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This paper addresses the "Grunt Noise" anomaly in Hydraulic Power Assisted Steering (HPAS) systems, detailing an extensive effort to resolve this disruptive issue. HPAS, while cost-efficient, faces challenges as it adapts to customer demands for reduced steering effort and enhanced handling. Intensified HPAS intervention requires components to withstand higher pressures and tighter tolerances, leading to occasional anomalies. "Grunt Noise" arises from Torsion bar (T-bar) resonance with fluid pressure pulsations. A comprehensive study identifies load conditions, transfer paths, and frequency bands, extending from vehicle to Pinion Valve assembly levels. Root cause analysis traces the issue from Steering Wheel to T-bar, validating the approach. The T-bar's twisting operation renders torsional stiffness crucial for Grunt Noise. Lower stiffness T-bar, when overpowered by liquid force, causes microsecond imprecise valve openings, leading to cavitation-induced Rack & Pinion vibrations.

With the advent of new technologies and rigorous research and development work going on vehicle engines, cars are becoming quieter and more refined than ever before. This has led to the observance of subjective noises being audible to passenger compartment which were earlier masked behind engine noise. The vehicle HVAC system has several moving parts and transient flow of refrigerant which can cause certain types of irritant noise. Thus having a refinement in of air-conditioning (AC) system would aid us in cutting down on this parasitic noise source. Thus noise refinement should be one of the important parameters during the design and development of the Heating, Ventilation and Air-Conditioning (HVAC) system for a vehicle program.

Worldwide automotive sector regulatory norms have changed and become more stringent and complex to control environmental noise and air pollution. To continue this trend, the Indian Ministry of Road Transport is going to impose new vehicle exterior pass-by noise regulatory norms IS 3028:2023 (Part2) to control urban area noise pollution. This paper studies the synthesis of M1 category vehicle driving acceleration, dominant noise source, and frequency contribution in exterior PBN level. A vehicle acceleration analysis study was carried out to achieve an optimized pass by noise (PBN) level based on the vehicle’s PMR ratio, reference, and measured test acceleration data. Based on the analysis, test gear strategy was decided to achieve a lower PBN level. This strategy involved increasing the effective final drive ratio and optimizing engine calibration, resulting in improvement with acceleration in the ith gear.

The Indian automotive industry is going through a rapid transformation phase. Regulatory emission norms such as, migration from BSIV to BSVI engine, increased adoption of μ-hybrid, full electric and autonomous cars are examples of such rapid transformation. The upgradation of internal combustion engines for compliance with new regulatory norms (e.g., from BSIV to BSVI) has caused a significant change in the automotive acoustic performance. As the powertrain system are being upgraded and getting quieter, the on-board Heating, Ventilation and Air-Conditioning system (HVAC) system emerges as one of the prominent noise sources which strongly influences overall refinement levels inside the cabin. This in turns is affecting overall feeling of passenger’s comfort. The HVAC system of an automobile is a compact and yet a complex system designed to provide thermal comfort inside the car cabin.

Vehicle NVH is one of the critical performance quality parameter and it consists of vibration levels at tactile points and noise levels at ear locations for different vehicle running conditions. There are many sources of noise and vibration in a vehicle, and powertrain is one of the main source. Therefore, it is important to understand and resolve powertrain induced noise and vibration issues at early design stage with efficient simulation techniques. The work presented here deals with the use of systematic CAE approach for prediction and resolution of structure borne in-cab noise due to powertrain excitations. During NVH testing of SUV vehicle, boom noise is observed at low frequency. Detailed full vehicle level simulation model consisting of vibro-acoustic trimmed BIW, front and rear suspension, and driveline with powertrain modal model is built.