The #256/August 2018 tech feature (“Porsche Aerodynamics”) provided a primer on aerodynamic basics and a history of the aerodynamic development of the Porsche 911. The subsequent #257/September 2018 article (“GT3 Aerodynamics”) focused on the aero upgrades of the track-focused GT series of 911s, which were often not far from the racing-only Cup and RS/RSR vehicles manufactured by Porsche. At the end of that article, your author speculated that Porsche might offer some form of active aerodynamics in future GT-series cars, and this has come to fruition in the latest 992 GT3 RS.
992 GT3 Aero
While much attention has recently been heaped on the next-level active aerodynamics of the 992 GT3 RS, the standard 992 GT3 is no slouch in terms of downforce. In addition to the highlight feature of an all-new double-wishbone front suspension system, the Porsche GT designers spent over 200 hours in the wind tunnel refining the aerodynamics of the 992 GT3, which resulted in a unique front end and rear wing.
A standard feature of the GT cars since the 996 GT2 and every GT3 since the 997.1 version is an aperture between the front bumper cover and the front hood to vent air from the center radiator. The regular 992 series front-end packaging was too tight to allow sufficient airflow via the usual narrow outlet grille, so Andreas Preuninger’s GT team devised the distinctive “nostril” air outlets to move the radiator vents rearward to ensure adequate flow while minimizing drag. These vents were more plausible for production because the 992 GT3 was the first non-RS Porsche GT car with a carbon fiber hood.
The “swan-neck” rear wing is another distinctive feature—this configuration has been en vogue in GT and sports prototype racing for the past decade, and the 992 GT3 was the first road-legal Porsche to use this type of wing. The swan-neck configuration works well because the underside of a downforce-generating wing is more sensitive to aero disturbances than the top side. Therefore, by suspending the wing from above, the wing is more aerodynamically efficient than conventional ones. This rear wing, combined with the upswept duck-tail section of the engine lid, generates more downforce than a similarly-sized rear wing while creating less drag.
Underbody panels cover the underside of the 992 GT3 to maintain consistent airflow to the fully enclosed rear diffuser, which alone generates more than 132 lbs (60 kg) of downforce. At the rear of the car, large vents at the intersection of each of the rear fenders and the rear bumper cover to evacuate high pressure from the rear wheel housings.
The sum of the 992 GT3’s aero elements is 50 percent more downforce than the last-gen 991.2 GT3 at the nominal, as-delivered settings. Both the front “air curtain” elements ahead of the front wheels and the rear wing are each manually adjustable to four different angles of attack. Porsche recommends adjusting each to like positions as the front and rear elements work together to provide balanced handling. With all elements adjusted to their maximum angle of attack, the 992 GT3 develops up to 150 percent more downforce than the 991.2 GT3 at 124 mph (200 kph).
The straight-line performance figures of the 992 GT3 may not eclipse that of its predecessor, but Porsche’s favorite performance metric is where it really shines: its lap time on the famed Nürburgring Nordschleife. Track officials in 2019 changed the method of recording official lap times to using the same starting and finishing point for a 12.9-mile (20.8-km) total lap distance versus the previous finish line that was 760 feet short of the starting point. That is why Porsche released two lap times for the 992 GT3 in early 2021, one at 6:59.9, and the other at 6:55.2. The latter time allows direct comparison to its predecessor, with an astonishing 17-second improvement on the 991.2 GT3, and over a second faster than the 991.2 GT3 RS (which generates more downforce than the 992 GT3!). The efficient aerodynamics and improved front-end grip and responsiveness of the double-wishbone suspension propelled the 992 GT3 to the next level, and prepared it for transformation into the next GT3 RS.
992 GT3 Touring Aero
The 992 GT3 Touring deserves a brief mention despite the lack of the regular model’s swan-neck rear wing. The Touring uses the same retractable rear wing as the 992 Carrera range, albeit with a steeper angle of attack while in the extended position. Interestingly, the four-position adjustable front air curtain elements remain. However, Porsche’s race circuit owner’s manual supplement implores Touring owners not to adjust the settings as this would cause an aerodynamic imbalance front to rear.
