Editor's Note: This article was orginally published Nov. 9, 2006. Some of the information may no longer be relevant, so please use it at your discretion.
According to BorgWarner Turbo Emissions Systems, 30 percent of all spark-ignition engines produced in Europe in the next five years will be fitted with a turbocharger. Even after 100 years, the development of turbocharger technology is by no means at an end.
Now that almost every diesel engine is equipped with a turbocharger, engine developers are increasingly focusing on turbocharging spark-ignition engines. In particular, the combination of gasoline direct injection and turbocharging offers great prospects for the future, says BorgWarner. Turbochargers with Variable Turbine Geometry (VTG), currently state-of-the-art in modern passenger car diesel engines, are about to continue their success in spark-ignition engines.
Following its debut in the Porsche 911 Turbo, BorgWarner expects VGT to become established on a wide scale over the next 10 years.
"The spark-ignition engine with exhaust gas turbocharging and gasoline direct injection will have an equally successful career as the diesel engine," predicts Hans-Peter Schmalzl, BorgWarner vice president for Technology, Turbo & Emissions Systems. Schmalzl says that the next generation of gasoline direct injection combined with turbocharging will open up even greater potential in terms of specific output, fuel consumption and driving dynamics.
The combination with gasoline direct injection will also offer further benefits, such as increased knock resistance. Optimizing the valve timing in the lower engine speed range will also make it possible to improve residual gas scavenging. This will increase the cylinder charge with fresh mixture, resulting in higher engine output.
"Compared to other turbocharging concepts, VTG offers the best cost/benefit ratio after the wastegate charger," says Schmalzl. "Without additional turbocharging, it achieves almost the same output and a similarly dynamic engine response as in normally aspirated engines with a larger displacement."
At the same time, he adds, these improvements are achieved with much lower fuel consumption: "This shows that modern spark-ignition engine turbocharging is not focused exclusively on increasing engine output, but also on combining exceptional engine performance with good fuel economy. Fuel savings of between 15 and 20 percent are achievable in normal driving."
Beating the heat
Until recently, VGT technology was limited to diesel engines. The technical challenge lay in developing materials that are able to withstand the much higher exhaust gas temperatures of up to 1,050
