E

Operation Section

1-57

(3) Injector with QR Codes

• QR (Quick Response) codes have been adopted to enhance correction precision. The QR code, which contains the

correction data of the injector, is written to the engine ECU. QR codes have resulted in a substantial increase in the

number of fuel injection quantity correction points, greatly improving injection quantity precision.

· QR Code Correction Points (Example)

Pressure

QR Codes

Parameter

10EA01EB

13EA01EB

0300 0000

0000 BC

ID Codes

Actuating Pulse Width TQ

Q000871E

< NOTE >

QR codes are a new two-dimensional code that was developed by DENSO. In addition to injection quantity correction

data, the code contains the part number and the product number, which can be read at extremely high speeds.

Operation Section

1-58

Handling Injectors with QR Codes (Reference)

- Injectors with QR codes have the engine ECU recognize and correct the injectors, so when an injector or the engine

ECU is replaced, it is necessary to register the injector's ID code in the engine ECU.

Replacing the Injector

- It is necessary to register the ID code of the injector that has been replaced in the engine ECU.

"No correction resistance, so no electrical recognition capability."

Spare Injector

Engine ECU

* Necessary to record the injector ID codes in the Engine ECU.

QD1536E

Replacing the Engine ECU

- It is necessary to register the ID codes of all the vehicle injectors in the engine ECU.

"No correction resistance, so no electrical recognition capability."

Vehicle-Side Injector

Spare Engine ECU

* Necessary to record the injector ID codes in the Engine ECU.

Q000985E

Operation Section

1-59

6. DESCRIPTION OF CONTROL SYSTEM COMPONENTS

6.1 Engine Control System Diagram (Reference)

Accelerator Position Sensor

Ignition Switch Signal

Supply Pump

Starter Signal

PCV(HP0)

Warm-Up Switch Signal

Vehicle Speed Signal

SCV(HP2·3·4)

TDC(G) Sensor

Fuel Temperature

Engine ECU

(HP0)

Sensor (HP2·3·4)

Charge

Circuit

EDU

Pressure Discharge Valve

Pressure Limiter

Rail

Flow Damper

Rail Pressure Sensor

(Large Vehicles)

Intake Air

Temperature

Airflow Meter

Sensor

(with Intake Air Temperature Sensor)

E-VRV for EGR

To Fuel Tank

Intake Air

Fuel Temperature Sensor (HP0)

Pressure Sensor

Injector

EGR Shut-Off VSV

Coolant Temperature Sensor

Cylinder Recognition Sensor

(TDC (G) Sensor: HP2, 3, 4)

Crankshaft Position Sensor

Flywheel

(Engine Speed Sensor)

Supply Pump

TDC (G) Sensor

Fuel Temperature Sensor

PCV

SCV

Fuel Temperature Sensor

SCV

Fuel Temperature Sensor

HP0

HP2

HP3

HP4

Q000874E

Operation Section

1-60

6.2 Engine ECU (Electronic Control Unit)

z The engine ECU constantly ascertains the status of the engine through signals from the sensors, calculates fuel injec-

tion quantities etc. appropriate to the conditions, actuates the actuators, and controls to keep the engine in an optimal

state. The injectors are actuated by either the EDU or the charge circuit in the engine ECU. This actuation circuit de-

pends on the specifications of the model it is mounted in. The ECU also has a diagnosis function for recording system

troubles.

Sensors

Engine ECU

Actuators

Actuation Circuit

EDU

Cylinder Recognition Sensor

Injector

Charge Circuit

(TDC (G) Sensor)

(Built into ECU)

Crankshaft Position Sensor

(Engine Speed Sensor)

Engine ECU

Supply Pump

(PCV : HP0, SCV : HP2 · HP3 · HP4)

Accelerator Position Sensor

Other Sensors

Other Actuators

Q000875E

6.3 EDU (Electronic Driving Unit)

(1) General Description

• An EDU is provided to enable high-speed actuation of the injectors. The EDU has a high-voltage generation device

(DC/DC converter) and supplies high voltage to the injectors to actuate the injectors at high speed.

Actuation Signal

Actuation Output

ECU

EDU

Check Signal

Q000876E

Operation Section

1-61

(2) Operation

• The high-voltage generating device in the EDU converts the battery voltage into high voltage. The ECU sends signals

to terminals B through E of the EDU in accordance with the signals from the sensors. Upon receiving these signals,

the EDU outputs signals to the injectors from terminals H through K. At this time, terminal F outputs the IJf injection

verification signal to the ECU.

