SsangYong Rexton. Manual - part 90

DI08-13

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

FUEL INJECSTION CONTROL

Fuel Injection Control

Injection control is used in order to determine the characteristics of the pulse which is sent to the injectors.

Injection control consists as below.

• Injection timing

• Injection volume

• Translating fuel injection timing and injection volume into values which can be interpreted by the injector driver.

- a reference tooth (CTP)

- the delay between this tooth and the start of the pulse (Toff)

- the pulse time (Ton)

Main injection timing control

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.

• 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.

During starting, the injection timing must be retarded in order to position the start of combustion close to the TDC. To do
this, special mapping is used to determine the injection timing advance as a function of the engine speed and of the
water temperature. This requirement only concerns the starting phase, since once the engine has started the system
must re-use the mapping and the corrections described previously.

Pilot injection timing control

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.

During the starting phase, the pilot injection timing is determined as a function of the engine speed and of the coolant
temperature.

DI08-14

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

FUEL FLOW CONTROL

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.

: The driver’s demand is compared with the value of the minimum flow determined by the idle speed controller.

• 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.

It is therefore the greater of these 2 values which is retained by the system. This value is then compared with the lower
flow limit determined by the ASR trajectory control system. As soon as the injected fuel becomes lower than the flow
limit determined by the ASR trajectory control system, the antagonistic torque (engine brake) transmitted to the drive
wheels exceeds the adherence capacity of the vehicle and there is therefore a risk of the drive wheels locking. The
system thus chooses the greater of these 2 values (main flow & pilot flow) in order to prevent any loss of control of the
vehicle during a sharp deceleration.

This value is then compared with the flow limit determined by the cruise control. As soon as the injected fuel becomes
lower than the flow limit determined by the cruise control, the vehicle’s speed falls below the value required by the driver.
The system therefore chooses the greater of these 2 values in order to maintain the speed at the required level.

This valve is then compared with the flow limit determined by the flow limitation strategy. This strategy allows the flow to
be limited as a function of the operating conditions of the engine. The system therefore chooses the smaller of these 2
values in order to protect the engine. This value is then compared with the fuel limit determined by the ASR trajectory
control system.

As soon as the injected fuel becomes higher than the fuel limit determined by the ASR trajectory control system, the
engine torque transmitted to the wheels exceeds the adhesion capacity of the vehicle and there is a risk of the drive
wheels skidding. The system therefore chooses the smaller of the two values in order to avoid any loss of control of the
vehicle during accelerations.

The anti-oscillation strategy makes it possible to compensate for fluctuations in engine speed during transient conditions.
This strategy leads to a fuel correction which is added to the total fuel of each cylinder. The correction is determined
before each injection as a function of the instantaneous engine speed.

A switch makes it possible to change over from the supercharge fuel to the total fuel according to the state of the engine.

• Until the stating phase has finished, the system uses the supercharged fuel.

• Once the engine changes to normal operation, the system uses the total fuel.

The main fuel is obtained by subtracting the pilot injection fuel from the total fuel.

A mapping determines the minimum fuel which can control an injector as a function of the rail pressure. As soon as the
main fuel falls below this value, the fuel demand changes to 0 because in any case the injector is not capable of injecting
the quantity demand.

DI08-15

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

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.

Y220_08009

Driver Demand

Engine status

Main flow < controllable min.flow

Main flow request

Driver’s request

Idle speed controller

ASR traction control

Cruise control

Flow limit

Speed limiter

ASR traction control

Anti-oscillation strategy

Overflow

Programmed engine stop

Pilot injection flow

0

DI08-16

CHANGED BY

EFFECTIVE DATE

AFFECTED VIN

ENGINE CONTROL SYSTEM

DI ENG SM - 2004.4

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,

the accelerated idle speed is activated to prevent the engine from stalling when operating in degraded mode.

- It is possible to increase or to reduce the required idle speed with the aid of the diagnostic tool.

• 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.

Idle Speed Controller

Flow Limitation

Pilot flow control

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 these 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.

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.

This correction is used to adapt the pilot flow according to the atmospheric pressure and therefore the altitude.

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