Research on Intake Sound Tuning Method by Valve Timing Modification for Enhance Sound Quality in V6 Outboard Engine

This paper explores methods to enhance the sound quality of V6 outboard engines. Previous research in the boat and outboard engine domain has underscored the importance of enhancing sound quality. Specific preferences and desired directions for outboard engine sound quality have been identified. It’s been suggested that controlling intake sound and gear noise is important to achieving desired sound quality according to customer preferences. However, there are few examples of methods for achieving this. This study aims to develop methods for enhancing sound quality by emphasizing low-frequency sounds through intake sound. Initially, various methods were evaluated, and intake valve timing modification was chosen. Simple simulations confirmed that delaying valve timing for some cylinders may introduce characteristics that are not present in conventional cases. Subsequent 1D simulations identified optimal intake valve timing, balancing intake pressure characteristics and horsepower reduction. We prototyped this valve timing and recorded outboard engine sound during actual operation. Using recorded sound from multiple outboard engines in the same output range, we conducted subjective evaluations using a paired comparison method. As a result, great sound quality enhancement was achieved through valve timing modification. Based on this, it was confirmed that a method for enhancing sound quality through intake sound modification could be validated in V6 outboard engines with the least amount of impact on output.