Back in the late 1990s, Volkswagen embarked upon the development of its first "three liter" car.

That number didn't refer to engine capacity, but a European fuel measurement of three liters per 100 kilometers--or 78 miles per gallon. That car was the Volkswagen Lupo 3L, a high-tech, lightweight diesel minicar.

The world has changed, and with the plug-in hybrid 918 Spyder supercar, Porsche is hoping to achieve a similar 3 litres per 100 km--despite having 770-horsepower on tap.

Porsche has now announced the first prototypes have been completed. The first production cars will go into production at the end of September 2013, with cars reaching owners before the end of 2013.

To achieve such a mix of performance and economy, the 918 Spyder uses two individual electric motors, to supplement its gasoline engine. One electric motor drives the front wheels, and the other is mounted between the engine and rear wheels, ready to provide a boost of power when necessary.

A carbon-fiber reinforced plastic monocoque construction will keep weight low, and to reach that "three liter" figure the 918 is a plug-in hybrid, so drivers will get to run on electric power only over a set distance.

The Porsche 918 Spyder is just one in a series of hybrid supercars due over the next few years--with Ferrari now revealing that its Enzo successor will also be a hybrid.

The sudden rush to develop hybrid supercars could be seen as a sign of the push towards greener transportation--but it's equally fair to say that supercar customers are also influenced by the increasing technology in modern auto racing too, with diesels, KERS hybrids and more appearing in top-level series.

Porsche's Wolfgang Hatz sums up the 918 quite succinctly--"What we are doing with the 918 Spyder is redefining driving fun, efficiency and performance."


Follow GreenCarReports on Facebook and Twitter.