FAA Powerplant Written Practice Test

In a 4-stroke engine, how many distinct strokes are there?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 4

In a 4-stroke engine, there are indeed four distinct strokes that make up one complete cycle of operation: intake, compression, power, and exhaust. During the intake stroke, the piston moves down the cylinder, creating a vacuum that draws in the air-fuel mixture. In the compression stroke, the piston moves back up the cylinder, compressing the mixture, which is essential for achieving higher efficiency and power output. The power stroke occurs when the compressed mixture is ignited, forcing the piston down again and producing work. Finally, during the exhaust stroke, the piston moves back up, expelling the combustion gases from the cylinder. This sequential process of four strokes is what characterizes the operation of a 4-stroke engine, differentiating it from 2-stroke engines, which complete their cycle in just two strokes. Understanding these distinct phases is crucial in analyzing engine performance and efficiency.