Aerodynamic Development of the New Honda FIT/JAZZ

This paper discusses the characteristic flow field of the new Honda FIT/Jazz as determined from the aerodynamic development process, and introduces the technique that reduced aerodynamic drag in a full model change. The new FIT was the first model to take full advantage of the Flow Analysis Simulation tool (FAST), our in-house CFD system, in its development. The FAST system performs aerodynamic simulation by automatically linking the exterior surface design with a predefined platform layout. This allows engineers to run calculations efficiently, and the results can be shared among vehicle stylists and aerodynamicists. Optimization of the exterior design gives the new FIT a moderate pressure peak at the front bumper corner as compared to the previous model, resulting in a smaller pressure difference between the side and underbody. For the platform development, CFD analysis of the flow field established a direction for enhancing aerodynamic performance and helped optimize the shape in detail. In order to restrain total pressure loss due to the flow from the front wheelhouse, the pressure difference in the front section must be reduced. A new shape was introduced in an effort to further increase the negative pressure on the front underbody, which adds a bump at the leading edge of the engine undercover. The paper illustrates how these changes are realized in the aerodynamic development process, using the CFD and reduced/full-scale wind tunnel testing. The difference of flow phenomena between the new and previous FIT is also discussed briefly in this paper.