Nuts and Bolts
With perhaps the most technically sophisticated hybrid powertrain available, the Lexus GS 450h is more about whirring motors than nuts and bolts.
As the first-ever rear-drive hybrid, the Lexus GS 450h is full of technological advancements that drive this sedan and its V6 powerplant into the 300-plus horsepower category. The engine is a 3.5-liter unit with variable valve timing that makes 292 horsepower at 6,400 rpm and generates 267 lb.-ft. of torque at 4,800 rpm. This is mated to a hybrid system that incorporates two motors. One, which outputs 180 maximum horsepower and 650V (volts), is for engine starting and speed. The other (650V, 197 hp) is for driving the rear wheels and for battery regeneration. The battery is a 288V nickel-metal hydride unit that outputs 35kW (kilowatts). When mated to the 3.5-liter V6 engine and the continuously-variable transmission (CVT), the combined power output reaches 339 horsepower.
That transmission is really the unsung hero when it comes to the GS 450h, as it marshals the power of this complicated system into a smooth stream. Lexus claims that this new CVT uses an advanced two-stage motor torque multiplication device to manage the power output. Interestingly, in a traditional sense, this transmission is more a part of the hybrid powertrain than it is a CVT. Unlike most, which are pulley-based units, the Toyota transmission consists of an electric motor, generator and three-way planetary gear connected to the drive shaft, engine and primary electric motor. The unit controls power output via two main ratios – high and low – which enables better low-gear torque and high-end performance, all with improved fuel economy. The transmission also has three settings – Normal, for the best balance between power and traction; Power, for acceleration; and Snow, for traction control.
Underneath, Lexus has installed an independent suspension setup that includes double wishbones up front and a multi-link arrangement in back, with Adaptive Variable Suspension (AVS) technology and driver-selectable shock absorber damping front and rear. The braking system is also new to the GS line, integrating four-channel, four-sensor ABS brakes with large, vented discs on all four wheels. The system is enhanced by Electronic Brake-force Distribution (EBD); Brake Assist (BA); Traction Control (TRC); and Vehicle Stability Control (VSC). Steering is a speed-sensing rack-and-pinion setup that’s integrated with Toyota’s Vehicle Dynamics Integrated Management system (VDIM). This system factors in data such as steering angle, yaw rate, deceleration, brake pressure and wheel speed, which triggers a number of actions to stabilize handling. The Lexus VDIM system anticipates dangerous situations and makes corrections by using all of the various active safety programs to slow down the car, stabilize it or control the steering. Systems integrated with VDIM include VSC, TRC, BA, ABS, Electronic Throttle Control with intelligence (ETC-i), Electric Power Steering (EPS), Variable Gear Ratio Steering (VGRS), and Electronically Controlled Brakes (ECB).
It’s all about keeping those 18-inch 245/40 tires on the ground and moving forward – or coming to a complete and safe stop. After all, from the electric motors to the engine and all the safety equipment, this baby’s expensive to build – how dare you crash it into a retaining wall!