The BMW i8, the second milestone model to emerge as part of BMW’s innovative ‘i’ sub-brand, earned the distinction as Green Car Journal’s 2015 Luxury Green Car of the Year™ at the recent Washington Auto Show in the nation’s capital. There are compelling reasons for this.
BMW’s flagship i8 not only breaks new ground in defining how a high performance vehicle can achieve environmental goals, but it does so in ways that do not impose limitations on the driving experience. Importantly, this car fits BMW's ‘Ultimate Driving Machine’ image while providing levels of environmental performance increasingly appealing to those buying aspirational vehicles.
BMW i8 LIFEDRIVE ARCHITECTURE
Beneath its stunning, gull-winged body is BMW’s innovative LifeDrive modular architecture. The Life module is essentially the i8's 2+2 passenger compartment constructed primarily of strong and lightweight carbon fiber-reinforced plastic (CFRP), created with carbon fiber manufactured at a dedicated SGL Automotive Carbon Fibers LLC facility in the State of Washington. The result of a joint venture between SGL Group and BMW Group, this manufacturing plant strengthens the i8’s environmental credentials further by producing carbon fiber using renewable hydroelectric energy.
The i8’s aluminum Drive module contains the gasoline engine, lithium-ion battery pack, electric motor, and associated electronic components. It uses a 228 horsepower, 1.5-liter turbocharged three-cylinder engine to power the rear wheels through a six-speed direct shift transmission. Front wheels are driven by a 129 horsepower electric motor and two-stage automatic gearbox. Energy is supplied by a 7.1-kilowatt-hour lithium-ion battery pack located within a tunnel between the two front seats. It can be fully charged in just an hour and a half.
Power can be provided solely by the electric motor for about 22 miles of zero-emission driving at speeds up to 75 mph. Together, the rear-mounted engine and front electric motor deliver all-wheel drive performance with a combined maximum power of 357 horsepower and 420 lb-ft of torque. Drivers are afforded the latest in advanced on-board electronics and safety systems expected in this class of vehicle.
Driving the i8 at speed provides a clear understanding of just what BMW has accomplished with its lightweight, high-tech luxury sports coupe. Green Car Journal editors found the i8’s handling superb and performance exhilarating. BMW’s Driving Dynamics Control allows choices of eDRIVE, ECO PRO, SPORT, and COMFORT drive settings. In Sport mode, the i8 can accelerate from zero to 60 mph in 4.4 seconds and deliver a top speed of 155 mph. Driving range is 310 miles under normal driving conditions. Engine overrun and regenerative braking are used to charge the battery pack and a start-stop feature helps conserve energy.
The BMW i8 blends thrilling performance, innovative design, and environmental achievement in an exceptional luxury sports coupe, while offering a combined EPA city/highway battery electric efficiency rating of 76 MPGe (miles-per-gallon equivalent). Its DNA is 'green' by nature and design, making it a natural selection for 2015 Luxury Green Car of the Year™.
Race car designers go to extreme measures to make competition vehicles as light as possible. Lighter is faster. It’s simple physics; less horsepower is required to accelerate a light vehicle compared to a heavy one. So on a given amount of horsepower, a lighter race car will be faster than one that weighs even a few pounds more. It also takes less energy to slow the car, providing better braking performance. A lighter car will generally handle better, too, since there is less mass working on the chassis through the corners.
Lighter vehicles are also more environmentally friendly since they require less energy to move from point A to point B. Shaving a few hundred pounds off a car design can yield major improvements in fuel economy. In addition to improved mileage, electric vehicles will see longer range between charges if they can be made lighter.
Trimming pounds off a production car is not as easy as it seems, however. Today’s road worthy vehicles must feature hundreds of pounds of federally mandated safety equipment that wasn’t required or available a few decades ago. Equipment like antilock brake systems, multiple airbags, advanced computer controls, and crash mitigating high-strength body structures all add weight to a vehicle design. Pile on the comfort and convenience equipment that most new car buyers expect in a modern car or light truck and the extra bulk adds up fast.
That’s why vehicle designs like the new BMW i3 and i8 are so intriguing. These models are revolutionary for mass production vehicles, featuring clean sheet designs that found BMW designers throwing traditional materials and production methods out the window, resulting in lightweight electric-drive cars with maximum strength for safety.
For example, the i3’s primary body and chassis structure are composed of two separate units that form what BMW calls the LifeDrive architecture. The primary body structure is the Life module and the Drive module incorporates the powertrain components. The passenger cell module is made from Carbon Fiber Reinforced Plastic, or CFRP. This is the first ever use of CFRP in a mass production vehicle. Carbon Fiber Reinforced Plastic is every bit as strong as steel yet is 50 percent lighter. When you can trim half the weight off something as large as a body structure, you are talking major weight savings.
