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August 31, 2009

2009 BMW Efficient Dynamics Concept

The BMW Vision concept car clearly demonstrates that the EfficientDynamics objectives are fully compatible when applied to a sports car. Conceived as a 2+2-seater with plug-in full-hybrid technology, this unique 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 outstanding result is made possible by the combination of BMW ActiveHybrid components with an extremely economical combustion engine, and outstanding aerodynamic qualities.

BMW EfficientDynamics Concept is the result of a "clean-sheet" development process to ensure that the correct achievements were made in the areas of efficiency, driving pleasure, technology, and emotional design. BMW EfficientDynamics Concept is the most comprehensive implementation of the EfficientDynamics philosophy seen so far. The powertrain provides a top speed limited electronically to 155 mph, with acceleration to 100 km/h in 4.8 seconds. Average fuel consumption in the EU test cycle is 3.76 liters/100 kilometers, equal to 62.6 mpg, and the CO2 emission rating is 99 grams per kilometer. CO2 emission management is even more outstanding when driving in the all-electric mode after charging the battery from a plug-in source: Taking all emissions in the generation of electricity into account, as prescribed by the EU formula, the car's emission rating is just 50 grams per kilometer.

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.

In its design, BMW EfficientDynamics Concept for the first time conveys the dynamic look of a BMW sports car to a hybrid vehicle. Developed with decades of experience in Motorsport, the body of this unique sports car is a result of intelligent lightweight technology and aerodynamic efficiency. In the design of the interior, the focus was likewise on both the fascinating driving experience and, in particular, on transparent, hands-on technology and maximum reduction of weight.

The combustion engine is a cutting-edge turbodiesel featured for the first time in the BMW EfficientDynamics Concept car. Displacing 1.5 liters 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 EfficientDynamics Concept 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.

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.

The energy cells featured in BMW EfficientDynamics Concept 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 EfficientDynamics Concept 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 3.7 V. 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 lb. 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 (220 V, 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 (380 V, 32 Amps) is available, the charge time is an even shorter 44 minutes.

The power delivered by the two electric motors and single diesel 3-cylinder engine gives the BMW EfficientDynamics Concept a level of performance superior to anything provided so far by a hybrid vehicle. Acceleration from a standstill to 100 km/h, for example, comes in just 4.8 seconds and the car could exceed its electronically-limited 155 mph top speed.

At the same time fuel efficiency and emission management now reach a standard only achieved, if at all, by far less powerful small cars conceived for city traffic and short distances. Applying the criteria of the EU test cycle, BMW EfficientDynamics Concept offers average fuel consumption equal to 62.6 mpg. CO2 emissions, in turn, are 99 grams per kilometer. These consumption and emission figures are measured on a consistent internal power balance, meaning that the batteries and storage media for electrical energy maintain the same charge level throughout the entire test cycle (with the same level at the beginning and end) and are charged while driving only by the car's on-board systems.

To further optimize the aerodynamic qualities of the entire vehicle and keep rolling resistance to a minimum, BMW EfficientDynamics Concept 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 EfficientDynamics Concept 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 EfficientDynamics Concept car a very low drag factor (CX) of just 0.22.

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