|The Lexus 2010 HS 250h hybrid. Click to enlarge.|
Lexus revealed the 2010 HS 250h, the first luxury dedicated hybrid vehicle, at the North American International Auto Show in Detroit. The HS 250h will be Toyota Motor’s second hybrid-only vehicle (after the Prius) and will be Lexus’ fourth hybrid and the most fuel-efficient vehicle in its lineup. It also will be the first Lexus to utilize carbon-neutral Ecological Plastic materials in a new futuristic cockpit and interior design.
The HS 250h sedan’s expected fuel efficiency will be more than 30% better than the most fuel-efficient model currently in the Lexus lineup, while earning a SULEV emissions rating utilizing regular 87-octane gasoline. Although the EPA numbers have not been finalized, city mpg for the HS 250h should be higher than that of the smart fortwo, said Mark Templin, Lexus Group Vice President and General Manager, at the reveal. (The 2009 smart fortwo coupe has an EPA city rating of 33 mpg US.)
The 250h represents Lexus’s first use of a four-cylinder gasoline engine. The 2.4-L Atkinson-cycle engine, as part of the latest Lexus Hybrid Drive System, contributes to a combined 187 hp (139 kW) for the total system.
The efficient Atkinson-cycle engine, enabled by the Variable Valve Timing with intelligence (VVT-i) system, allows the expansion/power stroke to be longer than the compression stroke, resulting in the more effective use of combustion energy for engine power. Among the technologies adopted in the 2.4-liter four-cylinder engine are cooling piston oil jets; an optimized balance shaft rate for improved Noise, Vibration and Harshness (NVH) characteristics; and a hot-air venting system mounted behind the radiator.
Like the new 2010 RX 450h hybrid utility vehicle that made its debut in November (earlier post), the HS 250h will include a new exhaust heat recovery system designed to improve efficiency.
The system consists of a thermostatically operated butterfly valve behind the catalytic converter which restricts the exhaust stream during warmup, and diverts much of the exhaust heat to a heat exchanger. Heat from the heat exchanger warms up engine coolant, which then transfers heat to intake manifold coolant passages as well as the cabin heater circuit, enabling the internal combustion engine to turn off earlier, more often, and for longer periods of time, while maintaining low emissions at startup. The result is an improvement in both fuel economy and emissions.
A windshield with infrared-ray (IR) reduction properties, which helps keep the interior cooler, has been adopted in order to decrease the amount of air conditioning needed to lower the cabin temperature. In addition to the exhaust heat recovery system and the IR windshield, available power-saving LED headlamps also contribute to improved fuel efficiency and emissions.
The HS 250h sedan’s 0.27 drag coefficient (Cd) makes it among the most aerodynamic in its class. A gull-wing-shaped roof-panel design reduces mass and overall vehicle height, thus reducing drag and improving fuel efficiency. The front spoiler, rear spoiler, rear under spoiler, and diffuser fins all reduce turbulence. Smooth A-pillar shape and the optimized angle and curvature of the bumper side panels also reduce wake turbulence, as does the increased taper of the fender side panels. The under-floor covers have been optimally positioned for reduced drag, while airflow restriction in the engine compartment has been lowered by optimizing the air-duct profiles around the radiator.
The aerodynamic design also contributes to decreased wind noise. A smoother transition between windshield (complete with a sound-insulating inner layer) and roof line has improved air flow and reduced turbulence.
The HS 250h incorporates plant-based, carbon-neutral “Ecological Plastics” or bio-plastics in specific interior areas. Ecological Plastic emits less carbon dioxide during a product’s lifecycle than plastic made solely from petroleum. Among the areas of utilization will be an industry-first use in luggage-trim upholstery. Other areas are the cowl-side trim, door scuff plate, tool box area, floor-finish plate, seat cushions, and the package tray behind the rear seats. Overall, approximately 30% of the interior and luggage area is covered with Ecological Plastic. Over the estimated lifecycle of the vehicle, the HS 250h will have approximately 20% fewer carbon-dioxide emissions as a result of utilizing the Ecological Plastic trim pieces.
The rack-and-pinion steering system utilizes a brushless Electric Power Steering (EPS) motor on the steering column, which provides improved steering feel, a reduction in harsh feedback, and better fuel economy and emissions by not draining engine power like conventional hydraulic systems.
The EPS is an integral part of an available lane keep assist system, a new driver assist that adds smooth steering torque to help the vehicle stay in the center of the lane. The amount of assisted torque is dependant on a lane-marker detection camera. It includes a lane departure warning feature that is designed to detect possible lane departure; it then gives the driver an audible warning and provides feedback via the steering wheel to encourage corrective action.
The HS is slightly longer than the IS and is taller than both the IS and ES. It also has a greater couple distance (distance hip to hip between front and rear passengers) than any other vehicle in its class other than the ES. The contoured front-seat backs also add to increased rear-seat legroom.
The HS 250h will also offer Lexus’ telematics systems, Lexus Enform and Safety Connect. Safety Connect will provide automatic collision notification, stolen vehicle location, 24/7 emergency and roadside assistance.
The 2010 HS 250h will reach dealerships nationwide in late summer.