Centurion
128-mpg Diesel-Powered Sports Car

Centurion combines diesel-engine efficiency with the effects of high engine loading, reduced vehicle weight, and good aerodynamics to push fuel economy well past the 100-mpg mark. And one of the most straightforward ways to reduce emissions is to reduce the amount of fuel consumed. In reality, many other variables affect engine-out emissions, but assuming equal technology, reduced fuel consumption loosely translates into reduced emissions.
         The technology used to produce Centurion's high fuel economy is very fundamental. An internal combustion engine runs most efficiently when it is operating at 60% to 90% of maximum output. When an engine is throttled, fuel economy plummets. Automobiles operate most of the time with the engine throttled to 5% or less of full power, such as when cruising at low speeds in urban traffic. Even on the highway, the average family sedan can cruise at 55 mph on a little as 8 to 10 hp, which is only a fraction of the power capability of the engine. An engine throttled into fractional power regions can use double or triple the fuel per horsepower output.
         Centurion first reduces road load by keeping weight and aerodynamic drag to a minimum with its sleek shape and low, 1,200-pound curb weight. Minimum installed power, tall gearing, and a transmission with high ratio selectivity combine to allow for high engine loading. With its 17-hp, 3-cylinder Kubota diesel engine coupled to the 5-speed transmission with overdrive in each gear, the engine can be loaded into its region of minimum brake specific fuel consumption at just about any speed. These are the primary factors responsible for Centurion's fuel economy at cruise. Stop-and-start fuel economy benefits from low weight, which translates into less energy lost to inertia in urban traffic. Reduced fuel consumption at idle and during braking results from the small-displacement engine.
         At 35 mph, Centurion delivers at 128 mpg. At 45-mph, fuel economy is 103 mpg, and at 55 mph it drops to 85 mpg. The poorest fuel economy recorded was 64 mpg, which occurred in downtown urban traffic. Turbocharging the engine would increase maximum power and performance, and improve fuel economy as well. As originally equipped, Centurion has a maximum speed of 65 mph.
         Centurion is one of our most expensive cars to build, primarily because of the cost of the diesel engine - new, about $2,500. Its Triumph Spitfire chassis, however, is relatively inexpensive if you purchase it from a wrecking yard or private party. The remainder of the cost is in fiberglass, paint, fixtures, and accessories. Total cost will be in the order of $5,000 - $7,000, depending on how the car is detailed. Using the original Spitfire engine, instead of the Kubota diesel, could save about 50% on costs. If you would like more information on building Centurion's body, click on One-Off Construction Using FRP/Urethane Foam Composite.
         Centurion was built in 1981 and featured on the cover of Mechanix Illustrated magazine in February 1982. It appeared as a background vehicle in the movie Total recall.