Diesel Engine Troubleshooting

Archive for the ‘DENSO CRS Operation’ Category

DPF System (Diesel Particulate Filter)

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This system reduces emissions of PM (particulate matter). In order to collect PM, a DPF cleaner with built-in catalytic filter is mounted on the center pipe. The collected PM is handled with combustion processing during operation

pic1 118 DPF System (Diesel Particulate Filter)

Exhaust Gas Temperature Sensor
• The exhaust gas temperature sensor is installed to the front and rear of the DPF to detect the temperature in these positions. The engine ECU controls the exhaust temperature for PM combustion based on the signals from this sensor. The sensor element is a thermistor.

pic1 119 DPF System (Diesel Particulate Filter)

Differential Pressure Sensor
• The differential pressure sensor detects the difference in pressure at the front and rear of the DPF, and outputs a signal to the engine ECU. The sensor portion is a semiconductor type pressure sensor that utilizes the piezoelectric effect through a silicon element, and amplifies and outputs the voltage with its IC circuit. When PM is collected and accumulated in the DPF, the filter clogs and the difference in pressure at the front and rear of the DPF increases. Therefore, based on the signals from this sensor, the engine ECU judges whether or not to subject PM to combustion processing.

pic1 120 DPF System (Diesel Particulate Filter)

By optimizing the injection pattern and controlling the exhaust gas temperature based on the exhaust gas temperature and the difference in pressure at the front and rear of the DPF, PM is collected, oxidized, and self-combusted. When the exhaust temperature is low, adding after-injection after the main injection raises the exhaust gas temperature to approximately 250?C and promotes oxidation of the PM. When the PM is collected and accumulated, the post-injection is added and HC is added to the catalyst to raise the catalyst temperature to 600?C, which is the self-combustion temperature for PM. This combusts the accumulated PM in a short time. The engine ECU controls the A, B, and C times and the injection times.

pic1 121 DPF System (Diesel Particulate Filter)

Written by Jack

March 11th, 2019 at 6:25 am

Exhaust Gas Control System

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The exhaust gas control system is provided to improve warm-up and heater performance. This system actuates the exhaust gas control valve VSV, which is attached to the exhaust manifold. It increases the exhaust pressure to increase the exhaust temperature and engine load, in order to improve warm-up and heater performance.

pic1 116 Exhaust Gas Control System

The exhaust gas control system operates when the warm-up switch is ON, and all the conditions listed below have been met.

Operation Conditions
– The EGR is operating.
– The coolant temperature is below 70°C.
– The ambient temperature is below 5°C.
– A minimum of 10 seconds have elapsed after starting the engine.
– The engine speed and fuel injection quantity are in the state shown in the graph below.

pic1 117 Exhaust Gas Control System

Written by Jack

March 11th, 2019 at 6:15 am

Electronically Controlled Throttle

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The electronically controlled throttle is located upstream of the EGR valve in the intake manifold. It controls the throttle valve at an optimal angle to regulate the EGR gas and reduce noise and harmful exhaust gases.

• Signals from the engine ECU actuate the stepping motor, which regulates the throttle valve opening.
EGR Control
• To further increase the EGR volume when the EGR valve is fully open, the vacuum in the intake manifold can be increased by reducing the throttle valve opening, which restricts the flow of the intake air.
Noise and Exhaust Gas Reduction
• When the engine is being started, the throttle valve opens fully to reduce the emissions of white and black smoke.
• When the engine is being stopped, the throttle valve closes fully to reduce vibration and noise.
• During normal driving, the throttle valve opening is controlled in accordance with the engine conditions, coolant temperature, and atmospheric pressure.

pic1 115 Electronically Controlled Throttle

Written by Jack

March 11th, 2019 at 5:45 am

E-EGR System Operation

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• After the vacuum pump generates a vacuum, the E-VRV (electric-vacuum regulation valve) regulates the vacuum and
directs it to the diaphragm chamber of the EGR valve. In response to this vacuum, the diaphragm pushes the spring
downward, which determines the opening of the EGR valve and controls the EGR volume.
• The EGR cooler, which is provided in the EGR passage between the cylinder head and the intake passage, cools the
EGR in order to increase the EGR volume.
• The EGR cutoff VSV, which opens the diaphragm chamber to the atmosphere when the EGR valve is closed, helps
to improve response.

pic1 113 E EGR System Operation

To Increase the EGR Quantity
– The E-VRV duty ratio is controlled*1. In the stable condition shown in the bottom center diagram, an increase in the current that is applied to the coil causes the attraction force FM in the coil to increase. When this force becomes greater than the vacuum force FV that acts on the diaphragm, the moving core moves downward. Along with this movement, the port from the vacuum pump to the upper chamber of the diaphragm opens. Consequently, the output
vacuum increases, which causes the EGR valve to open and the EGR volume to increase. Meanwhile, because “increased output vacuum equals increased FV”, the moving core moves upward with the increase in FV. When FM and FV are equal, the port closes and the forces stabilize. Because the vacuum circuit of the EGR is a closed loop, it maintains the vacuum in a stabilized state, provided there are no changes in the amperage.

To Decrease the EGR Volume
– A decrease in the current that is applied to the coil causes FV to become greater than FM. As a result, the diaphragm moves upward. The moving core also moves upward in conjunction with the movement of the diaphragm,
causing the valve that seals the upper and lower diaphragm chambers to open. Consequently, the atmospheric pressure in the lower chamber enters the upper chamber, thus reducing the output vacuum. This causes the EGR valve to close and the EGR volume to decrease. Because “decreased output vacuum equals decreased FV”, the moving core moves downward with the decrease in FV. When FM and FV are equal, the port closes and the forces stabilize.

pic1 114 E EGR System Operation

Written by Jack

March 11th, 2019 at 3:10 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 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

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