With its advanced technology, high performance and indulgent luxury, the rear-wheel-drive 2008 GS 450h is the premium model in the GS series. In addition to the GS 450h, Lexus also offers the RX 400h luxury utility vehicle and the new-for-2008 LS 600h L flagship hybrid luxury sedan. In addition to boosting performance and fuel efficiency while lowering emissions, Lexus Hybrid Drive technology also further elevates the brand's renowned smooth, quiet operation.
The GS 450h's unique version of the Lexus Hybrid Drive powertrain combines a powerful 3.5-liter V6 engine with a compact, permanent magnet electric motor – all driving the rear wheels. The hybrid powertrain collectively produces 340 horsepower and can effortlessly accelerate the GS 450h from zero-to-60 mph in just 5.2 seconds.
Just as impressive as the GS 450h's acceleration from a stop is how quickly and powerfully torque is delivered during mid-range acceleration. The hybrid system's electric-drive motor delivers maximum torque immediately upon demand. This unique power-delivery characteristic is most noticeable, and most useful, during 30-to-50 mph passing and in traffic-merging maneuvers.
The GS 450h returns nearly 30-percent better fuel efficiency than some V8 models, with EPA-estimated fuel economy of 22 mpg city/25 mpg highway/23 mpg combined. The GS 450h is certified as a Super-Low Emissions Vehicle (SULEV).
The GS 450h matches its powerful acceleration with responsive handling while maintaining the ultra-comfortable ride that is synonymous with the Lexus brand. Double-wishbone front and multilink rear suspension systems endow the GS 450h with engaging handling performance. Like the V8-powered GS 460 model, the GS 450h is equipped as standard with Adaptive Variable Suspension (AVS), a driver-selectable shock absorber damping system. The standard 18 x 8-inch aluminum alloy wheels have a finish that is unique to the GS 450h and are equipped with 245/40R18 Z-rated summer performance tires; all-season run-flat tires are available.
An optional Active Power Stabilizer system helps to further reduce body sway during cornering. The system uses an Electronic Control Unit (ECU) to calculate the force needed to counter excess body sway, which is then applied to the stabilizer bars by front and rear electric-powered actuators.
The GS 450h also showcases the brand's highest level of dynamic handling technology: the advanced Vehicle Dynamics Integrated Management (VDIM) system that goes beyond the capability of other stability and traction-control systems. VDIM is designed to anticipate the onset of a vehicle slide while cornering and then help to automatically correct the situation with a combination of braking, throttle and steering control in a way that is essentially transparent to the driver.
VDIM integrates Electric Power Steering (EPS), Variable Gear Ratio Steering (VGRS), Antilock Braking System (ABS), Electronic Brake-force Distribution (EBD), Brake Assist (BA), Vehicle Stability Control (VSC), Electronically Controlled Brakes (ECB), and Traction Control (TRAC).
The GS 450h hybrid powertrain uses two motor-generators, MG1 and MG2 (the drive motor). Each performs specific functions and can operate as both a motor and a generator, although MG1 is used as a starter motor and provides no motive force. The engine-driven generator (MG1) can charge the battery pack or provide additional power to MG2 as needed.
A 288-volt DC Nickel Metal Hydride (Ni-MH) battery pack is installed behind the rear seat area. The battery's power is directed through a "boost converter" that can efficiently raise voltage to a maximum 650V DC. An inverter changes this to AC, providing its elevated power to the 147-kW electric motor, which turns as high as 14,400 rpm. The trunk also contains a 12-volt auxiliary battery that powers various vehicle systems, including audio and navigation.
Power from the gas engine and electric drive motor (MG2) is distributed to the rear drive wheels via a planetary gear-type Electronically controlled Continuously Variable Transmission (ECVT). This special transmission, which eliminates specific gear ratios, features a two-speed torque-multiplication device that allows drivers to select from among three driving modes: power, normal and snow. "Normal" provides the smoothest operation and is ideal for city or suburban driving; "power" sharpens accelerator pedal response and "snow" mode softens accelerator pedal response making it easier to travel on slippery road surfaces.
