Kia Motors has unveiled its all-new Optima Hybrid sedan at the Los Angeles Show, a vehicle created primarily with the US market in mind.
The model employs a Kia-developed powertrain to deliver hybrid performance and 48mpg fuel efficiency.
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Arriving in US Kia dealer showrooms early next year, the Optima is the brand’s first-ever hybrid for North America and uses a ‘full parallel hybrid system’ to deliver acceleration to 62mph in 9.2sec, a top speed of 121mph – and 40.7% improvement in fuel economy compared to the standard Optima.
The hybrid’s 2.4L petrol engine is mated to a small electric motor and drives the front wheels via a six-speed automatic transmission – without a 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 the car can be operated with zero-tailpipe-emissions, full-electric drive mode from standstill up to 62mph. The system’s configuration does not require a high-capacity electric motor and generator.
When starting, 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.
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By GlobalDataThe 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.
When the car comes to a stop for more than a few seconds, the petrol engine automatically shuts off.
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.
Driving under all conditions the hybrid operation is automatic.
The hybrid’s 30kW Interior Permanent Magnet (IPM) synchronous electric motor produces 40.7ps 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 209ps and 265Nm.
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 uses a lithium polymer battery developed in partnership with LG Chem. The company says lithium polymer offers the benefits of lithium-ion – as used in laptops and cell phones – but adds robustness and packaging flexibility.
The new batteries, the company says, 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 mean the Optima’s battery pack will not require replacing during the vehicle’s lifespan – at least ten 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 43.6 kg.
The complete hybrid system is controlled by a hybrid control unit (HCU) which integrates the operation of the engine’s ECU, transmission’s TCU, battery management system (BMS), low voltage converter (LDC).
Kia has modified its 2.4L Theta II engine to operate on an Atkinson cycle, raising the compression ratio by 20% to maximise its efficiency and achieving a 10% fuel saving during the standard unit. This cycle generates a little less torque, but the electric motor compensates for any loss.
The car has been lowered by 5mm and new features include an ‘active air flap’ in the front grille, smooth underfloor panels, low-drag wheels and low rolling resistance tyres to achieve a Cd of 0.26.
