Exam 15: Fixed Geometry and Wastegated Turbochargers

Technician A says that when servicing the cooling system of an engine that uses a JWAC (jacket water aftercooler), bleeding air from the cooler is not necessary. Technician B says that the JWAC is a low point in the cooling system, so air can become trapped in the cooler and prevent proper functioning. Who is right?

Which of the following is the most likely cause of a pitted and worn turbocharger compressor wheel?

Two technicians are discussing turbocharger operation. Technician A says that turbochargers are used on diesel engines to improve their power output while decreasing engine size and displacement. Technician B says that turbochargers enhance engine efficiency. Who is right?

Moving the heated charge air through an ATAAC can drop the temperature from higher than 400°F to:

Technician A says that a barometric pressure sensor on an electronically controlled diesel engine prevents fixed-geometry turbocharger damage caused by overspeeding. Technician B says that waste gates provide turbocharger overspeed protection. Who is correct?

Technician A says that turbocharging pressure in a diesel engine is limited by the threshold at which a diesel combustion chamber will begin to detonate. Technician B says that diesel turbocharger pressures are designed to match the air-fuel ratio requirements of the engine combustion system. Who is correct?

Which of the following is changed when the diameter of a turbocharger turbine or compressor housing is increased?

Turbochargers are designed to turn faster at lower engine load factors, increasing power density, or power output per liter (or cubic inch) of displacement, of small-bore engines at low speed while minimizing:

When gas temperatures increase, molecules spread farther apart, so the gas loses:

Which of the following features is characteristic of engines that use waste-gated turbochargers?

Efficient and effective heat transfer is necessary to prevent:

Which of the following features is characteristic of engines that use waste-gated turbochargers?

The Ford 6.7 L Power Stroke uses a(n):

Technician A says that all engines lose power at higher altitudes due to lower air density. Technician B says that turbocharged diesel engines are an exception and that intake manifold air pressure remains the same regardless of altitude. Who is correct?

Technician A says that a supercharger uses energy from exhaust gases to turn a turbine wheel, which causes a compressor impeller to pressurize air for combustion. Technician B says that every engine reaches a limit where the addition of more fuel produces no increase in power because it cannot breathe in enough air. Who is right?

The ECM will disconnect which of the following devices when the engine is under boost pressure and when intake air temperatures need to be lowered?

Technician A says that turbocharging a diesel engine reduces most noxious emissions because the cylinder pressure is higher. Technician B says that turbocharging lowers emissions because it provides more air to completely burn fuel in the cylinders. Who is correct?

Increases in charge air temperatures result in higher combustion chamber temperatures, which increase the production of:

Technician A says that excessive wear on the thrust bearing will cause the compressor wheel to contact the compressor housing. Technician B says that only excessively worn center support bearings will allow the compressor wheel to contact the compressor housing. Who is correct?

Technician A says that small cracks do not warrant replacing a CAC (charge-air-cooler) system, because dirt ingestion into the engine through a crack is not likely when a cooler is pressurized. Technician B says that many manufacturers do not recommend replacing the cooler if the leak is small. Who is right?