COM

High Voltage

Generation Circuit

IJt#1

IJt#2

Control Circuit

IJt#3

ECU

IJt#3

IJt#4

IJf

GND

Q000877E

6.4 Various Sensors

Various Sensor Functions

Sensor

Functions

Crankshaft Position Sensor

Detects the crankshaft angle and outputs the engine speed signal.

(Engine Speed Sensor)

Cylinder Recognition Sensor

Identifies the cylinders.

(TDC (G) Sensor)

Accelerator Position Sensor

Detects the opening angle of the accelerator pedal.

Intake Air Temperature Sensor

Detects the temperature of the intake air after it has passed through the turbo-

charger.

Mass Airflow Meter

Detects the flow rate of the intake air. It also contains an intake air temperature sen-

sor that detects the temperature of the intake air (atmospheric temperature).

Coolant Temperature Sensor

Detects the engine coolant temperature.

Fuel Temperature Sensor

Detects the fuel temperature.

Intake Air Pressure Sensor

Detects the intake air pressure.

Atmospheric Pressure Sensor

Detects the atmospheric pressure.

Operation Section

1-62

(1) Crankshaft Position Sensor (Engine Speed Sensor) and Cylinder Recognition Sensor

{TDC (G) Sensor}

Crankshaft Position Sensor (Engine Speed Sensor)

• The crankshaft position sensor is installed near the crankshaft timing gear or the flywheel. The sensor unit is a MPU

(magnetic pickup) type. When the engine speed pulsar gear installed on the crankshaft passes the sensor section,

the magnetic field of the coil within the sensor changes, generating AC voltage. This AC voltage is detected by the

engine ECU as the detection signal. The number of pulses for the engine speed pulsar depends on the specifications

of the vehicle the sensor is mounted in.

Cylinder Recognition Sensor {TDC (G) Sensor}

• The cylinder recognition sensor is installed on the supply pump unit for the HP0 system, but for the HP2, HP3, or HP4

system, it is installed near the supply pump timing gear. Sensor unit construction consists of the MPU type, which is

the same as for the crankshaft position sensor, and the MRE (magnetic resistance element) type. For the MRE type,

when the pulsar passes the sensor, the magnetic resistance changes and the voltage passing through the sensor

changes. This change in voltage is amplified by the internal IC circuit and output to the engine ECU. The number of

pulses for the TDC pulsar depends on the specifications of the vehicle the sensor is mounted in.

Sensor Mounting Position (Reference)

Cylinder Recognition Sensor

Pulsar

(TDC (G) Sensor)

(Gearless Section)

Pulsar

For MPU

For MRE

Type

Engine Speed Pulsar

TDC (G) Pulsar

Crankshaft Position Sensor

(Engine Speed Sensor)

External View of Sensor

Circuit Diagram

ECU

NE-

VCC

Shielded

MPU

TDC(G)

TDC (G) Input Circuit

TDC(G)- TDC(G)

GND

Wire

NE+

Type

TDC(G)

VCC

MRE

TDC(G)

Type

GND

Engine Speed

Input Circuit

MPU Type MRE Type

Crankshaft Position Sensor

Cylinder Recognition Sensor

(Engine Speed Sensor)

(TDC (G) Sensor)

Pulse Chart (Reference)

360 CA

Engine Speed

Pulse

MPU

Type

TDC (G)

Pulse

MRE

Type

720 CA

Q000878E

Operation Section

1-63

(2) Accelerator Position Sensor

• The accelerator position sensor converts the accelerator opening into an electric signal and outputs it to the engine

ECU. There are two types of accelerator position sensor: the hall element type and the contact type. In addition, to

provide backup in the event of breakdown, there are two systems and the output voltage is offset.

Hall Element Type

- This sensor uses a hall element to generate voltage from change in the direction of the magnetic field. A magnet

is installed on the shaft that rotates linked with the accelerator pedal, and the rotation of this shaft changes the mag-

netic field of the Hall element. The voltage generated by this change in the magnetic field is amplified by an amplifier

and input to the engine ECU.

Amplifier No. 1

A-VCC

+5V

VACCP1

Magnets (Pair)

A-GND

A-VCC

+5V

VACCP2

A-GND

ECU

Accelerator Pedal

Amplifier No. 2

100

Hall Elements (2)

Q000879E

Accelerator Opening (%)

Contact Type

- The sensor uses a contact-type variable resistor. Since the lever moves linked with the accelerator pedal, the sen-

sor resistance value varies with the accelerator pedal opening. Therefore, the voltage passing the sensor changes,

and this voltage is input to the engine ECU as the accelerator opening signal.

