A car is a complicated piece of machinery with a simple purpose: motion. At its heart, all that motion is driven by a series of explosions inside the engine’s cylinders. But how do the cylinder dimensions help determine a car’s power?

In this lesson students calculate the total volume of the cylinders in different engines and relate volume to horsepower. They also examine how modifying an engine can affect its performance.

### Students will

• Given an engine cylinder’s bore (width) and stroke (height), calculate the volume of a single cylinder
• Calculate the total displacement of engines in different vehicles
• Examine the relationship between engine displacement and horsepower
• Determine which would have a larger effect on power, a change in bore or an equivalent change in stroke
• Find different combinations of bore/stroke modifications that would lead to the same increase in power
• Discuss the practical limitations of engine modification and limits on power production

### Before you begin

Students should be able to calculate a cylinder’s volume given its diameter and height. The should also be familiar with unit rates, e.g. the meaning of a phrase such as, “15 cubic centimeters per horsepower.”