Engine Operating Principles: Master the 4-Stroke Cycle for Automotive Performance

Question 1

During which stroke does the piston move down, drawing in air and fuel?

Accepted Answer

Intake

Answer

Compression

Answer

Power

Answer

Exhaust

Question 2

Which of the following components is responsible for opening the intake valve during the appropriate stroke?

Accepted Answer

Camshaft

Answer

Crankshaft

Answer

Piston

Answer

Timing belt

Question 3

What is the primary purpose of the compression stroke in an engine?

Accepted Answer

To increase the pressure and temperature of the air-fuel mixture before ignition

Answer

To force the piston downward, creating power

Answer

To expel exhaust gases from the cylinder

Answer

To cool the engine components

Question 4

Which of the following events occurs during the power stroke?

Accepted Answer

Ignition of the air-fuel mixture, driving the piston down

Answer

Intake of air and fuel into the cylinder

Answer

Expulsion of exhaust gases from the cylinder

Answer

Compression of the air-fuel mixture

Question 5

What is a primary function of the piston rings?

Accepted Answer

To seal the combustion chamber, preventing leakage of gases

Answer

To lubricate moving parts within the engine

Answer

To control the timing of valve opening and closing

Answer

To cool the engine by transferring heat away from the cylinder walls

Question 6

Which type of engine utilizes a spark plug to initiate combustion of the air-fuel mixture?

Accepted Answer

Gasoline engine

Answer

Diesel engine

Answer

Rotary engine

Answer

Steam engine

Question 7

What is the main purpose of the carburetor in an engine?

Accepted Answer

To mix air and fuel in the correct proportions for combustion

Answer

To store fuel for the engine

Answer

To control the timing of valve opening and closing

Answer

To cool the engine by circulating coolant

Question 8

What is the primary function of the timing belt in an engine?

Accepted Answer

To synchronize the rotation of the camshaft and crankshaft, ensuring proper valve timing

Answer

To control the flow of fuel into the engine

Answer

To drive the oil pump, ensuring lubrication of engine components

Answer

To cool the engine by circulating coolant

Question 9

Which stroke reduces the volume of the air-fuel mixture, increasing its temperature and pressure?

Accepted Answer

Compression

Answer

Intake

Answer

Power

Answer

Exhaust

Question 10

At the top of which stroke is the piston closest to the cylinder head?

Accepted Answer

Compression

Answer

Intake

Answer

Power

Answer

Exhaust

Question 11

Which valve remains closed during the intake stroke, preventing exhaust gases from entering the cylinder?

Accepted Answer

Exhaust valve

Answer

Intake valve

Answer

Both intake and exhaust valves

Answer

Neither intake nor exhaust valve

Question 12

What is the primary function of the spark plug in an internal combustion engine?

Accepted Answer

To ignite the air-fuel mixture

Answer

To compress the air-fuel mixture

Answer

To cool the engine

Answer

To regulate fuel flow

Question 13

How does a turbocharged engine differ from a naturally aspirated engine?

Accepted Answer

Turbocharged engines use forced induction, while naturally aspirated engines do not.

Answer

Naturally aspirated engines use forced induction, while turbocharged engines do not.

Answer

Naturally aspirated engines have a higher compression ratio than turbocharged engines.

Answer

Turbocharged engines have a higher compression ratio than naturally aspirated engines.

Question 14

Which of the following is NOT typically considered an engine performance problem?

Accepted Answer

Optimal operation

Answer

Misfiring

Answer

Knocking

Answer

Excessive oil consumption

Question 15

What is the purpose of an engine diagnostic code?

Accepted Answer

To provide information about potential engine problems

Answer

To reset engine settings

Answer

To improve engine efficiency

Answer

To increase engine power

Question 16

During the power stroke of a four-stroke engine, which event occurs?

Accepted Answer

Combustion forces the piston down

Answer

Intake valve opens

Answer

Fuel-air mixture compresses

Answer

Exhaust valve closes

Question 17

During the intake stroke of the four-stroke cycle, which of the following occurs?

Accepted Answer

The piston moves down in the cylinder, drawing in the air-fuel mixture.

