The Drag Coefficient – a little-known indicator

The drag coefficient, often denoted by Cx, is a keyfactor in automotive aerodynamics. While it is essential for engineers, it remains relatively unknown to the public. 

This coefficient measures the resistance a car encounters from air as it moves. The lower the Cx, the less resistance the car faces, which improves both energy efficiency and performance. 

Understanding the Drag Coefficient 

The Cx is a dimensionless value that generally varies between 0.20 and 0.40 for production cars. It is determined by the shape of the vehicle, the exposed frontal area and the driving speed. A low Cx means that the car is well designed to minimise air resistance, which is crucial for reducing fuel consumption and increasing the range of the car. electric vehicles. 

Examples of cars with a good drag coefficient 

Some cars stand out for their excellent drag coefficient. For example, theTesla Model S has a Cx of 0.208, making it one of the most aerodynamic cars on the market. The Porsche Taycanfollows closely behind with a Cx of 0.22, combining performance and energy efficiency. TheMercedes-Benz EQSis also remarkable, with a Cx of 0.20, optimising its electric range. The DS N°8, an electric SUV coupé, has a Cx of 0.24, giving it an impressive range of 750 km according to the WLTP cycle. In 1982, the Audi 100 achieved a Cx of 0.30, earning it the title of "aerodynamic champion of the world". More recently, the Audi A6 Avant e-tron boasts a drag coefficient of just 0.24 (and even 0.21 for the Sportback version). 

Benefits of a low drag coefficient 

A low drag coefficient brings several advantages. It reduces fuel consumption for combustion vehicles, benefiting both the environment and the driver’s wallet. For electric cars, a low Cx is even more critical as it increases driving range – a key factor for users. Lower air resistance allows electric vehicles to travel further on a single charge.

The relationship between Cx and range is significant: a 100% reduction in Cx can increase an Ev’s range by 5 to 8%. Even small aerodynamic improvements (such as integrated door handles) can have a notable impact. 

Additionally, a lower Cx enhances overall vehicle performance: better acceleration, higher top speed, and improved stability and quietness due to reduced wind turbulence at high speeds. 

Conclusion 

The drag coefficient is an essential indicator of a car's aerodynamic efficiency. Although it is often overlooked, it plays a crucial role in reducing fuel consumption and increasing a car's range. velectric vehicles. Models such as the Tesla Model S, the Porsche Taycan, the Mercedes-Benz EQS, the DS N°8 and the Audi 100 show that optimising Cx can lead to more efficient and energy-saving vehicles. It's time that this indicator was better known and taken into account by consumers when they buy their next vehicle.