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 (see: 2011 535i). 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.
Gallery: 2011 Hyundai Sonata Turbo
View the full article