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SsangYong Rodius (2013 year). Manual - part 86

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(3) Fuel Pressure Control

Fuel pressure is controlled by IMV opening according to the calculated value by ECU.

Pressure in the fuel rail is determined according to engine speed and load on the engine.

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When engine speed and load are high

The degree of turbulence is very great and the fuel can be injected at very high pressure in order to

optimize combustion.

When engine speed and load are low

The degree of turbulence is low. If injection pressure is too high, the nozzle's penetration will be

excessive and part of the fuel will be sprayed directly onto the sides of the cylinder, causing

incomplete combustion. So there occurs smoke and damages engine durability.

Fuel pressure is corrected according to air temperature, coolant temperature and atmospheric

pressure and to take account of the added ignition time caused by cold running or by high altitude

driving. A special pressure demand is necessary in order to obtain the additional flow required during

starts. This demand is determined according to injected fuel and coolant temperature.

Open loop determines the current which needs to be sent to the actuator in order to obtain

the flow demanded by the ECU.

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Closed loop will correct the current value depending on the difference between the pressure

demand and the pressure measured.

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If the pressure is lower than the demand, current is reduced so that the fuel sent to the high

pressure pump is increased.

If the pressure is higher than the demand, current is increased so that the fuel sent to the high

pressure pump is reduced.

Fuel Pressure

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Pilot injection timing control

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The pilot injection timing is determined as a function of the engine speed and of the total flow.

The elements are:

A first correction is made according to the air and coolant temperatures. This correction allows the

pilot injection timing to be adapted to the operating temperature of the engine.

A second correction is made according to the atmospheric pressure. This correction is used to

adapt the pilot injection timing as a function of the atmospheric pressure and therefore the altitude.

(4) Injection Timing Control

Injection timing is determined by the conditions below.

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Coolant temperature

Hot engine - Retarded to reduce Nox

Cold engine - Advanced to optimize the combustion

Atmospheric pressure

Advanced according to the altitude

Warming up

Advanced during warming up in cold engine

Rail pressure

Retarded to prevent knocking when the rail pressure is high

EEGR ratio

Advanced to decrease the cylinder temperature when EGR ratio increases

Main injection timing control

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The pulse necessary for the main injection is determined as a function of the engine speed and of the

injected flow.

The elements are:

A first correction is made according to the air and coolant temperatures.

This correction makes it possible to adapt the timing to the operating temperature of the engine.

When the engine is warm, the timing can be retarded to reduce the combustion temperature and

polluting emissions (NOx). When the engine is cold, the timing advance must be sufficient to allow

the combustion to begin correctly.

A second correction is made according to the atmospheric pressure.

This correction is used to adapt the timing advance as a function of the atmospheric pressure and

therefore the altitude.

A third correction is made according to the coolant temperature and the time which has passed

since starting.

This correction allows the injection timing advance to be increased while the engine is warming up

(initial 30 seconds). The purpose of this correction is to reduce the misfiring and instabilities which

are liable to occur after a cold start.

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A fourth correction is made according to the pressure error.

This correction is used to reduce the injection timing advance when the pressure in the rail is higher

than the pressure demand.

A fifth correction is made according to the rate of EGR.

This correction is used to correct the injection timing advance as a function of the rate of exhaust

gas recirculation.

When the EGR rate increases, the injection timing advance must in fact be increased in order to

compensate for the fall in termperature in the cylinder.

A. Main Flow Control

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

pilot flow represents the amount of fuel injected during the pilot injection.

The total fuel injected during 1 cycle (main flow + pilot flow) is determined in the following manner.

When the driver depress the pedal, it is his demand which is taken into account by the system in

order to determine the fuel injected.

When the driver release the pedal, the idle speed controller takes over to determine the minimum

fuel which must be injected into the cylinder to prevent the enigne from stalling.

The driver demand is the translation of the pedal position into the fuel demand. It is calculated as a

function of the pedal position and of the engine speed. The driver demand is filtered in order to limit the

hesitations caused by rapid changes of the pedal position. A mapping determines the maximum fuel

which can be injected as a function of the driver demand and the rail pressure. Since the flow is

proportional to the injection time and to the square root of the injection pressure, it is necessary to limit

the flow according to the pressure in order to avoid extending the injection for too long into the engine

cycle. The system compares the driver demand with this limit and chooses the smaller of the 2 values.

The driver demand is then corrected according to the coolant temperature. This correction is added to

the driver demand.

(5) Fuel Control

B. Driver Demand

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C. 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.

D. 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:

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.

E. 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

Content .. 84 85 86 87 ..