Aerodynamics and Air Routing
Aerodynamics and Air Routing
Like the 911 Turbo (996), the new 911 Turbo sets new standards against the competition with a drag coefficient of cd = 0.31 as well as extremely low lift coefficients which are carefully matched between the front and rear axles. In spite of the aerodynamically less favorable preconditions due to the higher cooling air requirement of the radiators, charge air coolers and brake cooling system, the wider rear tires and a wider body, the new 911 Turbo still achieves the very good cd value of the 911 Turbo (996). It was even possible to improve the slight downforce at the rear axle of the 911 Turbo (996) on the new 911 Turbo (997). The new 911 Turbo is among the class leaders in the high-performance sports car segment thanks to its exceptional aerodynamic properties.
Extensive optimization of many details was necessary in order to achieve this. The newly designed spoiler lip on the front apron reduces the air flowing under the vehicle, and therefore produces favorable front axle lift forces. The two openings in the spoiler lip with the downstream brake air ducts serve to cool the powerful brakes.
Compared with the 911 Turbo (996), the cross-section of the brake air ducts has been significantly enlarged and combined with new, chassis-fixed brake air spoilers with a larger effective area. This further improves the brake ventilation on the front axle. A new feature is the brake ventilation on the rear axle, which was further developed specifically for the new 911 Turbo to take into account the increased performance compared with the predecessor model. The cooling air is routed through NACA air inlets (NACA stands for National Advisory Committee for Aeronautics) in the rear underbody lining into connected air ducts, and is directed from there onto newly developed, chassis fixed brake air spoilers mounted on the rear axle and then onto the brake disc.
The aerodynamically very effective cooling air routing principle for the radiators which is familiar from the 911 Turbo (996) is also used on the new 911 Turbo. However, the air inlet openings are modified with a "bypass" compared with the predecessor in order to meet the higher cooling requirements of the engine and to make sure that sufficient cooling air is available. This connection from the center cooling air opening to the side openings permits significantly more effective air distribution to the three radiators in the front end.
As a further improvement, a deflection vane with an aerodynamically favorable shape was additionally mounted on the bottom of the front end for the outgoing air of the radiator. The deflection vanes for the side radiators were increased in size. These measures ensure that the higher cooling air requirement of the engine is provided, while at the same time maintaining the front axle lift force at the good level of the 911 Turbo (996).
The successful principle of the extendable wing element on the rear lid was adopted from the 911 Turbo (996). This just does not reduce generation of a lift force (wheel-load reduction on the rear axle), but actually achieves a slight downforce without significantly impairing drag. As on the 911 Turbo (996), the wing element is extended at a speed of approx. 75 mph (120 km/h) and retracted again at approx. 37 mph (60 km/h). The wing element is larger than on the previous model and has been made even more aerodynamically efficient in order to adapt it to the wide body of the new 911 Turbo.
The aerodynamic fine tuning in the front and rear areas is designed to guarantee an optimum balance in the lift coefficients at the front and rear axles. The air flow around the rear wheels is improved by sill covers which have been aerodynamically optimized compared with the 911 Turbo (996).
In order to further improve aerodynamics, the underbody of the new 911 Turbo is lined with a total of 5 (Tiptronic S) or 6 (manual gearbox) large-area polypropylene panels extending from the front axle to just in front of the engine. As a result of the enlarged and additional panels, the overall area of the underbody lining is almost doubled on vehicles with manual gearbox compared with the predecessor model (approx. 97 %).
This results in air guidance with significantly reduced turbulence and losses combined with a higher air speed under the vehicle. This in turn results in improved drag and lift forces.
Four matched ventilation ducts in the front underbody lining serve the purpose of ventilation for the front axle final drive. The rear underbody lining used in the new 911 Turbo with its optimized ventilation measures guarantees stable temperature conditions for the manual gearbox located above the rear axle and in particular for the Tiptronic S transmission.
In addition to providing harmonious contours, the form of the sill covers combines with the spoiler elements adapted to the new tire dimensions in front of the rear axle wheels to ensure that the air flow around the wheels is as aerodynamically efficient as on the 911 Turbo (996).
