LEXUS UX 250h HYBRID CROSSOVER GOES HEAD TO HEAD WITH PIONEERING RX 400h HYBRID SUV
- 15 years since the launch of the world’s first luxury hybrid, the Lexus RX 400h is still seen as a gamechanger for the Japanese luxury carmaker
- To mark this milestone, Lexus recently put its latest 4th generation UX 250h hybrid crossover ‘head to head’ against the pioneering hybrid SUV at its Zaventem Technical Centre in Belgium
- While the RX 400h exhibits “factory new” smoothness and drivetrain refinement even after 15 years of hard use, the new UX 250h resets benchmarks for hybrid efficiency and dynamic handling
|UX 250h||RX 400h|
|Power||135 kW||200 kW|
|Combined fuel consumption* (l/100km)||5,3||8,1|
|CO2 emissions* (g/km)||102||192|
*WLTP (approximate values for the RX 400h)
“I can still remember how much the RX 400h’s power and performance impressed me the first time I drove a prototype near the Nürburgring in Germany. Even today its linear acceleration, electrified V6 power and quietness are amazing. However, a lot has changed in 15 years and for me the UX 250h sets the new hybrid benchmark with its bold styling, razor-sharp handling and 4th generation Lexus Self-Charging Hybrid. Compared to the RX 400h it delivers more dynamic and engaging power, with the car’s speed and engine rpm better matched than on earlier Lexus hybrids,” comments Herwig Daenens, Technical Manager for 'Total Vehicle Evaluation and User Experience' at Toyota Motor Europe.
To celebrate over 15 years of leadership in self-charging hybrid technology, Lexus recently put its 4th generation UX 250h hybrid crossover ‘head to head’ against the first pioneering Lexus RX 400h hybrid SUV at its state-of-the-art Technical Centre and Proving Ground at Zaventem in Belgium. With the track evaluation performed by Herwig Daenens, hybrid drivetrain expertise was provided by Raf Schuermans, Technical Senior Manager for 'Advanced Powertrains' at Toyota Motor Europe.
1. DRIVING DYNAMICS
“The latest UX 250h demonstrates the vast improvement in driving dynamics that Lexus has achieved since 2005. Crafted for the European driver, with part of the development work performed by the Lexus R&D Centre in Zaventem, it was incredibly fun around the track today. This is thanks mainly to its new and super-rigid GA-C platform that makes extensive use of adhesives, its low centre of gravity resulting in reduced chassis roll and precision of the electric power steering,” enthuses Herwig Daenens
UX 250h delivers hatchback-like handling
In almost perfect conditions at the Zaventem Proving Ground, whilst the RX 400h luxury SUV delivered impressively refined performance, steering response and straight line stability, Herwig Daenens explained how the UX 250h benefits most from one person: Akio Toyoda, Lexus’ Master Driver, who insists that every new Lexus must be ‘fun to drive’. This ambitious goal meant creating a highly rigid new platform as the perfect foundation for the hybrid crossover’s hatchback-like handling.
Lowest centre of gravity in its class
Thanks to its new platform and the position of the hybrid battery, the UX 250h has the lowest centre of gravity in its class. This characteristic, central to the car’s dynamic performance, is complemented by weight-saving measures in the body construction, such as lightweight aluminium for the side doors, wings and bonnet.
2. HYBRID TECHNOLOGY
Combining the power of a petrol engine with one or more electric motors, Lexus Self-Charging Hybrids have always set the benchmark for luxury car electrification. As the name implies, Lexus hybrids charge themselves whilst they drive, slow down or brake, meaning owners never have to plug them in or worry about battery range. Now in their 4th generation, as well as offering refined power and control, Lexus Self-Charging Hybrids are more efficient and produce considerably fewer emissions than conventional petrol or diesel engines.
RX 400h: The hybrid pioneer
Orchestrating power from a 3.3-litre V6 petrol engine and front/rear electric motors, with the RX 400h, Lexus seized the initiative to become the leader in alternative powertrains, soon launching a range of Lexus Self-Charging Hybrids. Driving the RX 400h, Herwig Daenens was reminded just how very advanced the first luxury hybrid was and why it proved such a success.