Answer

The piston moves up in the cylinder, compressing the air-fuel mixture.

Answer

The spark plug ignites the air-fuel mixture, causing a power stroke.

Answer

The exhaust valve opens, allowing exhaust gases to escape.

Question 18

The ratio of the volume of the combustion chamber at the top of the cylinder stroke to its volume at the bottom of the cylinder stroke is known as the:

Accepted Answer

Compression ratio

Answer

Displacement

Answer

Bore

Answer

Stroke

Question 19

The primary purpose of the camshaft in an engine is to:

Accepted Answer

Control the opening and closing of the valves

Answer

Convert reciprocating motion to rotary motion

Answer

Store fuel for the engine

Answer

Lubricate the engine's moving parts

Question 20

Which of the following is a type of internal combustion engine that primarily uses diesel fuel as its fuel source?

Accepted Answer

Diesel engine

Answer

Spark-ignition engine

Answer

Rotary engine

Answer

Gas turbine engine

Question 21

In a spark-ignition engine, the spark plug is responsible for:

Accepted Answer

Igniting the air-fuel mixture in the combustion chamber

Answer

Controlling the flow of exhaust gases

Answer

Lubricating the engine's moving parts

Answer

Converting electrical energy into mechanical energy

Question 22

The function of the timing belt in an engine is to:

Accepted Answer

Synchronize the timing of the valves and crankshaft

Answer

Transfer power from the crankshaft to the camshaft

Answer

Circulate coolant throughout the engine

Answer

Store electrical energy for the engine

Question 23

The primary function of the catalytic converter in an exhaust system is to:

Accepted Answer

Reduce harmful emissions

Answer

Increase engine power

Answer

Improve fuel efficiency

Answer

Reduce exhaust noise

Question 24

How does optimizing valve timing enhance engine power output?

Accepted Answer

It improves cylinder filling and exhaust scavenging, resulting in higher cylinder pressure and increased power.

Answer

It reduces engine friction, leading to smoother operation and improved power transfer.

Answer

It optimizes fuel injection and ignition timing, enhancing fuel efficiency.

Answer

It minimizes emissions by optimizing valve opening and closing timing.

Question 25

How does the timing of the intake valve opening affect engine efficiency?

Accepted Answer

Earlier intake valve opening improves efficiency

Answer

Later intake valve closing improves efficiency

Answer

Earlier intake valve closing improves efficiency

Answer

Intake stroke efficiency has no impact on engine efficiency

Question 26

Which of the four strokes draws the air-fuel mixture into the cylinder?

Accepted Answer

Intake stroke

Answer

Compression stroke

Answer

Power stroke

Answer

Exhaust stroke

Question 27

Which valve in the engine opens to release exhaust gases from the cylinder?

Accepted Answer

Exhaust valve

Answer

Intake valve

Answer

EGR valve

Answer

Throttle valve

Question 28

In a gasoline engine, what is the purpose of spark plugs?

Accepted Answer

To trigger the ignition of the air-fuel mixture

Answer

To regulate the fuel flow into the cylinder

Answer

To adjust the timing of ignition

Answer

To lubricate engine components

Question 29

What is the ideal air-fuel ratio for a typical gasoline engine to operate at?

Accepted Answer

14.7:1

Answer

12:1

Answer

16:1

Answer

18:1

Question 30

Which of the following engine sensors specifically measures oxygen content in the exhaust?

Accepted Answer

Oxygen sensor

Answer

Mass airflow sensor

Answer

Manifold absolute pressure sensor

Answer

Coolant temperature sensor

Question 31

What is the critical function of the camshaft in the four-stroke cycle?

Accepted Answer

To open and close engine valves

Answer

To drive the oil pump

Answer

To regulate fuel injection

Answer

To control ignition timing

Question 32

What is the primary purpose of a turbocharger in an engine?

Accepted Answer

To increase the air intake pressure

Answer

To reduce harmful exhaust emissions

Answer

To improve fuel efficiency

Answer

To cool the engine

Question 33

What is the primary purpose of the intake stroke in a four-stroke cycle engine?

