Hyundai's corporate work ethic and frugality have resulted in a strong emphasis on developing and manufacturing key components in-house. By avoiding the hybrid technology used in the Sonata Hybrid's chief competitors-the Ford Fusion, the Nissan Altima, and the Toyota Camry-the company has smartly dodged the licensing fees of patented technology and tapped existing hardware for its first gasoline/electric car.
The homebrew hybrid
Primary propulsion for the hybrid Sonata comes from a 2.4-liter four-cylinder that's now running the Atkinson cycle and is tuned for fuel economy, resulting in a 169-hp output. Assistance is provided by a 40-hp electric motor mounted in place of the torque converter inside Hyundai's six-speed automatic transmission. At 209 hp and 195 lb-ft of torque, total output is slightly higher than the base Sonata's. In electric-only operation, a clutch between the engine and the motor disconnects the two power sources to eliminate the drag of the engine's spinning internals. A second, smaller electric motor restarts the engine from red lights or in stop-and-go traffic.
Hyundai uses the electric motor, in lieu of a torque converter, to dampen shift shock, an arrangement that works quite well. The Sonata climbs through its six gears seamlessly, with reasonable speed. On kickdown, though, gear changes feel slower the harder you squeeze the throttle. Off the line, the low-end torque of the electric motor transitions linearly to the engine's high-rpm thrust. When pushed, the Sonata Hybrid feels quicker than the factory's reported 0-to-62-mph run of 9.2 seconds.
Hyundai claims a top electric speed of 62 mph, but getting there under electric power alone from a stop is impossible. Our technique for maximum efficiency is to use the gas engine to accelerate up to city or suburban speeds and then massage the throttle to coax the car into electric mode. City fuel economy, at 37 mpg, falls 4 mpg short of the Fusion Hybrid's. But, at an estimated 40 mpg on the highway, the Sonata will claim the best EPA highway mileage among its hybrid mid-size sedan competitors.