A major breakthrough at the time was its high voltage hybrid battery pack, rated at 288-Volts and containing 30 9.6-Volt cells. Compact and lightweight, it is located under the rear seat. Compared to the petrol-powered RX 300, the RX 400h offered luxury SUV drivers a substantial 33% improvement overall in fuel consumption with a massive 67% in the city and assumed a pathfinder role in introducing Lexus owners to electrification without range anxiety, charging concerns or compromised packaging.
Advanced, maintenance-free hybrid engineering
On the test track the RX 400h still drives with the same smoothness and refinement as it did when leaving the Kyushu plant in 2005. This is because the majority of competing hybrid systems are based on multispeed direct transmissions or automatic transmissions, involving multiple clutches and actuators that are subject to wear and tear. Lexus’ hybrid transaxle design, by contrast, offers a system that, alongside minimal repair bills, ensures the premium driving experience remains over the car’s entire lifetime.
"Claiming the RX 400h is ‘good as new’ may seem clichéd, but this car’s reliability is a testament to the unwaveringly smooth performance of the Lexus hybrid drivetrain, even after so many kilometres on the clock. Importantly, because the UX 250h uses the same basic drivetrain architecture at the RX 400h, but with a vastly improved hybrid transmission with more compact electric motors and direct gearing for a more engaging drive, we can expect our latest urban crossover to deliver similar class-leading levels of QDR (quality, reliability and durability),” explains Raf Schuermans.
UX 250h: 4th generation Lexus Self-Charging Hybrid
Moving to the UX 250h, there’s been a quiet revolution under the bonnet of Lexus hybrids since the RX 400h. No longer a technology reserved for expensive flagship models, 4th generation Lexus Self-Charging Hybrids like the UX 250h and ES 300h achieve higher fuel economy and lower emissions, while enabling much greater distances to be covered in all-electric EV mode. At the same time, overall power, responsiveness and driving quality have been taken to a higher level.
This continuous progress has been achieved because Lexus engineers have focussed on developing ever more compact and refined components that deliver better performance. In fact, over the past 25 years, Lexus and Toyota have registered over 24,000 patents for self-charging hybrids and EV technology - more than any other carmaker. Signalling its leadership in the field, in 2018, the Toyota Motor Corp. announced that it would allow royalty-free access to its patents for hybrid and other vehicles using electrification technology.
Many of these innovations can be found on the new UX 250h tested in Zaventem:
World-class petrol engine efficiency
Whilst the RX 400h’s powerful 3.3-litre V6 petrol engine was ground-breaking at the time, the UX 250h’s all-new 2.0-litre engine incorporates engineering breakthroughs including fast-burn combustion technology that makes it the most thermally efficient engine to feature in any production vehicle. Around sixty different prototypes were engineered to evaluate new technologies before more than 10 million kilometres of road testing were carried out.
4th generation battery technology
Like the RX 400h, the UX 250h uses the luxury brand’s proven Nickel-metal hydride (NiMH) technology but in more advanced form. The number of cells has been increased, realising high power output and more proactive usage of battery power, and the size of the battery pack has been reduced through optimisation of the internal layout and adoption of a more compact cooling system.
More compact, lighter and extremely reliable batteries
Lexus has used Nickel-metal hydride (NiMH) battery technology to power most of its 1.8 million hybrids. This technology is extremely reliable, will normally last longer than the car and can be more easily recycled than other battery materials. Continuous ‘Kaizen’ improvements over the last 25 years mean this cost-efficient battery technology has reduced in weight by up to 50% and size by 60%.
Reengineered hybrid transaxle
Whilst the RX 400h introduced a hybrid transaxle that controls the electric and mechanical power sources, for the new UX 250h every element was scrutinised to see how the 4th generation unit could be made smaller and lighter. A new multi-axle arrangement of Motor/Generator1 (power generation) and Motor/Generator2 (drive) resulted in a more compact and lighter design. Frictional losses have been reduced by about 25% by changing to a simpler parallel shaft gear. While the new transaxle’s compact dimensions contribute to the UX 250h’s class-leading turning radius, a new system for returning cooling oil improves smoothness and reliability.
