Diesel Engine Troubleshooting

Archive for the ‘DENSO CRS Operation’ Category

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.

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.

• 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.

• Injection Quantity for Maximum Speed Setting
Determined by the engine speed. The injection quantity is restricted to prevent an excessive rise in engine speed

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

Written by Jack

October 1st, 2019 at 12:03 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.

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.

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.

Written by Jack

September 21st, 2019 at 2:57 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.

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

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.

Written by Jack

September 19th, 2019 at 3:01 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.

Written by Jack

September 12th, 2019 at 2:02 am

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).

Written by Jack

September 11th, 2019 at 3:08 am

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.

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.

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.

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.

Written by Jack

March 12th, 2019 at 2:03 am


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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.

Written by Jack

March 11th, 2019 at 3:18 pm