Ever since Hyundai announced at the Los Angeles Auto Show that it would add a turbocharged variant to its all-four-cylinder lineup in the new Sonata, there has been considerable speculation about how much power the engine would produce. The first time we saw a turbocharged direct injection engine in a car from the Hyundai corporate family was the 2008 Kia Koup concept that produced 290 horsepower. This same engine now powers the Sonata to the tune of 274 horsepower and 269 pound-feet of torque.
Like GTDI engines from Ford and the Volkswagen Group this new turbo Theta II engine has a broad, flat torque curve with the peak being sustained between 1,800 and 4,500 rpm. Hyundai is using a twin-scroll turbocharger like the one used by BMW in its latest engines. The exhaust flow from the pairs of cylinders is fed into the turbine by separate paths to insure optimum response. The turbo housing is an integral casting with the exhaust manifold to provide short exhaust flows to the turbine.
Hyundai's engine uses a comparatively low 9.5:1 compression ratio compared to some other GTDI engines, but the maximum boost is 17.4 psi. The turbo engine is only offered with a six-speed automatic transmission with paddle shifters on the steering wheel.
Particularly impressive is the fuel efficiency of this combination. Hyundai is estimating 22 mpg city and 34 mpg highway – just a tick less than the non-turbo models on the highway and significantly better than any of the V6 powered competitors. The turbo engine will be available on both the SE and Limited trim levels.