Dominique Petitjean

Advanced gasoline engine turbocharging technology for fuel economy improvements

Data on several hundred family sedan production vehicles over a ten-year period are analyzed to compare turbocharged with non-turbocharged engines. It is shown that for the same power turbocharging enables gasoline engine downsizing by about 30%, improves fuel economy by 8-10% while improving torque and acceleration performance. Data with experimental turbocharged, downsized gasoline engines also shows that in the same vehicle, for the same power and performance, downsized turbocharged engines can give about 18% improvement in fuel economy. The paper discusses these data and analyzes the benefits of engine downsizing and turbocharging and the possible mechanisms of these effects. It is shown that the same basic small engine can be turbocharged using a wide range of turbocharger matching to cover a power range normally covered by 4-5 engine families of progressively increasing displacement. Thus additional benefits can be obtained by rationalizing the engine product lines. Advanced turbocharging technology for gasoline engines is discussed including cold start emissions (catalyst light-off), high temperature materials, variable geometry mechanisms and electrically assisted turbocharging. It is shown that these technologies combined with an appropriate control logic can yield great benefits in driveability while at the same time giving all the fuel economy, weight and packaging benefits of engine downsizing.