Porsche has used the Rennsport Reunion event at Laguna Seca in the USA to reveal its new 911 GT3 R Rennsport track car with a power output of up to 620ps. Only 77 will be produced and the company says it sees the new model as a spiritual successor to the 935.
While it is based on the 911 GT3 R, only the hood and roof have been carried over from the standard model. The design team have adopted most of the aerodynamically optimized geometry of the vehicle’s nose, including its cooling air intakes and ducts and set visual accents in the area around the side fins and flics. They are now framed by a side cowl and protected against damage caused by external impact. The air intake and outlet panels of the front wheel arches have been modified and digital cameras replace exterior mirrors. The interior has been extensively modified, with a rigid roll cage that allows only for a driver’s seat, making the 911 GT3 R a single-seater race car.
At the rear the wing is the dominant component facing the airflow, designed in a way, Porsche says, is reminiscent of that of the legendary Brumos Porsche 935/77 with which Peter Gregg, Toine Hezemans and Rolf Stommelen took the seventh overall victory for a Porsche at the 24 Hours of Daytona in 1978.
Porsche says it has gone beyond the requirements of motorsport homologation or restrictions imposed by a balance of performance (BoP) though. The development team have combined more engine power with reduced weight and a sound similar to that of the 911 RSR to create what the company says it probably the hottest track tool it has ever made as a collector’s item.
The 4.2-liter six-cylinder boxer engine revs up to 9,400rpm with peak power peak of up to 620hp. This corresponds to a power output of as much as 148hp per liter of displacement, significantly more than the original power unit in the 911 GT3 R, depending on the BoP rating. The water-cooled four-valve engine with direct petrol injection has been designed to run on E25 fuels including bio-ethanol and reFuel, in addition to regeneratively produced e-fuels. With their lower knocking tendency, they are paving the way for more advanced ignition angles and increased compression in the six combustion chambers. While the engine has been developed with these fuels in mind, it can also run on conventional fuel.
The power transmission to the rear wheels, including the sequential 6-speed constant-mesh gearbox, originates from the 911 GT3 R with only minor modifications. Gear changes are made via steering wheel paddles that control an electronic gearshift actuator. The transmission ratio of the fourth, fifth and sixth forward gears corresponds to the Daytona set-up of the GT3 racing car. In sixth gear, with an engine speed of 9,000rpm, it gives the car a top speed that is around 12mph higher than the shorter FIA-homologated gear ratio of the GT3 R.
There is a choice of a silenced or un-silenced version, the former for circuits with noise restrictions and the latter featuring a racing exhaust system with centrally positioned twin tailpipes and an extremely emotional engine sound.
The chassis is basically identical to that of the GT3 racing car with a double wishbone suspension layout on the front axle and a multi-link suspension incorporated at the rear. Five-way adjustable racing shock absorbers from KW have a blow-off function and while Porsche Motorsport delivers the model with a specific basic set-up, further adjustments to the suspension can be made using shims.
Michelin has designed tires exclusively for the 911 GT3 R which feature a new construction associated with a new compound tread that the tire maker says results in an improved warm-up and drivability compared to the Michelin Pilot Sport M S9 (S9M).
An aluminum monobloc racing brake system from AP has been given brake pads with titanium backing plates that reduce the total unsprung masses by approximately 1kg. The new FT3.5 safety tank, with a capacity of 117 liters, is also a weight-saving feature, being 1kg lighter than the previous version and in future can also be used in the 911 GT3 R for racing events. Another weight saving feature is the elimination of the air conditioning system. Ventilation for the driver is provided by the 911 GT3 R’s seat cooling concept. Overall, the developers are aiming to achieve a curb weight of 1,240kg for the 911 GT3 R Rennsport, equivalent to a weight-to-power ratio of 2.0kg/hp.
“The new Porsche 911 GT3 R Rennsport offers the experience of driving a 911-based racing car in what is probably the most primal form,” said Thomas Laudenbach, vice president, Porsche Motorsport. “It gives you goose bumps whenever you look at it and it combines the finest motorsport technology with a design language that is typical of Porsche.”