CLASS - 8 Truck Streamlining Benchmark

[aerohead]

An advance apology,as I am not current with truck aero and I am not certain that the following is the most accurate data,however it may serve us until someone steps in with more current info.----------------------------------------------------------------------As of the early 1990s,the benchmark for a Class-8 combination was the Renault V.I.R.A.G.E.S. VE 10 concept truck.With the full compliment of tractor and trailer mods,and using data extrapolated from Renault's data summary,their 1986 tractor/trailer combination achieves Cd 0.292 with boat tail lengthened by an additional 16 inches ( 400 mm ).At 52,800 LBS GVW and 65 mph,the rig can return 9.012 mpg.The rig is a 10-wheeler,with radial super-singles,so benefits from the more narrow and lower frontal area wheel/tires( not to mention lower rolling resistance).---------------------------------------------------- The "highest" reported mpg for a semitrailer combination that I've managed to see so far,is that of the WHITEGMC Aero Series concept truck constructed for the American Trucking Association's "Tomorrow's Truck Program".--------- With 65,000 GVW,pulling a 13'-5" trailer with bias-ply tires at 55.8 mph,returning 11.5 mpg.------------------------------------------------ The WHITEGMC truck had a single drive axle,radial super-singles,sloped-hood,front airdam,side skirts,integrated rooftop air deflector and cab extenders,flush headlights,marker lights and turn signals.Only 59 horsepower is required to overcome aerodynamic drag at the tested velocity,168 horsepower overall.----------------------------------------------------- Speed remains the greatest factor to mpg,seconded by frontal area,and finally shape.----------------------------------------------------------- As an aside,the modern high-torque/low-rpm engine-powertrains are good for a 10% mpg improvement over the units of the 1970s.--------------------- Radial super-singles offer a 19% savings over conventional bias-ply tires.------------------------------------------------------------------- Combined with the aero-mods,this gives an 61.5% mpg advantage over yesteryear's rigs,and well over 100-mpg on a passenger/ton-mile basis.BSFCs are as low as 0.33 pounds per brake horsepower,and future materials technology and compound turbocharging will push BSFCs even lower.---------------------------------------------------------------- Hucho considers Cd 0.15 as a practical limit for realistic aerodynamics.At Cd 0.292 that leaves room for more mpg from aero if we have the stomach for it.