Turbo Vane Control Question
Thanks.
The turbo has a set of moveable vanes in the turbine housing that change the flow of the exhaust through the turbo. These vanes are internal to the turbine housing and are mounted around the outside circumference of the housing.
Changing vane position either restricts or increases the amount of exhaust gases allowed into the turbine housing. Each individual vane has a tab on it that attaches to a ring linking all the vanes together. When the ring is moved, all of the vanes move a corresponding amount.
A linear actuator attaches to the ring. Actuator position is changed by varying the amount of pressurized engine oil applied to either side of the actuator. The flow and placement of the oil is controlled by the VGT solenoid which is in turn controlled by the PCM.
The VGT solenoid is a pulse width modulated (PWM) solenoid. Increasing the current duty cycle to the VGT solenoid increases boost.
The solenoid routes oil to one side of the linear actuator forcing the actuator to move, which in turn moves the ring linking the vanes.
The vanes move to an open position allowing more exhaust gases into the turbine housing. More exhaust flow increases turbine speed with a resultant increase in boost.
The converse is also true. When the current duty cycle is decreased, boost levels also decrease.
The PCM monitors a variety of sensors to determine how to duty cycle the VGT solenoid.
In closed loop, the PCM uses exhaust backpressure, manifold and barometric pressures, accelerator pedal position, and engine RPM and calculated load for turbo control.
Changes in parameters for each of these sensors will result in a variation in VGT duty cycle. Higher load demands more duty cycle.
This is how the PCM controls the turbo boost to match engine load and requirements.
The turbo has a set of moveable vanes in the turbine housing that change the flow of the exhaust through the turbo. These vanes are internal to the turbine housing and are mounted around the outside circumference of the housing.
Changing vane position either restricts or increases the amount of exhaust gases allowed into the turbine housing. Each individual vane has a tab on it that attaches to a ring linking all the vanes together. When the ring is moved, all of the vanes move a corresponding amount.
A linear actuator attaches to the ring. Actuator position is changed by varying the amount of pressurized engine oil applied to either side of the actuator. The flow and placement of the oil is controlled by the VGT solenoid which is in turn controlled by the PCM.
The VGT solenoid is a pulse width modulated (PWM) solenoid. Increasing the current duty cycle to the VGT solenoid increases boost.
The solenoid routes oil to one side of the linear actuator forcing the actuator to move, which in turn moves the ring linking the vanes.
The vanes move to an open position allowing more exhaust gases into the turbine housing. More exhaust flow increases turbine speed with a resultant increase in boost.
The converse is also true. When the current duty cycle is decreased, boost levels also decrease.
The PCM monitors a variety of sensors to determine how to duty cycle the VGT solenoid.
In closed loop, the PCM uses exhaust backpressure, manifold and barometric pressures, accelerator pedal position, and engine RPM and calculated load for turbo control.
Changes in parameters for each of these sensors will result in a variation in VGT duty cycle. Higher load demands more duty cycle.
This is how the PCM controls the turbo boost to match engine load and requirements.
Bismic thank you for the detailed explanation.
My thought was that I could use a programmable controller to read signals from the TPS, rpm, boost, vehicle speed, and EGT's and with some trial and error program it to work on my intended project. Knowing that it uses a 12v PWM signal makes it so much easier.
As far as oil to actuate the vanes what is the necessary operating pressure of the spool valve? I could easily rig up an electric or engine driven pump to generate the necessary pressure if engine pressure is not sufficient.
Again thanks.
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