2010 Lexus HS 250h to Deliver 35 mpg
TORRANCE, CA --- Lexus said its 2010 HS 250h offers a highly efficient engine design, an exhaust heat recovery system, reduction in parasitic losses, a new evaporative emissions system and driver-selectable driving modes.
The HS 250h is expected to achieve an EPA-estimated 35 mpg city and 34 mpg on the highway for a combined 35 mpg, Lexus said. Careful drivers can use the Eco mode in conjunction with a new hybrid system monitor plus eco-driving indicator to improve on these numbers in certain conditions. The expected fuel efficiency is more than 20-percent better than the most fuel-efficient model currently in the Lexus lineup, while earning a SULEV emissions rating using regular 87-octane gasoline.
Lexus said it opted for an Atkinson-cycle engine design for the high efficiency and compatibility with hybrid operation in the new HS. The twin-cam engine uses four valves per cylinder and Variable Valve Timing with Intelligence (VVT-i) on the intake side.
The engine is undersquare, with an 88.5-mm bore diameter and 96 mm stroke and has a relatively high compression ratio of 12.5:1. Peak output equals 147 horsepower and in combination with the hybrid drive motor, the HS generates 187 total system horsepower. It also meets the California SULEV and federal Tier 2 Bin 3 exhaust emission standards, emitting 70 percent fewer smog-forming emissions than conventional vehicles. The vehicle is also augmented by a new system that reduces evaporative emissions to near zero.
The intake system design reduces engine pumping losses and its twin resonators minimize intake noise. The cooling system uses a modular construction that combines an aluminum engine radiator, hybrid system radiator, AC condenser and fan into a single assembly for minimal weight. Plus, the electric fan speed is controlled via pulse width modulation to reduce energy consumption and noise. Careful ducting of the cooling system prevents hot engine air recirculation that tends to occur at low speeds and while idling, further enhancing efficiency, Lexus said.