The heavy duty diesel engine market is changing. B.M.E.P. levels are rising, requiring higher pressure ratios and service overhaul lives are being extended. The demands made on the turbocharger manufacturer are, therefore, becoming greater, with improvements in performance, response, reliability and durability being required.To meet this challenge a new model, the H3, has been developed. This paper indicates the methods by which the design criteria were set and then reviews the procedures used for the design, development and testing of the new model.