Accelerator Position Sensor

Output Voltage Characteristic

Accelerator Position Sensor Circuit Diagram

Fully Open

Fully Closed

VPA2

Fully

VPA1

Closed

Open

Fully Closed Fully Open

EP2 VPA2 VCP2 EP1 VPA1 VCP1

Accelerator Pedal Position

Q000880E

Operation Section

1-64

(3) Intake Air Temperature Sensor

• The intake air temperature sensor detects the temperature of the intake air after it has passed the turbocharger. The

sensor portion that detects the temperature contains a thermistor. The thermistor, which has an electrical resistance

that changes with temperature, is used to detect the intake air temperature.

Thermistor

Temperature

Resistance -

Characteristic

Temperature

Q000881E

(4) Mass Airflow Meter (with Built-In Intake Air Temperature Sensor)

• The mass air flow meter is installed behind the air cleaner and detects the intake air flow (mass flow). This sensor is

a hot-wire type. Since the electrical resistance of the hot wire varies with the temperature, this characteristic is utilized

to measure the intake air quantity. The mass airflow meter also has a built-in intake air temperature sensor (thermistor

type) and detects the intake air temperature (atmospheric temperature).

Intake Air Temperature

Temperature

Sensor Resistance

Characteristic

Intake Air

Temperature

Sensor

E2G

THAF

Hot Wire

Temperature C ( F)

Q000882E

(5) Coolant Temperature Sensor

• The coolant temperature sensor is installed on the cylinder block and detects the coolant temperature. This sensor is

a thermistor type.

Coolant Temperature

Water Temperature

Sensor Resistance

Characteristic

ECU

+5V

Thermistor

VTHW

A-GND

Coolant Temperature

Q000883E

Operation Section

1-65

(6) Fuel Temperature Sensor

• This is a thermistor type sensor that detects the fuel temperature. In the HP2, HP3, and HP4 systems, this sensor is

installed on the supply pump unit, but in the HP0 system, it is installed on a leak pipe from an injector.

Resistance - Temperature

Thermistor

Characteristic

Temperature

Q000848E

(7) Intake Air Temperature Sensor and Atmospheric Pressure Sensor

• This sensor is a semiconductor type sensor. It measures pressure utilizing the piezoelectric effect that when the pres-

sure on the silicon element in the sensor changes, its electrical resistance changes. In addition, the air pressure on

this sensor is switched between the pressure within the intake manifold and the atmospheric pressure, so both the

intake air pressure and the atmospheric pressure are detected with one sensor. The switching between intake air

pressure and atmospheric pressure is handled by the VSV (vacuum switching valve). When any one of the conditions

below is established, the VSV is switched ON for 150 msec. by command of the engine ECU to detect the atmospheric

pressure. When none of the conditions below is established, the VSV is switched OFF to detect the intake air pres-

sure.

Atmospheric Pressure Measurement Conditions

- Engine speed = 0 rpm

- Starter ON

- Stable idling state

Pressure

PIM Output Voltage -

Characteristic

VC PIM E2

Absolute Pressure

Q000885E

Operation Section

1-66

7. CONTROL SYSTEM

7.1 Fuel Injection Control

(1) General Description

• This system effects more appropriate control of the fuel injection quantity and injection timing than the mechanical

governor or timer used in the conventional injection pump. The engine ECU performs the necessary calculations

based on the signals that are received from the sensors located on the engine and the vehicle. Then, the ECU controls

the timing and duration of the current that is applied to the injectors in order to obtain optimal injection timing and

injection quantity.

(2) Various Types of Fuel Injection Controls

Control

Functions

Fuel Injection Quantity Control

This control replaces the function of the governor in the conventional injection

pump. It achieves optimal injection quantity by effecting control in accordance with

the engine speed and accelerator opening signals.

Fuel Injection Timing Control

This control replaces the function of the timer in the conventional injection pump. It

achieves optimal injection timing by effecting control in accordance with the

engine speed and the injection quantity.

Fuel Injection Rate Control

This function controls the ratio of the fuel quantity that is injected from the orifice of

(Pilot Injection Control)

the injector within a given unit of time.

Fuel Injection Pressure Control

This control uses the rail pressure sensor to measure the fuel pressure, and it

feeds this data to the engine ECU in order to control the pump discharge quantity.

