by Dr Pandula Siribaddana

Created on: February 22, 2011   Last Updated: February 24, 2011

Gas mileage (mpg) of a vehicle is something that all motorists should be interested in especially when the gas prices gradually rise with each passing day. People tend to pay more attention on fuel efficiency at present than at any point in time and the manufacturers have realized that their survival depends on how the customers perceive their brands in relation to its mpg.

While there are many ways in which the gas mileage can be improved, aerodynamics seems to be one of the most important factors. It refers to how the air flows over the surface of a vehicle when it is travelling and lesser the drag and resistance towards the flowing air, higher the fuel efficiency would be. In the manufacturing plant, they can simulate the aerodynamics of the vehicle by doing ‘wind tunnel’ testing and it is done at each level of its development, as many factors will affect the vehicles aerodynamics apart from its outer body shape.

In relation to fuel economy, the engineers will often look at an entity known as coefficient of drag (Cd) and it simply refers to how easily the vehicle moves through air. However, it should be remembered that, drag is not the only factor influencing the aerodynamics. Thus, factors such as downforce, lift, yawing moment, and noise are some of the other factors affecting aerodynamics.

Traditionally, a Cd of less than 0.3 was considered as highly aerodynamic and in the category of ‘sports models’. However, in the modern car industry, many domestic vehicle models achieve a Cd of less than 0.3 which epitomizes the emphasize put on improving the aerodynamics of a vehicle by its manufacturers.

When looking at how the Cd would affect the fuel economy of a car, experts opinion that, when the Cd is improved by 0.01, the fuel economy can improve by about 0.2 mpg. However, the effect of aerodynamics on the vehicles fuel economy would be much higher when a vehicle is travelling at higher speeds than at lower speeds such as when traveling within the city limits. Thus, a vehicle travelling at 75 mph is expected to negotiate a force against the vehicle four times higher than when the vehicle is travelling at 35 mph.

Therefore, what are the methods in which manufacturers have improved the aerodynamics of a vehicle? Although there are many methods, among them, rounding of the edges in the front, tuning the grille and wheel openings, placing small spoilers in front of the tires, reduce the size and tune the shape of the outside mirrors, limiting drag under the vehicle by adjusting the front fascia and air dam, adding side skirts, tuning the deck height, installing rear spoilers, tucking up the exhaust system…etc can be highlighted.

Apart from these tips, motorists could also improve the aerodynamics of their vehicles by closing the windows and sun roofs when travelling at high speeds, avoiding unnecessary additions of body kits, reducing the use of roof racks, adding narrow tires, keeping the front air dam in good condition, and by lowering the vehicle more towards the ground.

Reference:

Welcome to the Beginner's Guide to Aerodynamics : National Aeronautics and Space Administration.

Learn more about this author, Dr Pandula Siribaddana.
Click here to send this author comments or questions.