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Recently, the concept of Mizen Boushi (reliability problem prevention) has been applied in automotive development as a tool to refine drawings to the greatest completion possible by the prototype stage. GD3 is a quality innovation process that supports this objective, based on the pillars of Good Design, Good Discussion, and Good Design Review. Good Design tries to nip problems in the bud, and Good Discussion and Good Design Review are used to formulate the best countermeasures to those problems. The process utilizes creative FMEA (Failure Mode & Effects Analysis), FTA (Fault Tree Analysis), and a System Design Review. These tools focus attention on the many potential problems that could occur due to a change in design or environment. The System Design Review is especially useful to examine potential failure modes, root causes, part drawings, and prototype part designs. This is followed by a Design Review Based on Failure Mode (DRBFM for short), as a tool to guide discussion.

The muffler layout in the exhaust system has been optimized for the attenuation of exhaust noise which has not been studied much to this date. As a result, “Exhaust Manifold Muffler” has been developed. This unit is capable of efficiently muffling the primary and secondary componemts of the engine explosion stroke noise. Such task is achieved without deterioration of engine performance by allocating the volume at the junction of the exhaust manifold branch pipes. Acoustic characteristics of “Exhaust Manifold Muffler” have been analyzed by FEM and experimental methods, which have shown that not only does the volume placed at the junction of the exhaust manifold branch pipes work as a conventional muffler, but also prevents the exhaust manifold branch pipes from amplifying exhaust noise. This is the reason why “Exhaust Manifold Muffler” can muffle more efficiently than the conventional muffler.