Operation Section

1-67

(3) Fuel Injection Quantity Control

General Description

• This control determines the fuel injection quantity by adding coolant temperature, fuel temperature, intake air temper-

ature, and intake air pressure corrections to the basic injection quantity. The engine ECU calculates the basic injection

quantity based on the engine operating conditions and driving conditions.

Injection Quantity Calculation Method

• The calculation consists of a comparison of the following two values: 1. The basic injection quantity that is obtained

from the governor pattern, which is calculated from the accelerator position and the engine speed. 2. The injection

quantity obtained by adding various types of corrections to the maximum injection quantity obtained from the engine

speed. The lesser of the two injection quantities is used as the basis for the final injection quantity.

Accelerator Opening

Engine Speed

Accelerator Opening

Basic Injection Quantity

Low

Corrected

Injector Actuation

Quantity

Final Injection

Period Calculation

Side Selected

Quantity

Engine Speed

Maximum Injection Quantity

Individual Cylinder

Correction Quantity

Speed Correction

Injection Pressure Correction

Intake Air Pressure Correction

Intake Air Temperature Correction

Engine Speed

Atmospheric Pressure Correction

Ambient Temperature Correction

Cold Engine Maximum Injection Quantity Correction

Q000887E

Operation Section

1-68

Set Injection Quantities

• Basic Injection Quantity

This quantity is determined by the engine speed and the accelerator opening. With the engine speed constant, if the

accelerator opening increases, the injection quantity increases; with the accelerator opening constant, if the engine

speed rises, the injection quantity decreases.

Accelerator Opening

Engine Speed

Q000888E

• Starting Injection Quantity

This is determined based on the basic injection quantity for when the engine starts up and the added corrections for

the starter S/W ON time, the engine speed, and the coolant temperature. If the coolant temperature is low, the injec-

tion quantity is increased. When the engine has completely started up, this mode is cancelled.

Coolant Temperature

High

Low

Starting

Base Injection

Quantity

STA ON Time

STA ON

Starting

Q000889E

• Injection Quantity for Maximum Speed Setting

Determined by the engine speed. The injection quantity is restricted to prevent an excessive rise in engine speed

(overrun).

Injection Quantity

for Maximum Speed Setting

Engine Speed

Q000890E

Operation Section

1-69

• Maximum Injection Quantity

This is determined based on the basic maximum injection quantity determined by the engine speed, and the added

corrections for coolant temperature, fuel temperature, intake air temperature, atmospheric temperature, intake air

pressure, atmospheric pressure, and full Q adjustment resistance (only for the 1st generation HP0 system), etc.

Engine Speed

QB0717E

Corrections

• Cold Engine Maximum Injection Quantity Correction

When the coolant temperature is low, whether during start-up or during normal operation, this correction increases

the injection quantity.

Engine Speed

Q000891E

• Intake Air Pressure Correction

When the intake air pressure is low, the maximum injection quantity is restricted in order to reduce the emission of

black smoke.

Intake Air Pressure

Correction Quantity

Engine Speed

Q000892E

Operation Section

1-70

• Atmospheric Pressure Correction

The maximum injection quantity is increased and decreased according to the atmospheric pressure. When the atmo-

spheric pressure is high, the maximum injection quantity is increased.

Atmospheric Pressure

Correction Quantity

Engine Speed

Q000893E

• Injection Quantity Delay Correction for Acceleration

During acceleration, if there is a large change in the accelerator pedal opening, the injection quantity increase is de-

layed in order to prevent black smoke emissions.

Change in Accelerator

Pedal Position

Injection Quantity

After Correction

Delay

Time

Q000487E

• Full Q Adjustment Resistance (Only for 1st Generation HP0 Systems)

The full Q resistance is for correcting the injection quantity for a full load. The maximum injection quantity is increased

or decreased by the car manufacturer to match to standards. There are 15 types of full Q adjustment resistance. The

appropriate one is selected and used.

ECU

+5V

VLQC

A-GND

Quantity Adjustment

Resistor Correction Voltage

Operation Section

1-71

(4) Fuel Injection Rate Control

• Although the injection rate increases with the adoption of high-pressure fuel injection, the ignition lag, which is the

delay from the start of injection to the beginning of combustion, cannot be shortened to less than a certain period of

time. Therefore, the quantity of fuel injected until ignition takes place increases (the initial injection rate is too high),

resulting in explosive combustion simultaneous with ignition, and an increase in NOx and sound. To counteract this

situation, pilot injection is provided to keep the initial injection at the minimum requirement rate, to dampen the primary

explosive combustion, and to reduce NOx and noise.

