Earlier investigations on the utilisation of Carbon black-water-diesel emulsion in a DI (direct injection) diesel engine reported that the engine performance was inferior to that of diesel operation at full load in the same engine. The HC (hydrocarbon), CO (carbon monoxide) and smoke emissions were reported to be higher than those of diesel operation at full load. The poor mixture formation and lower cetane number of the CBWD10 were believed to be the reasons for these results [1]. In this investigation, attempts have been made to improve the combustion and performance of the engine run on the CBWD10 emulsion by enhancing in-cylinder turbulence by providing two holes on the piston crown (internal jet piston). The performance characteristics for the CBWD10 emulsion with an internal jet piston is 1.9% higher than with a conventional engine piston at the full load, respectively. The internal jet piston operation with the CBWD10 emulsion exhibited the CO, HC and the smoke emissions lower by about 23.5%, 7.2% and 5.2% respectively compared to those of the engine operated with conventional piston. (C) 2015 Elsevier Ltd. All rights reserved.