The Lexus NX: Competitive Crossover for a Competitive Space
Here’s a look at the development of a new luxury crossover from the company that arguably created the segment in the first place with its RX 300. This time, it is a compact from Lexus.
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One thing to keep in mind about product development at Lexus is that although the company was originally set up for and focused on the U.S. market when it was launched in 1989 with the LS 400, a car that was largely decried by the OEMs of the Detroit-based companies as a car that was an impossibility given its quality, content, excellence of execution, and MSRP, Lexus is now “Lexus International.” This means that in addition to taking into account what drivers in Boston or Santa Barbara might want, there are many more considerations that have to be factored in from prospective customers in places like Beijing, Moscow, Paris, and London.
What’s more, over the past few years, vehicles in the sport-utility (SUV) and crossover utility (CUV) category have become increasingly important in the U.S. market. According to a recent report by IHS Automotive (ihs.com), in 2009, the retail market share for sedans was 36.3%, followed by SUV/CUVs, at 31.4%. In 2014 (through May), the sedans are at 35.4%, with the SUV/CUVs leading at 36.5%.
Another thing to keep in mind about the development of the 2015 NX compact crossover vehicle is that Lexus, with the RX, which it introduced in 1998, has been the leader in the midsize luxury crossover segment, which it arguably invented, ever since. The RX is the reliable stalwart in sales for Lexus, year in, year out. Consequently, chief engineer Takeaki Kato, who is based at the Lexus Development Center in Japan, had to make sure that the vehicle he and his team developed had sufficient market space as regards the RX.
That wasn’t particularly hard in one sense because Kato happened to have been the chief engineer on the current RX, so he knows that vehicle particularly well.
And speaking of his vehicular knowledge, he wanted the NX to be not simply a utility vehicle as in something that is comfortable, functional and having a higher H-point than a car, but something that had more than a bit of performance to it, something, say, with more than a touch of zest to it, something along the lines of the IS sedan. He was also responsible for the previous-generation IS performance sedan. (“I have been involved in vehicle development for 28 years,” Kato says. He joined Lexus product planning in 2005.)
One of the things that Kato gets out of the way right away is the elephant in the room: the Toyota RAV4. Arguably, it is to the Highlander what the NX is to the RX.
Kato says that the NX is based on a “newly developed platform that is loosely
connected to the RAV4.” He goes on to say that there are some 90% new parts and a 20% increase in structural rigidity for the NX compared with the RAV4.
The two vehicles share a single dimension: 104.7-in. wheelbase. The NX is longer (182.3 in. vs. 179.9 in.), wider (73.6 in. vs. 72.6 in.) and lower (64.8 in. vs. 65. 4 in.).
“The new vehicle is a Lexus,” Kato says. And while the Acura RDX is made in the same plant as the Honda CR-V (the East Liberty Plant in Ohio) and the Lincoln MKC is made in the same plant as the Ford Escape (the Louisville Assembly Plant in Kentucky), the NX is built at Toyota Motor Kyushu and the RAV4 is built at Toyota Motor Manufacturing Canada. So there is platform and physical space between the Lexus and Toyota models.
A word about how this car is put together, how the rigidity and stability are achieved. One part of it is material, as in the use of high- and ultrahigh-strength steels throughout. One part of it is architectural, as in straightening the cowl ridge line and passing a closed cross-section through the cowl outer laterally and by joining the front suspension tower and the cowl with plate steel for stability; using a front bumper reinforcement, front suspension member, tunnel bulkheads, and thick rear suspension member brace that connects left and right sides for rigidity. And one part of it is manufacturing processes, as in using body adhesives (e.g., between the front pillar and dash panel; at the front and rear door openings; between the wheel housing inner and outer panels; between the lower back and lower back reinforcement), laser screw welding between existing spot welds (e.g., at the front and rear door openings and the rear quarter panel opening), and increasing the number of spot welds (e.g., between the center pillar outer and rail outer, the back door opening, and at the #3 cross member).
Kato says that when they began developing the NX, they realized that this is a segment that was not only growing in the North American market, but which has serious traction in China. He also says that there was a recognition of some strong players in the category, like the BMW X3 and the Audi Q5, both vehicles that were benchmarked during NX development. So one of the things that they wanted to do was to develop a vehicle that is “inspiring and distinctive” and with its “cool exterior and fascinating interior” would “make customers fall in love at first sight.”
The design concept, Kato says, was “Premium Urban Sports Gear.” This was to emphasize the hoped-for connection with young, tech savvy consumers. The design theme was “Inner Bullet.” Part of this has something to do with concentrated mass, as well as the overall edginess of the design.
One of the key differentiators of the NX from all other vehicles in the category is the result of some extraordinary stamping, as there is not only an array of creases and edges, but there is precision in the way that the stamped panels meet so that the lines flow in an interrupted manner. Kato says that during the development process there was considerable challenge and commitment among the designers and engineers—product and process—in order to achieve the crisp forms: “Developing the NX required a new level of collaboration between design, engineering and manufacturing.”