The ECVT consists of a motor generator, motive power-dividing mechanism, two-stage motor-reduction device, electrically powered oil pump and hydraulic control system. The two-stage torque-multiplication device varies the gear ratio in two stages by controlling a planetary gear and two wet brakes, similar to the way a conventional automatic transmission operates.
This configuration allows the electric drive motor to operate in high or low ranges, with seamless transitions between the two. MG2 can therefore contribute power not just for acceleration, but at higher cruising speeds as well.
The GS 450h's power-steering pump and air-conditioning compressor are electrically powered rather than engine-driven to reduce parasitic losses to the engine and thereby improve fuel consumption. This is necessary because the gas engine often shuts down – a fuel-saving benefit of the hybrid system – especially when the vehicle is stopped or driven slowly through traffic. Ultraviolet and infrared ray-reducing tinted glass on all windows helps to reduce demand on the air conditioner.
A regenerative braking system further boosts system efficiency. When the vehicle is coasting or the brakes are applied, the electric motors function as generators, capturing kinetic energy that would normally be lost as heat through the brakes and transforming it into useable electricity to recharge the batteries.
The optional Pre-Collision System (PCS) can help the driver to avoid an accident. A millimeter-wave radar sensor helps detect obstacles in front of the car, while vehicle speed, steering-angle and yaw-rate inputs help to determine whether a collision is unavoidable.
Subtle visual differences distinguish the GS 450h from other GS models. These include a blue hybrid designation on the side rocker moldings, aluminum-and-blue enameled rear model designation, special 18-inch light-alloy wheels, a Lexis Hybrid Drive engine cover, blue front and rear "L" logos, a blue tint to the headlamps and tail lamps and a power meter that replaces the tachometer.
In designing the GS 450h, Lexus raised its own high standards for minimizing noise and vibration. Instead of attempting to mask noise, the engineers completely redesigned fans and motors, significantly reducing cabin-noise intrusion. Fluid-filled front-engine mounts, additional sound-absorbing asphalt sheets behind the instrument panel, and a new sound-absorbing windshield further enhance the quiet ride that redefines the term "Lexus-like."
Lexus designers strive to keep controls simple and intuitive, avoiding needless complexity. The SmartAccess keyless entry and push-to-start ignition allow the driver to keep the access fob in a pocket or purse. Audio and climate-control systems are easy to understand and operate, and the GS locates controls that are used less frequently behind a dash panel on the left side of the steering wheel.
The interior presents an indulgent environment with regency leather-trimmed seats in Ash, Cashmere or Black leather matched with wood trim in Dark Gray Bird's-eye Maple, Brown Bird's-eye Maple or Walnut, respectively.
The cabin is further enhanced with a wood and leather-trimmed three-spoke steering wheel – featuring audio and multi-information display controls – and a coordinating wood and leather-trim shift knob. The 10-way power-adjustable front driver and passenger seats are heated and ventilated, and there are height-adjustable headrests for all five seating positions.
A power-tilt and telescopic steering wheel helps ensure a comfortable driving position. The standard dual-zone climate-control system filters the air, and a standard rear power sunshade adds to passenger comfort on warm days. The GS 450h includes the convenience of a power trunk closer, rain-sensing windshield wipers and Intuitive Park Assist (IPA), which uses ultrasonic sensors to detect the presence of objects close by and warn the driver of their proximity.
The optional Lexus Navigation System includes voice-recognition that allows the driver to enter a destination by voice command. The display screen features a high-resolution 800 x 480 pixel display in 32,000 colors. On-screen details are crisp and clean, and maps and roads feature 3-D shadow effects.
The DVD-map database contains more than five million points of interest. The database for Chicago, Detroit, Los Angeles, and New York includes a building footprint display feature that can show graphic representations of buildings and structures to help the driver identify surroundings. System functions include multiple route calculations, route preview, simplified highway junction graphics, and a dual-map screen mode. Bluetooth® wireless technology allows the transfer of personal phone books to the navigation system, from which the driver can make hands-free phone calls via its touch-screen control panel.