Accepted Answer

To move air into the engine cylinder

Answer

To compress the air-fuel mixture

Answer

To ignite the air-fuel mixture

Answer

To remove exhaust gases from the engine cylinder

Question 34

During which stroke in a four-stroke cycle engine is the air-fuel mixture compressed?

Accepted Answer

Compression stroke

Answer

Intake stroke

Answer

Power stroke

Answer

Exhaust stroke

Question 35

Where is the spark plug typically located in a gasoline-powered four-stroke cycle engine?

Accepted Answer

In the cylinder head

Answer

In the intake manifold

Answer

In the exhaust manifold

Answer

In the piston

Question 36

What is the main function of the valves in a four-stroke cycle engine?

Accepted Answer

To control the flow of air and exhaust gases

Answer

To ignite the air-fuel mixture

Answer

To lubricate the engine components

Answer

To cool the engine

Question 37

Which engine component converts the reciprocating motion of the piston into rotational motion?

Accepted Answer

Crankshaft

Answer

Camshaft

Answer

Connecting rod

Answer

Flywheel

Question 38

What is the purpose of the timing chain or belt in a four-stroke cycle engine?

Accepted Answer

To synchronize the movement of the crankshaft and camshaft

Answer

To transfer power from the crankshaft to the wheels

Answer

To provide lubrication to the engine components

Answer

To cool the engine

Question 39

Which of the following is a common symptom of a worn timing chain or belt?

Accepted Answer

Engine knocking or rattling

Answer

Reduced fuel efficiency

Answer

Difficulty starting the engine

Answer

Increased exhaust emissions

Question 40

What is the primary function of the piston rings in a four-stroke cycle engine?

Accepted Answer

To create a seal between the piston and cylinder wall

Answer

To control the flow of air and exhaust gases

Answer

To ignite the air-fuel mixture

Answer

To lubricate the engine components

Question 41

Which of the following is a key advantage of a four-stroke cycle engine over a two-stroke cycle engine?

Accepted Answer

Higher efficiency and lower emissions

Answer

Smaller size and weight

Answer

Lower cost

Answer

Easier to maintain

Question 42

Which factors significantly influence valve timing during the four-stroke cycle?

Accepted Answer

Engine speed and load

Accepted Answer

Camshaft design and lobe profile

Answer

Intake manifold pressure and temperature

Question 43

Arrange the following events in the correct sequence for a four-stroke cycle engine:

Accepted Answer

Intake, Compression, Power, Exhaust

Answer

Intake, Exhaust, Compression, Power

Answer

Exhaust, Power, Intake, Compression

Answer

Power, Compression, Exhaust, Intake

Question 44

What is the main purpose of the intake stroke in an engine?

Accepted Answer

To draw the air-fuel mixture into the cylinder

Answer

To compress the air-fuel mixture

Answer

To remove exhaust gases from the cylinder

Answer

To generate power for the engine

Question 45

During which stroke does combustion take place in an engine?

Accepted Answer

Power stroke

Answer

Intake stroke

Answer

Compression stroke

Question 46

What is the primary function of the exhaust valve in an engine?

Accepted Answer

To release combustion gases from the cylinder

Answer

To provide lubrication for moving parts

Answer

To regulate engine speed

Answer

To control the flow of air-fuel mixture

Question 47

Which engine component is responsible for converting chemical energy in fuel into thermal energy?

Accepted Answer

Combustion chamber

Answer

Camshaft

Answer

Cylinder

Answer

Piston

Question 48

What is the main reason for engine lubrication?

Accepted Answer

To reduce friction and wear between moving parts

Answer

To cool the engine

Answer

To protect against corrosion

Answer

To improve engine power

Question 49

What is the primary function of piston rings in an engine?

Accepted Answer

To prevent combustion gases from entering the crankcase

Answer

To regulate engine speed

Answer

To lubricate the cylinder walls

Question 50

Which of the following is a type of engine valve train?

Accepted Answer

Overhead camshaft

Answer

Ignition system

Answer

Fuel injection system

Answer

Exhaust system

Question 51

What is the main purpose of the crankshaft in an engine?

Accepted Answer

To convert the reciprocating motion of the piston into rotary motion

Answer

To compress the air-fuel mixture

Answer

To control the timing of engine valves