When the swoopy new 2011 Sonata goes into production at Hyundai's plant in Alabama early next year, it won't offer a V6 engine anymore, but it will get the company's first ever direct-injected engine. This week in South Korea, Hyundai took the wraps off its 2.4-liter Theta II GDI four-cylinder. Like similar engines from other automakers, Hyundai's engineers have taken advantage of the charge cooling effect of direct injection by boosting the compression ratio to 11.3:1. As a result the engine produces 198 hp and 184 pound-feet of torque at 4,250 rpm in Korean spec.
The direct injection system is setup to use a two-pulse strategy similar to modern common rail diesels. The initial smaller pulse is ignited by the spark plug and then followed by a second larger pulse as the piston begins its downward stroke. GM uses a similar strategy for its 2.4-liter DI Ecotec because it helps warm the engine faster, heating the catalytic converter and reducing emissions. The GDI Theta II produces from 7-12 percent more torque across its rev range than the port-injected version of the same engine. Efficiency should also improve by about 10 percent although the final certification figures aren't complete yet. The Theta II also gets continuously variable valve timing on both camshafts to round out its high tech upgrades. In addition to the regular Sonata sedan, this engine will likely also be used for the new Sonata hybrid when it debuts late in 2010.