[Ordinary Injection]

[Pilot Injection]

Injection Rate

Small First-Stage

Large First-Stage

Combustion

Heat Release Rate

-20

TDC

-20

TDC

Crankshaft Angle (deg)

Q000895E

Operation Section

1-72

(5) Fuel Injection Timing Control

• The fuel injection timing is controlled by the timing of the current applied to the injectors. After the main injection period

is decided, the pilot injection and other injection timing is determined.

Main Injection Timing

- The basic injection timing is calculated from the engine speed (engine speed pulse) and the final injection quantity,

to which various types of corrections are added in order to determine the optimal main injection timing.

Pilot Injection Timing (Pilot Interval)

- Pilot injection timing is controlled by adding a pilot interval value to the main injection. The pilot interval is calculated

based on the final injection quantity, engine speed, coolant temperature, atmospheric temperature, and atmospher-

ic pressure (map correction). The pilot interval at the time the engine is started is calculated from the coolant tem-

perature and engine speed.

Basic Injection

Pilot Interval

Timing

Engine Speed

1. Outline of Injection Timing Control Timing

Actual Top Dead Center

Engine Speed

Pulse

Pilot Injection

Main Injection

Injector Solenoid Valve

INJ

Control Pulse

Nozzle Needle

lift

Lift

Pilot Injection Timing

Main Injection Timing

Pilot Interval

2. Injection Timing Calculation Method

Main

Injection Timing

Engine Speed

Basic Injection

Correction

Injection Quantity

Timing

Pilot

Injection Timing

Battery Voltage Correction

Intake Air Pressure Correction

Intake Air Temperature Correction

Atmospheric Pressure Correction

Coolant Temperature Correction

Q000896E

Operation Section

1-73

Split Injection

- The purpose of split injection is to improve the startability of a cold engine. Before the conventional main injection

takes place, this function injects two or more extremely small injections of fuel.

Main Injection

Pilot Injection

This is the same as

conventional

fuel injection.

Pilot Injection

Before the main injection, a small

quantity of fuel is injected.

Pilot Injection

Pre-Injection

Multi-Injection

If the temperature is low when the engine

starts, a small quantity of fuel is injected

divided over multiple injections before the

main injection.

Q000897E

Multi-Injection Control (Only for Some Models)

- Multi-injection control is when small injections (up to four times) are carried out before and after the main injection

in accordance with the state of the main injection and engine operation. This interval (the time A-D in the diagram

below) is based on the final injection quantity, engine speed, coolant temperature, and atmospheric pressure (map

correction). The interval during start-up is based on the coolant temperature and engine speed.

TDC

TDC (G) Pulse

Injection Rate

Q000898E

(6) Fuel Injection Pressure Control

• The engine ECU calculates the fuel injection pressure, which is determined by the final injection quantity and the en-

gine speed. The calculation is based on the coolant temperature and engine speed during start-up.

Final Injection Quantity

Engine Speed

Q000899E

Operation Section

1-74

(7) Other Injection Quantity Control

Idle Speed Control (ISC) System

• The idle speed control system controls the idle speed by regulating the injection quantity in order to match the actual

speed to the target speed calculated by the computer. The ISC can be automatic ISC or manual ISC.

Automatic ISC

- With automatic ISC, the engine ECU sets the target speed. The target engine speed varies with the type of trans-

mission (automatic or manual), whether the air conditioner is ON or OFF, the shift position, and the coolant temper-

ature.

Idle Speed Control Conditions

Conditions When Control Starts

Conditions Affecting Control

· Idle Switch

· Water Temperature

· Accelerator Opening

· Air Conditioning Load

· Vehicle Speed

· Shift Position

Engine ECU

Target Engine Speed Calculation

Comparison

Actual Engine Speed

Fuel injection Quantity Correction

Fuel Injection Quantity Instruction

Actuators

Q000900E

Operation Section

1-75

Manual ISC

- The idle engine speed is controlled by the setting on the idle setting button at the driver's seat.

ECU

A-VCC

+5V

V-IMC

A-GND

IMC Volume Terminal Voltage

Q000901E

Idle Vibration Reduction Control

- This control reduces engine vibration during idle. To achieve smooth engine operation, it compares the angle

speeds (times) of the cylinders and regulates injection quantity for each individual cylinder in the event of a large

difference.

(Make the

t for all the cylinders equal.)

Angular Speed

Correction

Crankshaft Angle

Q000902E

DENSO COMMON RAIL SYSTEM (CRS). SERVICE MANUAL (2007) - page 2