AG Mechanics CDE Practice Exam

The valves open and close in a one-cylinder engine in as little as:

1. 1/10 of a second

2. 1/20 of a second

3. 1/30 of a second

4. 1/50 of a second

The correct answer is: 1/10 of a second

This is because in a one-cylinder engine, each revolution involves four strokes (intake, compression, combustion, and exhaust). The valves have to open and close twice per stroke, which means they open and close eight times per revolution. Therefore, the time it takes for the valves to open and close once is four times shorter than the time for a full revolution. This is why 1/10 of a second is the correct answer, as it is the shortest time option provided. The other options are all longer time intervals, meaning the valves would open and close slower and would not be able to keep up with the necessary changes in the engine.