SYSTEM
EC-841
< SYSTEM DESCRIPTION >
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The ECM limits a engine torque in case of malfunction of engine component or ECM.
Depending on the engine components, ECM activates the fail-safe mode of the torque limitation level 1 (low
limitation), the level 2 (mean limitation), or the level 3 (strong limitation function of vehicle speed).
FAST SET-POINTS TO COMPLETE TORQUE REQUEST
For each combustion mode (the normal combustion mode, the regeneration combustion mode, and the pro-
tection combustion mode), a torque model is designed to calculate the total fuel mass quantity, the estimated
mean effective torque, the combustion efficiency and the current fuel consumption for the final torque set-point
and the engine current speed.
The total fuel mass quantity is corrected to take into account the main injection advance deviation and the
mass air flow deviation.
For each combustion mode, the after and the post injection relative efficiencies are calculated to determine the
fuel mass quantity needed to perform the engine inner torque.
The after injection relative efficiency is equal to one in normal combustion mode and to zero in a regeneration
combustion mode or in a protection combustion mode.
The post injection relative efficiency is function of the post injection timing and the difference between the cur-
rent and the basic post injection timing.
FINAL TORQUE REQUESTS SETTING
The final torque requests are computed by the arbitration with the driver request, the intersystem torque
request (VDC/ESP), the torque limitations and the curative anti-jerk correction.
The set-point torque is used for fuel mass calculation. It is filtered by the preventive anti-jerk and corrected by
the curative anti-jerk.
COMBUSTION CONTROL
COMBUSTION CONTROL : System Description
INFOID:0000000010935568
SYSTEM DESCRIPTION
The torque set-point is converted into a total fuel quantity injected. This quantity is split in various injections
according to a mapped injection pattern. Thus, a fuel quantity and an initial phasing of injection are allocated
for each injection. The choice of the number of injection (limited to five maximum) is given with different con-
straints such as acoustic, performance and emissions.
In the DPF (Diesel Particulate Filter) regeneration phase, post injections do not contribute to the torque elabo-
ration but to the increase of the DPF temperature. Therefore, the fuel consumption increases in the DPF
regeneration phase.
FUEL SUPPLY AND PRESSURE CONTROL SYSTEM
Fuel Supply System
The fuel supply system consists of two circuits: the fuel low and high-pressure circuit.
The fuel low-pressure circuit brings fuel from the tank to the high-pressure fuel pump through the fuel filter
(with fuel heater).
The high-pressure circuit function is to put the fuel under pressure and distribute it to the injectors:
• High-pressure fuel pump
• Fuel flow actuator
• Common rail
• Fuel injectors
The low-pressure fuel (coming from low-pressure circuit) is transferred to the high-pressure pump part via the
fuel flow actuator, which regulates the fuel flow quantity. The high-pressure fuel pump consists of a three-pis-
ton pump.
The fuel under pressure goes to the common rail, which distributes the fuel equally to each injector.
Finally, the commanded injectors deliver the fuel flow entering the cylinder.
Fuel Pressure Control
The combustion quality is influenced by the size of the droplets sprayed into the cylinder. In the combustion
chamber, smaller fuel droplets will have enough time to burn completely and will produce less smoke and less
unburnt particulate matter. To meet pollution requirements, the size of the droplets needs to be reduced and
hence so too do the injection orifices.
Since these orifices are smaller, less fuel can be injected for a given pressure, which in turn limits the power.
To counter this drawback, it is necessary to increase the quantity of injected fuel, which involves raising the
pressure (and the number of orifices on the injector nozzles). The pressure is continuously regulated to high