Question 1

What other condition can occur when the air to support combustion during turbo lag is not adequate?

Accepted Answer

A) White smoke" 
B) Black smoke" 
C) Blue smoke 
D) Grey smoke" 
A) White smoke" 
B) Black smoke" 
C) Blue smoke 
D) Grey smoke"

Question 2

Which of the following is NOT the result of an engine reaching a limit where the addition of more fuel produces no increase in power and cannot breathe in enough air?

Accepted Answer

A) Blue exhaust smoke" 
B) Black exhaust smoke" 
C) Decreasing fuel economy 
D) High exhaust temperatures" 
A) Blue exhaust smoke" 
B) Black exhaust smoke" 
C) Decreasing fuel economy 
D) High exhaust temperatures"

Question 3

What is the primary function of a turbocharger?

Accepted Answer

A) It operates only as an engine brake. 
B) It speeds up engine warm-up. 
C) It supplies addtional intake air mass. 
D) It enables the use of larger displacement engine. 
A) It operates only as an engine brake. 
B) It speeds up engine warm-up. 
C) It supplies addtional intake air mass. 
D) It enables the use of larger displacement engine.

Question 4

Why is a barometric pressure sensor used on an electronically controlled, fixed-geometry-turbocharged diesel engine?

Accepted Answer

A) To increase boost pressure." 
B) To lower air-fuel ratios." 
C) To minimize exhaust smoke at high altitudes. 
D) To prevent turbocharger overspeed." 
A) To increase boost pressure." 
B) To lower air-fuel ratios." 
C) To minimize exhaust smoke at high altitudes. 
D) To prevent turbocharger overspeed."

Question 5

Which of the following is NOT a disadvantage of fixed-geometry turbochargers?

Accepted Answer

A) Produces little boost at low speeds" 
B) Air-fuel ratios are also low at low-speed operation" 
C) High PM, HC, and CO emissions 
D) Air-fuel ratios are high at low-speed operation" 
A) Produces little boost at low speeds" 
B) Air-fuel ratios are also low at low-speed operation" 
C) High PM, HC, and CO emissions 
D) Air-fuel ratios are high at low-speed operation"

Question 6

Two technicians are explaining how to measure turbocharger radial bearing clearance. Technician A says that while rotating the turbine wheel, you check for any binding or roughness. Technician B says that any contact between the compressor wheel and housing indicates that the center support bearings are excessively worn. Who is right?

Accepted Answer

A) A only" 
B) B only" 
C) Both A and B 
D) Neither A nor B" 
A) A only" 
B) B only" 
C) Both A and B 
D) Neither A nor B"

Question 7

Consider an on-highway diesel engine that has a precisely matched turbocharger. Under which of the following conditions should turbine speeds be greatest to achieve maximum engine output?

Accepted Answer

A) Peak horsepower." 
B) Peak torque." 
C) Low engine rpm. 
D) High idle." 
A) Peak horsepower." 
B) Peak torque." 
C) Low engine rpm. 
D) High idle."

Question 8

A JWAC (jacket water aftercooler) is capable of lowering the turbocharger boost air temperature from approximately 300°F to approximately:

Accepted Answer

A) 200°F" 
B) 250°F" 
C) 100°F 
D) 150°F" 
A) 200°F" 
B) 250°F" 
C) 100°F 
D) 150°F"

Question 9

Technician A says that an engine that uses two turbochargers could use compressor and turbine housings of two different sizes. Technician B says that an engine that uses two turbochargers could use identical turbochargers, which is referred to as a parallel turbocharged engine. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 10

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?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 11

Which of the following reasons best explains how turbochargers maintain intake boost pressure (normalization) at high altitudes?

Accepted Answer

A) Greater exhaust heat from lean air-fuel mixtures at high altitudes. 
B) Less resistance to compressor wheel rotation offered by lower-density air at high altitudes. 
C) Greater pressure differential across the turbine wheel at high altitudes. 
D) The use of a boost pressure sensor to provide closed-loop feedback control over intake pressure. 
A) Greater exhaust heat from lean air-fuel mixtures at high altitudes. 
B) Less resistance to compressor wheel rotation offered by lower-density air at high altitudes. 
C) Greater pressure differential across the turbine wheel at high altitudes. 
D) The use of a boost pressure sensor to provide closed-loop feedback control over intake pressure.

