The paper describes the results of a major development programme in association with industry on a prototype variable geometry turbocharger turbine coupled to a wide mass flow range compressor, and the matching of this unit to a standard Perkins T 6.354 engine.The performance target for the turbine was a mass flow turn down ratio of 2:1 and achievement of potential torque back up of 50% at half of rated engine speed.The results are described under the following headings: 1. TURBINE PERFORMANCE ASSESSMENT - Rig testing in high speed dynamometer for various settings of V.G. device and discussion of experimental results. 2. V.G. TURBOCHARGED ENGINE PERFORMANCE ASSESSMENT. 2.1 Steady state performance results. 2.2 Transient performance results.The paper concludes with a discussion of the potential of V.G. turbocharging in commercial applications.