Weight-minimising measures courtesy of the BMW EfficientLightweight strategy enable the new BMW 7 Series models to tip the scales up to 130 kilograms lighter than their previous-generation model, despite significant additions to the roster of comfort and safety equipment on board. A central element here is the Carbon Core body structure of the luxury sedan.
The use of carbon fibre reinforced plastic (CFRP) for structural elements of the passenger cell based on hybrid construction with ultra-high-strength steels – such as the B-pillars – increases both the overall strength and the torsional and bending stiffness of the passenger cell. To this end, the configuration of sheet metal elements can be adjusted as required, allowing for a significant reduction in the weight of the body.
The foundations for the Carbon Core body were laid by the transfer of technology from the development of the BMW i models. The next generation of the BMW 7 Series therefore benefits from the BMW Group’s experience and expertise – unequalled by any other carmaker – when it comes to the appropriate use of CFRP in mass-produced vehicles. At the same time it leads the way in exploring new applications for the high-tech material. The new BMW 7 Series is the first car to use industrially manufactured CFRP in its body construction not as a visible material in the outer skin, but in combination with steel, aluminium and plastic. It is also the first car in which the CFRP has been fully integrated into the production process, largely based on a globally unique paint application process. Its Carbon Core is thus also an indicator of how significantly the CFRP technology developed for BMW i models can contribute to the minimisation of a car’s weight as well as its material strength and stiffness.
Furthermore, the intelligent material mix encapsulated by the BMW EfficientLightweight strategy includes the carefully calculated use of aluminium and ultra-high-strength steels in the body and chassis. This is complemented by the introduction of innovative, weight-minimising bonding technologies and at-source heat and soundproofing for the engine, which allow reductions in the overall quantity and therefore the weight of the insulation materials required.
As well as the development of ultra-lightweight concepts and an intelligent material mix, the BMW EfficientLightweight approach also drives a systematic process of detail optimisation for all components with the aim of achieving the best possible result for each class of car. For the new BMW 7 Series this has meant combining the model’s impressive driving dynamics with outstanding comfort. To this end, the engineers have explored innovative new directions in areas such as weight distribution, unsprung masses and acoustic concepts.
Unsprung masses have been reduced by as much as 15 per cent over the predecessor models through a focus on lightweight design for the suspension, brakes and wheels. The implementation of an at-source insulation concept and the use of super absorbers have led to excellent interior acoustics coupled with a reduction in weight.
The resulting integrated lightweight design concept also enables the car’s centre of gravity to be lowered still further and weight to be distributed between the two axles at a near-perfect 50:50 ratio. In this way, BMW EfficientLightweight technology does even more to ensure that the next generation of the BMW 7 Series can build on its lead in the area of driving dynamics while also offering outstanding ride and acoustic comfort.