Mazda also found that above a certain compression ratio, some of the bonds in gasoline molecules begin to break, generating heat. These reactions increase the total amount of energy released from the gasoline, improving efficiency, the company says. To take advantage of this phenomenon, the engineers set the ignition timing to occur after these bonds start to break.
Just as important for improving fuel economy were a new transmission and a redesign of the frame to use less steel, or to use lighter, high-tensile steel. Mazda also says it redesigned the suspension system to make it lighter without sacrificing performance. Mazda has also announced a diesel engine that could be about 20 percent more efficient than the new gasoline one.
The 70.5 mpg rating the car received in Japan isn’t a clear indication of what Mazda 2’s rating will be in the United States, which has different test procedures, safety requirements, and emissions requirements. The current version of the Mazda 2 was rated at 54 mpg in Japan, but only 35 mpg (for the manual transmission version) in the United States. Michael Omotoso, manager of the power train forecasting group at J.D. Power and Associates, estimates that the new car could be rated between 50 and 60 mpg in the U.S., giving it a chance to eclipse the 51 mpg rating of the Prius (which gets 48 mpg on the highway).
Mazda will introduce the new engine and transmission in a number of vehicles next year, although it has not announced the specific models, or when the new Mazda 2 will be available in the United States. The new engine and transmission will be introduced in the United States next year in a larger car that will get about 43 mpg.
Although the new Mazdas avoid the costly motor, power electronics, and battery pack required in a hybrid, the improvements will likely add to the cost of the cars. Volkswagen recently introduced an 83-mpg diesel vehicle that wasn’t successful because of the high costs of achieving these fuel economy levels, Omotoso says. Mazda hasn’t announced prices yet. “I would think they learned a lesson from Volkswagen,” he says.