The focus of this paper is to apply optimization strategy of PSO to search for optimal value of HVAC design parameters to create an accurate HVAC model for HIL testing of climate control ECU. In this paper the completed dynamics of HVAC cooling and heating circuit which include compressor, condenser, evaporator, expansion valve, heater, mixing box, blower, and compartment and environmental conditions are modeled. Now a day most of HIL hardwares are getting more powerful with the capability of multi core processing and FPGA based hardware architecture which gives an option either to simulate exact complex dynamics by choosing powerful processor or use simplified dynamics with diminishing accuracy. This paper also explore the computational capability of various DSPACE simulators to execute a vehicle climate system dynamics with both actual stiff model and lookup table based lump sum model with different step size. Also the deviation of both from actual system is being observed. Paper also explore possibility of tuning lookup table based modeling approach to bring response of lumped system closer to actual system which provides addition advantage of being executed on even low computational speed processor.