Kings of Aerodynamics: New Opel Astra Shares Calibra’s Crown

• Most aerodynamic: New Opel Astra hatchback and Sports Tourer lead their class
• Active full-face shutter: front grille opens and closes according to driving conditions
• Smooth airflow: aerodynamically optimized underbody for even lower drag
• IAA star: New Opel Astra makes world premiere at Frankfurt International Motor Show

New Opel Astra, which will make its world premiere at the IAA Frankfurt International Motor Show (public days September 12-22), has joined the legendary Opel Calibra and the Opel Insignia as the most aerodynamic automobiles the German carmaker has ever produced. With a drag coefficient of 0.26 for the Opel Astra hatchback as well as the Sports Tourer estate, the new compact Opel belongs to the most aerodynamic cars in its class. Drag has a major influence on fuel consumption. Aerodynamic efficiency is therefore key to reducing CO2 emissions.

Opel Calibra

As the king of aerodynamics, Opel Calibra has worn the crown for almost 30 years. With a drag factor of 0.26 Cd, the sleek coupé makes no secret of its wind-cheating talents; but the new Astra’s equally low drag has been reached by the optimization of details that are less obvious to the naked eye. Current model, which made its world premiere at the IAA in 2015 and was elected European Car Of The Year the following year, already has a low drag coefficient of 0.29. When it came to the development of the new Astra, the engineers in Rüsselsheim refused to rest on their laurels. Instead they gave themselves an ambitious new goal – class-leading aerodynamics for both the hatchback and the Sports Tourer estate versions of the compact bestseller.

New Opel Astra  Sports Tourer 

Using the Stuttgart University wind tunnel operated by the Research Institute of Automotive Engineering and Vehicle Engines, the development team concentrated on optimising the current Astra’s already excellent aerodynamics for the new model.

An automobile produces 40 to 50 per cent of its total aerodynamic drag in and around the underbody, the wheels and the wheel arches. Opel engineers therefore focussed much of their attention on these areas. They also formed a special cross-functional task force to develop a new full-face active shutter.

New Astra’s full-face active shutter further improves fuel efficiency by closing the top as well as the bottom of the grille. By combining thermal, electrical and aerodynamic considerations, intelligent control strategies for opening and closing the upper and lower portions of the grille – even independently from each other – can enable highly efficient driving under a variety of real-life conditions. For example, a ten per cent cut in drag results in a fuel consumption reduction of around two per cent in the New European Driving Cycle (NEDC), or up to five per cent when driving at 130 km/h.

Reduction in drag achieved by the full-face active shutter alone lowers CO2 emissions of the new Astra by up to 2.0 g/km.

Full-face active shutter: Thermal as well as aerodynamic benefits

The full-face shutter also delivers thermal advantages by delaying cooling down after switching off the engine, or by accelerating the engine warm-up after a cold start, which especially in winter provides significant benefits in fuel consumption and cabin heating comfort.

Despite the apparent simplicity and logic of the solution, the full-face active shutter represents a significant challenge for designers and engineers: they need to consider numerous factors, including not only styling, packaging, and pedestrian protection, but also insurance ratings, engine and transmission types, their corresponding thermal management and, of course, cooling requirements.

Underbody airflow-improvements include a cover under the engine and transmission, panels at the front of the floor, an enlarged fuel tank heat-shield that doubles as an air deflector, ride-height lowered by up to 10mm, depending on the model variant, and aerodynamically shaped control arms at the rear axle.

In total, the aerodynamic optimization of the new Opel Astra saves 4.5g of CO2 per kilometre in the WLTP cycle. In the context of increasingly strict CO2 standards, this is a hugely important saving: as of 2021, an average CO2 emissions target of 95 grams CO2 per kilometre for the new car fleet will apply in the European Union.

IAA star 1989: World premiere for aerodynamics champion Opel Calibra

New Opel Astra makes its world premiere at the IAA exactly thirty years after the Opel Calibra. Following the start of production in 1990, the two-door coupé from Rüsselsheim ruled for ten years as the most aerodynamic production car in the world, with a drag coefficient of only 0.26. Opel Calibra owed its reign to its long, low profile and a host of aerodynamic tweaks, such as optimum height of the front spoiler and the inward tapering of the rear end. Rocker mouldings between the front and rear wheels further reduced drag by preventing the air flowing underneath the car from spilling outward.

Aerodynamics champion: Opel Calibra

Opel Calibra was the most successful sports coupé of the 1990s, more than 238,600 units were produced between 1989 and 1997. The Calibra was available with a total of five power outputs, ranging from the 85 kW (115 hp) 2.0 litre to the 150 kW (204 hp) turbo. Highlight of the Calibra’s career in motor sport was victory in the 1996 International Touring Car championship.

ITC champion Manuel Reuter in Opel Calibra on the Hockenheimring track, May 1996. 

All-New Opel Corsa Top in Aerodynamics: For Lower Emissions and Higher Efficiency

• Model of aerodynamics: class-leading drag coefficient of only 0.29
• Every detail counts: active aero shutter, smooth underbody, rear roof spoiler
• Energy saver: efficient aerodynamics cut drag, fuel consumption, emissions
• IAA world premiere: Frankfurt Motor Show debut for all-new Opel Corsa

As with all other newly developed cars Opel optimised Corsa’s aerodynamics at the Research Institute of Automotive Engineering and Vehicle Engines in the wind tunnel of Stuttgart University.

