Power boosting technology of the diesel engine withno increase in the engine size has been developed with theevolution of the turbocharger which forces more air in theengine which increases more fuel injection and hence morepower output. The turbocharger increases engine efficiency byusing the energy of exhaust gases in the form of pressurizedgas and heat, to drive the compressor. Most of the turbochargerpreviously used was of waste-gate type having drawbacks likevolumetric efficiency limit, fix geometry. Hence the VariableGeometry Turbocharger (VGT) is used. It provides variablearea of inlet orifice. It provide small orifice area for the exhaustgas during resupplying to input air due to which more boostcreate at lower engine speed and provides large orifice areaduring higher engine speed for higher exhaust pressure createdduring nozzeling operation. This study shows how the variablegeometry obtains by the adjustable vanes which act as thenozzle around the central turbine and connected to actuator.Variable geometry turbocharger increases expansion ratio,output power, output torque. This study describes the improvedfull load performance of 2.5 liter DI diesel engine and itscomparison with the waste-gated turbocharger. Within thesame limitation of a maximum cylinder pressure as well asexhaust smoke levels, the low speed torque could be enhancedat its maximum and also reduces the exhaust smoke andimproves the fuel consumption.