The RS (short for the German RennSport, literally "racing sport" in English) is mainly a carryover of the Porsche 911 GT3, albeit it is lighter thanks to a polycarbonate rear window, carbon fiber hood and rear wing. Porsche Ceramic Composite Brake (PCCB) Carbon fibre-reinforced Silicon Carbide (C/SiC) ceramic composite brakes, which are also more heat and fade resistant than the cast iron units fitted as standard, are optional.

The RS has a slightly different engine specification to the GT3. The cylinder heads of the GT3 RS have reshaped intake and exhaust ports for race homologation. Porsche claim the same 381 hp (284 kW) power output as the standard GT3 but Porsche's control dyno showed a jump to nearly 400 hp (298 kW)

The RS has progressive springs rather than linear. The dampers are uprated and are between 10 and 15 percent stiffer than the normal GT3 in bounce and rebound.

The wheel carriers are totally redesigned to maximize the improved dynamic camber control. The suspension top mounts can be turned 120 degrees to a cup car position. Both front and rear control arms are adjustable. The RS is 3 mm (0.1 in) lower than the standard car.

Thanks to a close-ratio six-speed transmission with a single-mass flywheel, the engine revs up even more freely, thus enabling the 911 GT3 to sprint from zero to 100 km/h (62 mph) in 4.2 seconds[citation needed] (4.0 s in the 2010 gen 2 model)[citation needed] while reaching 200 km/h (124 mph) in 13.3 seconds. Maximum speed is 310 km/h (193 mph).

The RS is 20 kg (44 lb) lighter than the GT3, weighing in at 1,375 kg (3,031 lb). This weight-saving was achieved by the use of an adjustable carbon fiber wing, a plastic engine cover, and a lightweight plastic rear window. The weight savings gives the RS model corresponding engine power to curb weight ratio of 300 bhp (220 kW) per tonne.

One characteristic of the new RS is the body, which is 44 mm (1.7 in) wider at the rear (a legacy from the Carrera 4 models with which it shares its shell) by comparison with the 911 GT3. The muscular-looking rear end conceals a wider track that not only improves directional stability but also increases the potential cornering grip of the two-seater coupe. On the other hand, drag is increased, and top speed reduced.

In addition to the new technology featured in this flat six motor car, the paint scheme and body panels are all designed specially for this car. For the RS version, the limited edition orange color was mixed specially for this car.

The American version of the RS has a standard rear window (not plexiglas) and the smaller 911 fuel tank to comply with rules of SCCA, Grand-Am, and IMSA. For Grand-Am races, the central locking wheel nut is replaced with the standard five-lug pattern required under Grand-Am rules.

Production of the first generation 997 GT3 RS ended in 2009. An estimated 1,909 vehicles were delivered worldwide, with an estimated 413 of those directed to the United States.[17][18]

For 2010, the new (or second generation) 911 GT3 RS received an additional 35 PS (26 kW; 35 hp) due to a new 3.8-liter flat-six, bringing total power output up to 450 PS (331 kW; 444 hp). This car will not be raced in the United States as both IMSA American LeMans has not approved the new car for competition. Grand-Am originally did not approve the car, but after performance issues (a Porsche team did not compete at the Indy Grand Prix of Alabama round), Grand-Am approved the second-generation car in April 2010.[19][20]

The Porsche GT3 RS as Compared to the Porsche GT3 is:

44mm wider across the rear axle
The rear wing is carbon fiber. It is lighter with a larger surface area for more down force
Rear screen/glass is made of lightweight plastic saving nearly 3 kilos or 6.6 lbs
Contrasting color on wheels, side logos and exterior mirrors
The front spoiler is modified to create more front and down force
The interior is all black
Steering wheel is marked at 12 o’clock position
Standard feature include club sport package and lightweight bucket seats (optional on GT3)
415 hp, 305 kw 405 torque. Top speed 193 miles per hour
20 kilos (44 lbs) lighter than GT3
1/10th quicker to 100 kph doing it in 4.2 seconds
Single mass flywheel vs. Dual mass in GT3
Suspension is configured for race/competion driving
Rear track is wider than that of the GT3
GT3 RS has split rear wishbones
Wheel base is 5 mm longer than on the GT3
Rear wheel offset is smaller due to wider rear axle