Question 1

Technician A says the evaporation of diesel fuel from the tank of a diesel bus on a warm day produces more emissions than a car. Technician B says that diesel fuel does not produce a significant amount of emissions due to fuel evaporation. Who is correct?

Accepted Answer

Diesel fuel has a much lower volatility compared to gasoline, meaning it does not evaporate as easily. Therefore, it does not produce significant emissions from evaporation.

Question 2

Which diesel engine combustion chamber design will produce the fastest coolant warm-up times?

Accepted Answer

C

Question 3

Technician A says that a diesel engine's higher compression ratio helps it to produce more power and use less fuel. Technician B says that higher compression ratios only help the diesel engine produce more torque. Who is correct?

Accepted Answer

A

Question 4

Technician A says that high horsepower (kilowatts) is the most important attribute that an engine needs to pull heavy loads and accelerate quickly. Technician B says that high torque output is the most important attribute that an engine needs to quickly climb hills. Who is correct?

Accepted Answer

Torque is the measure of rotational force and is crucial for tasks requiring pulling power and climbing, as it determines the engine's ability to move heavy loads at lower speeds.

Question 5

Technician A says increasing an engine's compression ratio will produce better fuel economy but less power output. Technician B says increasing an engine's compression ratio produces more power but increases fuel consumption. Who is correct?

Accepted Answer

Increasing an engine's compression ratio generally improves both power output and fuel economy, as it allows the engine to extract more energy from the fuel.

Question 6

Technician A says that diesel engines can produce more power because air and fuel are not mixed during the intake stroke. Technician B says that diesel engines produce more power because they use excess air to burn fuel. Who is correct?

Accepted Answer

The answer of Technician A says that diesel engines can...

Question 7

At which of the following compression ratios does the efficiency of an engine begin to diminish with increasing compression?

Accepted Answer

At a compression ratio of around 23:1, the efficiency gains from increasing compression begin to diminish due to factors like increased heat loss and the onset of engine knocking.

Question 8

How many valves will most likely be used by a centrally located fuel injector?

Accepted Answer

A centrally located fuel injector is typically used in engines with four valves per cylinder, as this configuration allows for better air-fuel mixture and efficient combustion.

Question 9

Which one of the following conditions will be produced by prolonged ignition delay in a diesel engine?

Accepted Answer

Prolonged ignition delay in a diesel engine leads to a rapid and uncontrolled combustion of accumulated fuel, causing an engine knocking sound.

Question 10

Which combustion chamber design produces the best fuel economy in a diesel engine?

Accepted Answer

Direct injection in diesel engines is more efficient as it allows for better fuel atomization and combustion, leading to improved fuel economy compared to other designs.

Question 11

Which of the following best describes the term "ignition delay"?

Accepted Answer

The ignition delay is the time lag from initial injection to actual ignition.

Question 12

Which type of fuel nozzle is used in a direct-injection combustion chamber?

Accepted Answer

Multi-orifice nozzles are used in direct-injection combustion chambers because they provide a more uniform spray pattern and better fuel atomization, which results in improved combustion efficiency and reduced emissions.

Question 13

Technician A says that diesel engines inject fuel into the cylinder during the intake stroke. Technician B says that diesel engines inject fuel into the cylinder near the end of the compression stroke. Who is correct?

Accepted Answer

Diesel engines inject fuel into the cylinder near the end of the compression stroke to create high pressure and temperature for ignition.

Question 14

Technician A says that diesel engines supply only enough air to completely burn all the fuel in the combustion chamber. Technician B says that diesel engines supply excess air to the combustion chamber to completely burn all the fuel in the combustion chamber. Who is correct?

Accepted Answer

Diesel engines typically operate with excess air to ensure complete combustion of the fuel, which is why Technician B is correct.

Question 15

Technician A says a power stroke in a modern diesel engine uses only a single injection of fuel. Technician B says late-model diesel engines use multiple injection events during a combustion cycle. Who is correct?

Accepted Answer

Technician B is correct. Modern diesel engines often use multiple injection events during a combustion cycle to improve efficiency, reduce emissions, and enhance performance.

