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Family business - Lexus is set to launch its first all-hybrid passenger car benefiting from ‘hand-me-down’ technology, that’s courtesy of Toyota

Lexus has unveiled its hybrid luxury sedan, the HS 250h, for the US market. It will be the auto maker’s most fuel-efficient gasoline car when it joins the line-up in mid-2009.

Slotting into the range between the IS and ES models, HS shares a platform with the European-market Toyota Avensis. Its powertrain, a 2.4-liter, Atkinson-cycle I4-based hybrid system with CVT, is based on that of the current Toyota Camry Hybrid. However, for the Lexus application there have been numerous changes to the engine, which produces a total of 187bhp.

“Drivability was the most difficult aspect of using the Camry Hybrid system,” says Hiroyuki Koba, chief engineer for the HS. “A Lexus is a very luxurious vehicle. The refinement when you started the engine or accelerated was not good enough for a Lexus so tuning that portion was challenging.”

Dynamic dampers at each engine-mounting point reduce noise and vibration. Resonators improve the air-intake noise, and an optimized exhaust flow reduces exhaust sound. Other changes include: cooling-piston oil jets; an optimized balance-shaft rate for better NVH; and a hot-air venting system mounted behind the radiator. It’s not just refinement that benefits from changes to the engine. “I’m very pleased with the fuel economy,” says Koba. “The fuel economy of the HS is almost 30% better than any current Lexus gasoline model. “It’s very important for the customer, and we’ve improved on the Camry hybrid system by adding the exhaust heat-recovery system.”

The HS becomes the second Lexus to be fitted with such a system, after the RX 450h unveiled last year, with which it will share the Kyushu production plant. Emissions performance is also good, with the car achieving an SULEV rating on 87-octane gasoline. Emissions performance and fuel economy are further boosted by two non-powertrain elements: a windshield with infrared-ray reduction properties to help keep the interior cooler without using air-con; and power-saving LED headlamps. The two hybrids will be available in the USA by the start of the third quarter, with a price of around US$28,000.