Hanover. April 2015 – the role that weight can play in a car can sometimes be seen in the distribution of the mass. In the same vehicle, for example, a smaller, lighter engine can make more fuel than the heavier top-of-the-range engine – even if it delivers significantly more power. Now comes – not for the first time – the idea of using weight-saving plastic in the engine. The fraunhofer institute for chemical technology suggests that after the already rather lightweight add-on parts such as the cylinder head cover, intake manifold or oil pan, the solid cylinder crankcases should now also be made of plastic.

Because the driving dynamics experts among its customers feel every kilogram above the front axle, BMW has already addressed this problem in 2004 with its three-liter in-line six-cylinder gasoline engine called N52. The crankcase is made largely of a magnesium alloy, among many other lightweight design features. In this engine is to be still again 24 per cent lighter than a alugehause. However, this solution is also more expensive. While lightweighting is usually not primarily about fuel economy, but rather fuel economy, saved weight is crucial here as well.

Coarse series production with injection molding

Researchers from the project group new drive systems NAS of the fraunhofer institute for chemical technology ICT, together with the japanese company sumitomo bakelite high performance plastics SBHPP, have taken up an idea that has already been tested in this context. They want to show that it is also possible to build crankcases from plastic. Such components may "only" weigh up to 20 percent less than designs made of aluminum – but at roughly the same cost. In addition, they can also be produced inexpensively in rough series using injection molding technology.

To ensure that the component can withstand the high temperatures, preres and vibrations, it is reinforced at key points with metal inserts in addition to the fiber inserts. This includes the cylinder liner, which is better still made of metal, if only because of its wear and tensile strength and friction coefficient.