Question 1

Technician A says that technological developments now enable the injection of gasoline directly into the combustion chamber of spark-ignited gasoline engines. Technician B says that gasoline direct-injection (GDI) engines inject gasoline near the beginning of the compression stroke. Who is right?

Accepted Answer

The answer of Technician A says that technological developments now...

Question 2

There are _____ basic combustion chamber diesel engine designs but numerous variations on both.

Accepted Answer

There are two basic combustion chamber designs for diesel engines: direct injection and indirect injection.

Question 3

Which one of the following is NOT a reason for the IDI chamber being the most popular design in automotive applications in the early 1990s?

Accepted Answer

The IDI (Indirect Injection) chamber was not known for greater fuel efficiency; in fact, it was less fuel-efficient compared to direct injection systems. The other options were reasons for its popularity.

Question 4

DI chambers generally require no:

Accepted Answer

DI (Direct Injection) chambers generally do not require starting aids because they are designed to efficiently inject fuel directly into the combustion chamber, allowing for reliable starting without additional assistance.

Question 5

Technician A says that without adequate turbulence, air and fuel will not mix, resulting in lost performance and efficiency and in increased emissions. Technician B says that the semi-toroidal shape of the DI chamber is designed to mix the air and fuel. Who is right?

Accepted Answer

Adequate turbulence is necessary for proper air-fuel mixing, which affects performance, efficiency, and emissions. The semi-toroidal shape of the DI chamber is indeed designed to enhance this mixing.

Question 6

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 larger amount of fuel being injected before ignition, causing a rapid pressure rise and resulting in engine knocking.

Question 7

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

Accepted Answer

Ignition delay is the time lag between the start of fuel injection and the start of combustion in an engine.

Question 8

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 supply excess air to ensure complete combustion of the fuel.

Question 9

Identify the points on the PV (pressure volume) graph between which uncontrolled burn period occurs.

Accepted Answer

The uncontrolled burn period in a PV graph typically occurs between points B and C, where the pressure rises rapidly due to the combustion process in an internal combustion engine.

Question 10

Technician A says that injection quantities of fuel in a diesel engine at idle are very large. Technician B says that the cooling effect of excess air and prolonged idle has detrimental effects on the engine. Who is right?

Accepted Answer

Technician B is correct because prolonged idling in diesel engines can lead to cooling effects from excess air, which can cause issues like incomplete combustion and carbon buildup. Technician A is incorrect because injection quantities at idle are typically small, not large.

Question 11

Technician A says that small quantities of diesel fuel are adequate to create enough cylinder pressure to rotate the crankshaft but produce very little heat. Technician B says that less air in diesels dilutes the heat of combustion and lowers average cylinder temperatures. Who is right?

Accepted Answer

The answer of Technician A says that small quantities of...

Question 12

Which of these causes more heat retention by the engine around the exhaust ports, thus transferring more heat to the cooling system?

Accepted Answer

Exhaust backpressure can cause more heat retention by the engine around the exhaust ports, leading to increased heat transfer to the cooling system.

Question 13

What creates low exhaust temperatures and low cylinder temperatures, which have adverse consequences on engine life and operation?

Accepted Answer

Excess air in the combustion process leads to lower exhaust and cylinder temperatures because the additional air absorbs heat, reducing the overall temperature. This can adversely affect engine efficiency and longevity.

Question 14

Two technicians are discussing combustion slobber. Technician A says that low piston temperatures also mean the piston has not fully expanded and will easily allow lube oil into the combustion chamber. Technician B says that the black gooey liquid that leaks from exhaust manifold joints and the exhaust pipes when engines are excessively idled is called sludge. Who is right?

Accepted Answer

Low piston temperatures can prevent the piston from fully expanding, which may allow lube oil to enter the combustion chamber. Technician B is incorrect because the black gooey liquid is typically referred to as "combustion slobber," not sludge.

Question 15

The IDI combustion system uses fuel injected into a smaller, spherical, highly turbulent chamber that is connected to a main chamber through a narrow passageway called a(n):

Accepted Answer

The answer of The IDI combustion system uses fuel injected...

Question 16

Which of the following is NOT a major characteristic of the IDI chamber?

Accepted Answer

The IDI chamber does not use a Mexican hat piston.

Question 17

What happens to the coarse fuel droplets when fuel initially contacts the incandescent glow plug during start-up and then on the hot walls of the pre-chamber during regular operation?

Accepted Answer

They vaporize when fuel initially contacts the incandescent glow plug during start-up and then on the hot walls of the pre-chamber during regular operation.

Question 18

IDIs are capable of a faster top engine rpm limit due to a higher degree of _____ to produce more rapid and even mixing of air and fuel.

Accepted Answer

IDIs (Indirect Injection engines) have a pre-combustion chamber that creates more turbulence, allowing for better mixing of air and fuel, which supports a faster top engine rpm limit.

Question 19

Once the engine is operational, the controller will cycle the plugs on and off during the ________ period.

Accepted Answer

The "afterglow" period refers to the time after the engine starts when the controller cycles the plugs on and off to maintain optimal combustion and emissions.

Question 20

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

Accepted Answer

Indirect injection engines have a pre-combustion chamber that allows for faster heat transfer to the coolant, leading to quicker warm-up times.

Quiz 2: Introduction to Diesel Engines