You’ve undoubtedly heard engines described by their cylinders: a four-cylinder, or maybe a V6 or V8. But what does it mean, and why are there different sizes?

“It depends on what you want the vehicle to do,” says Hayato Mori, manager of product planning for Honda Canada.

“You want adequate power, but you also want very good fuel economy. You could put a V6 in a Civic and you would have lots of power, but there would be a heavy penalty on the fuel side when compared to a four-cylinder.”

Cylinders are exactly as they sound: hollow cylinders bored into the engine. They contain pistons, which rapidly move up and down when the engine is running.

The pistons are attached to a heavy central shaft, called a crankshaft, and their up-and-down movement turns the crankshaft just as your legs move up and down to power a bicycle. The crankshaft’s spinning motion is what eventually turns the wheels.

In the past, an engine with more cylinders was almost always more powerful. Today, thanks to various technologies, some four-cylinder engines can make as much or even more power than some six-cylinder engines.

Four-cylinder engines have their cylinders laid out in a row. This is called an inline four, or “I-4.” Most six-cylinders and all eight-cylinders have theirs slanted down toward the crankshaft in a “V” shape, which is why they’re known as a V6 or V8.

“It comes down to space,” Mori says. An engine with four inline cylinders is small enough to fit, but putting six or eight cylinders in a line would require too much room under the hood.

In addition to their cylinders, engines are also rated in litres, such as a 3.5-litre V6. This number is its displacement, which refers to the interior volume of all of the cylinders combined. Improved engine technologies also mean that you don’t necessarily need a larger-displacement engine to produce a lot of power.

Talk about speed …

•    Pistons move several thousand times a minute. Engines contain balance shafts, hydraulic engine mounts and other technologies to help reduce the vibration.