Diesel Engine Troubleshooting

Archive for the ‘DENSO CRS Operation’ Category

E-EGR System General Description

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The E-EGR system is an electronically controlled EGR system. The EGR system recirculates a portion of the exhaust
gases into the intake manifold in order to lower the combustion chamber temperature and reduce NOx emissions.
However, operation of the EGR system may reduce engine power output and affect drivability. For this reason, in the
E-EGR system, the engine ECU controls the EGR to achieve an optimal EGR amount.
Operation Conditions Example
– This operates in the operation region fulfilling the starting conditions below (one example).

pic1 112 E EGR System General Description

Written by Jack

March 11th, 2019 at 3:08 am

Other Injection Quantity Control

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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 transmission (automatic or manual), whether the air conditioner is ON or OFF, the shift position, and the coolant temperature.

pic1 109 Other Injection Quantity Control

Manual ISC
– The idle engine speed is controlled by the setting on the idle setting button at the driver’s seat.

pic1 110 Other Injection Quantity Control

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.

pic1 111 Other Injection Quantity Control

Written by Jack

March 11th, 2019 at 3:01 am

Fuel Injection Pressure Control

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The engine ECU calculates the fuel injection pressure, which is determined by the final injection quantity and the engine speed. The calculation is based on the coolant temperature and engine speed during start-up.

pic1 108 Fuel Injection Pressure Control

Written by Jack

March 11th, 2019 at 2:59 am

Fuel Injection Timing Control

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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 atmospheric pressure (map correction). The pilot interval at the time the engine is started is calculated from the coolant temperature and engine speed.

pic1 105 Fuel Injection Timing Control

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.

pic1 106 Fuel Injection Timing Control

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.

pic1 107 Fuel Injection Timing Control

Written by Jack

March 11th, 2019 at 2:57 am

Fuel Injection Rate Control

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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.

pic1 104 Fuel Injection Rate Control

Written by Jack

March 11th, 2019 at 2:51 am

Fuel Injection Quantity Control

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General Description

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

pic1 94 Fuel Injection Quantity Control

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.

pic1 95 Fuel Injection Quantity Control

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

pic1 96 Fuel Injection Quantity Control

• 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).

pic1 97 Fuel Injection Quantity Control

• 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.

pic1 98 Fuel Injection Quantity Control

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.

pic1 99 Fuel Injection Quantity Control

• 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.

pic1 100 Fuel Injection Quantity Control

• Atmospheric Pressure Correction
The maximum injection quantity is increased and decreased according to the atmospheric pressure. When the atmospheric pressure is high, the maximum injection quantity is increased.

pic1 101 Fuel Injection Quantity Control

• Injection Quantity Delay Correction for Acceleration
During acceleration, if there is a large change in the accelerator pedal opening, the injection quantity increase is delayed in order to prevent black smoke emissions.

pic1 102 Fuel Injection Quantity Control

• 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.

pic1 103 Fuel Injection Quantity Control

Written by Jack

March 11th, 2019 at 12:03 am

Intake Air Temperature Sensor and Atmospheric Pressure Sensor

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

Atmospheric Pressure Measurement Conditions
– Engine speed = 0 rpm
– Starter ON
– Stable idling state

pic1 93 Intake Air Temperature Sensor and Atmospheric Pressure Sensor

Written by Jack

March 10th, 2019 at 11:54 pm

Fuel Temperature Sensor

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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.

pic1 92 Fuel Temperature Sensor

Written by Jack

March 10th, 2019 at 11:52 pm

Coolant Temperature Sensor

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The coolant temperature sensor is installed on the cylinder block and detects the coolant temperature. This sensor is a thermistor type.

pic1 91 Coolant Temperature Sensor

Written by Jack

March 10th, 2019 at 11:51 pm

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

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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).

pic1 90 Mass Airflow Meter (with Built In Intake Air Temperature Sensor)

Written by Jack

March 10th, 2019 at 11:50 pm