Naoki Kobayashi is some 6,700 miles away from his office at the Lexus Development Center, Product Development Group, in Toyota City, where he is the assistant chief engineer. He’s in Austin, Texas, at Driveway Austin.
No, Driveway Austin is not a place where you park pickups.
Driveway Austin is a racetrack designed by Bill Dollahite, who’d spent some 20 years as a driver for Ferrari. As Dollahite explains, he wanted to develop a track that combined the best characteristics of courses that he’d run, a track that would allow a car to run through a variety of conditions. Fiorno. Spa. Laguna Seca. Road Atlanta. Monaco. Sweepers and tight corners. Elevation changes and decreasing radii. It’s all there.
Kobayashi is there because he is the chief engineer for the third generation Lexus IS, a compact, rear-drive sedan. And that model year 2014 vehicle—IS 250 RWD and AWD, IS 350 RWD and AWD, and F Sport variants of all aforementioned—is being driven on that track by a group of people who are interested in discovering its limits (which are generally beyond many of their limits).
While the IS has long been (Gen 1 became available in 2000; Gen 2 2005) the small, sporty car in the Lexus lineup, Kobayashi, whose engineering background includes working on the Toyota Supra before joining the Lexus team, acknowledges that one of his goals in the development of the new car was to develop “a much more performance-oriented vehicle.”
Thus, Driveway Austin.
“Actually,” Kobayashi continues, “what we targeted was deeper than that. Rather than just developing a car for circuit driving, we wanted to provide ride comfort, as well.” So the objective was to create a balance between a car that you drive on the track on Saturday and have a comfortable, confident drive the other six days of the week.
“We were not just looking for a sporting vehicle,” he says. “We were targeting a smart vehicle.” Smart as in right or correct, not necessarily smart as in intelligent, although there is that, too.
Rigidity matters both ways.
“To achieve the dual characteristics”—sportiness and comfort—“body rigidity is very, very important,” Kobayashi says. “In order to achieve body rigidity, you could easily achieve it by increasing the thickness of the steel used, but the weight would go up. So, to achieve light weight and rigidity, we developed a new bonding technology.” Bonding technology?
Well, there are other measures taken. Such as using an extensive amount of high-strength steel so the gage doesn’t have to go up. Like developing a revised platform and a reconfigured rear floor. The addition of a V-shaped underbody brace. A new rear subframe. Cowl-side braces connecting the front pillar section and apron member. Things like that.
But there is the bonding.
A lesson in spot welding & bonding.
Kobayashi explains that when performing spot welding, there is an inherent space between the spots: you can only weld so close, as in •-•-•-•. This means, of course, that while there is attachment at discrete points, there is no attachment between the points.
Now, it may be that it isn’t particularly discernible on a macro level. But Kobayashi explains that when driving a car even on an ordinary road, there is movement between two joined metal components “on a micro level relative to each other.” Micro, but remember that “Relentless Pursuit of Perfection” tagline?
So they’re applying an adhesive between pieces of metal, then performing the spot welding.
Not only does this enhance the rigidity (because there aren’t gaps between the spots), but it also helps dampen those micro movements. “It is very effective in handling performance and ride comfort,” Kobayashi says.
However, the structure isn’t fully bonded; there isn’t adhesive everywhere there are spot welds. “There are locations where bonding is more effective than at others,” he says. “We used both computer simulations and actual trial and error on hundreds of vehicles to find the best location.”
The finished car has 25 meters of adhesive bonding. They started the testing with as many as 100 meters.
Laser assembly, too.
Kobayashi says there is another way they’re achieving a better bond between metal pieces in certain areas of the car, the door openings and on the package tray to be precise. But what he isn’t precise about is how this process is actually performed.
It’s called “laser screw welding.” It is performed between the conventionally applied resistance welds. It is done to reduce cross-sectional deformation. There is a helical movement of the laser beam.
And that’s what we know. “I can’t tell you the details. It is top secret.”
