CONTROL SYSTEM
01–40–31
01–40
Control Outline
• The PCM constantly calculates the optimum target EGR valve position according to the engine operation
conditions and controls the EGR stepping motor step number so that the current EGR valve position is close to
the target.
• If the current EGR valve position is smaller than the target EGR position (deviation is a positive number), the
PCM increases the stepping motor step number and opens the EGR valve. If larger (deviation is a negative
number), the PCM decreases the stepping motor step number and closes the EGR valve. Step numbers are
increased or decreased by one step at a time.
Target EGR Valve Position
• The PCM determines the value to increase or decrease the EGR valve opening angle according to the engine
operation conditions. The PCM determines the target EGR valve position through each correction based on the
basic EGR valve position that is set according to the engine speed and load.
Target EGR valve position determination table
*1
: The charging efficiency is the ratio of the actual amount of intake air to the maximum air charging amount
(mass volume) of the cylinder. This value increases proportionately to the increase in engine load.
*2
: The correction is to restrict the basic EGR valve position value. Except for the above conditions and inhibition
conditions, the correction value is 100%, and the target EGR valve position equals the EGR valve position
value.
Inhibition Conditions
• To improve driveability and ensure exhaust emission performance, the EGR valve closes when any of the
following conditions are met.
— When throttle valve is fully closed
— When vehicle is stopped
— When the fuel injection control is in the high volume increase zone
— The engine coolant temperature is 50 °C {122 °F} or less
— During deceleration
— Engine speed is less than 1,200 rpm or more than 4,200 rpm
— Charging efficiency is less than 12.5% or more than 75%
— During traction control
End Of Sie
Contents Method for calculating or determining the EGR valve position and correction
Basic EGR valve position
Within steps 0—52 in the stepping motor determined as follows:
• When the engine speed is 1,200—4,200 rpm and the charging efficiency
*1
is within
12.5—75%, the engine speed and charging efficiency are determined to be at basic
position
• When the EGR control inhibition conditions are met, step 0
Correction
*2
Engine coolant
temperature
correction
Purpose: Improved driveability
Engine coolant temperature is 50—55 °C {122—131 °F}
• The step number is restricted between 0—50% of the basic EGR valve position (low
engine coolant temperature—low step number) according to the engine coolant
temperature.
Engine coolant temperature is 55—65 °C {131—149 °F}
• The step number is restricted between 50—100% of the basic EGR valve position (low
engine coolant temperature→low step number) according to the engine coolant
temperature.
Intake air
temperature
correction
Purpose: Improved driveability
Intake air temperature is 50 °C {122 °F} or less
• Step number is restricted to 100% of the basic EGR valve position (basic EGR valve
position = step number)
Intake air temperature is 50 °C {122 °F} or more
• Step number is restricted between 40—100% of basic EGR valve position (low intake
air temperature→large step number)
Acceleration/
deceleration
correction
Purpose: Improved driveability
During acceleration/deceleration, when the throttle valve opening angle
fluctuation rate is the set value or more
• During acceleration→step number is restricted to 20% of basic EGR valve position
• During deceleration→step number is restricted to 0% of basic EGR valve position
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