Lexus LC chief engineer Koji Sato and chief designer Tadao Mori have detailed how they overcame numerous technical challenges to create the striking new coupe.
The engineer and designer told Lexus of Europe in the first of a series in-depth of interviews focusing on the LC about their pursuit of optimum performance and packaging while retaining the dramatic styling and road presence of the concept vehicle that inspired it – the LF-LC. Mr Sato said the LC’s depth of development evoked that of the ground-breaking and award-winning original Lexus LS sedan.
“You might think the LC project simply involved turning the LF-LC concept into a road car, but in fact it was far more complex than that,” Mr Sato said. “(Akio) Toyoda-san loved the LF-LC design too, but knew that it was a great challenge for us, possibly the greatest challenge since Lexus created the original LS.
“As an engineer, I wanted the car to have great performance, while my chief designer colleague, Tadao Mori, wanted a great look. Despite our different disciplines, we essentially had the same goal and worked together to achieve some amazingly imaginative solutions.
“Every feature on the LC is the result of an integrated approach to design and engineering. The whole team worked together, engineers and designers alike. This is why we have been able to create such a great car,” he added.
Packaging challenges
Mr Mori said the most significant design test was achieving the ideal packaging outcome.
“Everything presented a challenge, but it was the packaging – how we made use of space in the car – that was the most demanding aspect: how to keep a low roof, but at the same time keep the cabin comfortable or how to fit the car with 21-inch wheels, but still have a low bonnet,” he said.
“In fact, to create the low bonnet, our suspension engineers had to rework the components many times before we achieved the effect we wanted. This took months of hard work, but the engineers were so excited about the LC’s design, they were prepared to do what was needed to make it happen.”
New features and driver response
Mr Sato said the range of technical features on LC brought him significant satisfaction, but that the response from drivers to the vehicle’s dynamics was of even greater importance.
“Obviously there are elements such as the carbon fibre and aluminium door construction, the introduction of Lexus Safety System+ and the new Remote Touch Interface that is being introduced with the 2017 multimedia system,” he said. “The LC also has a shift-by-wire system, which is a first for Lexus.”
“We also achieved another breakthrough with the front suspension towers, making them from aluminium which saved more than 10kg compared with conventional steel.
“But to tell you the truth I’m not overly concerned about the LC’s world-firsts, what’s more important to me is the overall result and seeing drivers fall in love with the car,” he added.
Mr Mori said he was proud of how the highly advanced head and taillight designs had helped craft other elements of the vehicle’s design.
“I was thrilled with how we were able to achieve the small front and rear overhangs by designing one of the world’s slimmest headlight units, which uses sophisticated lenses to focus the LED beams. We have also designed very compact rear lights that use twin mirrors to create infinite reflection patterns.” he said.
Concept elements and Akio Toyoda’s input
Mr Sato said the LF-LC concept design had set an effective path for creating the form of the production LC coupe.
“Because the LF-LC concept was very strong, the final form for the production car was clear from an early stage,” he said. “This meant we had a different design process to most cars.”
The input of Akio Toyoda played a key role in the design team changing elements of the LF-LC interior, Mr Mori said. “When Akio Toyoda sat in the LF-LC for the first time he was impressed but said he could not imagine it as the interior of a genuine driver’s car,” he said.
“We set to work to create a more welcoming space. We wanted to make the driver and passenger feel comfortable and at home, something you can see in details like the two handgrips placed next to the passenger seat.
“The designers spent a great deal of time driving the LFA and other high performance cars in order to get a deeper understanding of how the engineers’ passion for a great driving experience can be supported by the design of the cabin and the ideal positioning of instruments and controls.”
Mr Sato said a significant and specialised workforce was behind the LC project.
“There were – and are – more than 4,000 people involved in the LC project and they have done an amazing job,” he said. “The car and a completely new platform were delivered 12 months faster than the usual process. It was hard work, but a good test for everyone to focus on a common goal and make it happen.”
Multi Stage Hybrid System: optimum response
Mr Sato also provided detail on his team’s ambition to deliver pure driving pleasure on the LC 500h hybrid model via the revolutionary Multi Stage Hybrid System (MSHS).
The new system combines elements of a traditional full hybrid powertrain – including 3.5-litre V6 petrol engine, electric motor and lithium-ion battery pack – to a four-speed automatic gearbox mounted at the rear of the hybrid transmission.
Mr Sato said of MSHS: “In the past, people associated hybrid with ‘eco’. We wanted to change that perception and create a true high-performance package.
“We’ve taken our pioneering Lexus Hybrid Drive to the next level, combining a V6 petrol engine and motor generator with an automatic transmission. This meant we could engineer a system that responds much more directly to driver inputs while still delivering all the smoothness and efficiency characteristics of a Lexus full hybrid.”
Mr Sato said that the use of the automatic transmission was key to achieving the desired powertrain response; “The biggest hurdle we had to overcome was creating a control system for the new drivetrain that delivered on our aim to give the driver an amazingly responsive car, both on winding roads and on the Autobahn.”
“We had to harness the ‘torque on demand’ that is characteristic of electric motors to secure the right kind of sports driving. The new automatic transmission allows us to do this.
“The car will do exactly what the driver wants. If they are in a sporty mood, they can take advantage of the instant and linear torque delivery. In fact, there is more torque at start-up than with our V8 hybrid and you can drive at higher speeds on electric power, thanks to the Multi Stage Hybrid System.
This is the first Lexus hybrid that can spin its rear wheels, which is a sign of the amount of power on demand.” He noted that the decision to configure 10 speeds for the system was based on the ambition to provide the ultimate balance of performance driving.
“Like the best athletes, true performance cars are about rhythm. We wanted the LC 500h to have the same fundamental philosophy as the V8-powered LC 500 (which uses a 10-speed automatic transmission), we came up with 10 speeds as the result of our search for the perfect rhythm – it could have been 11 or nine, but 10 felt best during the many test drives we made.” he added.
The new LC 500h engine has been adapted from the 3.5-litre V6 Atkinson cycle petrol engine from the GS 450h sedan, though engineered to operate at a higher speed, Mr Sato said.
Mr Sato remarked “The engine has been extensively modified for the LC 500h,” he said. “In particular, its speed has been increased. So while it will reach 6,000rpm in the GS 450h, here it peaks at 6,600rpm, but still with the efficiency that the Atkinson cycle delivers.”
The engineering team also focused on delivering a stirring audible experience befitting of a high performance luxury coupe, Mr Sato said.
“We followed the same philosophy as with the LFA in wanting to create a unique sense of sound harmony, using the natural sound of the engine and adjustable acoustic valves in the exhaust system,” he said.
“We succeeded in creating a distinctive sound for the Multi Stage Hybrid System which responds in a linear fashion to the way the driver uses the throttle pedal to accelerate continuously up to the engine’s high rev band.”
Finally, Mr Sato said the choice of a lithium-ion hybrid battery – a first on a Lexus hybrid – was based on achieving optimum packaging and weight distribution. “This brought a number of advantages both in terms of packaging and vehicle dynamics. It’s compact so we can provide more space for luggage, and it’s lightweight (at just 50kg) which helps us improve weight distribution and the car’s yaw inertia moment.” he concluded.
The all-new V8 powered LC 500 will make its appearance in South Africa in the first half of 2017 with further detail to follow.
