The 3,456cc V6 engine develops 296 hp (218 kW) and 368 Nm of torque. Combined with a 200 hp (147 kW) permanent magnet motor generating 275 Nm of torque, the combined powertrain delivers output of 339 hp (253 kW)—essentially the performance of a modern V8 engine. The GS 450h accelerates from zero-to-60 miles per hour in approximately 5.2 seconds.

The all-aluminium engine combines Toyota’s D-4S dual port- and direct-injection system with high strength chain drive, roller rockers, and high torsional stiffness connecting rods.

Double slit, fan-shaped spray injectors optimize fuel/air mixture formation for maximum combustion efficiency, generating higher rpm and power output while reducing emissions. Coupled with variable timing for both intake and exhaust valves (VVT-i), the new D-4S system’s combination of direct and port injection increases engine efficiency throughout the power band.

Direct injection improves full-power engine performance, whilst both low-power engine fuel economy and emissions reduction are enhanced through the coalition of direct- and port-injection systems.

In addition to the engine and motor, the hybrid drive system also includes a 288V NiMH battery pack, a new, compact power control unit no larger than an auxiliary 12V battery, and a power split device which, via planetary reduction gears, combines and re-allocates power from the engine, electric motor and generator according to operational requirements.

The electric motor, generator, power split planetary gear mechanism and motor-speed reduction gearing are all housed in a lightweight, compact transmission casing comparable in size to that of a conventional gearbox.

Unique to the GS 450h, the new transmission system now incorporates two-stage motor speed reduction gearing. A hydraulic control unit incorporated within the continuously variable automatic transmission automatically switches the gearing between low and high motor reduction ratio settings.

The twin-stage gearing generates maximum low-gear torque for significantly enhanced acceleration, as well as extended high-gear performance for quiet, high speed cruising with improved fuel efficiency.

Via a center console-mounted switch, the new transmission offers a choice of three power settings:

• Normal, for the optimum balance of power and traction;

• Power, for maximum acceleration; and

• Snow, for excellent traction control under the most slippery road conditions.

With a manufacture-estimated combined fuel rating of 28 mpg, the GS 450h delivers an estimated 33% better fuel efficiency than its V8 competitors. Toyota expects a Super Ultra-Low Emission Vehicle (SULEV)/Tier 2-BIN 3 emissions rating for the luxury hybrid.

The car also uses Electronic Power Steering (EPS) with Variable Gear Ratio Steering (VGRS) and an electrically powered air conditioner.

Toyota will introduce the hybrid version of its flagship LS460 sedan at the New York auto show in April. (Earlier post.)