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Precise control over mixture formation withhigh fuel pressure and multiple injections allows Gasoline Direct Injection (GDI) engines to be operated satisfactorily at extreme conditions wherePort Fuel Injection (PFI) engines wouldnormally struggle due to combustion instability issues. Catalyst heating phase is one such important condition which is initiated after a cold engine start to improve the effectiveness of the three-way catalyst (TWC). For a given TWC specification, fast light-offof TWC is achieved in the catalyst heating phase by increasing the exhaust gas temperature with higher exhaust mass flow. The duration of this phase must be as short as possible, as it is a trade-off between achieving sufficient TWC light off performance and fuel efficiency.

In the recent past a lot of emphasis is given for the overall weight reduction of the sound package used in the vehicles. The paper presents a study of one of such materials used in the automotive market. The dash panel is a primary area for the engine noise transmission to the cabin. Hence the material selection of the dash inner acoustic insulation is critical. In the conventional method a barrier (EVA) and a decoupler (foam) is used. In the conventional design the surface weight of the barrier has to be substantially high for the dash insulation to perform effectively and hence adds to more weight. In the present application of light weight material also known as dual density absorbers and barrier is used for the dash acoustic insulator. The study reveals the good acoustic performance of the light weight dash mat in terms of passenger cabin noise reduction and improved sound quality along with weight reduction.

Continually increasing customer demands and legislative Requirements regarding fuel economy, emissions, Performance, drive ability and comfort need to be met by every OEM's developing vehicles worldwide. There is a serious pressure to reduce CO2 emission from automotive application which contributes to around 15.9% of the total CO2 production based on the Surveys done time to time. In a developing market like India, many foreign players are entering with lots of option for offering to this market. The parameters of prime importance here are fuel efficiency with good drive ability and at the same time affordable price. Diesel engines are finding these benefits and attracting the buyer over its counterpart (Gasoline). The road condition and the driving pattern in India compared with developed countries differ to a major extent. In India, the Low speed uses are predominating in Cities and in Ghats.

Reducing the vibrations in the powertrain is one of the prime necessities in today's automobiles from NVH and strength perspectives. The necessity of 4×4 powertrain is increasing for better control on normal road and off-road vehicles. This leads to bulky powertrains. The vehicle speeds are increasing, that requires engines to run at higher speeds. Also to save on material costs and improve on fuel economy there is a need for optimizing the mass of the engine/vehicle. The reduced stiffness and higher speeds lead to increased noise and vibrations. One more challenge a powertrain design engineer has to face during design of its transmission housings is the bending / torsional mode vibrations of powertrain assembly. This aggravates other concerns such as shift lever vibrations, shift lever rattle, rise in in-cab noise, generation of boom noise at certain speeds, etc. Hence, reducing vibrations becomes an important and difficult aspect in design of an automobile.

In current competitive environment automobile industry is under heavy pressure to reduce time to market. First time right design is an important aspect to achieve the time and cost targets. CAE is a tool which helps designer to come up with first time right design. This also calls for high degree of confidence in CAE simulation results which can only be achieved by undertaking correlation exercises. In automobiles most of the structures are subjected to vibration from dynamic loads. All the dynamic road loads are random in nature and can be very easily expressed in terms of power spectral density functions. In the current scenario structural durability of the parts subjected to vibration is done partially through modal performance and partially though frequency response analysis. The only question that arises is what amplitude to use at what frequency and how to map all the accelerated tests dynamic load frequency spectrum to simulation domain.

In today's competitive automobile market, customers have become more sensitive towards NVH behavior of the vehicle than ever. The noise generated by gear rattle is one of the main contributors towards customer's overall NVH perception. This paper adopts a model based design approach towards gear rattle phenomenon to predict the tendency of gear rattle at a very early stage of design. This up-front understanding of gear rattle will potentially reduce the expensive design changes and iterations at later stages. A single unloaded gear pair is modeled in AMESim software, which is then extended to the complete gearbox in neutral condition. The sensitivity of rattle index for different input parameters is studied. Analysis on uncertainty propagation is carried out to find the rattle index distribution for Gaussian variation of input parameters. A novel rattle index based on Jerk is proposed and compared with the existing index.

Ground clearance plays an important role in Sports Utility Vehicles (SUV). Designers are good in designing their own systems but when it comes to integration of systems, the impact of one system on others and cascading effects become the major problems in full vehicle development. The test vehicle is a monocoque construction with power train in transverse (east-west) direction. Vehicle shudder is observed in lateral direction exciting the steering column, floor during the low gear power train run up in Wide Open Throttle (WOT) condition. The shudder is felt predominantly on the front half of the vehicle. Being a low frequency phenomenon with high energy it becomes critical and the phenomenon is easily perceivable by passenger. The paper discusses the measurement and analysis procedures to identify the root cause of shudder. Different modifications are tried out based on the analysis and an optimum solution is selected.

