SsangYong Korando III (2010 year). Manual - part 368

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(3) Accelerometer Control

a. Resetting the pilot injection

The accelerometer is used to reset the pilot injection flow in closed loop for each injector. This method 

allows the correction of any injector deviations over a period of time. The principle of use of the 

accelerometer is based on the detection of the combustion noises.

The sensor is positioned in such a way as to receive the maximum signal for all the cylinders. The raw 

signals from the accelerometer are processed to obtain a variable which quantifies the intensity of the 

combustion. This variable, known as the ratio, consists of the ratio between the intensity of the 

background noise and the combustion noise.

A first window is used to establish the background noise level of the accelerometer signal for each 

cylinder. This window must therefore be positioned at a moment when there cannot be any 

combustion.

The second window is used to measure the intensity of the pilot combustion. Its position is such that 

only the combustion noises produced by the pilot injection are measured . It is therefore placed just 

before the main injection.

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2.

The accelerometer does not allow any evaluation of the quantity injected. However, the pulse value will 

be measured when the injector starts injection and this pulse value is called the MDP (Minimum Drive 

Pulse). On the basis of this information, it is possible to efficiently correct the pilot flows. The pilot 

injection resetting principle therefore consists of determining the MDP, in other words the pulse 

corresponding to the start of the increase in value of the ratio (increase of vibration due to fuel 

combustion).

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This is done periodically under certain operating conditions. When the resetting is finished, the new 

minimum pulse value replaces the value obtained during the previous resetting. The first MDP value is 

provided by the C3I. Each resetting then allows the closed loop of the MDP to be updated according to 

the deviation of the injector.

b. Detection of leaks in the cylinders

The accelerometer is also used to detect any injector which may have stuck open. The detection 

principle is based on monitoring the ratio. If there is a leak in the cylinder, the accumulated fuel self-

ignites as soon as the temperature and pressure conditions are favorable (high engine speed, high load 

and small leak).

This combustion is set off at about 20 degrees before TDC and before main injection.

The ratio therefore increases considerably in the detection window. It is this increase which allows the 

leaks to be detected. The threshold beyond which a fault is signaled is a percentage of the maximum 

possible value of the ratio.

Because of the severity of the recovery process (engine shut-down), the etection must be extremely 

robust.

An increase in the ratio can be the consequence of various causes:

Pilot injection too much

Main combustion offset

Fuel leak in the cylinder

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If the ratio becomes too high, the strategy initially restricts the pilot injection flow and retards the main 

injection. If the ratio remains high despite these interventions, this shows that a real leak is present, a 

fault is signaled and the engine is shut down.

c. Detection of an accelerometer fault

This strategy permits the detection of a fault in the sensor or in the wiring loom connecting the sensor to 

the ECU.

It is based on detection of the combustion. When the engine is idling, the detection window is set too low 

for the combustion caused by the main injection. If the ratio increases, this shows that the accelerometer 

is working properly, but otherwise a fault is signaled to indicate a sensor failure. The recovery modes 

associated with this fault consist of inhibition of the pilot injection and discharge through the injectors.

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HFM

Accelerator pedal

Coolant 

temperature

(4) Swirl control

a. Overview

Variable swirl valve

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The strong swirl caused by intake air is important element for anti-locking function in diesel engine. The 

swirl control valve partially closes the intake port to generate the swirl according to the engine conditions. 

When the engine load is in low or medium range, the swirl could not be generated because the air flow 

is slow. To generate strong swirl, there are two passages in intake manifold, and one of them has the 

valve to open and close the passage. When the valve closes the passage, the air flow through the 

another passage will be faster, and the strong swirl will be generated by the internal structure of the 

passage. This swirl makes the better mixture of air and fuel, eventually the combustion efficiency in 

combustion chamber could be improved. This provides the enhanced fuel consumption, power and 

EGR ratio.

Components

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D20DTF ECU

Crankshaft 

position sensor

Variable swirl 

valve

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b. Input/Output for variable swirl valve