Inside, the layout of the instrument panel is more analogous to the execution in, say, the IS than the RX. This is a space where it is more technical, not only from the perspective of electronics (yes, there is the excepted implantation with screens, displays and apps), but from the point of view of the metallic surfaces and knurled knobs. The center stack’s shape resembles that of the front spindle grille. On the passenger’s side, there is an interesting metallic inset that separates the top section of the IP from the top of the glove box area, again emphasizing the “sports gear” character of the design: think Oakley.
The NX features what is called a “Remote Touch Interface,” which essentially replaces the joystick that Lexus had been using with the ability to use a finger to swipe and select. Also, for those who have a Qi-enabled smartphone, there is a charging tray in the console box that allows wireless charging. (If you’re interested, here is a link to the Wireless Power Consortium’s list of Qi-certified products: wirelesspowerconsortium.com/products.)
The NX is nothing if not contempor-aneous from the point of view of propulsion. Kato says that downsized, turbocharged engines are “a key technology for the future,” so the NX 200t has a 2.0-liter four-cylinder engine that features a combination water-cooled cylinder head, integrated exhaust manifold and twin-scroll turbocharger. Because it is “key,” they decided that they would develop and produce the turbo in-house and not source it from a supplier. It’s also worth noting that this is the first turbo Lexus has offered, so it is a rather important execution. The reason why turbos are important for four-cylinder (and other) comparatively smaller engines is because engines are being downsized for purposes of increasing fuel efficiency, but then there is the issue of performance, which the turbo brings. So arguably, overall a turbocharged four is considered to be more environmentally correct, than, say, a six- or eight-cylinder, which might not be as fuel efficient. The manufacturing engineers have taken this idea of environmental correctitude all the way to the point where they developed the turbo such that is manufactured in an environmentally aware way, as in producing the impeller via near-net-shape forging (which means there is less machining required); using electron-beam welding for the turbine wheel (which is a low-distortion method, so there is less potential scrap); and making the turbine housing with a new heat-resistant cast steel that has reduced nickel content (nickel under certain conditions can have deleterious environmental effects).
The engine produces 235 hp @ 5,600 rpm and provides 258 lb-ft of torque at from 1,650 to 4,000 rpm. The engine features both port- and direct-injection to assure power at all speeds. The Dual Variable Valve Timing with intelligence (VVT-iW) system allows the engine to start in the Otto cycle and then run in the more fuel efficient Atkinson cycle (there is late intake valve closing during the Atkinson cycle which reduces pumping losses and boosts fuel economy; the “W” in the engine descriptor nomenclature stands for “wide,” as in a wider intake cam timing control).
And speaking of the future, there is a “G-force Artificial Intelligence” system that selects the appropriate gear and even downshift pattern for the new sequential six-speed automatic based on G forces encountered during driving.
And speaking of things with clutches and G forces, there is an active torque control all-wheel-drive system that’s based on an electronically-controlled coupling mechanism—consisting of two clutches. The system uses input from wheel-speed sensors, G sensors (front/rear, left/right) and the steering angle sensor, such that torque, depending on driving conditions (e.g., when starting off, when wheel slip is detected, during hard cornering), can be modulated from 100:0 to 50:50.
But all of this powertrain and chassis discussion to this point is about the NX 200t. There is another NX variant, the NX 300h. It is a hybrid. Consequently, the engine, transmission, and all-wheel-drive system are different than that of the 200t. So, for example, its all-wheel-drive system is called “E-Four,” as it uses, as needed, predicated on the sensor input, an electric motor to drive the rear axle and electric or gasoline power to drive the front, and or both.
More to the point of the hybrid system itself: it is based on an all-aluminum 2.5-liter DOHC four-cylinder engine that runs on the Atkinson cycle. The engine produces 154 hp @ 5,700 rpm and 152 lb-ft of torque @ 4,400 to 4,900 rpm. Then there is the hybrid transaxle that consists of a power split planetary gear, MG [motor generator] 1 and 2, a multifunction gear, and reduction gear, as well as a rear transaxle for vehicles with the E-Four system (this transaxle combines a 50-kW electric motor and a reduction drive mechanism). MG1, which is connected to the engine, mainly works as a generator, though it comes into play as a motor during starts, for example. MG2, which is connected directly to the final drive line, acts primarily as a motor. There is a 204-cell nickel-metal hydride battery pack (yes, nickel). The total system output is 194 hp (142 kW).
As for the fuel-efficiency of the respective vehicles, the NX 200h with all-wheel-drive returns an estimated 33/30/32 mpg (city, highway, combined); the front-drive version is 35.31/33 mpg. The non-hybrid comes in at 21/28/24 mpg for the all-wheel drive; 22/28/24 mpg for the front drive.
“We all pushed ourselves,” says Kato of the development of the NX.
And whether it is from the exterior appearance or the technology under the hood (e.g., developing a turbo is not a trivial exercise), it is clear that the push was enormous to create this compact vehicle.
Although the term “continuous improvement” is generally associated with another company, Honda is certainly pursuing that approach, as is evidenced by the Accord, which is now in its ninth generation.
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By James Gaffney, Product Engineer, Precision Grinding and Patrick D. Redington, Manager, Precision Grinding Business Unit, Norton Company (Worcester, MA)