Effect of unequal length of hot end legs on sound quality of vehicle interior noise of V6 engine

摘要

It can be concluded that correct placement of volume in the exhaust system is very important forvehicle exhaust acoutics. If volume placement is not at optimum position due to packaging orother reasons, drastic changes to exhaust system layout needs to be made to achieve necessaryvehicle interior and exterior sound quality. This paper demonstrates that unequal length of hotend legs excite half wave of intermediate pipe on this system architecture. Pipe resonances aredifficult to attenuate without dedicated tuning volume for pipe resonant frequencies. This halfwave of intermediate pipe can most effectively attenuated by installing Helmholtz tuner at peakamplitude of half wave mode i.e quarter wavelength of the half wave for this system architectureas demonstrated in CAE predictions and on-vehicle testing. Primary engine order 3EO at 75 Hzwas reduced significantly based on the volume of the Helmholtz tuner used. The 1.5EOcontributing to 75 Hz issue was also reduced to some extent due to communication between thelegs of the exhaust system where Helmholtz tuner is located. Location and Volume used for theHelmholtz tuner defines its effectiveness as measured by its ability to attenuate pipe resonance.