Loosely translated from the original German

The lighter a car is, the less energy it uses to achieve a certain performance. And the longer a car lasts, the better the energy required for its production is used - from the raw material to the finished car.

That is why Porsche and Alusuisse/Alusingen are pursuing the Porsche aluminum body study project. At the 1981 International Motor Show in Frankfurt (September 17th to 27th), Alusuisse/Alusingen presented this project, developed jointly with Porsche: a 928 body made exclusively from the new "Anticorodal-120 R" alloy. This body shell, which weighs just 161 kg, offers a weight advantage of 106 kg compared to the partially aluminum body of the standard Porsche 928, and even 141 kg compared to a comparable all-steel version.

Porsche has calculated that a vehicle based on this body study, taking into account the manufacturing energy and with extensive recycling, would save the energy content of 1,500 to 2,000 liters of fuel over a driving distance of 300,000 kilometers compared to a conventional steel body. In practice, the use of all-aluminium bodies compared to conventional steel bodies could result in an annual mileage of 35,000 kilometres at today's petrol prices (August 1981 around 1.60 DM/litre of premium petrol ... note: around 1.90 Euro/l in 2024), depending on the vehicle size can save up to 400 DM per year (note: around 480 Euro in 2024).

The all-aluminum body represents a contribution to the discussion about future body concepts. Based on the findings available so far, aluminum as a body material is expected to have good future prospects in terms of possible weight savings, the overall energy balance, recycling and corrosion behavior.

The goals of the study:

• Self-supporting all-aluminum body;
• service life of 300,000 km in normal road use;
• rigidity of the body shell corresponding to the Porsche 928 steel body;
• predominantly use of resistance spot welding as a type of connection;
• all sheets made of Anticorodal 120^R alloy (A1Mg 0.4 Si 1.2);
• retention of the Porsche 928 outer skin contours and the interior dimensions;
• Extensive use of series parts, such as fenders, doors, engine covers, as well as taking over the drive units, equipment and electrics

The joint scope of work includes the following basic studies, the results of which are available in work packages:

• Usability of aluminum materials in automobile body construction
• Availability of aluminum (raw material to recycling)
• Energy requirements of aluminum (raw material to recycling)
• Recycling material technology (from raw material to alloy technology)
• Material testing for mechanical, thermal and corrosive loads
• Elastomechanics Plastomechanics Forming technology
• Joining technology
• Surface technology Repair technology
• Acoustics

Technical data of the study project

"Porsche aluminum body"

Material

Anticorodal 120^R/AlMgO,4Si1,2

Sheet thicknesses

• Outer skin 1.15...1.25 mm
• Inner skin 1.15...1.25 mm
• Structure 2.00...2.50 mm

Weight

161 kg

Front end

Two-part longitudinal member as a repair-friendly solution in 1.75/2.00 mm.

Multi-part wheel arch for forming and strength reasons.

Roof structure

Use of an extruded aluminum profile to increase rigidity and operational strength as well as passive safety Cross sections remain unchanged for reasons of space.

Support structure

Enlargement of the cross sections by raising and widening the supports (without changing the body cutouts).

Flanges

Widened from 12 mm to 16 to 20 mm in order to be able to spot weld with the larger electrodes required.

Companies involved

Porsche Development Center Weissach (project management and prototype)

Alusuisse/Alusingen (Anticorodal 120^R)

A. Läpple, Heilbronn (tools and forming technology tests)

Sciaky, Paris (welding technology)