SAE International Understanding the Fundamentals of Boxer Engine Behavior on Sound Quality 2016-01-1766

An engine configuration has a significant influence on the sound quality from the powertrain. Whilst the fundamental order content can be readily apparent from the firing order over the engine, or bank of a V engine, some characteristics and how the engine design can influence them requires some more specific investigation. Understanding, on a fundamental level, the aspects of the engine design which influence these characteristics is critical to allow more detailed analysis and development work to be focused appropriately. The configuration of a Boxer engine gives a distinctive sound characteristic producing a unique sound compared to an In-Line configuration. Depending on the application it may be desirable to enhance or subdue some of these characteristics. The fundamental differences affecting the sound characteristics of a 4 cylinder Boxer engine in comparison to an In-Line engine are investigated by consideration of component loading and structural deformations across different excitation orders. Specifically fundamental comparisons are made on engine structural deformation, cranktrain-block interaction, piston loading and valvetrain loading. The process described in this paper can be applied to determine which critical aspects of the engine design should be a focus for helping to develop the desired sound characteristic. Finally it is discussed how this process can be applied to other configurations for the same purpose.