Lotus to Introduce Plug-in Series Hybrid

Shot of the Evora 414E Hybrid concept. Click to enlarge.

Lotus Engineering will unveil the Lotus Evora 414E Hybrid concept at the upcoming Geneva Motor Show. The concept is a high-performance technology demonstrator with a plug-in series hybrid drive system—featuring the Lotus Range extender engine and new technologies for enhanced driver involvement.

For the Lotus Evora 414E Hybrid—so-named because it produces 414 PS (306 kW, 408 hp) of power—Lotus Engineering developed a drivetrain system consisting of twin motors each limited to providing 152 kW (207 PS/204 hp) of power and 400 N·m (295 lb-ft) of torque to each wheel via independent, single speed, reduction transmissions integrated into a single housing, enabling torque vectoring dynamic control of the vehicle. The 414E Hybrid accelerates from 0-60 mph (97 km/h) in less than 4 seconds.

A conventional Evora. Click to enlarge.

A Lithium Polymer battery pack provides 17 kWh of energy storage capacity. The battery pack is optimized for energy density, efficiency and high power demand, with more than 100 kW discharge capability. All electric range is up to 35 miles (56 km), and total hybrid range is more than 300 miles (483 kilometers).

The 1.2-liter, 3-cylinder Lotus Range Extender engine provides 35 kW (48 PS/47 hp) of power at 3,500 rpm via the integrated electrical generator and features an innovative architecture comprising an aluminium monoblock construction, integrating the cylinder block, cylinder head and exhaust manifold in one casting. This results in reduced engine mass, assembly costs, package size and improved emissions and engine durability.

The engine uses an optimized two-valve, port-fuel injection combustion system to reduce cost and mass and can be operated on alcohol-based fuels and/or gasoline. The generator converts mechanical energy to electrical energy to replenish the battery pack charge and provides additional vehicle range in a small light weight package. The generator is also used as a motor to start the range extender engine. The low mass of the range extender unit (85 kg) and compact package makes it ideal for the series hybrid drivetrain in the Evora 414E Hybrid.

All the operation and management of the range extender engine, the power management of the batteries and motor control are controlled by Lotus’ electronic control units and software systems.

For everyday commuting journeys, up to 35 miles can be travelled using battery power. The battery can be charged overnight using a conventional domestic supply through a socket concealed by the rear number plate.

Lotus used its own vehicle simulation tools to determine the size, capacity, power and performance of all the components in the drivetrain system to optimize the system operation. Overall this is far more energy-efficient, weight-efficient and cost-effective than fitting the vehicle with a larger and more expensive battery, which for the majority of short journeys is a redundant weight, which increases energy requirements, Louts says.

Lotus claims that with regard to the total lifetime CO₂ emissions of the vehicle, including the energy required to manufacture and run it, the range extender solution has a lower overall CO₂ footprint than a fully electric car of comparable performance and operating range running with a larger battery.

Innovation has always been at the heart of Lotus and is needed now more than ever. The Evora 414E Hybrid is the perfect demonstration of Lotus Engineering’s core competencies: lightweight architectures, efficient performance, electrical and electronics integration and driving dynamics. The technology demonstrator represents an encapsulation of the advanced technologies that Lotus Engineering continues to develop to overcome the current environmental challenges facing the automotive industry and showcases the future direction that the sector is taking and why Lotus Engineering is perfectly placed to lead the technological development in this area.

—Robert Hentschel, Director of Lotus Engineering

Driver interaction. The Evora 414E Hybrid provides less of a psychological step change for people familiar with high-performance cars compared to other electric and hybrid sports cars. The car has a simulated paddle shift gear change offering ultra quick gear changes reminiscent of a dual clutch transmission, while actually single speed. This enhances the driver interaction with the vehicle and provides a driving experience similar to current internal combustion engine high performance sports cars. The Evora 414E Hybrid uses a column mounted paddle shift to simulate the gear change and a synthesized engine sound changes frequency with virtual gear selection. The drive torque is also modulated to simulate a physical feeling of a gearshift jolt.

The virtual gearshift simulation, like a conventional gearbox, is used to change the driving characteristics and response of the vehicle. The most significant aspect that this offers the driver is the ability to control the vehicle deceleration by simulating engine braking through a virtual downshift in gears. Unlike true engine braking, the Lotus system does not dissipate the energy of the moving vehicle through internal engine friction but uses the electric motors to regenerate the energy back into the battery. While many electric and hybrid vehicles provide engine braking, this is generally at a fixed rate or preselected rate. In some driving situations this can either be too aggressive, slowing the vehicle unnecessarily, or too light, requiring additional braking application.

The Lotus system effectively allows the driver to select the appropriate level of regeneration by simulating stepping down by one, two or even three gears. The simulation of engine braking through both the gear noise change and the retardation of the vehicle is fully intuitive to a driver familiar with a conventional gearbox. The simulated gearchange capability can be selected for greater driving involvement or switched off for more relaxed driving.

The Evora 414E Hybrid uses the Lotus Engineering and Harman International developed HALOsonic suite of noise solutions. The first of which is Electronic Sound Synthesis. This generates engine sounds inside the vehicle through the audio system where it provides an exciting sports sound in line with the brand and nature of the vehicle together with a high level of driver feedback in an intuitive manner. In addition, it also generates sound on the outside of the vehicle through speakers mounted at the front and rear to provide a warning to increase pedestrian safety, which is especially important for electric and hybrid vehicles which can be difficult to hear at slower speeds.

There are four driver selectable engine sounds currently on the vehicle, two of which have been designed to have characteristics of a multi-cylinder conventional V6 and V12 engine. There is also a futuristic sound and a combination of a conventional engine and a futuristic sound, enhancing the brand identity of the vehicle as a step forward in electric vehicle design.

The addition of this Lotus patented simulated gearshift concept not only provides for an exciting and involving driving experience that customers would expect from a Lotus, but also enhances the driver’s control of the vehicle while providing the capability for more efficient operation through a greater use of energy regeneration.

Structure. The Lotus Evora 414E Hybrid structure is the same award-winning, versatile vehicle architecture (VVA) used on the Lotus Evora. The low volume architecture was designed with the upmost flexibility in mind. The Evora 414E Hybrid is an example of how to integrate a compact packaged drivetrain, offering excellent performance and range, while using this underpinning. The complete chassis has remained unchanged from the Evora which maintains the structural integrity and strength performance of the original car.

The structure progresses the Lotus ‘bonded and riveted’ technology with new and unique extrusions and folded panels, whilst providing production build modularity and lower cost repairs. The chassis has been designed for scalability so that it can be extended in width, length and height. The strength and stiffness of the low volume VVA chassis can be modified cost effectively by varying the wall thickness of the extrusions, without altering the exterior dimensions. The ability to lengthen or shorten extrusions with the option to tailor the chassis stiffness vastly increases the number of vehicles that can be developed from this vehicle architecture.

Lotus is also showcasing a series hybrid vehicle technology application, including the Lotus Range Extender Engine, in the PROTON Concept to be unveiled at Geneva.

Source: Green Car Congress