Being the world’s first gas/electric hybrid-powered luxury utility vehicle, Lexus inaugurated a new era in luxury in vehicles with the introduction of the 2006 RX 400h. Lexus has broadened the RX 400h’s appeal with a new front-wheel-drive model and revamped offerings in both standard and optional equipment.
The RX 400h sold nearly 30,000 units in its first full year on the market – more than some conventionally powered luxury SUVs – accounting for nearly 25% of all RX model sales. Significant both for being the 1st Lexus hybrid vehicle as well as for launching a new era in luxury vehicles, the RX 400h that features Lexus Hybrid Drive technology, set a new benchmark for luxury SUV performance and environmental compatibility. For 2007, Lexus is broadening this breakthrough vehicle’s appeal thus further solidifying the brand’s luxury hybrid leadership by introducing GS and LS hybrid models, too.
The RX hybrid is a true step forward in hybrid technology with its enhanced-performance dimension, combining the power of a 3.3 liter V6 gasoline engine and an electric drive motor to deliver performance on par with V8-powered luxury SUVs and with a far better fuel efficiency. The all-wheel-drive RX 400h’s EPA – estimated city/highway rating is 31/27 mpg, having a city rating of more than double that of most V8 luxury SUVs. The EPA-estimated combined fuel economy rating of 29 mpg exceeds the average for new compact sedans. The RX 400h front-wheel-drive model has an EPA-estimated fuel-economy rating of 32 mpg city/27 mpg highway.
In addition, the RX 400h achieves Super Ultra Low Emission Vehicle (SULEV) certification in California (Tier 2-Bin 3 in other states), producing nearly 70% fewer smog-forming emissions than conventionally powered vehicles. The RX 400h is also certified as a zero evaporative emission vehicle in California and those states that adopted California standards.
Another plus for this vehicle is the seamless power delivery of the hybrid powertrain, extending even smoother driving than conventionally powered vehicles. The city and highway driving is effortless due to the generous combination of engine and electric-motor torque, with an impressive 30-50 mph passing power.
There is a great difference between RX 400h and RX 350 from visual point of view. The RX 400h features its own grille design, a different front fascia with additional air intake and round foglamps, and Light Emitting Diode (LED) tail lamps. Specific suspension tuning gives the RX 400h sportier handling than the RX 350. Instead of a tachometer, a power meter displays the level of power generated by the hybrid powertrain. The gas-electric power distribution can be monitored on the multi-information display or on the optional navigation system’s seven-inch touch panel display screen.
Wider Choices for 2007
When revising badging on the 2007 RX 400h, a blue “400h” on the rear door was included. Standard wheels are now 17-inch aluminum alloy, with 18-inch wheels optionally available.
Closely following the RX 350 in terms of standard and optional equipment, the RX 400h is provided with a standard high-quality fabric interior, with leather trim available in several option packages. The RX 400h gains a standard 10-way power front-passenger seat in place of the previous 8-way seat, with power lumbar adjustment. Additionally to the standard brushed aluminum interior accents, customers can now also specify wood trim with any interior color for the 2007 model.
Other features previously standard on the 2006 RX 400h are now offered separately or in option packages in the 2007 model, including: power tilt/telescope steering wheel with memory; power tilt/slide moonroof with one-touch open/close feature and jam protection: memory for driver’s seat and outside mirrors; towing-preparation package; roof rack and roof rails; and Dynamic Laser Cruise Control, which measures and maintains a set distance from the vehicle traveling ahead.
The vehicle is also provided with the 5th generation touch-screen Lexus DVD Navigation System with rear back-up camera which integrates Bluetooth wireless capability and voice activation, now being offered in an option package with the Mark Levinson audio system. Customers can order High Intensity Discharge (HID) headlamps with the Adaptive Front-lighting System (AFS) which helps to illuminate a turn or curve as the driver steers into it, as a stand-alone option for 2007. The available DVD rear-seat entertainment system features a new, larger 9-inch LCD screen.
Lexus Hybrid Drive Technology
The Lexus Hybrid Drive system is one of the most advanced powertrains in the world, yet it operates so seamlessly that it enhances the luxury experience rather than calling attention to itself. The system combines a V6 engine with a high-torque electric drive motor-generation. In the all-wheel-drive model only, an additional, rear-mounted electric-drive motor generator provides on-road all-wheel-drive capability.
Along with a combined system output of approximately 268 horsepower and more significantly, 3500 lb-ft of axle torque at launch, the RX 400h delivers rapid acceleration. At 7.3 seconds, acceleration from 0 to 60 mph is better than many V8-powered competitors.
Defined as a “full hybrid”, meaning that it is capable of operating in electric-only or gas-engine-only models, the Lexus RX 400h can also combine the power of the gas engine and electric motor. Lexus hybrid technology allows extended electric-mode operation during low speed or stop-and-go driving conditions, reducing fuel consumption and noise. In contrast, other hybrid technologies require constant gas-engine operation.
The RX 400h offers a 3.3 liter V6 gas engine with modifications to the Variable Valve Timing with intelligence (VVT-i) and Electronic Throttle Control (ETC) systems to promote smooth integration with the hybrid system. Energy is stored by a 288-volt DC Nickel Metal Hydride (Ni-MH) battery pack that fits meatly under the rear seat. The battery’s power is directed through a boost converter that efficiently raises voltage to 650 VDC. An inverter changes this to 650V AC, 123 kw electric motor that turns as high as 12,400 rpm.
