Efficient Aerodynamics

  • Jun 27, 2014
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The science of cutting through air is paramount in achieving good fuel efficiency. Here's how knowing this science can help your ownership experience

Porsche 911 GT3 RS to depict efficient Aerodynamics

Imagine crashing your car into a block of concrete… What would happen? Depending on your speed, the car would get damaged and maybe even you might find it hard to get out of the crash unhurt. That’s because the concrete block is resistance to a car moving forward. Now replace the concrete with air. When you drive through air, the air provides resistance as well. Much less, but it does and it goes up as your speed increases. The faster you go the more power is required to wade through wind and the resistance this wind provides affects the fuel efficiency of your vehicle. 

The science of aerodynamics studies how a car performs when subject to wind resistance and helps analyse and change a car’s design to make it more streamlined. Lesser the resistance, lesser the consumption. As weight of cars began to increase, the need to make them more ‘slippery’ started taking importance. There are few things you can keep in mind while purchasing a new car to ensure you have a car that’s the most aerodynamic for your budget. 

Drag Coefficient

First and foremost, find out the car’s coefficient of drag (Commonly denoted as Cd). The lowest score is the most aerodynamic car. A Volkswagen XL1 has a drag coefficient of 0.186, a BMW i8 scores 0.26 Cd while a Hummer H2 had a drag coefficient of 0.57. Clearly a body style changes a lot, large bulky SUVs offer more resistance and hence are not as efficient. Most manufacturers provide these numbers.


Drive with the windows rolled up. Air gets into the cabin and works like a massive resistant similar to a deployed parachute. Rolled up windows seal the surface of a car like a cocoon, reducing the amount of drag. Rolling up your windows and turning on the air conditioning can consume lesser fuel than driving with the air-con off and the windows down.

Body style 

This isn’t as clear cut a way to find a car with low Cd as it might seem. Of course an SUV or an MPV will have more drag than a sport car but between cars in the same segment, it is hard to spot the more efficient one. You can look for clues like vertical panels and anything that can act as strong wind barriers. Next have a look at panel gaps. Large gaps are bad as they end up disturbing air flow along the surface of a car. 

Body parts

One is reducing resistance for economy and next is helping guide air along the surface of a car. Parts like air dams, diffusers, shapely mirrors and a rear wing can all help make a car more slippery to air and improve high speed stability. Most mass market cars don’t have these as they add to the cost of a car and are more effective in cars that pack a lot of power and speed.

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