The customer perception about the door slam noise and its feel would indicate the brand image of the car. In this paper the authors have made an effort to improve the door slam noise quality of the vehicle, which is currently in production. This paper describes the probable areas in the door to improve the slam noise quality by attempting modifications in the door design factors, such as door alignments, door panel stiffness, door trims, window glass rattle, latch striker alignment, door seals, air extractor. Since the door closing event is a transient phenomenon, it requires special tools such as wavelet transforms, Zwicker loudness to understand the slam events precisely. Subjective jury evaluations have been conducted to understand the effect of these modifications and rank the modifications based on their contributions to the door slam quality.

BSR (Buzz, Squeak and Rattle) is one of the oldest concerns in automobiles which directly reflect the build, assembly and manufacturing quality of a vehicle. In a cabin all the areas where there is relative motion between two components, such as trims, instrument panel and seats, are prone to squeak. This paper explains the study of seat squeak measurement and diagnosis which is a major concern for one of the products which is already in the market. Since squeak is a friction induced non stationary phenomenon, lot of effort was required to generate squeak in both component as well as vehicle level. At component level, electrodynamic shaker was extensively used for generation of squeak signals. In Vehicle level, driving through different road patterns, pave track and forced excitation on four posters are performed for generation of squeak signals. In this paper usage of wavelet and Zwikker loudness are explained for the diagnosis of seat squeak to identify the problematic frequencies.

Whole Body Vibration (WBV) of tractors was measured on different surfaces in real world usage pattern of Indian customers on tractors of various capacities. Vibration levels were measured at the interface of the seat and the operator, on the seat base/floor and on the head. The mean weighted Root Mean Square (RMS) values along the different axes, the vector sum of weighted RMS values along the three orthogonal axes, the crest factor, Vibration Dose Value (VDV) and 8 h exposure levels were calculated according to ISO 2631-1. In addition to the above parameters, the transmissibility between the seat base and the seat interface (SEAT) and between the seat interface and the operator head (TR) were also calculated. Finally, these parameters were correlated with the subjective feel of customers which was captured through suitable questionnaires. It is observed that the Indian tractor operators are exposed to WBV that exceeds the cautionary boundaries set in place by the ISO 2631-1.

The traditional approach of engine thermal behavior of engine during startup has largely been dependent on experimental studies and high fidelity simulations like CFD. However, these techniques require considerable effort, cost and time. The low fidelity simulations validated with experimental results are becoming more popular due to their ease in handling the several parameters such as cost effectiveness and quick predictive results. A four point mass model of engine thermal behavior during cold start has been developed to study the engine warm up temperature behavior. The four point mass model considers the lumped mass of coolant, mass of engine directly associated with the coolant, mass of engine oil and mass of engine directly associated with the engine oil. The advantage of four point model is to predict the coolant temperature as well as lubricant temperature during the transient warm up cycle of the engine.

Idle NVH (Noise Vibration Harshness) is one of the major quality parameters that customer looks into while buying the vehicle. Idle shake is undesirable vibrations generated from Engine while it is in idling condition. These low frequency vibrations affects both driver and passenger comfort. Vibrations are perceived by customer through the interfaces such as the seats, floor, and steering wheel. The frequencies of vibration felt by customer ranges between 10-30 Hz and varies based on engine configurations. There are two factors that are critical to the vehicle idle NVH quality, 1. Engine excitation force and 2. Vehicle sensitivity to excitation forces (Transfer function). Even though the engine excitation forces are governed by cylinder combustion process inside the cylinder and engine mass, it is also largely affected by how well the engine and transmission are supported on vehicle through isolators.

Sound package material selection plays a vital role in maintaining passenger comfort by suppressing noise inside cabin. Sound package development in static condition minimizes the extrinsic variables which influence the measurements. The consideration of static condition favors simulation and its correlation with test data. Once correlation is achieved, simulation inputs are used for further optimization and improvements. Noise control can be done in three levels by working either on source, path or receiver. In automobiles, there are many sources of noise such as engine, tire and wind. This topic deals with quantification of various transfer paths between source and receiver location using Power Based Noise Reduction (PBNR) method. This methodology is used in both simulation and testing along with its overall scope for improvement. It is best to quantify path strength in terms of energy levels instead of mere amplitude due to its independency on external test conditions.

