SsangYong Korando III (2010 year). Service manual — part 73

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3. Idle Speed Controller

The idle speed controller consists of 2 principal modules:

The first module determines the required idle speed according to:

* The operating conditions of the engine (coolant temperature, gear engaged)

* Any activation of the electrical consumers (power steering, air conditioning, others)

* The battery voltage

* The presence of any faults liable to interface with the rail pressure control or the injection control. In

this case, increase the idle speed to prevent the engine from stalling.

The second module is responsible for providing closed loop control of the engine's idle speed by

adapting the minimum fuel according to the difference between the required idle speed and the

engine speed.

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4. Flow Limitation

The flow limitation strategy is based on the following strategies:

The flow limitation depending on the filling of the engine with air is determined according to the

engine speed and the air flow. This limitation allows smoke emissions to be reduced during

stabilized running.

The flow limitation depending on the atmospheric pressure is determined according to the engine

speed and the atmospheric pressure. It allows smoke emissions to be reduced when driving at

altitude.

The full load flow curve is determined according to the gear engaged and the engine speed. It

allows the maximum torque delivered by the engine to be limited.

A performance limitation is introduced if faults liable to upset the rail pressure control or the

injection control are detected by the system. In this case, and depending on the gravity of the fault,

the system activates:

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Reduced fuel logic 1: Guarantees 75 % of the performance without limiting the engine speed.

Reduced fuel logic 2: Guarantees 50 % of the performance with the engine speed limited to 3,000 rpm.

Reduce fuel logic 3: Limits the engine speed to 2,000 rpm.

The system chooses the lowest of all values.

A correction depending on the coolant temperature is added to the flow limitation. This correction makes

it possible to reduce the mechanical stresses while the engine is warming up. The correction is

determined according to the coolant temperature, the engine speed and the time which has passed

since starting.

Superchager Flow Demand

The supercharge flow is calculated according to the engine speed and the coolant temperature. A

correction depending on the air temperature and the atmospheric pressure is made in order to increase

the supercharge flow during cold starts. It is possible to alter the supercharge flow value by adding a flow

offset with the aid of the diagnostic tool.

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5. Pilot Flow Control

The pilot flow represents the amount of fuel injected into the cylinder during the pilot injection. This

amount is determined according to the engine speed and the total flow.

A first correction is made according to the air and water temperature.

This correction allows the pilot flow to be adapted to the operating temperature of the engine. When

the engine is warm, the ignition time decreases because the end-of-compression temperature is

higher. The pilot flow can therefore be reduced because there is obviously less combustion noise

when the engine is warm.

A second correction is made according to the atmospheric pressure.

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During starting, the pilot flow is determined on the basis of the engine speed and the coolant

temperature.

6. Cylinder Balancing Strategy

Balancing of the point to point flows

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The pulse of each injector is corrected according to the difference in instantaneous speed measured

between 2 successive injectors.

The instantaneous speeds on two successive injections are first calculated.

The difference between these two instantaneous speeds is then calculated.

Finally, the time to be added to the main injection pulse for the different injectors is determined. For each

injector, this time is calculated according to the initial offset of the injector and the instantaneous speed

difference.

Detection of an injector which has stuck closed

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The cylinder balancing strategy also allows the detection of an injector which has stuck closed. The

difference in instantaneous speed between 2 successive injections then exceeds a predefined threshold.

In this case, a fault is signaled by the system.

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e. MDP Learning Control

MDP (Minimum Drive Pulse ) refers to the

minimum power supply pulse for injection which

the injector can perform. It is possible to control

the fuel volume for each injector accurately

through correct learning for the MDP value. The

basic process of MDP learning is that the pulse

slightly higher than MDP is supplied and then (b)

the vibration generated from the cylinder is

detected. The knock sensor detects the vibration

from the engine after a small volume of fuel is

injected. And the time interval between the points

of injection and vibration is measured so that

MDP can be learned. MDP learning is helpful to

prevent engine vibration, high emission and

power reduction through performing calibration

for the old injectors. During MDP learning, a little

vibration and noise can be occur for a while. This

is because the fuel pressure is increased

instantaneously and the exact injection value is

not input, so that the exact engine vibration

timing can be detected.

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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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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).