SsangYong Rodius (2013 year). Manual - part 87

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F. 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.

G. 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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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.

(6) MDP Learning Control

A. MDP Learning

When the pulse value that the injector starts injection is measured, it is called minimum drive pulse 

(MDP). Through MDP controls, can correct pilot injections effectively. Pilot injection volume is very 

small, 1 to 2 mm/str, so precise control of the injector can be difficult if it gets old. So there needs MDP 

learning to control the very small volume precisely through learning according to getting older injectors.

Control the fuel injection volume precisely by MDP learning even for the old injector.

ECU corrects the pilot injection effectively by MDP control.

MDP learning is performed by the signal from knock sensor.

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The system measures the pulse at initial injection to reduce the engine vibration.

B. Purpose of MDP learning

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C. Learning Conditions

Idle MDP learning

Drive MDP learning

Coolant temperature

over 60℃  

over 60℃ 

Vehicle speed

Idling

over 50km/h (over 5 seconds)

Engine rpm

2,000 to 2,500 rpm 

Fuel temperature

0 < Fuel temperature < 80℃

Learning

2 times for each cylinder (every 5 

seconds)

2 times for each cylinder 

(every 5 seconds)

If MDP learning is not properly performed, engine vibration and injection could be occurred.

MDP learning should be performed after replacing ECU, reprogramming and replacing injector.

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D. Injector characteristic curve for rail pressure

The fuel injection curve is also called injection characteristic curve as shown above. The amount of 

injected fuel is proportional to the square root of injection period and rail pressure.

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(7) Knocking Control

A. Resetting the pilot injection

The knocking control 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 

knocking control 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 knock sensor 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 knocking control 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 knock sensor 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).