Improving aerodynamics is the key factor to improving the fuel economy of Class 8 trucks and is going to be a major focus of trucking research and development dollars in the future.
"At 65 mph, aerodynamic drag represents 50% of the truck's fuel consumption, with rolling resistance contributing 32% and powertrain efficiency 18%," explained Ron Schoon, chief engineer for aerodynamics for International Truck and Engine Corp. during a special heavy-truck symposium held in Chatham, Ontario, home to its Class 8 truck plant. "And as the speed of the vehicle increases, the drag increases exponentially, resulting in far higher fuel consumption."
Schoon pointed to several key areas on a Class 8 truck where improving aerodynamics can result in fuel savings. "Air fairings are far and away the largest aerodynamic improvement you can make, reducing drag upwards of 10.5%," he said. The rest are side extenders to minimize the gap between the truck and trailer (3% drag reduction), chassis skirts around the battery box and fuel tanks (3% reduction), lower bumper to drag underneath the vehicle (1.5% reduction) and aerodynamic mirrors (1%).
For flatbed carriers, Schoon added, side fairings can reduce drag over 6%, but air fairings don't have as much impact. He also noted that favored traditional trucking designs such as dual exhausts and external-mounted air cleaners negatively impact aerodynamics - each increasing drag between 2% to 4%.