BOOST CONTROL [SKYACTIV-D 1.8]
id0140s1988600
Outline
• The PCM controls the air charging pressure to improve the variable geometry turbocharger responsiveness, the acceleration performance and fuel economy of the vehicle.
• To obtain optimum air charging pressure according to the driving conditions, the PCM drives and controls the turbocharger solenoid valve.
Block Diagram
Operation
• The PCM controls the turbocharger solenoid valve according to the engine operation conditions (engine speed and fuel injection amount) so that optimum air charging pressure is obtained.
• If driving conditions require increased air charging pressure, the duty value of the signal sent to the turbocharger solenoid valve is higher. At that time, the variable nozzle of the VG turbocharger moves in the closed direction.
• If driving conditions require decreased air charging pressure, the duty value of the signal sent to the turbocharger solenoid valve is lower. At that time, the variable nozzle of the VG turbocharger moves in the open direction.
• The PCM calculates the target air charging pressure of the variable nozzle based on the input signal and performs feedback control.
Target lift of variable nozzle
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― Target lift of variable nozzle is calculated based on the engine speed and target torque.
Target air charging pressure
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― Target boost pressure is calculated based on the engine speed and target torque.
• The PCM adjusts the variable nozzle to the optimal opening angle in mainly 4 control ranges.
Control range (light load range to all ranges) conceptual diagram
—: Not applicable
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Item
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Turbocharger solenoid valve drive condition
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Variable nozzle operation condition
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Control status
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(1) Light load, mid speed range
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Duty 45—80%
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Open Û Closed
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Feedback control relative to target lift of variable nozzle
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(2) Mid to high load range
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Duty 0—80%
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Open Û Closed
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Feedback control relative to target air charging pressure
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When engine is stopped by i-stop control
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Duty 60%*1
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Fully closed
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Variable nozzle lift fixed at fully closed
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No-load racing
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Duty 0%
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Fully open
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Variable nozzle lift fixed at fully open
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*1 :By applying approx. 60% or more duty ratio sent to the turbocharger solenoid valve, the variable nozzle lift of the variable geometry turbocharger is fixed at fully closed.
