Free EETC Four-Stroke Engines Questions and Answers

Question 1

In a two-cylinder, four-stroke engine, how many power strokes will occur in two rotations of the crankshaft?

Accepted Answer

Two

Answer

Explanation:
In a two-cylinder, four-stroke engine, each cylinder completes one power stroke in every two rotations of the crankshaft. Since there are two cylinders, there will be two power strokes in total during two rotations of the crankshaft. This occurs because each cylinder completes its power stroke once every two revolutions of the crankshaft in a four-stroke engine cycle.

Question 2

During the intake stroke in a four-stroke engine, what are the positions of the valves?

Accepted Answer

The intake valve is open and the exhaust valve is closed

Answer

Explanation:
During the intake stroke of a four-stroke engine, the intake valve is open to allow the entry of air-fuel mixture into the cylinder from the intake manifold. Simultaneously, the exhaust valve remains closed to prevent any exhaust gases from escaping. This configuration ensures that a fresh air-fuel mixture is drawn into the cylinder for combustion during the subsequent compression stroke.

Question 3

What is used to ignite the air/fuel mixture inside the cylinder in a four-stroke engine?

Accepted Answer

A spark plug

Answer

Explanation:
In a four-stroke engine, the ignition of the air/fuel mixture inside the cylinder is achieved by a spark plug. The spark plug generates an electric spark that ignites the compressed air/fuel mixture, initiating the combustion process. This controlled ignition leads to the expansion of gases, driving the piston downwards during the power stroke.

Question 4

What causes pre-ignition in a four-stroke engine?

Accepted Answer

A hot spot in the combustion chamber

Answer

Explanation:
Pre-ignition in a four-stroke engine occurs when the air/fuel mixture ignites before the spark plug fires, often due to a hot spot in the combustion chamber. This premature ignition can lead to knocking, engine damage, and reduced performance. Identifying and addressing hot spots is crucial in preventing pre-ignition issues in four-stroke engines.

Question 5

What does a four-stroke engine primarily convert into mechanical energy?

Accepted Answer

Chemical energy to mechanical energy

Answer

Explanation:
In a four-stroke engine, the primary conversion that occurs is from chemical energy stored in the fuel into mechanical energy. This process involves the combustion of the air/fuel mixture inside the cylinder, which generates heat and pressure, leading to the movement of the piston and ultimately producing mechanical work.

EETC - Equipment & Engine Training Council Practice Test

EETC - Equipment & Engine Training Council Practice Test

Free EETC Four-Stroke Engines Questions and Answers