Since modern engines make more power than older engines, you'd expect them to be larger. But if you look at the example of the Chevrolet Malibu we used on the previous page, you'll notice that while engine power increased, engine size decreased.
The incredibly shrinking engine in today's cars can be chalked up to improved efficiency. Car makers have learned that you don't have to make the engine bigger to get the power consumer's want. You just have to make the engine work smarter. The same technology that helps modern engines work more efficiently also means that modern engines can make more power without needing a larger package.
The best example of this is Ford F-Series trucks. Long the best selling truck (and often the bestselling vehicle, period) in America, the 2011 Ford F-150 is a textbook example of a smaller engine doing the same work as a larger one. The 2011 F-150 has an optional 3.5-liter V-6 engine that makes 365 horsepower. The available 5.0-liter V-8 makes 360 horsepower. As a rule of thumb, a bigger engine will still make more power than a smaller one. The F-150 has an available 6.2-liter V-8 that makes 411 horsepower, which pretty much blows the 3.5-liter V-6 out of the water. But, the fact that a V-6 engine can compete with a smaller V-8 in terms of power is pretty impressive. As consumers call for better fuel economy, expect to see smaller engines doing the work that was once reserved for monster V-8s.