For decades, engine size was one of the easiest ways to talk about performance. Want more power? Build a bigger engine. It sounds logical: more displacement means more air and fuel can enter the cylinders, so the engine should be able to make more power. Except it doesn't always work that way.
A modern small-displacement turbocharged engine can make substantially more horsepower than a much larger naturally aspirated engine. Even two naturally aspirated engines with the same displacement can produce very different amounts of power. The reason is that displacement tells you how much space the cylinders have, not how effectively the engine uses that space.
