In both the UK and Europe as a whole, the new RX300 has proved an outstanding success. Since launch in May 2003, European sales have risen by 86 per cent year on year to more than 7,300 units. Up to the end of December, new registrations in the UK totalled 2908, up by 72 per cent on 2002.
Lexus engineers have developed a completely new Hybrid Synergy Drive system for the RX400h, redesigning and refining the electrics, mechanical driving components and control elements to achieve the power and performance appropriate for a luxury four-wheel drive SUV.
The Hybrid Synergy Drive is a series/parallel system which uses two powerful electric motors and a highly efficient petrol engine in tandem. This significantly improves low to mid-speed acceleration, braking performance and fuel efficiency and minimises carbon dioxide emissions. Using an electric motor at the rear provides the car with four-wheel drive capability.
In addition to the dual power sources, the system also features a generator and a high-performance nickel-metal hydride battery. A power split device combines and re-allocates power from the engine, motors and generator, according to where it is needed in the drivetrain, and a power control unit governs the high-speed interaction of the system’s components.
For the driver, a single gearshift on the dashboard engages the drive system, which operates as a seamless, continuously variable transmission.
In the course of any journey, the Hybrid Synergy Drive system will operate in several different modes to maximise the all-round efficiency of the vehicle. The motor driving the rear wheels introduces four-wheel drive performance at appropriate times, such as when starting up, accelerating, turning and driving on slippery surfaces.
Improvements to the efficiency of the V6 petrol engine and a transmission system with a torque-increasing deceleration gear, allied to a more efficient regenerative braking system, all serve to optimise the Hybrid Synergy Drive system’s energy management qualities.
The combination of the 3.3-litre V6 engine, the powerful front-mounted electric motor and further rear electric motor produces a maximum power of about 270bhp (200kW). This gives the RX400h a top speed comparable to that of the US specification RX300, but stronger performance with nought to 62mph acceleration in less than eight seconds.
Furthermore, the RX400h has the world’s lowest CO2 emissions figures for an SUV, complying with Euro IV standards, and fuel consumption figures which compare to typical family car performance. In the US-specification model it will be possible to cover 625 miles on a single tank of fuel.Published 7 January 2004