Two cars in one – on reaching a speed of 80 km/h, the Mercedes-Benz Concept IAA switches automatically from design mode to aerodynamic mode, at which point numerous active aerodynamic measures alter its appearance. As a result of this transformation, the Cd value improves from 0.25 to 0.19 – a new world record for a four-door four-seater. The frontal area totals 2.16 m2.
The designers employed the latest algorithmic design methods to handle the complex geometric design. The individually adapted software enables dynamic design in three-dimensional space. This dynamic modelling makes it possible to display and model different states simultaneously. The resultant highly complex geometries were turned into reality with the aid of innovative production technologies (rapid prototyping).
The Concept IAA aerodynamics were initially evolved with the aid of numeric flow simulation. In around one million CPU hours, the aerodynamics experts simulated the flow characteristics, calculating some 300 variants. This roughly corresponds to the scope of work involved in developing a production model. Fine tuning then took place in the wind tunnel in Sindelfingen – another parallel with series production development.
The Concept IAA also offers a look into the future in areas which are not apparent at first glance. The study features Car-to-X technology, for example, which enables the study to communicate with other vehicles or other sources of information. This represents a major advance in helping to avoid accidents, as obstacles or events which are not visible to the vehicle itself can be detected - the Concept IAA is able to look around the corner, as it were. With this and its interior and operating concept, the Concept IAA also offers a foretaste of the business saloon of the near future.
The Concept IAA is 5040 millimetres long (5430 mm in aerodynamic mode), 1995 mm wide and 1305 mm high. Its wheelbase measures 2975 mm, and the front/rear track widths are 1710 and 1770 mm respectively. The concept car is powered by a petrol/electric plug-in hybrid drive with a total output of 205 kW (279 hp). This provides it with a top speed of 250 km/h (electronically limited). CO2 emissions and electric range depend on the mode in which the vehicle is tested: in aerodynamic mode the Concept IAA manages an all-electric range of 66 kilometres and emits 28 g CO2 per km. In design mode the range stands at 62 km and CO2 emissions at 31 g per km.
The active aerodynamic measures at a glance:
The front flaps in the front bumper in front of the wheel arches move outwards by 25 millimetres and 20 millimetres to the rear, up to the rear edge of the wheel crescent. This substantially improves the inflow of air to the wheels and the flow of air over the front wheel arches.
The louvre in the front bumper moves 60 millimetres to the rear, improving the flow of air towards the underbody. An adjustable radiator grille shutter helps to reduce drag. When only low cooling requirements apply, the concentric louvres in the radiator grille are closed in order to prevent air from entering into the engine compartment. Basic ventilation then takes place primarily via the Mercedes star and the cooling air opening in the bumper.
The Active Rims alter their concavity with the aid of centrifugal force from 55 to 0 millimetres, transforming them from sporty 5-spoke wheels into flat disc wheels offering exemplary aerodynamic characteristics.
In conjunction with the diffuser, the rear extension which is extendable by up to 390 millimetres, ensures that the air flow hugs the vehicle more closely and that the wake behind the vehicle's rear end is substantially smaller.
This results in a considerable reduction in drag. The rear extension in boat tail design consists of eight segments produced in CFRP in a sandwich structure which close to form a ring.
As a result of the streamlined design, the downward slope of the roof line begins further towards the front. In order to offer the rear passengers sufficient headroom, the roof thus incorporates two rises over the rear seats.
Numerous other aerodynamic optimisations contribute to the vehicle's excellent performance in the wind tunnel. These include windows which fit flush on the outside, the omission of door openers and lowering of the chassis, resulting in a ground clearance of only 100 millimetres. The underbody panelling comprises partial covering of the centre tunnel, with perforation of the panelling here to allow cooling of the exhaust system, and extensive cladding on the rear axle.
The vertical aero flaps extend to the sides for an ideal air flow around the front wheels. During extension, that is, when switching over to aerodynamic mode, the edges of the wings light up in blue. Cameras in the side air outlets behind the front wheel arches monitor the rear view. Their images are projected onto the split-screen rear view mirror in the interior. This makes exterior mirrors superfluous.
Said Thomas Weber, Member of the Daimler Board of Management:
“Fascinating and technically sophisticated cars form the core of Mercedes-Benz. The 'Concept IAA' applies intelligent innovations to resolve the conflicting aims of functionality and aesthetics and shows that we still have plenty of ideas on how to achieve further improvements in efficiency.”