Question 12

Technician A says that turbocharger lag is caused by the inertia of heavy compressor and turbine wheel assemblies. Technician B says turbocharger lag is caused by the slow buildup of fuel rate by the high-pressure injection system. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 13

Technician A says that fixed-geometry turbochargers that lack controls are designed to provide maximum boost pressure at rated speed or peak horsepower. Technician B says that a properly matched turbocharger will need to provide maximum boost pressure at the highest cylinder pressure, which is peak torque. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 14

Which of the following is the most likely cause of bent and distorted turbocharger compressor blades?

Accepted Answer

A) Contact with a 1/4" (6 mm) nut. 
B) Turbo overspeed. 
C) Overheating. 
D) Air cleaner sealing gasket ingestion. 
A) Contact with a 1/4" (6 mm) nut. 
B) Turbo overspeed. 
C) Overheating. 
D) Air cleaner sealing gasket ingestion.

Question 15

A restricted, undersized, or otherwise damaged exhaust system is easily overlooked when investigating complaints about:

Accepted Answer

A) loss of power under load at high speed" 
B) loss of power under load at low speed" 
C) loss of power with no load at high speed 
D) loss of power with no load at low speed" 
A) loss of power under load at high speed" 
B) loss of power under load at low speed" 
C) loss of power with no load at high speed 
D) loss of power with no load at low speed"

Question 16

Why is a barometric pressure sensor used on an electronically controlled, fixed-geometry-turbocharged diesel engine?

Accepted Answer

A) To increase boost pressure. 
B) To lower air-fuel ratios. 
C) To minimize exhaust smoke at high altitudes. 
D) To prevent turbocharger overspeed. 
A) To increase boost pressure. 
B) To lower air-fuel ratios. 
C) To minimize exhaust smoke at high altitudes. 
D) To prevent turbocharger overspeed.

Question 17

When a turbocharger turns at high speed, the compressor can supply air to the combustion chambers at pressure above:

Accepted Answer

A) 15.7 psi" 
B) 12.7 psi" 
C) 13.7 psi 
D) 14.7 psi" 
A) 15.7 psi" 
B) 12.7 psi" 
C) 13.7 psi 
D) 14.7 psi"

Question 18

If intake or underhood intake air temperature is 75°F (24°C) at atmospheric pressure (15 psi [103 kPa] at sea level), the turbo outlet temperature will be:

Accepted Answer

A) 185°F" 
B) 285°F" 
C) 385°F 
D) 485°F" 
A) 185°F" 
B) 285°F" 
C) 385°F 
D) 485°F"

Question 19

Technician A says that if a turbocharger is disassembled and a new compressor wheel is installed, then the turbocharger will need to be balanced. Technician B says that a compressor wheel's light weight will not affect turbocharger operation one way or another. Who is correct?

Accepted Answer

A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B 
A) Technician A 
B) Technician B 
C) Both A and B 
D) Neither A nor B

Question 20

Two technicians are explaining how to measure waste-gate movement. Technician A says that you apply a calibrated amount of air pressure to the waste-gate actuator, usually around 100 psi. Technician B says that you compare maximum boost pressure to the manufacturer's specifications to determine waste-gate operation threshold. Who is right?

Accepted Answer

A) A only" 
B) B only" 
C) Both A and B 
D) Neither A nor B" 
A) A only" 
B) B only" 
C) Both A and B 
D) Neither A nor B"

What other condition can occur when the air to support combustion during turbo lag is not adequate?

Which of the following is NOT the result of an engine reaching a limit where the addition of more fuel produces no increase in power and cannot breathe in enough air?

What is the primary function of a turbocharger?

Why is a barometric pressure sensor used on an electronically controlled, fixed-geometry-turbocharged diesel engine?

Which of the following is NOT a disadvantage of fixed-geometry turbochargers?

Consider an on-highway diesel engine that has a precisely matched turbocharger. Under which of the following conditions should turbine speeds be greatest to achieve maximum engine output?

A JWAC (jacket water aftercooler) is capable of lowering the turbocharger boost air temperature from approximately 300°F to approximately:

Technician A says that an engine that uses two turbochargers could use compressor and turbine housings of two different sizes. Technician B says that an engine that uses two turbochargers could use identical turbochargers, which is referred to as a parallel turbocharged engine. Who is correct?

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?

Which of the following reasons best explains how turbochargers maintain intake boost pressure (normalization) at high altitudes?

