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Till recently supercharging was the most accepted technique for boost solution in gasoline engines. Recent advents in turbochargers introduced turbocharging technology into gasoline engines. Turbocharging of gasoline engines has helped in powertrains with higher power density and less overall weight. Along with the advantages in performance, new challenges arise, both in terms of thermal management as well as overall acoustic performance of powertrains. The study focuses mainly on NVH aspects of turbocharging of gasoline engines. Compressor surge is a most common phenomenon in turbochargers. As the operating point on the compressor map moves closer to the surge line, the compressor starts to generate noise. The amplitude and frequency of the noise depends on the proximity of the operating point to the surge line. The severity of noise can be reduced by selecting a turbocharger with enough compressor surge margin.

The bolted joints in suspension systems are subjected to severe external service loads during vehicle operation. To prevent the loaded joint from loosening and allowing it to retain its potential energy stored during assembly, a holistic design approach is needed. This paper explains the methodology to design and optimize bolted joints for the suspension systems of a modern 7-seater sports utility vehicle.

In today's competitive scenario, understanding mental modal map of individual customer perception plays a major role to create the brand image of vehicle. Among them “comfortable sound” is one of the important criteria for customer satisfaction, especially in case of diesel vehicle, where in-cab sound quality plays a crucial factor. Often customer perception concerning comfort in automotive industry relies on subjective comfort evaluation method. Converting the customer perception into objective measurements and to correlate them is often tough task for NVH engineers. It is because of human sensation behavior differs from persons to person, mental map, geographical location and domain knowledge. In addition acoustic & comfort relevant aspects are often subjectively evaluated based on jury trials conducted on the prototype vehicle and class competitive benchmark vehicles to get the feel & confidence of product for different gateways.

The ever-increasing customer expectations put a lot of pressure on car manufacturers to constantly reduce the noise, vibration, and harshness (NVH) levels. This paper presents the holistic approach used to achieve best-in-class NVH levels in a modern high-power density 1.5 lit 4-cylinder diesel engine. In order to define the NVH targets for the engine, global benchmark engines were analysed with similar cubic capacity, power density, number of cylinders and charging system. Moreover, a benchmark diesel engine (considered as best-in-class in NVH) was measured in a semi-anechoic chamber to define the engine-level NVH targets of the new engine. The architecture selection and design of all the critical components were done giving due consideration to NVH behaviour while keeping a check on the weight and cost.

Original Equipment Manufacturers (OEMs) should innovate ways to delight customers by creating affordable products with improved drive experience and occupant comfort. Vehicle refinement is an important initiative that is often take-up by the project teams to ensure that the product meets the customer’s expectations. A few important aspects of vehicle refinement include improving the Noise Vibration Harshness (NVH), ride and handling performance pertaining to the Functional Image (FI) of the product. Optimizing the suspension design variables to meet both ride and handling performance is often challenging as improving the ride will have a deteriorating effect on handling and vice-versa. The present work involves Multi-Objective Design Optimization (MDO) of the suspension system of an automotive Sports Utility Vehicle (SUV) platform considering both ride and handling requirements, simultaneously.

The focus on driver and occupant safety as well as comfort is increasing rapidly while designing commercial vehicles in India. Improvements in the road network have enhanced road transport for commercial vehicles. Apart from the cost of operation and fuel economy, the commercial vehicles must deliver goods within stipulated time. These factors resulted in higher speed of operation for commercial vehicles. The design should not compromise the safety of the vehicle at these higher speeds of operation. The vehicle should obey the driver’s intended direction at all speeds and the response of the vehicle to driver input must be predictable without much larger surprises which can lead to accidents. The commercial vehicles are designed with rigid axle and RCB type steering system. This suspension and steering design combination introduce steering errors when vehicle travel over bump, braked and while cornering.

Squeak and rattle concerns account for approximately 10% of overall vehicle Things Gone Wrong (TGW) and are major quality concern for automotive OEM’s. Objectionable door noises are one of the top 10 IQS concerns under any OEM nameplate. Door trim significantly contributes to overall BSR quality perception. Door trim is mounted on door in white using small plastic clips with variable properties that can significantly influence BSR performance. In this paper, the performance of various door clips is evaluated through objective parameters like interface dynamic stiffness and system damping. The methodology involves a simple dynamic system for the evaluation of the performance of a clip design. Transmissibility is calculated from the dynamic response of a mass supported by clip. Parameters such as interface stiffness and system damping are extracted for each clip design. Variation of inner panel thickness is also considered when comparing clip performance.

