Lexus RX 400h emerges as first hybrid-powered luxu
Bob Plunkett, Sun, 25 Sep 2005 08:00:00 PDT
HONOKAA, Hawaii -- On the lush side of the Big Island, Old Mamalahoa Highway runs in a narrow ribbon of frayed asphalt down lava-laced slopes of a volcano to the coast overlooking a vast blue ocean.
We're using this rough and winding road to sample the ride quality and test the get-up-and-go attitude of the world's first hybrid-powered luxury vehicle.
It's a high-tech treatment of the RX 330, mid-size luxury crossover SUV from Lexus, the elite spin-up line from Toyota of Japan.
Badged as the RX 400h (with the lower-case 'h' denoting the vehicle's status as a 'hybrid' machine), this SUV for the Class of 2006 brings the exuberant acceleration of a V8-powered vehicle but the miserly fuel economy of a four-cylinder compact.
The RX 400h carries the advanced Hybrid Synergy Drive (HSD) powertrain, a concept which Toyota developed over the past decade with the hybrid Prius sedan.
For RX 400h, however, the HSD system is more extensive -- and far more powerful -- than any previous hybrid.
It teams an efficient but strong 3.3-liter V6 gasoline-powered engine modified off the RX 330 with a pair of high-voltage and high-torque electric motors -- one to turn the front wheels and the other to work so many power accessories as well as crank up the V6 engine and recharge a load of on-board batteries.
Sum of all powertrains is the equivalent of 268 hp.
The HSD controls all energy produced by these plants and applies it directly to the front wheels in infinitely variable measures through an electronically-controlled continuously variable transmission (CVT).
And for the optional all-wheel-drive (AWD) edition of RX 400h, there's a third electric motor aboard to drive the rear wheels as the HSD varies torque distribution electronically front and rear depending on traction conditions.
Supplying electrical juice to all of the motors in the Lexus hybrid system is a direct-current nickel metal hydride (Ni-MH) battery tucked beneath the cabin's back seat.
It never needs to be plugged in for recharging, as would a purely electric vehicle, because motors on the RX 400h also work as generators when the wagon coasts or brakes. The motors/generators capture the kinetic energy of heat from the brakes and transforms it into electricity that's returned to the battery for the recharge.
Net effect is a driving range which exceeds 500 miles and fuel economy numbers up to 31 mpg but with no detectable sacrifice of engine power for off-the-line accelerations or passing in the quick lane.
In fact, this hybrid acts zippy fast when you stomp on the accelerator -- it's quicker even than the RX 330.
In acceleration tests for a run from zero to 60 mph, the Lexus hybrid covers the distance in 7.3 seconds, which beats many SUVs with V8 engines.
Although the technology motivating the RX 400h is incredibly complex, the beauty of the Lexus hybrid system is that this wagon looks and rides and drives like a conventional crossover SUV.
It's also a refined luxury vehicle with a passenger compartment lined in leather and loaded with electronic gear and power-operated devices to regulate the interior climate, adjust the front bucket seats, lower the windows and open the tail-side liftgate.Stylists inscribed fluid aerodynamic lines on a sleek shell of the RX 400h with a tapered body distinguished by the low-canted roofline and muscular flanks.
Its aggressive face features corner headlamp clusters glimmering through multiple lenses with xenon high intensity discharge (HID) headlamps.Lexus adds the adaptive front lighting system (AFS) where a pair of swivel lamps -- each keyed to the angle of the steering wheel -- rotates up to five degrees during turning maneuvers to keep a light shining on the vehicle's forward path.
Externally, the design for the Lexus hybrid SUV varies only slightly from the RX 330.Up front there's a revamped grille and fascia added with larger air intake vents and round foglamps.In back the taillights switch to high-visibility light-emitting diode (LED) assemblies.And big 18-inch graphite-polished alloy wheels mount on the RX 400h with 235/55VR18 rubber by Goodyear or Michelin.
Ride quality for the wagon feels smooth and refined, even on rough pavement like the Old Mamalahoa Highway.The suspension employs MacPherson struts and coil springs in front and dual link struts in back. Struts gain internal rebound springs and linear control valves, as Lexus tunes the rig firmly for sporty handling traits.Many safety systems are in place, including side curtain-style air bags set above front and rear side windows plus frontal air bags for front buckets and large seat-mounted side air bags to cover the rider's torso, abdomen and pelvis, even an air bag to shield the driver's knees.
A disc brake mounts on each of the four wheels with all managed through a new electronically-controlled braking (ECB) system.Lexus adds a vehicle stability control system called vehicle dynamic integrated management (VDIM). It coordinates the anti-lock brake system (ABS) and brake assist (BA) with the vehicle stability control (VSC), traction control (TRAC) and electronic throttle control (ETC) systems.Even the rack and pinion steering device goes electric with an electronic power steering (EPS) boost.
The cabin dresses up as strictly first-class.Soft leathers and trim accents in brushed aluminum set the mood.The seat plan is conventional, however, with a pair of comfortable buckets up front and a rear bench for three with the folding seatback split 40/20/40 in sections. Driver's seat gets 10-way power controls with 8-way power applied to the front passenger's seat.In the instrument panel, a tachometer is replaced by a meter showing how much power is made by the hybrid system.
Standard equipment includes electro-luminescent instruments in a triple-pod display, a moonroof overhead and power-everything. Options extend to a navigation system, laser-guided cruise control, a backseat DVD video entertainment kit and a high-watt audio package by Mark Levinson.
The MSRP for RX 400h stands at $48,535.