He continued, "Due to the X90's size, bad aerodynamics would have magnified the effect on fuel consumption and handling. Thus, it became important in the early phase to see if aerodynamic qualities alone would decide which design proposal would be selected. Since the three proposals differed most in roof lengths and the rear-window slope, it was decided to compare designs aerodynamically only above the beltline, since features below the beltline could be 'fixed' later in the project. This was done by wind tunnel testing a scale model with interchangeable greenhouses. Since two of the designers were in California, I designed the wind tunnel model on the computer and the data was used to 'mill' the model out from plastic blocks in Sweden, where it was tested in Volvo's wind tunnel by Johan Janson and Mark Bannister. They showed that the two greenhouses which differed the most only differed 0.5% in air resistance."
The reason why the second design, which became the XC90, did almost as well as those with a longer sloped roof is explained partly by the computed streamlines from work done by Lydia Darrieutort in Sweden. The sloped D-pillars create a loose vortex that draws the streamlines in the middle of the car downward. And once the XC90 design direction was selected, aerodynamic development began in earnest with full-size models on real chassis, including a functional radiator behind the grille. Mark Bannister, Johan Janson and others spent countless hours in Sweden to refine critical areas such as engine cooling and rainwater run-off from the windscreen as well as air resistance and downforce.
There are two unique aerodynamic aspects of the XC90. The corners of the front bumpers are features that Doug Frasher originally developed for a concept car called the "Eye-car." They not only offer protection in low-speed impacts, they also help direct the air around those parts of the vehicle. And the rear-roof extensions, not devices for directing the air to blow dirt off the rear window as in many other SUVs, are instead carefully designed wings to reduce drag and provide some downforce. This is why it has the unique "duck-tailed" shape. The end result is a Cd of 0.36.
With all the safety technologies, high standard of quality materials and excellent powertrains, the XC90 has what it takes to compete in the world's most competitive automotive segment. And it's just what Volvo needs to significantly expand its footprint in the U.S. market. The almost 135,000 Volvos sold in North America in 2001 marked the third consecutive record-breaking year for the firm's sales team, and the introduction of the XC90 should go a long way toward fulfilling the goal of 200,000 Volvos sold here by 2005. With such competition as the Mercedes-Benz ML, Lexus RX300, BMW X5 and Acura MDX, it's going to be a tough challenge for the XC90. However, this segment of the market is expected to surpass annual North American sales of 250,000 by 2005, so there seems to be plenty of elbow room for this newest, coolest Volvo.