More efficient Power Control Unit (PCU)
Far smaller and lighter than that on the original RX 400h, the UX 250h’s new PCU is mounted immediately above the transaxle, thus realising compactness and weight reduction of the entire hybrid system and providing more space inside the engine compartment. Finally, a new and smaller power card features double-sided cooling efficiency, while optimising the output filter has reduced noise levels.
Over 50% of the time in zero-emissions mode
Driven in large part in busy urban areas, the UX 250h takes the benefits of Lexus’ self-charging hybrid technology to a new level. Recent tests in Belgium show that for 57% of the time the UX 250h is driven with the petrol engine switched off, with almost 45% of the car’s drive power sourced from the electric motor and 34% of the power used to drive the wheels produced simply by the act of braking or slowing down.
Compact E-FOUR AWD system
With the trend towards urban crossover driving with limited off-road demand, the UX 250h AWD features a much smaller and more compact rear electric motor than the RX 400h’s relatively large 50 kW unit. The UX 250h’s E-FOUR all-wheel drive system uses a separate, dedicated hi-torque motor generator integrated into the rear differential. Power distribution between the front and rear axles is automatically optimised between 100:0 and 20:80 by the Vehicle Stability Control (VSC) system when accelerating, cornering, or driving on slippery surfaces.
3. EXTERIOR DESIGN
A lot has changed at Lexus since the RX 400h was unveiled, not least its approach to design. A tribute to the skills of the craftspeople at the company’s Kyushu plant in Japan - a factory specially built to craft the luxury brand’s hybrid models. Back then, the first Lexus hybrids featured bespoke hybrid wheels, front grille, fog lights and transparent rear lights.
“Whilst the RX 400h’s iconic shape displays elegance and class, next to it, the UX 250h looks much more dynamic with its sculpted lines and bold Lexus signature grille. From a performance point of view, I like its numerous aerodynamic refinements and low driving position for a more engaging drive,” comments Herwig Daenens.
Parked alongside its pioneering stablemate, the latest UX 250h displays a bolder design and a much more athletic stance, accentuated by the sharply sculpted bodywork, Lexus signature grille and L-motif triple LED headlights. To the rear is a one-piece combination light that is not only eye-catching but also aerodynamically efficient. Fins are integrated into the light to reduce turbulence, enhancing rear stability during cornering as well as in sidewinds. Now the best-selling Lexus model in Europe, the UX 250h crossover has made the Lexus Self-Charging Hybrid available to a far wider range of owners.
4. INTERIOR DESIGN AND TECHNOLOGY
Seated behind the wheel, the roomy RX 400h cabin still exudes an undeniable sense of SUV luxury and refinement. Leatherwork, cabin mouldings and all instruments have worn well and still look ‘factory new’. The RX 400h’s equipment list is impressive too, with technologies like multi-zone climate control, 11-speaker Mark Levinson® premium audio and High Intensity Discharge (HID) headlamps that would not seem out of place in any luxury specification today.
"Inside the RX 400h offers both room and refinement and still looks very fresh after 15 years of daily use. Interestingly, the UX 250h’s Takumi-crafted interior contains many of the design features we first developed for the Lexus LFA supercar back in 2010. Things like the driver-focussed cockpit and instruments, figure-hugging leather seats and LFA-inspired steering wheel all put me in the mood for driving today,” said Herwig Daenens.
More than anything, it’s the advance of in-car communication technology that stands out. Once reserved for flagship models, today UX 250h owners enjoy innovations like a 10.3-inch multimedia display with Panoramic View Monitor, extra-large Head-Up Display and a 13-speaker Mark Levinson® Premium Surround Sound system. Perhaps most importantly, whilst the RX 400h was the first SUV to benefit from Vehicle Dynamics Integrated Management (VDIM), the new UX 250h comes with the pioneering Lexus Safety System + that includes a Pre-Collision System, now with daytime/night-time pedestrian detection and bicycle detection during daylight hours.
More about the UX 250h: www.lexus.eu/ux
More about Lexus Self-Charging Hybrid line-up : https://www.lexus.eu/hybrid/#discover