New fuel system allows V6 engine to run leaner, improving fuel economy.
Automakers are trying to get the best fuel economy from their engines. Mercedes-Benz is launching a technology called stratified fuel injection in this year’s launch. This technology should bring a slight increase in economy.
Bart Herring is the general manager of product development at Mercedes-Benz USA. He says the stratified system allows engine designers to be more precise in timing the injection spray. The stratified system allows the engine to inject fuel at the compression stroke. This is almost identical to a diesel engine. He says, “The injection actually takes place on the upstroke.” Mercedes can now run lower-load fuel mixtures with greater precision, Herring states, which allows for more fuel economy and “basically no sacrifices in power.” One problem with ultra-lean mixtures is the increased emissions of nitrogen oxides, a major pollutant. To reduce harmful emissions, Mercedes’ stratified injection engines will require NOx traps similar to those found on diesel cars. Mercedes already stated that it will begin equipping gasoline engines with particulate filter starting in 2017. The traditional direct injection and stratified systems are “very similar,” with only minor changes to the injectors.
The technology will be available on a V6 engine if Mercedes renews an engine with that engine before December 31, though Herring would not provide any further details about the application. The engine’s horsepower and torque ratings will remain the same, but the fuel economy should increase slightly. Ultra-low sulfur gasoline is the biggest enabler of stratified direct injection. The increased availability of ultra-low sulfur gasoline in the United States is the key to stratified direct injection. All gasoline sold in the country will have a lower sulfur content starting in 2017. “The fuel is America’s biggest problem” until that switch occurs.