Exhaust Pressure Sensor
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From: Duncan, OK
Exhaust Pressure Sensor
I have a question for any ASE diesel mechanic:
Given that the EP sensor is located between the exhaust manifold and turbocharger, and that the catalytic converter is down stream from the turbo, will removing the cat effect the amount of pressure sensed by the EP?
If it does, I would assume it would always sense less pressure under any given condition. I am concerned that removing the cat could result in a constant state of overboost.
Dufus
Given that the EP sensor is located between the exhaust manifold and turbocharger, and that the catalytic converter is down stream from the turbo, will removing the cat effect the amount of pressure sensed by the EP?
If it does, I would assume it would always sense less pressure under any given condition. I am concerned that removing the cat could result in a constant state of overboost.
Dufus
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Joined: Nov 2003
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I am certainly not an ASE mechanic, but your Turbo is a VGT (Variable Geometry Turbo). It has "vanes" that can be opened and closed to control boost. Your PCM is aware of the boost through the boost sensor.
Below is the best explanations I have come across:
The Ford Variable Geometry Turbocharger (VGT) uses a PCM controlled electronic variable vane hydraulic control valve to control intake manifold pressure. The VGT control solenoid, coupled with an oil pressure actuated linear actuator, control the turbocharger vane positions. Changes in vane position increase or decrease exhaust flow and velocity across the turbine dependant upon engine demand.
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.
(..........................AND I Stayed at a Holiday Inn Express last night)
Below is the best explanations I have come across:
The Ford Variable Geometry Turbocharger (VGT) uses a PCM controlled electronic variable vane hydraulic control valve to control intake manifold pressure. The VGT control solenoid, coupled with an oil pressure actuated linear actuator, control the turbocharger vane positions. Changes in vane position increase or decrease exhaust flow and velocity across the turbine dependant upon engine demand.
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.
(..........................AND I Stayed at a Holiday Inn Express last night)
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