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Dipl.-Ing. Werner Bender, Dr. Bertold Engels Academy VTG Turbocharger for Heavy Duty Commercial Diesel Applications with High Braking Performance 1. INTRODUCTION The requirements of modern truck engines increase with each step of the emission legislation. In the same way the charging system as a part of the air management system has to be improved. This leads to more and more complicated solutions such as Regulated – Two – Stage (R2S), combinations of super- and turbochargers (e.g. eBooster) and turbos with Variable Turbine Geometry (VTG). In particular the VTG is a solution of highest interest because it is able to fulfil most of the required development objectives for commercial diesel engines as • Higher torque (boost pressure) at low engine speeds • Better transient response (drivability) • BSFC improvement • Drive EGR at part and full load to reduce emissions An additional advantage compared to other systems is that the installation dimensions are nearly the same as the standard (waste-gated) turbocharger. Never the less this excellent tool for a controllable air management system, even after two decades of development never found access to the large truck fleets world wide! During all steps of emission legislation many customers showed interest and made tests with the product, but in the end nearly always a maybe less comfortable but cheaper solution was introduced to series production because VTG was a „ nice to have“ and not a „must“. To launch the VTG, an additional feature to increase the benefit for the customers was required. As a new objective, the use of the VTG for engine braking was defined. The prospects of additional benefits for the customers were: • Replacement o...