(Photo: BorgWarner)
This pressure falls as the vanes are opened. As a result, the bypass system with the wastegate valve that is a feature of conventional turbochargers can be eliminated. The entire exhaust gas flow can then pass through the turbine wheel and be immediately converted into increased boosting.
This considerably improves engine response in the lower rpm range, compared to a conventional turbocharger with a wastegate typically used in gasoline applications, says Wood.
Downsized gasoline engines with VTG technology can achieve the same output and dynamic engine response as normally aspirated engines with a larger displacement. At the same time, these improvements are achieved with much lower fuel consumption. Fuel savings is estimated at 15 and 20 percent, compared to a larger traditional or port-injected gasoline engine without a turbocharger.
Until recently, VTG technology was limited to diesel engines. The technical challenge lay in developing materials capable of withstanding the much higher exhaust gas temperatures that are generated in gasoline engines. To address the challenge of high exhaust temperature, the company used high-temperature-resistant alloys for the VTG cartridge and vanes. These materials are also used in aviation and space technology.
In cooperation with Porsche, BorgWarner developed the first turbocharger with VTG technology for the automaker's 911 Turbo. BorgWarner Turbo & Emissions Systems expects this technology to become established on a broad number of applications over the next 10 years.
Already, the company has indicated that several other automakers are exploring application possibilities for VTG technology in gas engines. Worldwide, the use of turbocharged gasoline direct-injected engines is expected to grow to 2 million engines in 2011, from about half a million in 2006. About 70 percent of these engines are expected to be produced in Europe, with the rest of the production in Japan, China and North America.
(Source: BorgWarner Turbo & Emissions
Systems)