Question 16

Technician A says that most diesel engines used today have direct-injection combustion chambers. Technician B says that most diesel engines built today use multi-orifice spray nozzles. Who is correct?

Accepted Answer

Most modern diesel engines use direct-injection combustion chambers and multi-orifice spray nozzles for efficient fuel delivery and combustion.

Question 17

Technician A says that a knocking sound in a diesel is normal and is caused by a sharp rise in cylinder pressure. Technician B says that a knocking sound in a diesel is caused by ignition delay of fuel. Who is correct?

Accepted Answer

Both technicians are correct. The knocking sound in a diesel engine is normal and is caused by a sharp rise in cylinder pressure due to the ignition delay of fuel.

Question 18

Which diesel engine combustion chamber design will produce the fastest coolant warm-up times?

Accepted Answer

Indirect injection engines typically have faster coolant warm-up times due to their design, which includes a pre-combustion chamber that allows for more rapid heat transfer to the coolant.

Question 19

Which of the following diesel engine combustion chambers requires a glow plug to start?

Accepted Answer

Indirect injection diesel engines typically require glow plugs to preheat the air in the combustion chamber for easier starting, especially in cold conditions.

Question 20

Which combustion chamber design has traditionally operated with the least amount of noise?

Accepted Answer

Indirect injection engines typically operate with less noise because the combustion process is more controlled and gradual compared to direct injection systems.

Quiz 2: Introduction to Diesel Engines

Technician A says the evaporation of diesel fuel from the tank of a diesel bus on a warm day produces more emissions than a car. Technician B says that diesel fuel does not produce a significant amount of emissions due to fuel evaporation. Who is correct?

Which diesel engine combustion chamber design will produce the fastest coolant warm-up times?

Technician A says that a diesel engine's higher compression ratio helps it to produce more power and use less fuel. Technician B says that higher compression ratios only help the diesel engine produce more torque. Who is correct?

Technician A says that high horsepower (kilowatts) is the most important attribute that an engine needs to pull heavy loads and accelerate quickly. Technician B says that high torque output is the most important attribute that an engine needs to quickly climb hills. Who is correct?

Technician A says increasing an engine's compression ratio will produce better fuel economy but less power output. Technician B says increasing an engine's compression ratio produces more power but increases fuel consumption. Who is correct?

Technician A says that diesel engines can produce more power because air and fuel are not mixed during the intake stroke. Technician B says that diesel engines produce more power because they use excess air to burn fuel. Who is correct?

At which of the following compression ratios does the efficiency of an engine begin to diminish with increasing compression?

How many valves will most likely be used by a centrally located fuel injector?

Which one of the following conditions will be produced by prolonged ignition delay in a diesel engine?

Which combustion chamber design produces the best fuel economy in a diesel engine?

Which of the following best describes the term "ignition delay"?

Which type of fuel nozzle is used in a direct-injection combustion chamber?

Technician A says that diesel engines inject fuel into the cylinder during the intake stroke. Technician B says that diesel engines inject fuel into the cylinder near the end of the compression stroke. Who is correct?

Technician A says that diesel engines supply only enough air to completely burn all the fuel in the combustion chamber. Technician B says that diesel engines supply excess air to the combustion chamber to completely burn all the fuel in the combustion chamber. Who is correct?

Technician A says a power stroke in a modern diesel engine uses only a single injection of fuel. Technician B says late-model diesel engines use multiple injection events during a combustion cycle. Who is correct?

Technician A says that most diesel engines used today have direct-injection combustion chambers. Technician B says that most diesel engines built today use multi-orifice spray nozzles. Who is correct?

Technician A says that a knocking sound in a diesel is normal and is caused by a sharp rise in cylinder pressure. Technician B says that a knocking sound in a diesel is caused by ignition delay of fuel. Who is correct?

Which diesel engine combustion chamber design will produce the fastest coolant warm-up times?

Which of the following diesel engine combustion chambers requires a glow plug to start?

Which combustion chamber design has traditionally operated with the least amount of noise?