EXCEPTIONAL AERODYNAMICS. ANOTHER LINK BETWEEN SAAB 9-3 VIGGEN AND ITS JET FIGHTER NAMESAKE
Form follows function in development of aerodynamic enhancements for new Viggen
Norcross, GA - Nowhere is the connection between the Saab 9-3 Viggen and its namesake, the Saab 37 Viggen jet fighter stronger than in their exceptional aerodynamics. At Saab, form has always followed function, and that philosophy is again apparent in the aerodynamic elements of the 9-3 Viggen. Saab's chief designer, Einar Hareide doesn't compromise this design tradition. He believes that good aerodynamics should be an inherent part of all Saabs, and that "any additions to the aerodynamics should have a purpose, rather than simply being cosmetic."
The 9-3 Viggen's aggressive front spoiler, rocker panel extensions, rear bumper cover and rear wing aren't just stylish - they serve a purpose. Fully integrated into the already sleek shape of the Saab 9-3, these elements give the Viggen dramatically improved aerodynamic properties. The Viggen's coemcient of drag (Cd) has been decreased a full 8% to 0.31 Cd, and Saab's chief aerodynamic engineer, Hakan Danielsson, has also reduced lift forces at the rear wheels by 60%.
Instrumental in decreasing the Viggen's drag to 0.31 Cd is the deep front spoiler and pronounced rocker panel extensions. The front spoiler pushes more of the airflow at the front of the Viggen over the surface of the body rather than allowing it underneath. The integrated rocker panels contain and channel what airflow there is under the body rather than allow it to dissipate from the sides. When the limited and directed underbody airflow exits at the rear it properly integrates into the airflow off the rear wing. Working together to reduce drag these elements not only improve the Viggen's stability at speed, but also reduce both wind noise and fuel consumption.
However, the advantages of utilizing such an aggressive front spoiler do present another challenge. Increased airflow over the car adds to the lift forces at the rear of the car, which can have a destabilizing effect under heavy braking from high speeds. To counter this possibility, the rear wing was designed to dramatically reduce lift forces at the rear and regain the front/rear balance of the car.
To optimize the overall aerodynamic package, and particularly the rear wing, Saab designers spent many hours in wind tunnels with 1:5 and 1:3 scale models before testing with full-scale Viggens. Six full-scale tests were carried out at the Motor Industry Research Association (MIRA) facility in Nuneaton, England, before final verification was completed at the Research Institute for Automotive Technology (FKFS) facility in Stuttgart, Germany. "We used FKFS as our reference tunnel," says Danielsson, "because it is state-of-the-art and highly accurate. FKFS also gave us the ability to perform tests up to 155 mph whereas MIRA is limited to 80 mph. Obviously, with a high performance car like the 9-3 Viggen, everything must be tested at high speed - but the FKFS tests simply confirmed the MIRA tests were very good." The end result was a 60% reduction in lift forces from the standard 9-3's coeffficient of lift (Cl) of 0.15 to an amazingly low 0.06 Cl for the Viggen.
The Saab 37 Viggen's delta wing design provides the lift and agility necessary to enable this multi-purpose jet fighter to perform its airborne duties. In contrast, the inverted rear wing designed for the 9-3 Viggen, with greater surface area on top than on the underside, keeps the earthbound Viggen firmly planted on the ground by creating an area of low pressure beneath the wing. This brings back the desired front/rear balance, providing greater high speed stability and a more linear response to hard braking, preventing the 9-3 Viggen from "nose diving" during high speed deceleration. Balance is the key, not only for Saab 37 Viggen jet fighter pilots, but also for pilots of the new, low flying Saab 9-3 Viggen automobile.