BMW Vision EfficientDynamics diesel hybrid concept
The BMW Vision concept car is the latest in a string of “EfficientDynamics” ideas by the German automaker. Conceived as a 2+2-seater with plug-in full-hybrid technology, this concept car combines the performance of a BMW M vehicle with a standard of fuel efficiency and emission management that exceeds even the current levels achieved by the latest small cars. This result is made possible by the combination of BMW ActiveHybrid components with an economical combustion engine and good aerodynamic qualities.
The powertrain provides a top speed limited electronically to 155 mph, with acceleration to 62 mph in 4.8 seconds. Average fuel consumption in the EU test cycle is 62.6 mpg.
The power and performance are made possible by combining a fuel-efficient 3-cylinder turbodiesel with one electric motor on each axle. The intelligent combination of these units, together with precisely controlled energy management, simultaneously enhances the dynamic performance and the efficiency of the car. Overall system output is 356 horsepower, and peak torque is 590 lb-ft. The special arrangement of the two motors and diesel engine allows all-wheel drive when driving in all-electric mode. The result is minimum power loss and a harmonious transmission of the power available under all conditions.
The combustion engine is a cutting-edge turbodiesel featured for the first time in the BMW Vision EfficientDynamics concept car. Displacing 1.5L on three cylinders, the engine consistently follows the downsizing principle of using a relatively small engine combined with a turbocharger to reduce fuel consumption.
Through its compact dimensions, the 3-cylinder fits conveniently in front of the rear axle like in an agile mid-engine sports car, despite the two seats at the rear. Fuel is injected by the latest generation of High Precision Direct Injection, and the turbocharger features variable intake geometry for maximum efficiency. Engine output is 163 hp with peak torque of 214 lb-ft.
The specific output of 109 hp per liter sets a new benchmark in diesel technology. The power delivered by the turbodiesel is conveyed to the rear axle by means of a double-clutch transmission (DCT). This advanced transmission technology, which already offers a particularly dynamic driving experience in BMW’s M3 and Z4 Roadster, allows the driver to shift gears without the slightest interruption of power. BMW Vision EfficientDynamics features a newly-developed version of BMW’s DCT with six speeds for maximum efficiency and flexibility.
The combustion engine is supplemented by two electric motors. Consistently applying the BMW ActiveHybrid philosophy, development engineers followed the principle of “Best of Hybrid,” choosing the optimum combination of a hybrid synchronous motor on the front axle and a full-hybrid system at the rear.
In this concept, the driver benefits from the efficiency of the electric motors over a far wider speed range than with a conventional hybrid car. The rear axle comes with a second-generation full-hybrid system corresponding to the technology in the BMW ActiveHybrid 7 production model. The compact electric motor positioned between the diesel engine and the DCT outputs a consistent 33 horsepower and is able to reach a peak of up to 51 hp. Maximum torque for the rear electric motor is 214 lb-ft, the power, either supporting the diesel engine or in all-electric motoring. When coasting or applying the brakes, the electric motor acts as a generator and feeds electric power to the lithium-polymer battery in the car. The electric energy developed in this way is therefore captured without any additional consumption of fuel through the principle of Brake Energy Regeneration. Energy wasted on the brakes of a conventional car is thus saved within the new power system for subsequent use in driving the car.
A second electric motor acts on the front axle. This engine, a hybrid synchronous motor, offers continuous output of 80 horsepower and peak torque of 162 lb-ft. Extra power of 112 horsepower is available for a period of up to 30 seconds, and, for a 10-second “burst,” the electric motor is able to develop 139 horsepower. The power is transmitted through a 2-stage, single-speed reduction gearbox.
BMW Vision EfficientDynamics is able to run completely under electric power, with the power of the turbodiesel engine alone, or through an infinite combination of the three power sources. Depending on driving conditions, the two electric motors may be used both for accelerating and for regenerating energy when applying the brakes and while coasting. This principle ensures efficient energy management, with the charge status of the lithium-polymer battery constantly remaining within the optimum range. When accelerating, the electric motors help to boost the car for even greater performance, ensuring immediate response and a significant reduction in fuel consumption. For a short time, such as in passing maneuvers, the cumulative maximum output of all three engines increases to 356 hp, with maximum torque generated by the three engines reaching 590 lb-ft.
The energy cells featured in BMW Vision EfficientDynamics are housed in a chassis element running from front to rear through the middle of the car. The front unit is the lithium-polymer complex, an ongoing development of the lithium-ion battery. Overall, BMW Vision EfficientDynamics comes with a total of 98 lithium-polymer cells, each offering a capacity of 30 amp/hours and developing continuous output of 600 Amps at a voltage of 3.7V. For a period of 30 seconds, each cell is even able to develop maximum output of 1,200 Amps.
