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Regardless of what power source a car is using, the less its aerodynamic drag, the less energy will be needed to travel at any given speed. A great deal of effort has gone into designing the Insight around the goal of achieving excellent aerodynamics, the end result being a drag coefficient of only 0.25, the lowest achieved by any mass produced car. In comparison, the Honda Civic Hatchback, with roughly the same 1.9 square-meter frontal area as the Insight, has a Cd of 0.36, and needs around 32 percent more power to operate at the same speed as the Insight.
Tapered Tear-Drop Shape
The Insight's body is tapered so that it narrows towards the back, creating a shape that approaches the optimal tear-drop shape. To allow the body to narrow, the rear wheel track places the rear wheels 4.3 inches closer together than the front wheels. The cargo area above the wheel wells is still narrower. The floor under the rear portion of the car actually slopes upwards, while the downward slope of the rear hatch window also contributes to an overall narrowing of the car at the rear.
At the very back of the Insight, the teardrop shape is abruptly cut off in what is called a Kamm back (a distinctive design feature also shared by the Honda CRX). The Kamm back takes advantage of the fact that beyond a certain point there is little aerodynamic advantage to be gained by rounding off or tapering and extending the tail section of an automobile, so one might as well abruptly truncate it at that point. The Kamm back is a design feature that has been incorporated into many high-performance automobiles and racing cars over the years.
Flat under-body Covers
Another important aerodynamic detail that greatly contributes to the Insight body's low coefficient of drag is the careful management of underbody airflow. The Insight body features a flat underbody design that smoothes airflow under the car, including three plastic resin underbody covers. Areas of the underside that must remain open to the air, such as the exhaust system and the area around the fuel tank, have separate fairings to smooth the airflow around them.
In order to minimize air leakage to the underside, the lower edges of the sides and the rear of the body form a strake that functions as an air dam. At the rear, the floor pan rises at a five-degree -angle toward the rear bumper, creating a gradual increase in underbody area that smoothly feeds underbody air into the low-pressure area at the rear of the vehicle.
Note that high voltage cables that are passed above the underbody covers, and so the covers must be replaced if removed for any reason.
Other Aerodynamic Features
Other aerodynamic features includes: