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Editors' note: Portions of this review were taken from our evaluation of the, since the two vehicles are very similar.
Kia reuses the 2.4-liter engine block from the standard Optima in its hybrid, but makes a few changes to the head. Gone is the direct-injection system; it's been replaced with a more traditional port-injection setup and a change to the Atkinson combustion cycle. We, at first, scoffed at this perceived aspirational downgrade, but Kia's engineers tell us that when combined with the electric motor, the Atkinson cycle proved to be as efficient as the direct-injection setup, and was also less expensive for the consumer--and Kia's all about making things less expensive.
Working in tandem with the gasoline engine is Kia's hybrid electrification system, a doughnut-shaped electric motor and generator that sits between the engine and the six-speed automatic transmission. The engine, motor, and gearbox are all connected with a wet clutch, which ideally is more efficient than the more common automatic transmission torque converter.
The motor is able to accelerate the vehicle from a stop under pure electric energy--and usually does so up to about 18 mph to 20 mph. Once up to speed, the motor can also provide electric assist, boosting the power of the gasoline engine, or allow the vehicle to cruise for periods in EV mode. We were surprised to look down at the instrument cluster and see the Optima occasionally illuminate the EV mode light at upward of 70 mph (on a slight downgrade, of course) despite the fact that Kia's materials state an EV cap of 62 mph.
Of course, when it's not motivating the vehicle, the motor can also act as a generator, sending power back to the battery pack through regenerative braking. There was an obvious difference between the regenerative braking and when the conventional brakes activated, which led to some pretty inconsistent stopping distances during our testing. At low speeds, such as during parallel parking, the brakes were grabby and difficult to modulate. At higher speeds--for example, while rolling to a stop at a traffic light--the brakes didn't shave off speed as quickly as we felt they should, leading to a few hair-raising close calls. Stabbing the brakes for an emergency stop always produced immediate and sharp deceleration, so perhaps the regen blend just takes more getting used to.
Power comes from a 95-pound lithium polymer battery pack that sits just aft of the rear seats at the front of the trunk. This pack is some 30 percent to 40 percent lighter than the battery pack in other automakers' first- and second-generation hybrids. The 270-volt battery holds about 1.4 kWh of energy and features its own active cooling system that draws air through the battery pack and out of the vehicle.
The Hybrid also has a few other green tricks up its sleeve. For example, an active shutter behind the grille shuts at about 35 mph, redirecting air underneath the car, limiting the amount of air slamming into the radiator at high speed, and reducing drag. Beneath the vehicle is an air shroud that helps that redirected air to pass quickly and smoothly. The flush wheels are designed to reduce turbulence and wind resistance and are shod with low rolling-resistance tires. All in, Kia was able to lower the Optima Hybrid's drag coefficient to a slippery 0.26. For comparison, the 2010 Prius hangs out at a slightly slipperier 0.25 and the average sedan in the Optima's class runs about 0.30 to 0.35.
Kia also gives us a variety of dashboard systems to help drivers maximize their fuel economy. Primarily, this consists of a default active Eco mode that further optimizes the vehicle's performance, throttle mapping, and electric assist for increased fuel economy. This system can be deactivated with a steering wheel button. In the place where the vehicle's tachometer once lived, you'll now find a temperature gauge, a battery charge gauge, and a sort of efficiency meter that shows how thriftily you're driving on a scale of green to red. There are also a few hybrid monitoring displays in a new color LCD that sits at the center of the instrument cluster.