The Porsche 911 GT3 RS 4.0 (997) is a limited edition of the 911 GT3 RS, with 600 units manufactured. As its name suggests, the car utilises a 4.0L flat-six engine with an unaltered crankshaft from the GT3 RSR, which produces 500bhp at 8,250rpm. The power output of the engine is the highest among any naturally aspirated engine for the road models of the Porsche 997.