Mar 10, 2016
Rüsselsheim. Aerodynamics have become increasingly important in motorsports. In the past, aerodynamic problems have often been hidden by simply increasing engine performance. However, the key to success in modern motorsports is now the same as in serial production: efficiency. This was one of the most important development goals for the Opel Astra TCR that was created to compete in the Touring Car Racer Series (TCR).
Aerodynamic efficiency is the result of a well-balanced ratio of downforce and drag. In order to achieve the perfect combination of high speeds through the corners and on the straights, engineers strive to have as much as possible downforce while simultaneously reducing drag as far as possible. The new Astra comes with the perfect prerequisites for a close to serial production touring car. The “Car of the Year 2016” has an outstanding drag coefficient for hatchbacks of 0.272. It therefore is perfectly suited to serve as the base for a fast racing car.
Compared to its serial production sibling the width of the Opel Astra TCR has been increased to 1,950 millimeters – the maximum permitted by the rules. The bumpers, fenders and side panels have also been modified. The front splitter and the rear wing are the main elements creating the decisive downforce. Both features have been defined as standard components in the TCR regulations to keep costs down. Manufacturers can thus not change the shape or finish but they can fine-tune the mounting position. The location of the rear wing is especially important. According to the regulations, the rear wing is not allowed to protrude the roofline. Furthermore, it is not allowed to protrude by more than 1,050 millimeters – measured from the center of the rear wheel hub.
The downforce created by the rear wing increases the more it stands in the wind. However, this simultaneously increases drag, which is detrimental for top speed. Therefore, a compromise between drag and downforce needs to be found. The same goes for the setting angle of the front splitter. It needs to be as flat as possible while being steep enough to the keep the front axle stable when braking and to prevent understeer in the corners. Once again the aerodynamic balance in decisive, i.e. the downforce ratio between front and rear axle. This ratio needs to be well balanced so that the car remains stable no matter what the driving situation.
In order to get as close to this delicate balance as possible from the very start, the development team around Opel Motorsport’s Senior Manager Dietmar Metrich put the Astra TCR through an aerodynamics test lasting several days. The team decided to use the wind tunnel of Stuttgart University for the tests. “It has a rolling floor and can simulate speeds of up to 250 km/h. That makes it ideal for our purposes,” explains Metrich.
Time in the wind tunnel is expensive and therefore calls for meticulous preparation. “We used models to prepare various solutions. This gave us to chance to test and change the configurations when we were on site,” says Metrich. “It was mainly about the position of the rear wing, the angle of the front splitter and the design of the fenders and the side sills.”
Dietmar Metrich suddenly turns very quiet when it comes to communicating data and measurements. “I can tell you this much: we feel perfectly prepared thanks to the excellent suitability of the base model. We will only find out where we stand when the cars compete on the race track but that makes the whole thing really exciting!”
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