A sophisticated genetic Algorithms (GA)/PSO-hybrid algorithm for application to real-world optimization problems was reported. The new hybrid algorithm was applied to two test function problems, and the results indicated that the search ability was improved by suitable tuning of the configurations. The configurations for GA and PSO in a fully coupled hybrid algorithm were investigated to achieve improvements in diversity and convergence simultaneously for application to real-world engineering design problems. The design of a diesel engine combustion chamber is considered as an application to a real-world design problem. The new hybrid algorithm showed robust search ability regardless of the selection of the initial population. The new hybrid algorithm was also applied to a diesel engine combustion chamber design problem.