Audi"s A5 coupe has...

Audi"s A5 coupe has been on a crash diet! A prototype car has had it"s overall weight slashed by 100kg as part of what the German firm calls "efficiency optimisation measures".

The car utilises Audi"s "Space Frame"; made famous in 1993 when an unpainted, polished aluminium A8 was unveiled at the Frankfurt Motor Show. The following year, when that car was put into production, it became the first large-volume production car with an aluminium body.

With the lighter ASF chassis the A5 can use a more efficient 2.0-litre, 211hp turbo engine and achieve a power to weight ratio of 161hp/tonne. A standard steel chassis coupled with the less economical 265hp, 3.2-litre V6 engine can achieve a not too dissimilar power to weight ratio of 172hp/tonne.

Audi sees this lightweight technology as vital to the future of economical driving; they claim that every 100kg of weight saved corresponds to a reduction of 8-11 grams of CO2 emitted per kilometre. Meanwhile, in the longer term the featherweight bodies achieved through using this technology are perfect for the heavy batteries of future electric and hybrid vehicles.

Although, this new lightweight A5 is unlikely to make it into production, the same technology is expected to be used on the high performance RS5, expected next year.