The performance, NVH performance, and fuel economy advantages of variable-geometry turbines are well understood and have made them a fixture in advanced Diesel engines. However, the longstanding and very significant barriers to translating these benefits to the broader world of gasoline engines were equally well understood. Mainly this is due to the temperature extremes and variations of a gas engine's exhaust stream. By forging an innovative customer partnership with Porsche and adapting aerospace materials, BorgWarner Turbo & Emissions Systems broke through longstanding barriers and created a winning entry with their VTG variable-geometry gasoline turbo.
VTG's ability to optimize intake airflow has enabled significant benefits in acceleration, and effectively broadens an engine's optimum operating range while moderating the typical "turbo-lag" and waste-gate induced "peaki-ness." The advantages of variable-geometry turbines have long been sought by gasoline engine builders, but the extreme heat and the extreme variation of heat cycles in a gas engine's exhaust pushed requirements beyond the limits of traditional materials and production processes. BorgWarner's VTG is the first time a variable-geometry turbo has ever successfully been installed in a gasoline engine series production vehicle.
For automakers at large, the benefits of VGT are obvious, that the trend to smaller engines may still be met with good, responsive performance. and its impact in the Diesel market suggests that it will follow the same path. For BorgWarner's competitors, the bar has clearly been raised, as VTG gives automakers a more flexible solution for optimizing the balance between small engine fuel economy and performance than traditional turbos.
Variable Turbine Geometry launch is on Porsche's flagship 2006 911-Turbo (997), and is also slated for several programs in the sub-two-liter class of engines.