2004 Nissan 3.5L Cam Cover Material Study: Aluminum, Magnesium and Composite 2005-01-0727

The present study compares the NVH performance of three different materials used on cam covers in automobiles, Aluminum (Al), Magnesium (Mg) and Thermoplastic (TP). The cam cover design used for this comparison was the 2004 Nissan Maxima 3.5L production cam cover which is made of a thermoplastic (TP). The Al and Mg covers for this study were created by sandcast, due to time constraints, via laser scanning techniques using the 2004 Nissan Maxima 3.5L production thermoplastic cover design. Note that sand-cast covers generally provide a less quiet sound field than the standard casting method. The Nissan production cover comes with a production baffle made of a similar material as the cover. Testing was conducted with and without the production baffle for all covers. The study was conducted for the production boundary condition of a non-isolated cover and a Freudenberg-NOK (FNGP) partially isolated cover. Isolated bolt assemblies using elastomeric grommets were used to isolate the cover. Dynamic Mechanical Thermal Analysis (DMTA) of the thermoplastic part was performed and compared to thermo-set bulk moulding compound (BMC). A general correlation between damping was established revealing that for this application the material which allows the least damping provides the best NVH, data and analysis will be presented to support this. The results show that the isolation frequency and NVH levels (dB) for the metal covers are lower than for the thermoplastic for the semi isolated case and noticeably lower in the isolated case. Numerical and experimental methods were used in this study.