Dual mass flywheel (DMF) is an excellent solution to improve the noise, vibration and harshness (NVH) characteristic of any vehicle by isolating the driveline from the engine torsional vibrations. For the same reason, DMFs are widely used in high power-density diesel and gasoline engines. However, the real-world usage conditions pose a lot of challenges to the structural robustness of the DMF. In the present work, a new methodology is developed to evaluate the robustness of a DMF fitted in a compact sports utility vehicle (SUV) with rear-wheel drive architecture. The abuse conditions (mis-gear, sudden braking, etc) in the real-world usage could lead to a sudden engine stall leading to an abnormally high angular deceleration of the driveline components. The higher rate of deceleration coupled with the higher rotational moment of inertia of the systems might end up in introducing a significantly high impact torque on the DMF.

As a car OEM, we continuously strive to set the bar for competitors with every product. Consumer travel experiences are enhanced by increasing passenger cabin silence. There is only one steering system opening in the firewall panel, which is used for allowing intermediate shaft's fitment on the pinion shaft of the steering gear. The steering grommet is the sole component that covers the firewall cut-out without disrupting steering operations, which has a substantial impact on the NVH performance of the vehicle. It is typically used in cars to eliminate engine noise and dust entering to passenger compartment. The part is assembled inside the vehicle where the steering intermediate shaft passing through BIW firewall panel. We use a bearing, plastic bush, or direct rubber interference design in the steering grommet to accommodate the rotational input the driver provides to turn the automobile.

The automobile industry strives to develop high-quality vehicles quickly that fulfill the buyer’s needs and stand out within the competition. Full utilization of simulation and Computer-Aided Engineering (CAE) tools can empower quick assessment of different vehicle concepts and setups without building physical models. Vehicle execution assessment is critical in the vehicle development process, requiring exact vehicle steering system models. The effect of steering system stiffness is vital for vehicle handling, stability, and steering performance studies. The overall steering stiffness is usually not modeled accurately. Usually, torsion bar stiffness alone is considered in the modeling. The modeling of overall steering stiffness along with torsion bar stiffness is studied in this paper. Another major contributing factor to steering performance is steering friction. The steering friction is also often not considered properly.

Parametric model of a production hybrid (made up of reactive and dissipative elements) muffler for tractor engine is developed to compute the acoustic Transmission Loss (TL). The objective is to simplify complex muffler acoustic simulations without any loss of accuracy, robustness and usability so that it is accessible to all product development engineers and designers. The parametric model is a 3D Finite Element Method (FEM) based built in COMSOL model builder which is then converted into a user-friendly application (App) using COMSOL App builder. The uniqueness of the App lies in its ability to handle not only wide range of parametric variations but also variations in the physics and boundary conditions. This enables designers to explore various design options in the early design phase without the need to have deep expertise in a specific simulation tool nor in numerical acoustic modeling.

Accurate ride and handling prediction is an important requirement in today's automobile industry. To achieve the same, it is imperative to have a good estimation of damper model. Conventional methods used for modelling complex vehicle components (like bushings and dampers) are often inadequate to represent behaviour over wide frequency ranges and/or different amplitudes. This is difficult in the part of OEMs to model the physics-based model as the damper’s geometry, material and characteristics property is proprietary to part manufacturer. This is also usually difficult to obtain as a typical data acquisition exercise takes lots of time, cost, and effort. This paper aims to address this problem by predicting the damper force accurately at different velocity/ frequency and amplitude of measured data using Artificial Neural Networks (ANN).

Manual transmission (MT) is still the most preferred solution for emerging markets due to the lower cost of ownership and maintenance coupled with a higher transmission efficiency. In this regard, continuous improvement of the transmission shift quality is quite essential to meet the growing customer expectations. In the present work, a detailed evaluation of the gear-shift impulse (experienced at the gear-shift knob) is conducted between two different architectures of a manual, high-torque (450 Nm input torque) inline transmission meant for a sports utility vehicle (SUV). The conventional manual inline transmission architecture comprises a common gear pair at the input of the transmission. While this input reduction architecture is the most widely used architecture, having the common gear pair at the output of the transmission is also another option. The synchronizers of the manual transmission need to match the speed of the rotating components just before the gear-shifting event.

NVH is becoming one of the major factor for customer selection of vehicle along with parameters like fuel economy and drivability. One of the major NVH challenges is to have a vehicle with aggressive drivability and at the same time with acceptable noise and vibration levels. This paper focuses on the compact utility vehicle where the howling noise is occurring at higher rpm of the engine. The vehicle is powered by three cylinder turbocharged diesel engine. The noise levels were higher above 2500 rpm due to the presence of structural resonance. Operational deflection shapes (ODS) and Transfer path analysis (TPA) analysis was done on entire vehicle and powertrain to find out the major reason for howling noise at higher engine rpm. It is observed that the major contribution for noise at higher rpm is due to modal coupling between powertrain, half shaft and vehicle sub frame.