Serial arrangement of the lithium-polymer cells serves to generate nominal voltage of 364 volts, the gross storage capacity of the battery is 10.8 kW/h. With an unusually high discharge capacity of 80 percent, the battery delivers 8.6 kW/h for driving the car. This superior performance comes on overall weight of the entire energy storage system of just 187 lbs. A further advantage is that through their optimum dimensions tailored to the specific qualities and features of the car, the lithium-polymer cells, together with the operating strategy chosen with a concept of “forward looking” energy management, reduces the thermal load acting on the battery to such an extent that there is no need for active cooling.
Brake Energy Regeneration captures electric power generated while driving without additional fuel consumption, which is subsequently used to supply power to the electric motors and on-board network. A further option is to connect the lithium-polymer cells to a conventional power socket for a simple and efficient charge process, using a plug-in connector in the front-right wing of the car. Connected to a standard EU power outlet (220V, 16 Amps), the system requires a maximum of 2 ½ hours to fully charge the lithium-polymer cells. And wherever a power source with higher voltage and amperage (380V, 32 Amps) is available, the charge time is an even shorter 44 minutes.
In addition to electrical energy storage, BMW Vision EfficientDynamics comes with a conventional fuel tank at the rear end of the central chassis tunnel, offering a capacity of 6.6 gallons. Running on diesel fuel alone, BMW Vision EfficientDynamics is able to cover a distance of approximately 400 miles with its combustion engine. Benefitting from an extra range of up to 31 miles in the all-electric mode, the car offers an overall range of approximately 431 miles. As a result, this unique concept car offers all the requirements for using energy with maximum efficiency and at the same time experiencing the dynamic performance typical of BMW without any restriction of everyday driving qualities.
As a plug-in hybrid, BMW Vision EfficientDynamics is able to cover the entire drive cycle for measuring fuel consumption also with its combustion engine completely switched off. Then, to subsequently charge the lithium-polymer cells to the same status as when setting off, all the driver has to do is connect the car to an external power grid. To determine the consumption of electric power, the only requirement is to compare the charge level of the battery before and after the test cycle. Applying this measurement process, the BMW Vision EfficientDynamics concept car consumes 17.5 kW/h per 62 miles.
To determine the total volume of CO2 emissions when driving in the all-electric mode, new legal standards for measuring the level of fuel consumption are currently being prepared for hybrid and electric cars with a plug-in power supply. Applying this calculation method, the CO2 emission ratings generated by BMW Vision EfficientDynamics are reduced further to just one-third of the original figure of 99 grams per kilometer. Clearly, this significant reduction of emissions opens up a new dimension in BMW’s EfficientDynamics development strategy in this unique concept car.
BMW Vision EfficientDynamics also takes a new approach in its design and streamlining, the body and the interior clearly expressing the unique combination of supreme efficiency and the sporting performance of the brand. Following BMW’s design language, this concept car visualizes both highly efficient aerodynamics and intelligent lightweight construction.
In its design, BMW Vision EfficientDynamics differs from the usual low-emission car concepts. The principle of “form follows function” is not just for the overall look of the car, but embraces each and every detail. Measuring 48.8″ in height and boasting a sweeping, arch-like roofline, BMW Vision EfficientDynamics offers the slender silhouette of a classic Gran Turismo. With the combustion engine fitted in front of the rear axle, the designers have succeeded in giving the car a very low front end, with the flow of air being further smoothened by active louvers in front of the radiator, which close completely when the need for cooling air is low. This efficient function follows in the footsteps of the active air flap control already used as a feature of BMW EfficientDynamics in some of BMW’s current production models. As a further highlight, BMW Vision EfficientDynamics guides air smoothly and exactly as required into the car through an active air intake at the front.
To further optimize the aerodynamic qualities of the entire vehicle and keep rolling resistance to a minimum, BMW Vision EfficientDynamics comes with tires and wheels of quite unusual size on a sports car. The tires measure 195/55, while large 21-inch wheels provide a contact surface on the road otherwise offered only by a much wider tire. In combination with the sophisticated axle geometry, this ensures agile driving behavior.
The extra-large wheel covers extending over part of the tire flanks add to the unique, very different look of BMW Vision EfficientDynamics from the side. The blade profile integrated in the wheels serves furthermore to reduce the negative effect of the turning wheels on the overall aerodynamics of the car. In all, these features optimizing the aerodynamic qualities of the car give the BMW Vision EfficientDynamics concept car a very low drag factor (CX) of just 0.22.
Measuring 181.1″ in length, 74.8″ in width and 48.8″ in height, this unique concept car offers ample space for up to four passengers and their luggage. Thanks to the consistent lightweight construction strategy applied on the car, curb weight is 3,076 lb, with the center of gravity remaining very low. In its power-to-weight ratio, the BMW Vision EfficientDynamics concept car is far superior to all other hybrid cars, achieving the same standard as extremely dynamic sports cars with a conventional combustion engine.
Carrying a maximum payload of 981 lb, this unique 2+2-seater is fully suited for everyday traffic. Luggage capacity of 5.3 cu ft, in turn, allows the driver and passengers to conveniently take along two golf bags. And to meet additional loading requirements the backrests of the two rear seats may be tilted down individually to provide extra storage space.