992 GT3 RS Aero
The 2023 992 GT3 RS represents a new stratosphere of aerodynamic performance for Porsche’s GT-series cars. Andreas Preuninger and his development team were unfettered by the restraints of racing series rulebooks, so after over 250 hours of development in Porsche’s wind tunnel at Weissach, the new GT3 RS active aero package allows performance that eclipses some of the factory-made racing cars.
The highlight downforce figures are already well-known by Porsche enthusiasts but are worth repeating: 900 lbs (409 kg) at 124 mph and 1,895 lbs (860 kg) at 177 mph, with Porsche reminding us that the latter is the same weight as a 356A! This is twice as much top speed downforce as the 991.2 GT3 RS and three times as much as the 992 GT3.
The massive amount of downforce was made possible by re-packaging the entire front of the GT3 RS. While achieving a large amount of rear downforce can be as simple as installing a very large rear wing with steep elements, balancing this with a consummate front downforce level is much more difficult. A single, central radiator was the first step in creating monster downforce.
One of the highlight features of the new GT3 RS is the elimination of the side radiators at the front corners of the car, which had been a feature of water-cooled mid- and rear-engine sports cars since the 986 Boxster was introduced in the late 1990s. In terms of aerodynamics, the front wheel housings are a high-pressure area in any automobile, and the high-output engines of GT-series Porsches require a large throughput of air through the radiators. The hot air evacuating from the side radiators only adds to the pressure inside the wheel housings, which was partially solved by the large fender extractors first seen in the 2016 991.1 GT3 RS.
Beginning with the 991 GT3 RSR racing car and the current 992 GT3 R, the side radiators were eliminated to improve front downforce (which also mitigated the common problem of broken side radiators as the result of a minor racing shunt), with a large central radiator canted forward 43 degrees to allow air to efficiently exit via the hood vent. The 992 GT3 RS road car sacrifices its front luggage space to use this setup, with the efficient radiator ducting contributing to the front downforce by efficiently channeling air over the front splitter.
The copious amount of hot air exiting the radiator while the car is at speed presented a challenge to Porsche aerodynamicists because this air would usually be channeled straight over the roof and into the engine air intakes mounted on the engine lid—this could reduce engine output by up to 20 hp on a warm day. The team devised a unique set of angled radiator outlet “boomerangs” to guide the air out and around the car, with an extra set of fins to keep the hot air from spilling back into the path of the engine intake. The air that is allowed to flow over the center of the car is channeled via the cutout roof section that was introduced with the 991.1 GT3 RS.
The elimination of the side radiators allows space for a pair of active aerodynamic elements ahead of each front wheel, with movable main flaps that can be rotated by over 80 degrees in 0.3 seconds via electric motors, along with a smaller upper flap at the end of the brake air duct. The suspension also plays its part in the aero department: because of the amount of air channeled through the front wheel housings, the upper and lower suspension wishbones and the steering tie rod arms are airfoil-shaped as in a Formula One car to minimize drag and provide up to 88 lb (40 kg) of downforce at top speed.
The fender top air extractors alone would be insufficient to evacuate all the air from the front wheel housings, so the GT aerodynamicists added an additional outlet at the rear of the wheel housing in the vein of the 1998 version of the 911 GT1 race car. The vertical vanes aft of the front wheels ensure smooth, laminar airflow along the lower section of the doors, which are made of carbon fiber and specially shaped to enhance the effect of the front wheel housing outlets by promoting smooth airflow along the sides of the car.
The underside of the 992 GT3 RS is fully clad, as with its GT3 stablemate, with the addition of fourteen vanes to direct airflow underneath the car. The central vanes guide air to the large rear diffuser, which is a similar design to the normal 992 GT3 but is deeper and has slightly different strakes to maintain proper aero balance under all conditions. The outboard vanes are angled turning vanes to guide excess air from underneath the car and channel it around the rear wheels. The 992 GT3 RS features rear fender intakes as in the Turbo models, but instead of providing an air inlet for the engine/intercooler, their purpose is to help evacuate high pressure from the rear wheel housings.
