Question 1

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

Blue exhaust smoke is typically associated with oil burning in the engine, not with the condition described, which is more related to fuel and air mixture issues.

Question 2

Exhaust gas energy would normally vent directly to the atmosphere. Instead, which of the following can recover some of that energy to improve engine efficiency?

Accepted Answer

Turbochargers recover energy from exhaust gases to improve engine efficiency by using it to drive a turbine that compresses the intake air, increasing engine power output.

Question 3

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?

Accepted Answer

A supercharger is driven by the engine's crankshaft, not exhaust gases. Technician B is correct about the limit of air intake affecting power.

Question 4

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

Accepted Answer

A turbocharger can supply air to the combustion chambers at pressures above the standard atmospheric pressure, which is 14.7 psi.

Question 5

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

Accepted Answer

The answer of Why is a barometric pressure sensor used...

Question 6

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

Both technicians are correct. Turbocharging increases cylinder pressure, which reduces emissions of nitrogen oxides (NOx). It also provides more air to the cylinders, which helps to burn fuel more completely, reducing emissions of particulate matter (PM) and hydrocarbons (HC).

Question 7

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?

Accepted Answer

Turbochargers are used to increase the power output of diesel engines by forcing more air into the combustion chamber, which allows for more fuel to be burned. This can lead to improved power output without increasing engine size and displacement. Additionally, turbochargers can enhance engine efficiency by improving the engine's ability to burn fuel more completely.

Question 8

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

Accepted Answer

A restricted, undersized, or otherwise damaged exhaust system can cause a loss of power under load at high speed.

Question 9

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

Accepted Answer

The answer of Which of the following features is characteristic...

Question 10

What causes the pressure to drive the turbine wheel of the turbocharger?

Accepted Answer

The energy of unexpanded exhaust gas drives the turbine wheel of the turbocharger by utilizing the kinetic energy from the exhaust gases.

Question 11

Which of the following can prevent exhaust gas from expanding?

Accepted Answer

Narrow exhaust manifold runners can restrict the flow of exhaust gases, preventing them from expanding as they exit the engine.

Question 12

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

Accepted Answer

Black smoke can occur when there is inadequate air for combustion during turbo lag, leading to incomplete combustion and excess fuel being burned.

Question 13

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

The answer of Technician A says that turbocharger lag is...

Question 14

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

Accepted Answer

Fixed-geometry turbochargers typically have low air-fuel ratios at low speeds, not high, which is why option D is not a disadvantage.

Question 15

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:

Accepted Answer

Turbochargers are designed to minimize turbocharger lag, which is the delay between the demand for power and the turbocharger's ability to provide it, especially at lower engine speeds.

Question 16

Smaller displacement engines will not need to turn as fast to produce what is known as:

Accepted Answer

Power density refers to the amount of power produced per unit of engine displacement. Smaller displacement engines can achieve high power density by producing more power without needing to turn as fast.

Question 17

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

Turbine speeds should be greatest at peak horsepower to achieve maximum engine output, as this is when the engine requires the most air and fuel to produce the highest power.

Question 18

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

Technician A is correct because installing a new compressor wheel in a turbocharger requires balancing to ensure proper operation and prevent damage.

Question 19

The inlet to the turbine is located on the outside radius of the turbine housing and attaches to the:

Accepted Answer

The inlet to the turbine is connected to the exhaust manifold, which directs exhaust gases from the engine to the turbine, causing it to spin and drive the compressor.

Question 20

What is shaped like the turbine housing but with the opposite direction of gas flow?

Accepted Answer

The compressor housing in a turbocharger is shaped similarly to the turbine housing but directs air in the opposite direction, compressing it before it enters the engine.

Quiz 15: Fixed Geometry and Wastegated Turbochargers