内燃机照常轰鸣

    Another method is turbocharging. According to Honeywell Transportation Systems, turbochargers were in about 25% of new cars sold globally, and could end up in 40% of cars as soon as 2017. The technology itself is nearly a century old, but automakers are increasingly embracing it. A few turbocharged engines: Ford's EcoBoost, Mazda's Skyactiv, BMW's EfficientDynamics. Turbocharging uses a car's own exhaust to power a pump that forces more air into the cylinders. That compressed air can mix with more compressed fuel (hello, direct injection), resulting in more power.

    Supercharging is a more expensive, but similar option. Superchargers do essentially the same thing as turbochargers, but instead of being powered by a vehicle's exhaust, they're mechanically driven, usually by the engine's fan belt. The supercharger's advantage is that there's no need to wait for exhaust to come out for the boost to kick in. The supercharger is more commonly used for performance rather than fuel economy.

    This has been largely deemed too pricey to justify the extra power by U.S. automakers, Ford included (except for one high-performance Mustang variant). These firms have largely opted for turbochargers instead. However, some vehicles -- like the Volkswagen 1.4-liter TSI Twincharger four-cylinder engine -- have both. Volkswagen and its overseas counterparts were early pioneers of combining efficiency technologies, including diesel power, in engines for hyper-fuel conscious European customers.

    Other increasingly common tactics include, but aren't limited to, reducing friction wherever there are moving parts. And variable valve timing, which was rare a decade ago and is now almost ubiquitous. Honda (HMC) pioneered the technology, with its VTEC system, which even got its own meme. And BMW has also made strides with its Valvetronic system. In cars equipped with the system, a computer intelligently times the opening and closing of air intake and exhaust valves to match a vehicle's speed and load.

    In the future, expect big gains from variable valve timing systems becoming more precise, says Eric Fedewa, director of IHS Inc.'s global powertrain and component forecasting. Also expect more hybrid electric engines to work as a support to traditional engines. At the same time, transmissions will get more speeds, in an effort to make engines operate at their most efficient. In 10 years: "engines will necessarily be a lot smaller and probably as powerful or more powerful than they are now," Fedewa says. In the past, gains have focused on power. "You've essentially got consumers driving race car engines," Fedewa says of today's cars. In the future, gains will focus on efficiency.

    The impact of all these innovations is substantial. According to analysis by the University of Michigan Transportation Research Institute, fuel economy for light-duty vehicles has improved 18% since 2007, to 23.8 miles per gallon. Part of the credit for those gains goes to smarter engines, along with a host of other incremental improvements in vehicle efficiency. The increase isn't huge in real terms, but it's a giant leap compared with the scant 23% gain in the fuel economy of all vehicles between 1923 and 2007.

    Of course, the world is still a long way from breaking its gasoline habit, and internal combustion won't change that. There's a physical limit to how small an automaker can make an engine and have it still power a car, and we've already hit it in large and midrange vehicles, says Automotive Engineering International senior editor Lindsay Brooke, and we're close in other classes. After that, to reduce fuel consumption the country will need more public chargers for electric cars, better batteries, and maybe even a new take on internal combustion. (Several startups are working on it.) But for now, it looks like the old-fashioned engine will be with us for a long time still -- and that might not be so bad.