Recently, utilization of CFD (Computational Fluid Dynamics) at the initial stage of motorcycle development is increasing the importance and is becoming indispensable to environment matters. This paper describes a CFD system, which was developed based on PCC (Partial Cells in Cartesian coordinate) method CFD code. The code does not require the mesh generation at each computation. The merit of this system is a full automation after the solid modeling by a 3D-CAD system, such as geometry data transferring, starting of processes, and mailing the results. Moreover, an example of a combination between CFD and DOE (the design of experiment) will be explained. It is an application of an exhaust muffler design of motorcycles. In the past, the decision concerning to the power output during an exhaust muffler design could be done by only a few skilled engineers, but the decision became possible to designers who use this system.