Toyota President and CEO Akio Toyoda used the Detroit show to tout his plan for a more emotional Lexus brand in place of the “well made, but boring” brand consumers see it as today.
Citing research with such comments, Toyoda says it is his goal that “boring” and “Lexus” never again appear in the same sentence, and he unveiled the LC 500 coupe as his company's latest salvo in that battle. “This LC 500 is what a more emotional Lexus looks like to me,” Toyoda crowed as he revealed the car.
What the LC 500 also looks like is the Lexus LF-LC Concept from the Detroit show in 2012. That concept was meant as something of a hint at the brand’s design direction, not as a planned production model. But overwhelmingly favorable comments on the car encouraged Lexus to approve it for production.
The problem was, how to do that. The LF-LC’s dramatic lines that so enamored its fans terrified production engineers who couldn’t comprehend how they could build such a thing. Asked to identify the biggest challenge in bringing the LC500 to production so closely resembling the LF-LC, Chief Engineer Koji Sato quipped, “Most of this vehicle is a challenge!”
He did identify the rear bodywork as a notable example. “The fender line and rear quarter panel is a very deep press,” he said. “It was a great effort, but finally, we did it,” Sato stated.
As the LC 500 will be the flagship Lexus coupe, taking its place in the product line above the well-regarded RC coupe, it is a vehicle of superlatives. It is the very first Lexus built on Toyota’s new Global Architecture for Luxury (GA-L), a front-engine, rear-drive platform that serves as the blueprint for future such Lexus models.
The team focused on centralizing mass in the GA-L platform and putting mass as low as possible to improve the center of gravity and reduce the polar moment of inertia. Engineers referred to the effort as the “inertia spec.”
Even the front seats are lower and closer together to put occupant mass near the vehicle’s center, and the engine mounts behind the front axle. Naturally, the car’s battery mounts in the trunk.
There is an available carbon-fiber roof panel, and carbon fiber is also used for the doors’ inner structure and for the trunk’s floor panel. Door skins are aluminum, and the rest of the car contains the highest percentage of high-strength steel of any Lexus to date.
The LC 500 will be available only with run-flat tires, which eliminated the mass of a spare and helped shrink rear overhang because less space was needed to house a tire. Lexus showed the prototype LC500 wearing Michelin Pilot Sport tires with concept tread. Wheels will be standard 20-in machined aluminum or optional 21-in forged aluminum.
The overall result is a front/rear weight balance of 52/48, and the use of advanced materials accounts for a reduction of mass of 100 kg (220 lb), Sato reported.
The GA-L platform features aggressive use of lightweight and high-strength materials to bolster stiffness in a bid to ensure crisp driving response. The chassis is 35% stiffer in bending and 60% stiffer torsionally than that in the RC, making it the most rigid chassis Lexus has yet produced.
Some of the critical parts include cast aluminum front shock towers, a ring structure at the rear fenders to reinforce them, and a web of steel braces in the engine bay that keep it from twisting.
The front suspension uses two ball joints on the upper and lower control arms to optimize geometry and improve steering response and feel. All but one of the control arms are aluminum, reducing unsprung mass.
Naturally, significant development work was necessary to sort the myriad variables inherent in such a complex suspension.
“We spent more than triple the usual amount of R&D time to pursue linear steering and to find the sweet spot for road contact feel,” Sato said. “We also focused our efforts on suspension rigidity and enhancing geometry. We are now at a world-class level for suspension rigidity and performance when lateral gs are applied.”
With all this new hardware, Lexus was conservative in selecting a powerplant. The LC 500 uses the 467-hp (348-kW), 389-lb·ft (527 N·m) 32-valve 5.0-L V8 seen previously in the RC-F and GS-F.
However, it is matched to an all-new Aisin ten-speed planetary automatic transmission that uses aluminum gears to reduce mass. Not only does this new ten-speed weigh less than the eight-speed Lexus currently uses, but it also has a faster shift time of less than 0.2 s, according to Sato. Heat treatment of the gears provides the needed hardness for aluminum to serve in that role, he said.
Lexus has announced an official 0-60 mph acceleration target for the LC 500 of 4.5 s, but the real goal is 4.0 s flat, Sato confided. Six-piston front and four-piston rear brake calipers will stop the car following acceleration tests.
In the event LC 500 occupants want to ignore the mechanical music resulting from all this hard work by the engineering team, Lexus is prepared to indulge them, offering a standard Pioneer audio system or an optional Mark Levinson system.
The car is still fully a year from production, arriving next year as a 2018 model, so many more details remain to be finalized. It is easy to guess that Toyoda rushed the LC 500’s announcement a little earlier than usual because he was so proud of his company’s achievement in developing a production model so closely resembling the much-liked concept.Continue reading »