The latest GT3 RS introduces yet another abbreviation to the Porsche lexicon: PAA, or Porsche Active Aerodynamics. A central controller orchestrates the angles of the movable front and rear aerodynamic elements in response to a myriad of inputs, including vehicle speed, lateral acceleration, steering angle, selected driving mode, and more. The swan-necked rear wing has a fixed leading element and a hydraulically adjustable rear element, which is actively and infinitely adjustable within its range of motion of 34 degrees.
During normal driving, the front and rear wings default to their flattest angles to achieve a drag coefficient of 0.39 (compared to 0.34 for the normal 992 GT3 at its nominal aerodynamic settings). Even at the “low downforce” setting, Porsche claims 674 lbs (306 kg) of total downforce, which is more than the base 992 GT3 generates at its max adjustments.
The active aerodynamics allow the integration of an air brake function, which maximizes the angle of attack of the front and rear wing elements to aid deceleration during periods of heavy braking. A Formula One-inspired drag reduction system (DRS) function enables the driver to reduce the angles of the front and rear wing elements to reduce drag on long straight sections and allow a higher top speed—if the driver pushes the DRS button, the function is only allowed if the steering angle and lateral acceleration rates are minimal.
If the car is set to the proper driving mode, DRS will automatically deploy if the throttle opening is more than 95 percent, the engine rpm is above 5,500, and there is less than 0.9G of lateral acceleration. Even with DRS enabled, the top speed of the GT3 RS is 184 mph, thanks to increased aerodynamic drag (the standard 992 GT3 can hit 198 mph).
Porsche’s GT team designed the 992 GT3 RS to maintain an aero balance of 30 percent front/70 percent rear under all conditions. This is made possible in part by a stiffer suspension, with spring rates up 50 percent in the front and 60 percent in the rear compared to the normal 992 GT3—the stiffer springs resist the compressive forces imparted by the aero aids. Passive anti-dive suspension geometry is also used to maintain aero balance.
As mentioned in the #247/August 2017 tech article (“Porsche 911 Suspension Geometry”), the angle of the control arms (as viewed from the side of the car) can be altered to resist the normal compression forces that occur during heavy braking. Porsche chassis engineers lowered the mounting points of the forward ball joints of the front lower control arms to increase the angle of the imaginary swing arm that acts upon the vehicle’s center of gravity, which allows the front aero aids to maintain effectiveness during heavy braking.
All this aerodynamic prowess results in potential cornering speeds on road-legal Michelin Pilot Cup 2R tires, which, given sufficient driver skill, can exceed that of the GT3 R racer on slick tires! Despite its engine output of “merely” 518 hp, the latest GT3 RS manages to shave over 11 seconds off the Nürburgring (old 12.8-mile/20.6-km configuration) lap time of its 991.2 GT3 RS predecessor and the normal 992 GT3—its 6:44.8 time is only 1.2 seconds shy of the current record-holder, the Mercedes AMG GT Black Edition, which has a 730-hp twin-turbo V8!
Watching the official Porsche onboard video of the 992 GT3 RS’ fastest Nürburgring lap, factory driver Jorg Bergmeister can be observed engaging the DRS low-drag configuration whenever possible, even during long sweeping curves. However efficient the GT3 RS aero aids are, the engine simply cannot overcome the high amount of drag on the long Döttinger Höhe straight, with acceleration visibly dropping towards the end of the lap.
One can only wonder what Preuninger and his crew will come up with next. A turbocharged 992 GT2 RS version is a logical next step, but packaging the turbochargers, the intercoolers, and the requisite inlets and outlets impinge on the carefully packaged aerodynamics of the GT3 RS. Only time will tell, but an electric supercar using such aero aids would be quite a fast car!