(While on the subject of lasers: laser brazing is used to join the roof to the side members, which is the first time the process is being used on a Lexus vehicle.)
One more assembly process.
There is extensive use of high-strength and ultrahigh strength steels in the 2014 IS. Kobayashi notes that they’re using a hot-stamped steel to form the B-pillar, rocker inner, and portion of the roof rail such that an “H” is formed (with the H being on its side). This is done primarily for purposes of safety and rigidity. “Mainly safety,” he says.
But there is also aluminum used on the IS: For the hood inner and outer. The joining process for creating the hood is a combination of adhesive bonding and hemming.
(While on the subject of hemming: they’re using a precise hemming process on the wheel arches so that the tires more fully fill the openings. The hemming they’re performing reduces the distance from the wheel arch outer to the tire to 11 mm. It was 20 mm on the last-generation IS.)
Kobayashi worked on the IS project for six years. During that time, there were some other Lexus vehicles launched, like the fourth-generation 2013 GS and the fifth-generation LS.
Remember the redesigned rear floor portion of the IS and the V-shaped brace? Turns out that during the development process they concluded that it was such a good engineering design that they used it on the GS, as well. The steering gear box developed for the IS was purposed for the GS, too.
The IS and GS program development overlapped, so there was actually movement of engineers between the two. “Many things that we learned in IS went over to GS,” he says.
The GS program started earlier, which explains why its line-off preceded that of IS.
And as for the adhesive bonding: “We used it first on the LS,” Kobayashi says. “The development was done for the IS, we found it was good, so we used it on the LS first.”
“The development of the IS,” Kobayashi says, “was effective for the overall development of the Lexus series.” Clearly, “continuous improvement” isn’t limited to a single product.
Like any good car in the luxury class, the IS offers standard eight-way power driver and front-passenger seats. The cushion length is increased for better side support; the seat bottom cushion is reshaped for better fit.
So what else is new, right?
Something rather significant in the F Sport models, Kobayashi says.
He explains that when seats are typically made, there is the frame and the foam on the inside and a surface cover wrapped over it on the outside. “It is difficult to make a curved surface because there is a gap between the cover and the foam beneath,” he says.
If there is too little tension in the outer material, then wrinkling occurs. Unsightly. If there is too much tension, then the outer surface is too hard. Uncomfortable.
The ideal, he says, is to achieve a contoured shape with the outer material soft and the foam firm. But that can’t be readily achieved with the stretch-and-sew approach.
So what they’ve done is develop a method whereby the outer seat material is sewn to the desired shape, then the foam material is injected into that foam. “There is no space between the surface and the inside material,” Kobayashi says. “We wanted to use it in all of our cars, but because it is newly developed, we don’t have the production capacity at this time.”
Although the IS is a performance sedan, it doesn’t have something that some people think is fundamentally characteristic of a car in that category: a manual transmission. There are two carryover six-speed automatics, one for the IS 250 RWD and one for both AWD versions. And there is an eight-speed automatic standard on the IS 350 RWD. All have paddle shifts for those so inclined.
There are selectable modes (e.g., Normal, Eco, Sport) that provide adjustments to the throttle and the electric power steering.
While it may not have a manual, it has something more contemporary: artificial intelligence in the eight-speed. Kobayashi explains that when the
eight-speed is put in the Sport mode, there is the deployment of G AI-SHIFT control. What this does is select the optimal gear ratio based on inputs from a variety of G-force sensors that are used by the vehicle (to do such things as provide inputs for stability control). He says this is the first time AI has been used in a Lexus transmission application.
Meanwhile . . .
As Kobayashi talks, the ISes out on the Driveway Austin track continue to wail with varying levels of pitch as the drivers put the cars through their paces.
Kobayashi comments, “When one is tired, going home from work, a lot of noise is bothersome.” Either of the V6 engines—the 204-hp, 2.5-liter or the 306-hp, 3.5-liter—might get somewhat tedious were they to sound like the cars on the track while on a daily commute.
“Below 4,000 rpm we have made the car very quiet, for normal driving,” he observes.
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