Optima Hybrid (Republic of Korea, 2011)

Kia’s Optima Hybrid made its world debut at the 2010 Los Angeles Auto Show. The hybrid version of the sedan was developed for the US market. The model is powered by a Kia-developed powertrain that promises to deliver performance at 48 mpg fuel efficiency.

The Optima Hybrid arrives to US Kia dealer showrooms in early 2011 and is the brand's first-ever hybrid for North America. The hybrid version uses a ‘full parallel hybrid system', which combines performance, being able to reach a top speed of 195 km/h and improving 40.7% on fuel economy when compared to a regular Optima.

The powertrain technology featured in the Optima Hybrid is a simple and cost-effective ‘parallel hybrid system'. The 2.4-litre petrol engine is combined with a small electric motor and drives the front wheels via a six-speed automatic transmission, leaving behind the traditional torque converter. A special clutch has been placed between the engine and motor, enabling the petrol engine to be de-coupled from the powertrain so that Optima can be operated in zero-tailpipe-emissions, full-electric drive mode from standstill up to 100 km/h. Thanks to its’ configuration, the system does not require a high-capacity electric motor and generator.

When starting, the Optima Hybrid operates in Electric Mode. With the vehicle speed raising the Hybrid Starter motor/Generator (HSG) starts the petrol engine and the clutch is closed, allowing the engine to take over the task of propelling the car. Switching into hybrid operation, the electric motor is used as secondary engine (during full acceleration and hill-climbing) and a generator to recharge the battery pack as necessary. The petrol engine shuts off automatically whenever the car comes to a stop for more than a few seconds, completely eliminating tailpipe emissions. When braking, the electric motor converts kinetic energy into electricity for storage in the battery pack. The 8.5 kW HSG also functions as a generator to re-charge the battery pack if the state of charge is low and when the car is stationary.

Kia's Optima Hybrid features a lithium polymer battery array which has been developed in partnership with LG Chem. Lithium polymer offers the benefits of lithium-ion (used in laptops and cell phones), but adds robustness and packaging flexibility, making it ideal for automotive applications. These new batteries offer a better balance between power delivery, energy density and thermal stability. The 2.4-litre Theta II engine has been modified for this hybrid version in order to operate on an Atkinson cycle, raising the compression ratio by 20%, and to maximize its efficiency. The result a 10% fuel saving, compared to a regular Theta engine.

Finally, in order to maximize the Optima Hybrid's performance and minimize its fuel consumption, engineers paid special attention to the aerodynamics. The Optima Hybrid has been lowered by 5 mm and features a new ‘active air flap' in the front grille, smooth underfloor panels, low-drag wheels and low rolling resistance tyres. The drag coefficient in the Optima Hybrid has been lowered to Cd 0.26.