Last issue’s tech section featured a primer on aerodynamic concepts and traced the evolution of the aerodynamic evolution of the Porsche 911 street car. The high-performance GT-series of track-focused street cars was briefly mentioned, but in light of the stellar Nürburgring lap times of the latest 991 GT2 RS and GT3 RS variants, a closer look at the aerodynamic features of these cars is warranted.
The GT-series cars pose a unique challenge to Porsche’s aerodynamicists. Low aerodynamic drag is always desirable, yet the reduction of aerodynamic lift (or even the generation of aerodynamic downforce) is desirable to improve stability at high speeds and enhance cornering grip. The high specific output of the GT engines requires a large amount of ambient intake air charge and efficient heat exchangers for both engine and transmission cooling, all of which add drag.
Nonetheless, Porsche’s engineers have always managed to deliver an efficient aerodynamic package for the GT cars, aided by parallel development with the company’s 911-based Cup, RS, and RSR racing cars. This is especially remarkable when considering the constraints imposed by the production 911 bodyshell and strict homologation rules dictated by the various sanctioning bodies of the racing series in which these cars compete.
996 GT3 & GT3 RS
The first 911 GT3 road car was introduced for the “Rest of the World” (RoW) market for the 1999 model year, but it did not reach the U.S. until 2004. It was worth the wait, however, as the GT3 truly embodied the (often over-used) adage of a “race car for the road.”
The GT3 built on the base 996’s use of large plastic underbody panels to smooth airflow underneath the car while directing cooling air to the transmission. A prominent front chin spoiler was used to deflect airflow under the car and reduce lift (and began the unfortunate tradition of the GT front spoiler being a sacrificial member during contact with the driveways and dips encountered during street driving). The GT3’s 30-mm (1.2-inch) lower ride height also served to reduce the frontal area and reduce unwanted airflow underneath the car.
The 996 GT3’s less obvious aerodynamic details also mattered. As in the normal 996, airflow exiting the radiators was directed towards the front brakes by ducts in the wheel housing liners (with the GT3 featuring partially enclosed brake cooling ducts for better heat dissipation from the brakes). This system also served to reduce pressure buildup in the wheelhousing for reduced aero drag and lift. Specially-shaped side skirts help to direct air around the wide rear wheels smoothly.