A hydraulic control unit, similar to a very compact automatic gearbox, automatically switches the gearing between low (3.900) and high (1.900) motor reduction ratio settings. In normal conditions, during acceleration, the reduction system will perform an imperceptible gear change at around 90 km/h (56 mph). Hence, the twin stage gearing generates maximum low-gear wheel torque for significantly enhanced acceleration.


E-CVT with Sequential Shift Mode

In conjunction with the Lexus Hybrid Drive system, the new GS 450h further benefits from an E-CVT (Electronicallycontrolled Continuously Variable Transmission) with Sequential Shift Mode. E-CVT is the principle behind the operation of the hybrid transmission, which, by coordinating the speed of the engine and electric motor, can create an effect of continuous gear ratio variation that resembles a conventional CVT.

Moreover, and once again unique to the new Lexus, the GS 450h's E-CVT incorporates a 6-speed sequential mode, accessed through the "S" position on the gearlever. When the gear selector is in the "S" position, each of the 6 sequential "steps" in gearing offers an equal number of engine brake force levels in the manner of a conventional sequential-mode automatic transmission. This new feature improves vehicle control and further enhances the new Lexus's dynamic driving experience.

By selecting a lower gear under braking or deceleration, the brake control ECU will increase the amount of engine braking as a percentage of the total brake force applied to the rear wheels, thus increasing the load on the generator to both charge the battery and make the engine spin faster.


Mode Select

For the first time on a hybrid car, the new hybrid system offers a choice of three power settings: Normal, for the optimum balance of power and traction, Power, for a more active throttle response, and Snow, for excellent traction control under the most slippery road conditions. The three modes can be selected via a centre console mounted Mode Select switch.


LEXUS HYBRID DRIVE IN OPERATION

Over the course of any journey, the new Lexus Hybrid Drive system operates in several different modes to maximise the GS 450h's overall efficiency. When the engine is cold and the ignition is switched on, the system will start the engine to warm the unit. Thereafter, at rest, the engine stops automatically to conserve fuel. However, if the vehicle is at idle for prolonged periods, the engine will automatically run whenever necessary to charge the high-voltage battery via the generator.

Under operating conditions of low engine efficiency such as start up and low range speeds, the vehicle runs on the electric motor alone, thus eradicating emissions. Furthermore, the system imbues the vehicle with similar in-gear "creep" to that of a conventional automatic transmission.

Under normal driving conditions, engine output is divided by the Power Split Device to both drive the wheels directly and power the generator, which, in turn, drives the electric motor and simultaneously charges the high-voltage battery. In these circumstances, power allocation is constantly monitored and adjusted between engine and motor to maximise efficiency. When sudden acceleration is required, engine and electric motors again operate in tandem, with extra power supplied from the battery to boost motor response.

During deceleration and under braking, the engine switches off and the high-output electric motor acts as generator to effect regenerative braking, optimising energy management in the Lexus Hybrid Drive system by transforming kinetic energy into electrical energy for storage in the high output battery. Furthermore, under all driving conditions, battery power level is constantly managed via the engine driven generator to obviate any requirement to recharge the system from an external source.


UNIQUE DRIVING EXPERIENCE

The new Lexus Hybrid Drive powertrain equips the GS 450h luxury sedan with performance characteristics that position it between the luxury E-segment V8 models and the top performance sports saloons of the same class.

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