From the Goodwood Festival of Speed: what's driving the development of EV hypercars.
When I wrote last month that Ferrari is appointing a CEO from the semiconductor industry in pursuit of its electrification strategy, I didn’t imagine a few weeks later I’d be out at a show for supercars and hypercars and talking to the car designers about electric vehicle (EV) and hybrid vehicle strategies and design challenges.
But lo and behold, just a couple of weeks ago, I was asked to cover the Goodwood Festival of Speed. Having never been to this event, I thought maybe as it’s a motorsports event, there might not be much to cover for EE Times. For most of the 160,000 car enthusiast visitors to the show, it’s all about performance and speed as they watch motors roaring around the track all day long for four days, and gape at huge open air exhibition of race track cars, hypercars, vintage cars and performance road cars.
It was clear once I started talking to product managers and asking the right questions, it was easy to get down to talking about the technologies, the powertrain, the electronics and the communications architectures relevant, and anything that helps optimize for speed and super performance — as well as weight.
The show saw debuts of both EV hypercars as well as pure internal combustion engine (ICE) cars. Companies like Zenvo, a small Danish company that makes only five hypercars a year, said they don’t have plans for pure electric hypercars as they cater to a market of car enthusiasts. The 25-person company makes the TSR-S track focused but also road-legal car fully in Denmark, including all the electronics and powertrain. Interestingly, they opted to use a standard iPad for the display as it has an interface that everyone uses. CEO Angela Hartman told us that they are looking at a hybrid strategy in the future, but their first plans were to start selling in the U.S. from October and up their production to 20 cars a year.
Meanwhile, Louis Kerr, chief platform engineer at Lotus, took time out to explain the company’s work on the Lotus Evija, an all-electric hypercar currently in prototype phase. While the focus at this year’s Goodwood was on the launch of the brand-new Lotus Emira, the company’s last ever petrol engine car launch, the Evija is really driving its design thinking of the future.
At the heart of the Evija is an ultra-advanced all-electric powertrain, developed by technical partner Williams Advanced Engineering, known for its success in motorsport, from Formula One to electrifying the first four seasons of Formula E. The battery pack is mid-mounted immediately behind the two seats and supplies energy directly to four independently controlled high-power density e-motors. These feature integrated silicon carbide (SiC) inverters and an epicyclic transmission on each axle of the four-wheel drive powertrain.
The motors and inverters are supplied by Integral Powertrain Ltd. Four compact, extremely light and highly efficient single-speed, helical gear ground planetary gearboxes transfer power to each driveshaft. Each gearbox comes packaged with the e-motor and inverter as a single cylindrical electrical drive unit (EDU). With a target power of 500 PS per e-motor, this is the most efficient and elegant engineering solution to deploying so much power with precision.
Torque-vectoring, enabled by the four e-motors, provides good dynamic response and agility on the road. This fully automatic, self-adjusting system can instantly distribute power to any combination of two, three or four wheels within a fraction of a second. In track mode the ability to add more power to individual wheels enables the radius of corners to be tightened, potentially reducing lap times.
Kerr told us that the biggest challenge in the electronics design was the complexity of the control logic to enable optimal control of each axle. He added that the Evija had a full cloud connected computing solution behind it. The main aim for this is to be able to monitor cars which might be anywhere in the world, and to be able to reliably predict when a customer might need a car servicing so they can send relevant support.
Weight reduction: the holy grail
The common theme most manufacturers we talked to was around minimizing weight to enable better power delivery efficiency, intelligent airflow management to reduce drag and improve performance, and effective delivery of power to the axle for precision control by the driver.
McLaren made a big deal about weight in its new Artura showcased here at Goodwood: it said minimizing weight was key to the design of the all-new electrified powertrain, engineered to offer the advantages of internal combustion and electric power in one package and establish new benchmarks for combined performance and efficiency in the supercar class.
The axial flux design of its e-motor is one of the Artura benchmarks. It is similar in size to a McLaren brake disc and at just 15.4kg it is only a little heavier than a conventional iron rotor component, yet it can generate up to 95PS and 225Nm as well as enable journeys of up to 30 km in near-silent pure EV mode. Providing the electric-only capability is a 7.4kWh five-module lithium-ion energy dense battery pack. Fully integrated into the Artura’s McLaren lightweight architecture (MCLA) chassis, the battery pack is positioned low-down in the car behind the driver, incorporated into the floor and protected on three sides by the main carbon fiber structure and from behind by the engine. This positioning also helps to optimize both center of gravity and the polar moment of inertia, benefiting dynamic agility.