Technician A says that turbocharger lag is caused by the inertia of heavy compressor and turbine wheel assemblies. Technician B says turbocharger lag is caused by the slow buildup of fuel rate by the high-pressure injection system. Who is correct?

Which of the following is the most likely cause of bent and distorted turbocharger compressor blades?

A restricted, undersized, or otherwise damaged exhaust system is easily overlooked when investigating complaints about:

Why is a barometric pressure sensor used on an electronically controlled, fixed-geometry-turbocharged diesel engine?

When a turbocharger turns at high speed, the compressor can supply air to the combustion chambers at pressure above:

If intake or underhood intake air temperature is 75°F (24°C) at atmospheric pressure (15 psi [103 kPa] at sea level), the turbo outlet temperature will be:

Technician A says that if a turbocharger is disassembled and a new compressor wheel is installed, then the turbocharger will need to be balanced. Technician B says that a compressor wheel's light weight will not affect turbocharger operation one way or another. Who is correct?

Introduction to Diesel Engines

Diesel Engine Emissions

Cylinder Blocks and Crankshafts

Cylinder Components

Cylinder Heads and Valve Train Mechanisms

Diesel Engine Cooling and Lubrication Systems

Diesel Fuel and Low Pressure Fuel Systems

Functions of High Pressure Fuel Systems

Governors and Electronic Control Systems

Hydraulic Nozzles

Heui Injection Systems

Common Rail Fuel Systems

Air Induction and Crankcase Ventilation Systems

Variable Geometry and Series Turbochargers

Exhaust Gas Recirculation

Exhaust Aftertreatment Systems

On Board Diagnostics

Filters

Exam 15: Fixed Geometry and Wastegated Turbochargers

What other condition can occur when the air to support combustion during turbo lag is not adequate?

Which of the following is NOT the result of an engine reaching a limit where the addition of more fuel produces no increase in power and cannot breathe in enough air?

What is the primary function of a turbocharger?

Why is a barometric pressure sensor used on an electronically controlled, fixed-geometry-turbocharged diesel engine?

Which of the following is NOT a disadvantage of fixed-geometry turbochargers?

Consider an on-highway diesel engine that has a precisely matched turbocharger. Under which of the following conditions should turbine speeds be greatest to achieve maximum engine output?

A JWAC (jacket water aftercooler) is capable of lowering the turbocharger boost air temperature from approximately 300°F to approximately:

Technician A says that an engine that uses two turbochargers could use compressor and turbine housings of two different sizes. Technician B says that an engine that uses two turbochargers could use identical turbochargers, which is referred to as a parallel turbocharged engine. Who is correct?

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?

Which of the following reasons best explains how turbochargers maintain intake boost pressure (normalization) at high altitudes?

Technician A says that turbocharger lag is caused by the inertia of heavy compressor and turbine wheel assemblies. Technician B says turbocharger lag is caused by the slow buildup of fuel rate by the high-pressure injection system. Who is correct?

Which of the following is the most likely cause of bent and distorted turbocharger compressor blades?

A restricted, undersized, or otherwise damaged exhaust system is easily overlooked when investigating complaints about:

Why is a barometric pressure sensor used on an electronically controlled, fixed-geometry-turbocharged diesel engine?

When a turbocharger turns at high speed, the compressor can supply air to the combustion chambers at pressure above:

If intake or underhood intake air temperature is 75°F (24°C) at atmospheric pressure (15 psi [103 kPa] at sea level), the turbo outlet temperature will be:

Technician A says that if a turbocharger is disassembled and a new compressor wheel is installed, then the turbocharger will need to be balanced. Technician B says that a compressor wheel's light weight will not affect turbocharger operation one way or another. Who is correct?

Introduction to Diesel Engines

Diesel Engine Emissions

Cylinder Blocks and Crankshafts

Cylinder Components

Cylinder Heads and Valve Train Mechanisms

Diesel Engine Cooling and Lubrication Systems

Diesel Fuel and Low Pressure Fuel Systems

Functions of High Pressure Fuel Systems

Governors and Electronic Control Systems

Hydraulic Nozzles

Heui Injection Systems

Common Rail Fuel Systems

Air Induction and Crankcase Ventilation Systems

Variable Geometry and Series Turbochargers

Exhaust Gas Recirculation

Exhaust Aftertreatment Systems

On Board Diagnostics

Filters