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Fuel rail pressure
sensor
(2) Components for ECU Input
CAN
- ABS & ESP
- GCU
- Instrument
cluster
- TCUSwirl valve position
sensor
Differential
pressure sensorE-EGR valve
position sensorCamshaft position
sensorCoolant
temperature senso
r
Exhaust gas
temperature senso
r
HFM sensorOxygen sensorT-MAP sensor
Crankshaft position
sensor
Accelerator pedal
sensorThrottle position
sensorKnock sensor
-Auto cruise switch
- Rear right wheel
speed (without ABS)
- Refrigerant pressure
sensor
- Clutch pedal signal
- Blower switch signal
- Brake pedal signal
Water sensor
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(3) Components for ECU Output
CAN
E-EGR cooler
bypass valve
- Instrument cluster
- TCU
- Self diagnosis
PTC heaterCooling fan
E-EGR valve
Variable swirl valveE-VGT actuatorIMV valve
A/C compressorInjectorThrottle position
sensor
- Glow plug unit
- ABS & ESP unit
- GCU
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2) ECU Control
(1) Function
a. ECU Function
ECU receives and analyzes signals from various sensors and then modifies those signals into
permissible voltage levels and analyzes to control respective actuators.
ECU microprocessor calculates injection period and injection timing proper for engine piston
speed and crankshaft angle based on input data and stored specific map to control the engine
power and emission gas.
Output signal of the ECU microprocessor drives pressure control valve to control the rail pressure
and activates injector solenoid valve to control the fuel injection period and injection timing; so
controls various actuators in response to engine changes. Auxiliary function of ECU has adopted
to reduce emission gas, improve fuel economy and enhance safety, comforts and conveniences.
For example, there are EGR, booster pressure control, autocruise (export only) and immobilizer
and adopted CAN communication to exchange data among electrical systems (automatic T/M
and brake system) in the vehicle fluently. And Scanner can be used to diagnose vehicle status
and defectives.
<00760097008c00990088009b00900095008e0047009b008c00940097008c00990088009b009c0099008c0047009900880095008e008c00470096008d0047006c006a007c00470090009a0047009500960099009400880093009300a000470054005b005700
47009b009600470052005f005c00b6006a004700880095008b> protected from factors like oil,
water and electromagnetism and there should be no mechanical shocks.
To control the fuel volume precisely under repeated injections, high current should be applied
instantly so there is injector drive circuit in the ECU to generate necessary current during injector
drive stages.
Current control circuit divides current applying time (injection time) into full-in-current-phase and
hold-current-phase and then the injectors should work very correctly under every working
condition.
b. Control Function
Controls by operating stages
To make optimum combustion under every operating stage, ECU should calculate proper
injection volume in each stage by considering various factors.
Starting injection volume control
During initial starting, injecting fuel volume will be calculated by function of temperature and
engine cranking speed. Starting injection continues from when the ignition switch is turned to
ignition position to till the engine reaches to allowable minimum speed.
Driving mode control
If the vehicle runs normally, fuel injection volume will be calculated by accelerator pedal travel
and engine rpm and the drive map will be used to match the drivers inputs with optimum
engine power. -
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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. -
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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. -
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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 ESP system.
As soon as the injected fuel becomes lower than the flow limit determined by the ESP 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.
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.
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. -
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(5) Fuel Control
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.
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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. -
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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: -
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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
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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. 1.
2.
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).
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This is done periodically under certain operating conditions. When the resetting is finished, the
new minimum pulse value replaces the value obtained during the previous resetting. The first MDP
value is provided by the C3I. Each resetting then allows the closed loop of the MDP to be updated
according to the deviation of the injector.
B. Detection of leaks in the cylinders
The accelerometer is also used to detect any injector which may have stuck open. The detection
principle is based on monitoring the ratio. If there is a leak in the cylinder, the accumulated fuel
self-ignites as soon as the temperature and pressure conditions are favorable (high engine
speed, high load and small leak).
This combustion is set off at about 20 degrees before TDC and before main injection.
The ratio therefore increases considerably in the detection window. It is this increase which allows
the leaks to be detected. The threshold beyond which a fault is signaled is a percentage of the
maximum possible value of the ratio.
Because of the severity of the recovery process (engine shut-down), the etection must be
extremely robust.
An increase in the ratio can be the consequence of various causes:
Pilot injection too much
Main combustion offset
Fuel leak in the cylinder -
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If the ratio becomes too high, the strategy initially restricts the pilot injection flow and retards the
main injection. If the ratio remains high despite these interventions, this shows that a real leak is
present, a fault is signaled and the engine is shut down.
C. Detection of an accelerometer fault
This strategy permits the detection of a fault in the sensor or in the wiring loom connecting the
sensor to the ECU.
It is based on detection of the combustion. When the engine is idling, the detection window is set
too low for the combustion caused by the main injection. If the ratio increases, this shows that the
knock sensor is working properly, but otherwise a fault is signaled to indicate a sensor failure.
The recovery modes associated with this fault consist of inhibition of the pilot injection and
discharge through the injectors.
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(9) EGR control
A. Overview
The EGR (Electric-Exhaust Gas Recirculation) valve reduces the NOx emission level by
recirculating some of the exhaust gas to the intake system.
To meet Euro-V regulation, the capacity and response rate of E-EGR valve in D20DTR engine
have been greatly improved. The EGR cooler with high capacity reduces the Nox, and the bypass
valve reduces the CO and HC due to EGR gas before warming up.
Also, the engine ECU adjusts the E-EGR opening by using the air mass signal through HFM
sensor. If the exhaust gas gets into the intake manifold when the EGR valve is open, the amount
of fresh air through HFM sensor should be decresed.
B. Components
E-EGR cooler
Accelerator pedal
moduleD20DTR ECU
Coolant
temperature senso
r
Oxygen sensor
HFM (intake air
temperature)Electric throttle
body
Crankshaft position
sensor
E-EGR valve
T-MAP sensor