Case Study: Vehicle Body Boom Problem

Case description

• Automotive gasoline turbocharged engine
• Problem: audible low frequency boom from engine bay at high engine speeds
• Possible excitation of vehicle body
• Suspected cause - radiated noise from surfaces of plenum-in-V inlet manifold and intake orifice

Approach and Solution

• GT-Power NVH analysis of inlet plenum pressure signature confirms origin of  problem
• Problem caused by inlet plenum/ zip tube coupling - effectively a ‘Helmholtz-like’ mode
• Resonant frequency controlled by length and diameter of zip tube and volume of plenum
• Parametric study using GT-Power led to an acceptable solution in terms of package and minimal impact on engine performance
• Design changes to plenum/intake runners recommended as a solution

Conclusions   Powertrain analysis tools are now routinely used across the industry Powertrain modelling is fast, cost effective, and reliable MIRA can provide a proven consultancy service in this specialist area