Bơm ECD-V - P - Determining the Injection Timing
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10
SERVICE TECH Vol.470 04-2
The engine ECU determines the "Target Injection Timing" by using the signals received from the various sensors to
correct the "Basic Target Injection Timing". This is calculated from the engine speed and accelerator position. The
"Actual Injection Timing" is also calculated, based on the crankshaft angle standard position signal (TDC signal). In
order to make the "Actual Injection Timing" match the "Target Injection Timing", the duty ratio of the timing control
valve is calculated. Feedback control is performed to make the injection timing the same as the target value.
• Calculating the Injection Timing
Target injection timing formula
• Basic Target Injection Timing
The engine ECU calculates the engine load from the
engine speed and accelerator position signals, and
determines the "Basic Target Injection Timing". The
higher the engine speed, or the larger the accelerator
position, the longer the advance.
Target Injection Timing
=
Basic Target
Injection Timing
+
Intake Air Pressure
Correction
+
Coolant Temperature
Correction
+
Intake Air Temperature
Correction
1
1
Determining the Injection Timing
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SERVICE TECH Vol.470 04-2
The engine ECU compares the "Target Injection Timing" and "Actual Injection Timing" that have been calculated. It
then performs duty actuation on the timing control valve (TCV) in order to match the two timing values. As a result,
the injection pump roller ring turns, and the injection timing changes.
2
2
Injection Timing Control Method
Crankshaft
Position Signal
Crankshaft
Position Signal
Engine Speed
Sensor Signal
Target Injection
Timing
Actual Injection Timing
Signal from Engine ECU
Engine Speed
Sensor Signal
Signal from Engine ECU
(Retard Condition)
(Actuating the Advance Side)
Actual Injection
Timing
Target Injection
Timing
Transfer
Retard
Timing Control Valve
(Duty Ratio: Large)
[Present Condition]
(Duty Ratio: Medium)
[After Control]
#
0
#
0
Injection
Timing Control
Timing Control Valve
Advance
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SERVICE TECH Vol.470 04-2
In addition to fuel injection volume and timing control, the ECD system performs other types of control to enable the
comfortable operation of the engine and the vehicle.
• Idling Speed Control
• EGR Control
• Intake Restriction Control
• Glow Control
• Others
3
3
Various System Controls
Main System Controls
3-1 Outline of System Controls
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SERVICE TECH Vol.470 04-2
This control function minimizes the variation in the idling speed caused by changes in the engine load. A
"Target Speed" is calculated to meet the engine and driving conditions, which is used to control speed when
the engine is idling.
The engine ECU detects the "Refrigerant Temperature, Shift Position, Air Conditioner Operation" signals,
and compares the calculated "Target Speed" with the engine speed (engine speed sensor signal) at that
time. If the engine speed is different, the fuel injection volume is adjusted, and feedback control is
performed in order to match it with the target idling speed.
• Engine speed is lower than target speed - - - - - - - - - - - - - - - - - -Injection volume is increased
• Engine speed is higher than target speed - - - - - - - - - - - - - - - - - -Injection volume is decreased
The "Target Engine Speed" for each engine
condition has already been stored in the engine ECU
memory. When the ECU receives information about
the engine conditions from the sensors and
switches, it searches its memory and determines
the appropriate target value.
4
4
Idling Speed Control (ISC)
4-1 Control Outline
4-2 Speed Control Method
Detection of Idling Conditions
Idling Speed Control
4-3 Determining the Target Engine Speed
