The 2011 Sonata now on sale, with its direct-injection 2-liter four, is already the market's roomiest and most fuel-efficient conventional midsize sedan. Later this year, two new Sonatas, the turbo and Hybrid, will deliver a potent encore. Let's start with the Sonata 2.0T. Like other turbos, the engine uses exhaust gases to spin a turbine, which pumps compressed air into cylinders to boost power. But the Hyundai's twin-scroll turbocharger—typically found on pricier sportscars—directs exhaust to the turbine via two pathways instead of one. This creates steadier pulses of exhaust gas and reduces "turbo lag," the delay between punching the gas and the rush of acceleration. The 2-liter turbo promises to deliver 274 horsepower, more than the Honda Accord's 3.5-liter V6, to achieve 22 mpg city and 34 mpg highway while using 20 percent less gas.