The RX 400h front-wheel-drive model’s hybrid powertrain uses 2 motor-generators, known as MG1 and MG2. Each one performs specific functions and each does double duty as motors and generators, although MG1 is a starter and provides no motive force. The engine-driven generator (MG1) can charge the battery pack or power other electric motors as needed. The all-wheel-drive RX 400h adds a 3rd motor-generator, MGR, to drive the rear wheels.
Power from the gas engine and front electric drive motor (MG2) is distributed to the drive wheels via a planetary gear-type continuously variable transmission, which eliminates specific gear ratios. Two planetary gear units are used in the system. The Power-Split unit divides the engine’s drive force 2 ways: one to drive the wheels and the other to drive MG1 so it may function as a generator. The Motor Speed Reduction unit reduces the speed of MG2 and increases its drive torque, significantly boosting acceleration performance. MG2 produces peak torque from 0 to 1500 rpm, giving the RX 400h powerful and instantaneous response that will be felt in low and mid speed performance, especially in 30-50 mph merging and passing maneuvers.
Besides to its motor-generator duties, MG1 adds 2 functions: one, as a starter motor for the gas engine; and two, as a regulator for the amount of electrical power it generates. MG1 controls the output speed of the translate through the planetary gearset - without clutches or a viscous coupling. This is one of the key elements of the hybrid powertrain and is how it eliminates the “shift shock” that is typically felt as even the most refined modern automatic transmissions change gears.
The all-wheel-drive model uniquely generates rear-wheel power with a separate 50 kw electric motor that provides up to 650 lb-ft of additional drive torque on demand. Thus, the RX 400h does not require power-transfer gearing or a driveshaft from the front. The system electronically varies front and rear torque distribution depending on traction conditions.
The power-steering pump, water pump and air-conditioning compressor are driven electrically rather than by the engine. That is because the gas engine often shuts down – a fuel-saving benefit of the hybrid system – especially when the car is stopped or driven slowly through traffic. Driving these components electronically notably reduces parasitic losses to the engine and improves fuel consumption.
Efficiency is further boosted by a regenerative-braking system. When the RX 400h is coasting or its 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.
Proactive Vehicle Stability Control
The RX 400h was the 1st Lexus model to feature Vehicle Dynamics Integrated Management (VDIM). The vehicle’s stability control system goes well beyond conventional controls that simply react to challenging conditions. Instead, VDIM anticipates loss of vehicle control in virtually any direction and can make corrections while allowing higher dynamic capability.
Electronically Controlled Brakes (ECB) are a vital element of VDIM. It is an advanced braking system that translates brake pedal stroke speed and pressure and generates the precise amount of combined electric regeneration and hydraulic pressure needed for virtually any driving condition.
Under guidance from VDIM, such precise brake control at individual wheels helps allow more optimized operation of the vehicle’s dynamic handling systems that employ the brakes, including ABS, Brake Assist, Vehicle Stability Control (VSC) and Traction Control (TRAC). VDIM also interfaces with the electronic-throttle control system, allowing it to modify vehicle power when needed and a new Electric Power Steering (EPS) system to help optimize steering assist for individual situations.
EPS uses DC motor and gear-reduction system built into the steering gear housing to provide steering assist. This compact unit contributes to fuel economy by eliminating the traditional power-steering plump and by providing computer-controlled assist only when called for by the driver. EPS also allows a more precise and timely control of steering assist than conventional engine-driven hydraulic system.
Vehicle motion is calculated by signals from a yaw rate and deceleration sensor, speed sensor and steering sensor. With these inputs, VDIM controls all of the vehicle’s dynamic handling systems and can employ them collectively and seamlessly. This allows to quickly detect the onset of a loss of traction in turns and correct it.
Comprehensive Safety Systems
The RX 400h features the same passive-safety protection for occupants as the RX 350 model. A high-strength cabin design and comprehensive Supplemental Restraint System (SRS) are designed to provide a high level of crash-energy management for the passengers. SRS includes advanced front airbags for the driver and passenger, a knee airbag for the driver and front-seat-mounted side airbags designed to manage impact forces to the torso, abdomen and pelvis. The front-airbag technology takes into account several factors: crash severity, front passenger weight and driver-seat position on the seat track.
Side-curtain airbags are designed to offer additional crash energy management for the front and rear-seat occupants. A roll sensor signals the side-curtain airbags to inflate if a predetermined threshold of vehicle tip-up is detected.
Lexus Luxury and Impressive Utility
The RX 400h does not sacrifice space, comfort or versatility to deliver the benefits of hybrid technology. The rear seatbacks offer a versatile 40/20/40-split design and the seats have both sliding and reaching adjustments. The about 38-cubic-foot rear-cargo capacity expands to nearly 85 cubic feet with the rear seatbacks folded down. An automatic retracting tonneau cover adds a measure of security and convenience to the cargo area.
The vehicle’s luxurious design includes dual-zone automatic climate control and 10-way power front seats with memory. It also features easy-to-use controls for the audio system, trip computer and multi-information display in the speedometer. A rear back-up camera projects a color image of what the camera lens can detect behind the vehicle onto the navigation screen when reverse gear is engaged.
The RX 400h also comes with an auto-dimming rearview mirror with an integrated digital compass, auto-dimming, heated exterior mirrors, a sliding centre console to enhance roominess, a power-rear liftgate and integrated Homelink transmitter.
The supremely quiet interior of the RX 400h provides the ideal environment to enjoy the optional Mark Levinson audio system that features 11 speakers and an in-dash, 6-disc CD changer. Rear passengers can enjoy the optional factory-installed rear-seat DVD entertainment system with individual wireless headphones and, for 2007, a larger 9-inch LCD screen.