This paper focuses on reducing abnormal noise originating from suspension when driving on rough road at the speed of 20 kmph. The test vehicle is a front wheel driven monocoque SUV powered by four cylinder engine. Cabin noise levels are higher between 100 to 800 Hz when driven on rough road at 20 kmph. Vibration levels are measured on front and rear suspension components, front and rear subframe, subframe connections on body to identify the noise source locations. Since the noise levels are dominant only in certain rough patches at very narrow band of time, wavelet analysis is used for identification of frequency at which the problem exist. Based on wavelet analysis, it is identified that the vibration levels are dominant on front lower control arm (LCA). The dynamic stiffness of LCA bushes is reduced by ~ 40% to improve the isolator performance which reduced the noise levels by ~ 9 dB (A) at the problematic frequency band.

The customer demand for all wheel drive (AWD) vehicles is increasing over the period of time which also requires NVH performance on par with front wheel drive vehicles. AWD vehicles are equipped with power transfer unit, propeller shaft and independent rear differential assembly to achieve their functional requirement. The additional drive train components in AWD vehicles may amplify torsional fluctuations in the drive line. Hence achieving the NVH performance of AWD vehicles on par with FWD vehicles without any major change in the existing design is a major challenge. In this work, an AWD vehicle with severe body vibration and booming noise is studied. The operational measurements are taken throughout the drive train on all sub-systems from engine to the rear part of the body in the problematic operating condition. An operational deflection shape analysis is conducted to visualize the vibration behavior of the drive train.

This paper presents the analysis and experimental validation of c-spring and its stiffness properties in the gear shift synchronizer system. A synchronizer assembly for a transmission comprises of a synchronizer hub carried by a torque delivery shaft and a cone clutch member carried by a gear and a synchronizer blocking ring. The gear shift sleeve is meshing over the teeth of the clutch hub. The c-spring is positioned in the inner circumference of the rim position of the clutch hub and strut keys will be positioned at the slots on the clutch hub, which are usually 120 degree apart. As the sleeve moves while gear shifting, it pushes down the strut keys which compress the C-spring radially inward; this gives the strut load. The strut keys, which are pushed down by the sleeve, will apply force on the c-spring from radial directions. Since the c-spring is in the shape of an arc it is assumed as a curved beam for the analysis.

Plastics are prone to photo oxidative and thermal oxidative degradation under usage conditions due to their chemical nature. From sustainability and cost standpoint, there is an increasing focus on Mold-In-Color (MIC) plastic materials. Simultaneously customer’s expectations on the perceived quality of these MIC parts has been increasing with attractive color and glossy appearance. A study was conducted to analyze the product quality and durability aspects over a prolonged exposure to accelerated weathering condition. Material selected for this study were injection molded specimens of ABS and PC-ABS used in automotive passenger vehicles. Comparative analysis was conducted before and after weathering exposure at defined intervals by using Fourier Transform infra-red spectrometer (FTIR), differential scanning colorimetry (DSC), universal testing machine (UTM), Izod impact tester and microscope to understand the impact on their chemical and mechanical properties.

Manual transmissions are the preferred transmission for drivers who love sporty gear shifts. Manual transmission vehicles are cheaper, very efficient, and offer quick gear shifts. Worldwide manual transmission contributes to 36.15% and in India it contributes overall 80% of today's market share. The customers expect a very smooth gearshift which is a challenge to achieve in all ambient temperatures. In a gear shift event, the synchronizers synchronize the speed of the gears. The force applied at the gear shift knob, generates the cone torque and stops the rotating input shaft for the Neutral (N) to 1 gear shifting. The early morning gear shifts have high gear shift effort. This effort is getting reduced with the increase in temperature. This is due to the drag in the gearbox which is inevitable. This work focuses on improving the very first gear shift event of N to 1 after the engine crank from cold (8°) to hot (80°) condition.

Twist beam is a type of suspension system that is based on an H or C shaped member typically used as a rear suspension system in small and medium sized cars. The front of the H member is connected to the body through rubber bushings and the rear portion carries the stub axle assembly. Suspension systems are usually subjected to multi-axial loads in service viz. vertical, longitudinal and lateral in the descending order of magnitude. Lab tests primarily include the roll durability of the twist beam wherein both the trailing arms are in out of phase and a lateral load test. Other tests involve testing the twist beam at the vehicle level either in multi-channel road simulators or driving the vehicle on the test tracks. This is highly time consuming and requires a full vehicle and longer product development time. Limited information is available in the fatigue life comparison of multi-axial loading vs pure roll or lateral load tests.