GDI offers greater control of the fuel mixture at the optimum moment achieved by direct injection improves efficiency. The fuel is injected by a camshaft-driven, high pressure pump that operates at pressures up to 2,175 psi. Direct injection also utilizes a higher than normal 11.3:1 compression ratio for increased power. The pistons are dished to increase combustion efficiency in the cylinder.

At launch, the 2011 Sonata will deliver an estimated 23 mpg city/35 mpg highway fuel economy with the available six-speed automatic transmission with SHIFTRONIC. When equipped with the six-speed manual, the Sonata achieves an estimated 23 mpg city/34 mpg highway fuel economy rating. The preliminary horsepower and torque ratings for the Theta II GDI are 198 hp (148 kW) and 184 lb-ft (250 N·m) of torque. In the SE trim which includes a standard dual exhaust, the engine delivers 200 hp (149 kW).

This high-tech, all-aluminum, 16-valve engine features Continuously Variable Valve Timing (CVVT) on both camshafts and a Variable Induction System (VIS) for better engine breathing. A version of this engine also meets Partial Zero Emission Vehicle (PZEV) standards.

New transmission. Hyundai’s all-new six-speed automatic A6MF2 transaxle helps the company meet its goals of improving fuel efficiency and reducing emissions. An option of manual control is available through the SHIFTRONIC feature, accessible by moving the gear selector into a separate gate. Pushing the selector forward or pulling it rearward will shift the transmission up or down sequentially, adding to driver control. The SE trim will also feature steering wheel-mounted paddle shifters. A clear LCD readout on the instrument panel shows the gear being used.

Designed for transverse engine applications in passenger cars and SUVs, the new compact transmission puts Hyundai into a class of auto manufacturers who have designed their own proprietary six-speed automatic transmissions. The strength of the design is its unique layout which makes it smaller, more compact and lighter than other six-speed transmissions on the market today.

In this application, the six-speed helps brings a 9% gain in fuel economy (35 mpg versus 32 mpg). The gearbox has no dipstick because it is filled with automatic transmission fluid that is good for the life of the vehicle under normal usage conditions, thereby reducing maintenance costs.

Developed over a four-year period, this new six-speed automatic is 26.4 pounds lighter than the five-speed it replaces. It also is 1.6 inches shorter and considerably simpler, having 62 fewer parts, which is a key to increased durability, lighter weight and lower cost.

The addition of a sixth gear enables closer spacing between gear ratios providing a better balance of performance and fuel economy while the wide overall gear ratio helps deliver strong acceleration.

The gearbox has three planetary gearsets and a unique flat torque converter that shortens the unit’s overall length by 0.47 inches. Four pinion differentials improve durability and further minimize size.

Slight manufacturing deviations from one solenoid valve to the next often times cause fluctuation in the hydraulic pressure and affect shift precision and quality. The transmission featured in the Sonata integrates adjustment screws in the valves that enable each of the eight valves to be calibrated at the factory. This feature ensures stable hydraulic pressure at any shift point which facilitates a high degree of precision and control needed to deliver fast, smooth and precise shifts throughout the rpm range.

Sonata is rich in ultra-high-strength steel, leading to world-class body rigidity. The 2011 Sonata is 25% stiffer in torsion and 19% stiffer in bending rigidity than its predecessor, yet it is lighter than many midsize sedans, also offering more interior room.