Next year, Mazda will sell a car in Japan that gets 70.5 miles per gallon (mpg), or 30 kilometers per liter. The fuel economy rating won’t be nearly this good in the United States because of differing requirements, but even so, the car will likely use about as little fuel as a hybrid such as the Toyota Prius–without that car’s added costs for its electric motor and batteries.
The Mazda, a subcompact called the Demio in Japan and the Mazda 2 elsewhere, will include a package of changes that improves fuel economy by about 30 percent over the current model. These include a more efficient engine and transmission, and a lighter body and suspension. The Mazda 2, and a range of new cars from other automakers that have been engineered to meet more stringent fuel economy standards, demonstrate what some experts have been saying for some time–internal combustion-powered cars are far from outdated. Indeed, improvements to gas-powered cars can reduce worldwide fuel consumption more quickly than introducing hybrids or electric vehicles, because variations on traditional engines tend to be less expensive and can be quickly implemented on more cars.
“We’ve been making engines for 100 years, and we keep figuring out how to make improvements in them. We will continue to figure out further improvements,” says Greg Johnson, the manager of Ford’s North American powerpacks. “For another 50 years, if not more, the internal combustion engine will be the primary driver.” This week, Ford announced changes to its Focus model that improve its fuel economy by about 17 percent, to an estimated 40 mpg.
Mazda says the biggest source of improvement for the Mazda 2 is a new engine that compresses the fuel-air mixture in the engine far more than conventional gasoline engines do. Ordinarily, gas engines have about a 10-to-1 compression ratio. Mazda increased this to 14 to 1, a level typically seen only in diesel engines. Increasing compression has long been known to increase efficiency, but compressing the fuel-air mixture too much causes it to ignite prematurely–before the spark sets it off–a phenomenon called knocking. That decreases performance and can damage the engine. Mazda has introduced innovations to avoid knocking.
As a number of automakers, including Ford, are doing, Mazda has introduced direct injection–which involves spraying fuel directly into the engine’s combustion chamber rather than into an adjacent port. Doing this cools the chamber, which helps prevent premature ignition. Mazda also modified the exhaust system–increasing the length and shape of the exhaust pipes to allow more exhaust gas to escape after combustion. Removing these hot gases also keeps the temperature down, but it has the drawback of interfering with emissions controls. That required other changes in the engine, including modifying ignition timing and the shape of the pistons.