Comprehensive evaluation and development of a single cylinder engine vehicle for refinement of NVH characteristics

The scale of worldwide population presents its own set of difficulties, especially in densely populated cities. Almost every individual has some form of personal transport, which leads to congestion and limited parking space. Automotive manufacturers are scaling down the size of vehicles to resolve these issues to some extent. This paper is based on the NVH development of a single-cylinder diesel engine vehicle. It provides an insight into the comprehensive vehicle level NVH refinement approaches adopted. The NVH characteristics of the benchmark two-cylinder diesel and baseline vehicle were measured and analyzed for target setting. The performance of each subsystem, such as engine mounting, vehicle structure, intake and exhaust, was evaluated, and gap analysis was performed against set targets. It was found that the engine mounting system and vehicle structure were inefficient in isolating the excitation forces. The design and location of the mounting system was evaluated using CAE and modified to improve modal performance and force isolation. The vibrations were evident at tactile locations and found to correlate with engine excitation frequency at certain locations. Hence, cradle and body structure analysis were carried out to reduce vibration transfer. Additional stiffeners and channels were added to vehicle structure, which helped in eliminating problematic frequencies and noise levels. The acoustic pack of the vehicle was updated to reduce airborne transfer of noise and improve sealing of the vehicle. The intake system was evaluated, and the air filter with resonator size and position were modified to improve noise levels. Similarly, the exhaust muffler design was analyzed and modified to improve noise levels. Each modification was implemented and evaluated for its individual contribution in improving noise and vibration by validating it on a mule vehicle. After implementation of all feasible updates, the noise and vibration targets were achieved for the new vehicle.