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Kia Motors Corporation today held the
world premiere of its all-new Optima Hybrid sedan at the Los Angeles
Auto Show. Created primarily with the US market in mind, the latest
model in Kia’s design-led transformation employs a truly innovative
Kia-developed powertrain that promises to deliver exceptional hybrid
performance and 48 mpg class-leading fuel efficiency.
Arriving in US Kia dealer showrooms early
next year, the Optima Hybrid is the brand’s first-ever hybrid for North
America and uses a ‘full parallel hybrid system’ to deliver a unique
blend of performance – acceleration to 62 mph in 9.2 seconds, top speed
121 mph – and economy, achieving a 40.7% mpg improvement compared with
a regular Optima. |
“Kia Motors is proud to unveil its
first-ever hybrid for the North American market,” comments Hyoung-Keun
Lee, Vice Chairman of Kia Motors Corporation. “The new Optima Hybrid
features a unique architecture and is packed with innovative
technologies that demonstrate Kia’s on-going commitment to investing in
R&D, and to developing environmentally friendly vehicles for the future.
“Although these new technologies
presented our engineers with a series of complex challenges to overcome,
the resulting Optima Hybrid delivers a fully automatic, seamless and
enjoyable drive, together with real-world benefits for our customers,”
adds Mr. Lee.
The Kia Optima Hybrid is equipped with
an ingenious, simple and cost-effective ‘parallel hybrid system’. The
2.4-litre petrol engine is mated to a small electric motor and drives
the front wheels via a six-speed automatic transmission – without the
traditional torque converter. A special clutch is fitted 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 62 mph. The system’s
configuration does not require a high-capacity electric motor and
generator, saving weight and cost.
Automatic, seamless daily
driving experience
When
setting off the Optima Hybrid operates in Electric Mode. As vehicle
speed rises, 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. The electric motor switches into hybrid
operation and serves as both a secondary engine (during full
acceleration and hill-climbing) and a generator to recharge the battery
pack as necessary. Whenever the car comes to a stop for more than a few
seconds, the petrol engine automatically shuts off to completely
eliminate 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. Throughout the entire driving experience, under all
conditions, the entire hybrid operation is automatic and seamless.
An unusually responsive and rewarding
drive is guaranteed by the Optima Hybrid’s 30kW Interior Permanent
Magnet (IPM) synchronous electric motor, which produces 40.7 ps and 205
Nm of torque from 0-to-1,400 rpm in electric mode, and the combined
(electric motor plus petrol engine) hybrid powertrain output of 209 ps
and 265 Nm.
Described by Kia engineers as a
Transmission-Mounted-Electric-Drive (TMED), the 30kW IPM electric motor
sits within the car’s extended transmission casing (between the petrol
engine and the automatic gearbox) and is the world’s first oil-cooled
system.
Kia’s Optima Hybrid employs a lithium
polymer battery array 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 provide an optimum
balance between power delivery, energy density and thermal stability.
Compared with nickel-metal hydride
batteries, lithium polymer batteries weigh 20-to-30% less, occupy 40%
less volume and are 10% more efficient. They also hold their charge for
25% longer than nickel metal hydride batteries and are so reliable that
the Optima’s battery pack will not require replacing during the
vehicle’s lifespan – at least 10 years and 150,000 miles.
The power and energy density of this
new type of battery enabled Kia engineers to create a lighter more
compact power pack – with a 34 kW output and weighing just 43.6 kg –
designed to minimize intrusion of the Optima’s boot space.
The complete hybrid system is
controlled by the Optima’s Hybrid Control Unit (HCU) which acts as the
car’s mastermind and integrates the smooth operation of the engine’s
ECU, transmission’s TCU, battery management system (BMS), low voltage
converter (LDC). This brain also gives the Optima a ‘Fail-Safe’ back-up
capability and a ‘Limp-home’ mode.
Optimizing the Theta II petrol
engine
Taking
advantage of the instant and continuously available torque from the
electric motor, Kia modified its popular 2.4-litre Theta II engine to
operate on an Atkinson cycle, raising the compression ratio by 20% to
maximize its efficiency and achieving a 10% fuel saving over a regular
Theta engine. This cycle generates a little less torque, but the
electric motor compensates for any loss and consequently, the Optima
Hybrid’s overall power and torque outputs are greater than the regular
model.
For the Optima Hybrid, Kia has modified
the six-speed automatic transmission found on the conventional Optima
for hybrid application. The traditional torque converter is replaced
with an electric motor and a high-efficiency oil pump. This new gearbox
allows EV mode operation, maximizes regeneration of kinetic energy
during braking and also provides a more responsive drive than a CVT
system.
To maximize the Optima Hybrid’s
performance and minimize its fuel consumption, special attention has
been paid to its aerodynamics. The car is lowered by 5 mm and new
features include an ‘active air flap’ in the front grille, smooth
underfloor panels, low-drag wheels and low rolling resistance tyres.
The drag coefficient is lowered to a remarkable Cd 0.26.
Energy and fuel-saving technologies
features in the Optima Hybrid include a regenerative braking system,
electric – rather than hydraulic – assisted power steering, and an
electric air compressor capable of delivering high air-conditioning
performance.
Two independent liquid cooling systems
are fitted to the Optima Hybrid powertrain. The standard
high-temperature circuit manages engine cooling and passenger
compartment heating. The second low-temperature circuit cools the
hybrid starter-generator and the power electronics. The boot-mounted
battery pack does not require liquid cooling and its temperature is
controlled by a simple ventilation fan beneath the rear parcel shelf.
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