Ride is essentially the outcome of coupled dynamics of various involved sub-systems which make it too complex to deal analytically. Tires, amongst these, are known to be highly nonlinear compliant systems. Selection of tires specifications such as rated tyre pressure, etc. are generally decided through subjective assessment. While experts agree that tyre pressure affects the attributes such as ride to a noticeable degree, the quantification of the change often remains missing. In the current work, vibration levels of various sub-systems relevant to ride in an SUV are measured for three different tyre pressures at different speeds over the three randomly generated roads. For the purpose, artificial road profiles of classes A, B and C are synthesized from the spectrum of road classes defined in ISO 8608:2016 and reproduced on a four-poster test rig.

In the current era, vehicle manufacturers focus has increased towards passenger comfort and one of the key areas is NVH. Vehicle level NVH targets are cascaded to component level for obtaining better refinement in cabin. One such performance attribute is sloshing noise of urea in diesel vehicles. Migration from BS4 to BS6.2 norms demand complex technological changes to automobile manufacturers to add extra components to the vehicles which is a big challenge in identifying the locations at critical stage of the project phase. In one of the developments of mid SUV category vehicle, sloshing noise from urea tank is perceived as objectionable during low-speed braking and while passing over speed breakers. This paper addresses the measurement conditions of sloshing noise and its evaluation procedure to quantify the sloshing noise at vehicle level. The sloshing noise is perceived in the frequency band of 50 to 1000 Hz.

Globally all OEMs are moving towards electric vehicle to reduce emission and fuel cost. Customers expect highest level of refinement and sophistication in electric vehicle. At present, the customers are sensitive to high pitched tonal noise produced by electric powertrain which gives a lot of challenges to NVH engineers to arrive at a cost-effective solution in less span of time. Higher structure borne tonal noise is perceived in electric vehicle at the vehicle speeds of ~ 28 kmph, 45 kmph and 85 kmph. The test vehicle is front wheel drive compact SUV powered by motor in the front. The electric drive unit is connected to cradle and subframe with help of three mounts. Transfer path analysis (TPA) using blocked forces method is carried out to identify the exact forces of the electric drive unit entering the mounts. Powertrain mount is characterized by applying the predicted forces and dynamic stiffness at problematic frequency is measured.

In automotive market, with competitive car prices, build quality of a car will be a major distinguishing factor. Consumer's need for acoustic comfort has evolved from the removal of annoying noises to perceived sound quality. Operational sounds from electromechanical systems like sunroof system, window regulator, door lock system, HVAC etc. directly interact with users’ senses. The perceived acoustics comfort of these sounds are direct indicators of vehicle character and can influence customer’s buying decision. With the reduction in product development time and stringent cost constraints, a proper structured target setting methodology to benchmark & evaluate these operational sounds is crucial. In this paper, such a target setting methodology is proposed and discussed for operational sound quality evaluation. Electromechanical noises from various vehicles are measured using binaural head measurement system.

The test vehicle is All Wheel Drive (AWD) vehicle which is powered by four-cylinder engine. The power is transferred from the powertrain to the wheel through power transfer unit (PTU), propeller shaft, flexible rubber coupling and Integrated Rear Differential Assembly (IRDA) . Higher boom noise and vibration levels are observed when driving the vehicle in 4th gear WOT conditions. NVH levels are dominant between 1150 rpm to 2100 rpm and at 2200 rpm in 2nd order and 4th order respectively. Operational deflection shape (ODS) analysis is carried out on entire vehicle to identify the location where maximum deflection is observed at the problematic frequency. It is identified that higher torsional excitation from the powertrain is exciting the IRDA pitching mode and the propeller shaft bending mode which is the reason for higher 2nd order and 4th order NVH levels. The driveline forces are entering the body through the IRDA and rear cradle bushes.

Electric vehicles (EV) are much quieter than IC engine powered vehicles due to less mechanical components and absence of combustion. The lower cabin noise in electric vehicles make customers sensitive to even small noise disturbances in vehicle. Road boom noise is one of such major concerns to which the customers are sensitive in electric vehicles. The test vehicle is a front wheel driven compact SUV powered by electric motor. On normal plain road, noise levels are acceptable but when the vehicle has been driven on coarse road, the boom noise is perceived, and the levels are objectionable. Multi reference Transfer Path Analysis (MTPA) is conducted to identify the path through which maximum forces are entering the body. Based on MTPA, modifications are proposed on the suspension bushes and the noise levels were assessed.

In the current automobile era, weight, emission, and fuel efficiency were driving the overall powertrain development without compromising on the performance. Due to light weight and high-performance engines, the increased level of excitations in terms of torsional, axial, and bending frequency on crank shaft during combustion is inevitable. The axial and bending moment exerted from crankshaft during combustion causes vibration of the clutch diaphragm spring, in turn these vibrations are transferred through the hydraulic release system to clutch pedal which induces undesirable pedal pulsation and vibration during clutch pedal operation. The subjective perception on Noise Vibration and Harshness (NVH) becomes more essential in the Vehicle development process of modern high-performance vehicles.