Hybrid cars normally combine conventional engines with battery-powered electric motors. But many carmakers are developing alternative types of hybrids—some of which were on display this month at the Frankfurt Motor Show in Germany.
Hybrid systems recover kinetic energy—from the engine or from the vehicle itself—and use it to boost the efficiency of the engine. A typical hybrid car does this by charging up a battery.
Scuderi, based in West Springfield, Massachusetts, has altered the way the internal combustion engine operates to convert kinetic energy into the potential energy of high-pressure air. It splits the four parts of the internal combustion cycle across two cylinders synchronized on the same crankshaft. One cylinder handles the air intake and compression part of the cycle, pumping compressed air via a crossover passage into the second cylinder. The crossover contains the fuel-injection system, and combustion and exhaust are handled in the second cylinder.
When the vehicle does not need power—when traveling downhill, braking, or decelerating—the second cylinder is disabled and the first cylinder’s air is diverted into a high-pressure air-storage tank. This air can be used to help run the engine, boosting its efficiency.
Recently, Scuderi has combined this system with a “Miller-cycle” turbocharger, which picks up energy off the exhaust and uses it to compress air into the intake cylinder. This allows the compression side to be shrunk down and reduces the amount of work done through the crankshaft. “The engine is producing much higher output at higher efficiency, we’re producing less emissions, and our torque level is very high,” said Scuderi group president Sal Scuderi at the Frankfurt show. “Our gasoline engine will rival the torque of any diesel engine on the market, but it does that while maintaining low pressure inside the cylinders, which reduces wear and tear.”
Scuderi has now released results of a computer simulation of its engine against a European economy-class engine of comparable power. The air hybrid achieved a fuel economy figure of 65 miles per gallon, compared with 52 miles per gallon for the conventional engine. It also emitted 85 grams per kilometer of carbon dioxide, compared with 104 grams per kilometer for the conventional engine.