Porsche has revised and refined its 911 GT3 R Hybrid racer for another attempt at the Nürburgring 24 Hours race this weekend.

The car has had its power re-rated down to 448bhp due to new regulations from the organisers of the race. Nicknamed "Version 2.0" by Porsche, the latest hybrid 911 race car compensates for the lower power output by reducing its overall weight by some 20%. Porsche says this will allow the new car to lap in the same time as last year's car but with improved fuel economy.

Despite the 4.0-litre petrol engine going down in power, the twin electric motors that power the front wheels have been made more powerful. Each motor now produces 75 kilowatts, giving the driver an additional 200bhp for several seconds at a time. The driver can call on this power automatically or select it manually for overtaking.

Recharging the batteries that power the electric motors is achieved by an electric flywheel generator that spins at up to 40,000rpm. This flywheel stores the energy kinetically rather than in heavy batteries.

Other changes to the Porsche 911 GT3 R Hybrid include a neater, less cluttered cockpit and front wings that do without the cooling louvres of last year's car. This helps to make the 2011 racer more aerodynamic and further saves fuel.

Driving the Porsche 911 GT3 R Hybrid at this year's Nürburgring endurance race are Jorg Bergmeister, Richard Lietz, Patrick Long and Marco Holzer, who have all helped develop the car.

Alisdair Suttie - 23 Jun 2011