Environmental and economic factors are driving the development of lower emission and more fuel efficient off-highway vehicles. While a great deal of this development is focused on hybrid technology and novel system architectures, the simple application of a Digital Displacement® Pump (DDP) in place of a conventional pump can deliver significant fuel savings and productivity benefits, whilst also acting as an enabler for more radical future development. This paper describes the ‘DEXTER’ project, in which a tandem 96cc/rev DDP was installed in a 16 tonne excavator. The energy losses in the unmodified excavator are calculated based on test data, confirming the scope for efficiency improvements. Next, the basic operating principle and efficiency of the DDP and its application to the excavator system are outlined, alongside simulation based fuel saving predictions. The model based design and ‘operator in the loop’ testing of the control system are then described. Side by side testing of the modified excavator and a standard excavator showed that when the modified excavator was operating in ‘efficiency mode’ a fuel saving of up to 21% and productivity improvement of 10% is possible. In ‘productivity’ mode, a 28% productivity improvement was recorded along with a 10% fuel saving. These results are validated with reference to the higher efficiency of the DDP and improved control system which allows the engine to run closer to its torque limit.

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