Opel Corsa has always been an innovation leader and the newest model (which makes its world premiere at the 2019 IAA Frankfurt International Motor Show) is no exception. This year’s IAA is open to trade visitors and the general public September 12-22, 2019.

Sixth generation of the small car from Rüsselsheim not only has more driver assistance systems than most of its rivals, it also has superior aerodynamics.

Result is drag coefficient of only 0.29 – compared to its predecessor further reduced frontal area of only 2.13 m2, making All-New Opel Corsa one of the most aerodynamic cars in its class.

As with all the other newly developed cars Opel optimised the Corsa’s aerodynamics at the Research Institute of Automotive Engineering and Vehicle Engines in the wind tunnel of Stuttgart University.

Low drag means that less energy is needed to move the car, which in turn results in reduced fuel consumption and lower emissions.

Result is a drag coefficient of only 0.29 – an excellent value for a car of this size – and compared to its predecessor a further reduced frontal area of only 2.13 m2, making the new Corsa one of the most aerodynamic cars in its class. Also, the new generation of Opel’s bestseller already meets the future Euro 6d emissions standard. 

“Aerodynamics is just one area where Opel is increasing the efficiency of its automobiles”, said Managing Director Engineering, Christian Müller.

“Aerodynamics is just one area where Opel is increasing the efficiency of its automobiles”, said Managing Director Engineering, Christian Müller. “Advanced petrol and diesel powertrains and state-of-the-art electrification are the other tools we are using to significantly cut fuel consumption and CO2 emissions. All these technologies are fully embraced by our new Corsa, which will also be available for the first time as the all-electric Corsa-e.” 

Due to the challenges posed by CO2 reduction, perfect aerodynamics are gaining great importance in the automotive industry as well as among customers. Low drag means that less energy is needed to move the car, which in turn results in reduced fuel consumption and lower emissions.

All-new Opel Corsa also features spoiler at the rear edge of the roof, which improves the airflow and reduces the turbulence that causes drag.

For example, a ten per cent cut in drag results in a fuel consumption reduction of around two per cent in the New European Driving Cycle (NEDC), or up to five per cent when driving at 130 km/h.

Opel’s engineers achieved this leading drag factor of 0.29 Cd by paying attention to every detail that helps improve the new Corsa’s aerodynamics.

For example, the underbody from the engine compartment to the rear axle is covered with flat panelling to improve the underbody airflow.

All-new Opel Corsa also features a spoiler at the rear edge of the roof, which improves the airflow and reduces the turbulence that causes drag.

Spoiler cuts aerodynamic lift on the rear axle too, which further improves the new Opel Corsa’s straight-line stability, especially at the higher speeds typical of the German autobahn.

Revolutionary in small cars: Active shutter improves aerodynamic efficiency

All-new Corsa also benefits from an active shutter which lowers drag and improves fuel efficiency by automatically closing the frontal opening when cooling air is least needed. So far this innovation has just been featured in much more expensive cars from higher segments.

When closed, the shutter system enhances aero performance by redirecting airflow around the front of the vehicle and down the sides, rather than through the less aero efficient engine compartment. 

The shutter is open or closed depending on engine coolant temperature and speed. For example, the shutter opens when the car is traveling up a hill or in hot city driving. Shutter closes when less engine cooling is required, for example at urban-road speeds.

Sixth generation of Opel’s bestselling small car is not the first aerodynamically optimised Corsa to make its debut at the IAA. At the 1995 Frankfurt show, Opel surprised the industry with an engineering study based on the Corsa for a so-called “three litre car”, i.e. it was designed to return an average fuel consumption of less than 3.5 litres per 100 kilometres.

Opel Corsa ECO 3 concept

Opel Corsa ECO 3 featured, among others, a roof spoiler derived from the GSi, spoilers ahead of the front wheels and flared rocker mouldings in front of the rear wheels.

Opel Corsa ECO 3 concept: roof spoiler derived from GSi, spoilers ahead of the front wheels and flared rocker mouldings in front of the rear wheels. 

Result of all the streamlining was a particularly low drag coefficient for a small three-door hatchback - only 0.29 Cd. Twenty-four years later a series production car has achieved the same excellent result: All-New Opel Corsa.

!NEW! Outstanding Aerodynamics: Best Conditions for the Opel Astra TCR

• Efficient aerodynamics are one of the keys to success in touring car racing
• Meticulous wind tunnel work important element of vehicle development
• Already excellent aerodynamics of serial production Astra as the perfect base

Key to success: Aerodynamic efficiency is the result of a well-balanced ratio of downforce and drag. 

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).

New Opel Astra TCR: Wind tunnel testing for efficient aerodynamics.

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.

Increased width: The front splitter and the rear wing are the main elements creating the decisive downforce.

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.

Meticulous preparation: Wind tunnel work about the position of the rear wing, the angle of the front splitter and the design of the fenders and the side sills.

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!”