Variable Geometry turbine (VG) technology for gasoline
Whereas VG for diesel vehicles have existed for a while, VG for gasoline has only recently become reality. Due to changes in emission legislation, VG for gasoline is now becoming an increasingly attractive method to boost car engines as performance can be maintained, while emission is lowered. One of the challenges which had to be overcome, is that the VG for gasoline has to be able to withstand much higher temperatures than the VG for diesel, as well as a different kind of exhaust gas composition. It was therefore necessary to seek out a new composition of materials before the VG for gasoline could be realized, which could also be made at a reasonable price. After years of investigations, a perfectly suitable material composition was found, and VG for gasoline is slowly becoming mainstream in new gasoline vehicles.
The VG system consists of a regular turbocharger equipped with a pack of vanes in the turbine throat area that are adjustable using an electric actuator. In the event of low energy at the turbine, the vanes will be closed, resulting in a small throat area. A small turbocharger is then virtually present on the engine. In order to meet the maximum flow required to operate the engine at high rpm, a virtually big turbocharger is needed as well. This is achieved by opening the vanes, thereby increasing the turbocharger throat area. In between these two maximum positions of the vanes, the turbocharger boost is continuously adjustable. During all engine operating points, the position of the vanes are continuously set on such position to always create the correct turbocharger output.
MTEE continuously improves the quality and performance of VG turbochargers. Engineering challenges are related to the maximum T3 temperature >1020 degC, decreasing inside tolerances, increase efficiencies, reduce overall weight, and to reduce the total amount of sub components.