by David Finlay (09 Jun 05)

Mercedes-Benz has developed a new "bionic" concept car which investigates the possibilites of a new type of construction and a way of reducing emissions. DaimlerChrysler took its inspiration for the car's shape from nature, specifically an underwater chap called the boxfish.

The boxfish is notable for being almost cube-shaped but at the same time very streamlined. DaimlerChrysler established the efficiency of its form by constructing a scale model and putting it in a wind tunnel, where it proved to have an astonishingly low drag coefficient of 0.06. Later, a 1/4 scale model of the concept car was also measured, and although it couldn't achieve quite that figure it did turn out to have a drag coefficient of 0.095.

The concept car itself achieved a coefficient of 0.19, which is quite something considering it's fully roadworthy has space for four occupants and their luggage. Any production car which can beat 0.30 is regarded as doing exceptionally well.

None of this has anything to do with the word "bionic". That's a reference to the fact that the concept car also uses the boxfish as a model for its construction techniques. The skin of the fish is made up of a great many bony hexagonal plates which provide maximum strength for minimum weight.

DaimlerChrysler engineers came up with a calculation process to transfer this feature to car design. If applied to the entire bodyshell of the car, it can reduce weight by around a third without affecting the strength or crash safety.

You may be relieved to hear that the method of reducing exhaust emissions has nothing to do with any kind of fish. The concept car uses a 140bhp diesel engine with Selective Catalytic Reduction technology (not available in passenger cars at present but quite common in Mercedes-Benz commercial vehicles), a maintenance-free particulate filter and a system for injecting a urea solution known as AdBlue into the exhaust system.

The upshot of all that is that the concept car achieves around 66mpg on the combined EU fuel economy cycle, while nitrogen oxide emissions (for an explanation of which see our separate feature) can be reduced by up to 80%.

The bionic Mercedes had its world premiere at this week's DaimlerChrysler Innovation Symposium in Washington. It will be fascinating to see how quickly its advanced features reach our showrooms.

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