Diesel Engine Troubleshooting

Archive for the ‘DENSO CRS Operation’ Category

Image Of Combustion Chamber Interior

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With conventional injection methods, because an excessive quantity of fuel was injected in the initial period, the explosion pressure rose excessively, leading to the generation of noise such as engine knocking sounds. To improve this condition through pilot injection, initially only the necessary and adequate quantity of fuel is injected. At the same time, the combustion chamber temperature is raised, and main injection combustion is assisted while working to prevent noise and vibration.

pic1 127 Image Of Combustion Chamber Interior

Written by Jack

March 12th, 2019 at 3:27 am

Higher Injection Quantity Control Precision

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Power output adjustment in a diesel engine is accomplished by regulating the fuel injection quantity. Poor injection quantity control precision leads to increased exhaust gas emissions, noise, and poor fuel economy. For this reason, electronically controlled systems have been developed to ensure high precision injection quantity control.

Written by Jack

March 12th, 2019 at 3:21 am

Higher Injection Timing Control Precision

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Reducing exhaust gas emissions and fuel consumption and optimizing the injection timing are important. It is extremely difficult to achieve the desired exhaust emission reduction levels through methods that adjust the injection timing according to speed (or centrifugal force), such as the conventional mechanical timer. For this reason, electronically controlled systems have been adopted to freely and precisely control the injection timing in accordance with the engine characteristics.

pic1 126 Higher Injection Timing Control Precision

Written by Jack

March 12th, 2019 at 3:19 am

Optimized Injection Rates

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The injection rate is the ratio of the changes in the fuel quantity that is injected successively from the nozzle within a given unit of time.

pic1 124 Optimized Injection Rates

As the injection pressure increases, the injection rate increases accordingly. The increase in injection rate leads to an increase in the volume of the air-fuel mixture that is created between the start of injection until ignition (the ignition lag period). Because this mixture is subsequently combusted at once, it creates noise (diesel knock) and NOx. For this reason, it is necessary to appropriately control the injection rate by maintaining a low injection rate at the beginning of injection and supplying a sufficient quantity after the ignition. To meet this need, two-spring nozzles have been adopted and a pilot injection system has recently been developed.

pic1 125 Optimized Injection Rates

Written by Jack

March 12th, 2019 at 2:03 am

Higher Injection Pressure

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The fuel that is injected from the nozzle turns into finer particles as the fuel injection pressure increases. This improves combustion and reduces the amount of smoke contained in the exhaust gases. Initially, the maximum injection pressure of the in-line pump (A type) and the distributor pump (VE type) was 60 MPa. Due to advancement in high-pressure applications, there are some recently developed fuel injection systems that inject fuel at a pressure of 100 MPa or higher. The second-generation common rail system injects fuel at an extremely high pressure of 180 MPa.

pic1 123 Higher Injection Pressure

Written by Jack

March 12th, 2019 at 2:02 am

DPNR SYSTEM

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This system reduces the emissions of PM (particulate matter) and NOx. The DPNR catalyst mounted in the center
pipe collects and regenerates PM and reduces NOx all at the same time. The collected PM is handled with combustion
processing during operation.

pic1 122 DPNR SYSTEM

Written by Jack

March 11th, 2019 at 3:18 pm

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