A rather interesting twist in the never-ending search for better fuel economy was recently presented by the infamous MythBusters TV show on the Discovery Channel. In a quest to determine whether a dirty car will get different fuel mileage than a clean one, the MythBusters duo went their usual one-step-farther and applied the proven, flight distance enhancing, dimpled-surface of a golf ball to the exterior of an automobile.
The science behind the dimpling on golf balls holds that the dimples produce more turbulence in the air flow over the ball and that the turbulent flow sticks to the surface better than a laminar flow of air over a smooth surface. The turbulent flow of air sticking to the surface creates a smaller area of vacuum drag behind the ball, and the ball travels farther and faster due to less drag behind it. Smooth balls have “looser” air traveling over them and the area of vacuum drag behind a smooth ball will be about the same size as the ball itself. In this latest experiment, the MythBusters wanted to see if the travel-enhancing effect of dimpled golf balls would work on much larger objects, like cars.
The result? It works.
The MythBusters crew realized over 10% improvement in fuel economy in a heavily pock-marked Ford Taurus sedan. The Ford was first covered in a coat of smooth modeling clay and the fuel economy was determined to be 26 miles per gallon at a constant 65 miles per hour. After removing about 1,000 ice-cream scoop-size clay dimples from the surface of the car, all of the dimples removed were put back inside the car to keep the weight constant. Tests with the dimpled car showed that gas mileage (at a constant 65mph) had improved from 26 mpg to 29mpg. That equals an astounding 11.5% improvement!
Exactly what this might mean for the future of automobiling is a bit uncertain. In an era when manufacturers zealously guard technologies that yield 1 or 2 mile per gallon improvements, 11% percent is huge, and unlikely to be ignored. While it might be a reach to conclude all new cars will begin to look like golf balls, it could be a safe bet to imagine some sort of surface dimpling will be at least partially employed on various car surfaces in the future. Automotive racing might be affected too, as a 10% increase in fuel mileage would be a tremendous advantage in any form of competition that involves refueling during an event. All other factors being equal, a dimpled car would outrun a smooth car every time.
The Dimple Effect will probably require more time and more testing before you will be able to purchase the technology at your local dealership. It might also be a while before Body Shops start charging to put dents into cars instead of taking them out. In the meantime, all you need to start your own testing is a hammer.
A dimpled surface creates less vacuum drag “wake” behind an object in motion.
The odd golf-ball-style dimpled surface on this Ford Taurus improved fuel economy at highway (constant 65mph) speeds by over 11%.