The hybrid battery sits on a cooling manifold, which is shared with the new electric heating, ventilation and air conditioning system also used to control air temperature in the cabin. Incorporating technology first developed for the McLaren Speedtail, the batteries are thermally controlled using dielectric oil — a technology also used to keep the e-motor at operating temperatures that deliver the highest level of performance.
To further optimize packaging and weight, the battery management unit sits alongside the modules, with the power distribution unit (PDU) integrated into the battery. An integrated power unit (IPU) acts as a DC/DC converter for the vehicle’s 12v system, further reducing weight by removing the need for a separate alternator and on-board battery-charger.
An Artura driver can adjust how the electric motor is deployed to prioritize range or power, or choose to shut off the internal combustion engine for silent running. Energy harvesting is achieved purely from the combustion engine in order to maintain brake pedal feel, yet the battery can be charged from low to 80% full within minutes under normal driving conditions.
Ian Howshall, a global product manager at McLaren, explained to us that the complete architecture of the car is brand new to accommodate the high voltage battery required. He also said that the main fundamental change is to move from the large wiring harnesses to ethernet, plus the use of decentralized electronic control systems, with separate domain based electronic control units (ECUs) for different domains. These both help minimize weight, as well as improving critical signal response times where it is needed.
No-rules track car
Among the other new or experimental hypercars, McMurtry Automotive was exhibiting its experimental, pure electric, track car concept, the McMurtry Spéirling. The company said it had created the ultimate no-rules track car by exploring the route that uninhibited technical evolution would have taken from the golden age of racing to shape the motorsport of today.
David Turton, a mechanical design engineer at the company, told us, “Our aim is to change perceptions on small cars, so we want to produce extremely small, fast, exciting and efficient electric cars. Today we’re unveiling the no rules track car, which is akin to a hypercar to demonstrate the technologies that are required to excite people about electric cars in this form factor.”
The development of the car is funded by Irish billionaire and inventor, Sir David McMurtry, who founded Renishaw, a precision metrology company. His backstory is that he initially trained as an apprentice in the aerospace industry in the U.K, and then became the youngest ever assistant chief of engine design for all Rolls-Royce engines manufactured in Filton, Bristol. Whilst there, he invented the 3D touch-trigger probe to solve a measurement problem faced with the Olympus engines for the supersonic Concorde aircraft, and then founded Renishaw Electrical in 1973 with John Deer to commercialize the product.
Hence Turton explained, “We’re in a very fortunate position that Sir David McMurtry who founded the company, is supporting us for the three-year design and build phase of this car. Not many companies are able to do such a radical concept for such a long time in complete secret and then reveal a fully working prototype at one of the biggest motoring events in the world.”
Turton said the car being shown at Goodwood is a high-performance track car concept with extremely low drag. “There’s no front or rear wing, but instead our downforce comes from an onboard downforce on demand system, which is a fan-based downforce system with over 80 horsepower sucking the car to the track. What it means is when you’re going extremely high speed, your car is low drag, which reduces energy consumption. But you also get 100% downforce from 0 miles an hour. Hence launching off the line, taking hairpins and going through high-speed corners, you’re getting peak downforce at all times.”
He added the key thing about the car that makes it small and compact and lightweight and under a ton is that the battery and chassis are integrated together. “We’ve iterated to get the battery integrated right alongside the driver in the side part of the car and underneath the driver’s legs and that battery layout is patented to our to our company. In the battery pack, we’ve had extremely high-power cells, so we can charge and discharge at an extremely high rate. And because our car is so low drag, we get the best of both worlds. You’re getting the high power for acceleration and charging, and the low drag for speed and range. The battery is over 800 volts.”
A clear message we were getting from most of the engineers and product managers is that by pushing the limits for experimental track hypercars, or even those going into production, these pave the way for being translated to commercial application in road cars and other areas.
As Turton said, “Our long-term goal is to produce road cars, but it’s important for us to demonstrate something that’s really exciting and never been seen before.”
This article was originally published on EE Times.
Nitin Dahad is a correspondent for EE Times, EE Times Europe and also Editor-in-Chief of embedded.com. With 35 years in the electronics industry, he’s had many different roles: from engineer to journalist, and from entrepreneur to startup mentor and government advisor. He was part of the startup team that launched 32-bit microprocessor company ARC International in the US in the late 1990s and took it public, and co-founder of The Chilli, which influenced much of the tech startup scene in the early 2000s. He’s also worked with many of the big names – including National Semiconductor, GEC Plessey Semiconductors, Dialog Semiconductor and Marconi Instruments.