Fuel Flow Control; Main Flow Control - SSANGYONG 2004 Rexton 2.7XDi Workshop Manual

DI08-14

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.
CHANGED BY
EFFECTIVE DATE
AFFECTED VIN
ENGINE CONTROL SYSTEM
DI ENG SM - 2004.4