Exam 16: Variable Geometry and Series Turbochargers

A typical VGT produced since 2010 will most commonly respond to electrical signals transmitted ____________.

Technician A says that a single-sequential turbocharger (SST) integrates four turbochargers into a single component. Technician B says that a single housing unit supports two compressor wheels, a configuration that reduces space requirements. 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?

Technician A says that creating higher backpressure speeds up the turbocharger, which decreases boost pressure. Technician B says that vanes surrounding the turbine wheel can move from open to a closed position to regulate the flow of exhaust gases across the turbine. Who is right?

Approximately _____ percentage of the intake charge in diesels can be exhaust gas.

What is the primary purpose of a variable-geometry turbocharger (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?

A typical VGT produced since 2010 will most commonly respond to electrical signals transmitted ____________.

Since the VGT (variable-geometry turbocharger) pressure ratios are higher, more discharge heat is generated by the compressor wheel, which often requires:

Two technicians are explaining how to replace a VGT (variable-geometry turbocharger) actuator. Technician A says that you hold and shake the sector gear inside the turbocharger to check for excessive movement, which would indicate a failed bearing in the sector shaft. Technician B says that if the sector gear does not sweep freely, the turbocharger will need to be replaced. Who is right?

What exhaust backpressure is required in some engines to force enough exhaust gas into the fresh-air intake turbochargers?

Technician A says that single-sequential turbochargers have two separate compressor and turbine housings. Technician B says that single-sequential turbochargers use two turbine wheels and one compressor wheel. Who is correct?

Which of the following does NOT cause a vibration that is synchronized to specific engine speed?

Technician A says that VGT engines have less turbo lag. Technician B says VGT engines have more exhaust backpressure in the exhaust manifold than single-stage turbochargers have. 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?

A VGT (variable-geometry turbocharger) has the functional capability of changing intake boost pressure and exhaust backpressure independent of:

Technician A says that coolant passageways through the turbocharger housing are used to keep the turbocharger bearings and other parts cooled when the engine is running. Technician B says that coolant passageways are used primarily to circulate coolant after the engine has been shut off. Who is correct?

What is experienced as a delay between the driver's demand for power from the engine and the point in time when the engine responds with power in proportion to the driver's demand?

In most engines, at what vehicle speed do the VGT (variable-geometry turbocharger) vanes close to provide the engine with a natural retarding force that more closely resembles a gasoline-fueled engine with a throttle plate?

Which of the following strategies best explains how the VGT operates as an engine brake?