The following is direct from Porsche AG's web site, European side only.

Power to Weight

The true key to the capability of the car is its exemplary power-to-weight ratio of 280 bhp per tonne – approximately 4% more than the 911 GT3 Clubsport. To gain that advantage, we’ve dispensed with all excess weight from every area of the car. The bodyshell is lighter, the front lid and rear wing are made from pure carbon fibre, and the rear screen is made from plastic. All soundproofing materials have been removed from the car, while the dashboard and door panels have been lightened.

Engine

 

 Power is supplied by the latest evolution of the flat-six engine originally developed for the Le Mans-winning GT1. This naturally aspirated and water-cooled unit features four valves per cylinder as well as VarioCam variable valve timing on the inlet side. The dry-sump lubrication system has an external reservoir and a dedicated oil-cooler unit. The engine is located behind the rear axle-line in the traditional 911 position. Offering 280 kW (381 bhp) at 7,400 rpm, the 3.6-litre unit has an exceptional specific output of 77.8 kW (105.8 bhp) per litre. Maximum torque of 385 Nm is available at 5,000 rpm. Depending on gear selection, the engine can rev up to 8,200 rpm.

Among the key characteristics of the RS engine are optimised cylinder charging, exceptional balance in all moving masses, and cultured performance at all times. With its free-revving capability, it offers an instantaneous response to every throttle input.