Aluminum has been used as a lightweight material in the transportation industry for many years. The i3’s rear Drive module that houses the electric drive motor, rear suspension, and optional range extending gasoline engine is made of aluminum. While both are light and strong, Carbon Fiber Reinforced Plastic is even 30 percent lighter than aluminum. Materials throughout the i3 were selected for their weight saving properties and for their sustainability characteristics.
Beneath the flat floor (there is no transmission tunnel) of the i3 is a space-saving 22-kWh lithium-ion battery pack that tips the scales at 450 pounds. Power is delivered by a hybrid synchronous electric motor. The motor produces 170 horsepower with 184 lb-ft torque and can spin up to 11,400 rpm. The compact electric motor offers immediate torque and weighs just 110 pounds. With a curb weight of just 2,700 pounds, the i3 is nimble and great fun to drive. As in racing, automakers strive to save weight because it gives them a competitive edge. Sometimes, less is more.
BMW is planning to offer the i series of electric, plug-in hybrid, and range-extended electric vehicles beginning in late 2013. This entirely new model line will offer BMW’s usual focus on premium engineering and style, but critically, it will also feature a consistent focus on eco sustainability and urban living. BMW is serious enough about this to have worked with New York University to develop a report, ‘Urban Mobility in the 21st Century.’ The report finds that 80 percent of us drive less than 50 miles per day, and that by 2050 the world’s urban population will grow by 80 percent, from 3.5 billion to 6.3 billion. In short, BMW thinks we need cars that work in megacities and also don’t pollute.
The large volume, five-door i3 hatchback will be constructed of lightweight carbon-fiber reinforced plastic containing the i series ‘life’ passenger cell and ‘drive’ electric propulsion cell, powered by a 170 hp electric motor driving the rear wheels. A range-extender engine will be optional. In a departure for BMW, the i3 will have rear ‘coach doors’ hinged at the rear of the doors rather than the front, plus bench seats to make city living (and parking) easier.
The seductive, two seat i8 coupe/cabriolet combines the same lightweight engineering with a 131 hp electric motor driving the front wheels and a 223 hp, 1.5-liter 3-cylinder turbo gas engine at the rear. These powerplants can be used together or separately. The car’s combined 354 horsepower accelerates the i8 from 0 to 60 mph in under six seconds. The i8 also features an electric-only range of 20 miles, a top speed of 155 mph, and up to 80 mpg.
BMW’s long-term mobility plan seems a good one. It integrates lessons learned from data gleaned from its extensive Mini-E and ActiveE electric vehicle field trials and focuses on sustainable manufacturing, practicality, and pollution reduction in an entirely new series of vehicles. BMW’s new i series could be poised to make a huge impact on how electric vehicles are designed and built.
BMW's Concept Active Tourer, a through-the-road plug-in hybrid, uses a front-mounted engine to drive the front wheels and an electric motor to drive the rear, with no mechanical connection between the two. In most hybrids the output of the engine and motor are combined. The Concept Active Tourer is the first additional application of the eDrive system used in the i8, which incorporates an electric motor, lithium-ion battery, and intelligent engine control. BMW will use the eDrive designation for all its electric and plug-in hybrid vehicles.
Like BMW’s latest four- and six-cylinder engines, the BMW Concept Active Tourer’s 1.5-liter three-cylinder gasoline engine uses BMW TwinPower turbo technology. Even though it has only three-cylinders, BMW claims it is very smooth running even at low speeds and emits the sporty sound expected of a BMW.
The synchronous electric motor can power the car for up to 18 miles exclusively on a fully charged battery. It also augments the gasoline engine to provide over 190 horsepower when maximum power is required. BMW expects it will get an impressive 94 mpg, achieved partly through automatic engine start/stop and regenerative braking energy supplied the rear axle during deceleration. A high-voltage generator connected to the 1.5-engine also charges the battery while driving.
BMW’s Concept Active Tourer has an ECO PRO mode to help reduce fuel consumption. When appropriate, it reduces air conditioning and other electrically powered creature comforts to increase fuel efficiency. Linked to the navigation system, ECO PRO mode gives drivers advice on how to reach a destination using minimum fuel. ECO PRO mode also completely shuts off the engine at speeds up to nearly 80 mph, and then decouples the engine from the drivetrain up to 100 mph to make full use of the kinetic energy already generated.
The Efficient Dynamics strategy uses information from the navigation system to optimize electric motor and battery efficiency. For example, it calculates in advance the most suitable driving situations and sections of a route for electric-only operation or to charge the battery. This optimized charging strategy can achieve an energy savings up to 10 percent and thus increase electric range.
While small on the outside, the Tourer is very roomy on the inside. It rides on a long 105 inch wheelbase and has an overall length of 171 inches. A tall roof allows a raised seating position for an excellent all-around view. Batteries are located entirely beneath the floor so there’s no intrusion into passenger or cargo space.
Will the BMW Concept Active Tourer appear in dealer showrooms? BMW has a good track record for putting concept vehicles into production, so here’s hoping.