Exam 16: Variable Geometry and Series Turbochargers

Which of the following conditions is required to increase the turbine speed of a VGT?

Technician A says that VGT engines can electronically vary turbocharger boost pressure. Technician B says that boost pressure from VGTs is typically higher than boost pressure from fixed-geometry turbochargers. Who is correct?

What characteristic of VGTs requires the use of titanium alloys for compressor wheels?

Technician A says the operation of the VGT actuator's electric motor is inspected during a bounce test. Technician B says the motor needs to be removed and checked by using an ohmmeter to determine whether it is faulty. Who is correct?

Higher turbine speeds are possible when using:

Technician A says that exhaust backpressure is built up in the exhaust manifold before entering the turbocharger. Technician B says that an EGR flow control valve diverts intake air into the intake manifold. Who is right?

Consider the operation of a single-sequential DualBoost turbocharger. What combination of air inlets and outlets are used?

Technician A says that the calibration code on a Garrett electric actuator must match a specific engine calibration for the turbocharger to operate correctly. Technician B says that a sticking nozzle ring will eventually overload the electric motor in the VGT (variable-geometry turbocharger) actuator and cause it to burn out. Who is right?

Which of the following conditions is required to decrease the turbine speed of a VGT?

The VGT (variable-geometry turbocharger) electronic actuator communicates with other:

Increased inertia from heavier turbine and compressor wheel mass, along with bigger housings, means the turbocharger will take longer to spool, or build boost pressure, which in turn increases:

Technician A says that air reaches a cylinder more slowly in comparison to fuel, which can change dramatically from one combustion event to the next. Technician B says that smaller turbocharger compressor housings and wheels can produce proportionally greater airflow for better performance and reduced emissions. Who is right?

After two technicians had listened to the noise made by a VGT when the key was switched on but before starting the engine, Technician A said the noise was the actuator moving to a default spring-loaded position after it had been shut down in a wide-open position. Technician B said the turbocharger actuator was relearning maximum and minimum actuator sweep positions during a self calibration process. Who is correct?

While two technicians are discussing series turbocharging, Technician A says the high-pressure turbocharger has an exhaust bypass valve that prevents overspeeding. Technician B says the low-pressure turbocharger uses a waste gate to direct exhaust gases to the high-pressure turbocharger. Who is correct?

Technician A says that without power to the VGT actuators, some actuators will typically provide a lot of boost, because the vanes are as much as 95% closed. Technician B says the turbocharger will not provide very much boost, because the vanes always default to an open position. Who is correct?

What diesel engine, code-named Scorpion Diesel, uses a unique, patented single-sequential turbocharger (SST)?

Consider the operation of a single-sequential DualBoost turbocharger. What combination of air inlets and outlets are used?

Technician A says the turbocharger speed sensor is used to sense and prevent a turbocharger overspeed condition. Technician B says the speed sensor is used by the OBD system to detect faults with the turbocharger. Who is correct?

Consider a VGT. When intake boost pressure is at its highest value, what can most likely be observed regarding exhaust backpressure in the exhaust manifold?

VGTs (variable-geometry turbochargers) are built along ____ designs.