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In current competitive automobile sector, gear shift quality has become significant factor for vehicle evaluation. OEMs are sensibly focusing on improving gear shift quality to meet customer’s expectations. Though there are different gear shifting habits in different drivers, diagonal shifting is the fastest way of shifting gears in manual transmission vehicle. So the components linked with shift system should be designed to facilitate smooth diagonal gear shift pattern. This paper enlightens the process of defining chamfers on internal gear shifting components for smooth diagonal shifting movement of gear shift lever. It is hard to define chamfers by analytical or practical approach. Creo-mechanism is very useful simulation tool which can be used to understand diagonal shift patterns and to define the chamfers.

Breather assembly is mounted on transmission to maintain the pressure equilibrium inside transmission. Breather allows the transmission to breathe air when the air inside transmission expands or contracts due to heating and cooling of lubricating oil during vehicle running. Breather allows the hot air to escape and cool air to enter into the transmission to prevent overheating issue. Failure of breather assembly can lead to pressure buildup inside transmission and further leading to leakage from transmission oil seals. Oil leakage through the breather assembly is governed by parameters such as opening pressure, location and orientation of breather etc. The transmission undergoes different operating conditions of input speed, load, temperature, inclination etc. Also, breather assembly is designed and positioned in such a way that there is no leakage through breather due to oil splash inside the transmission.

In today’s manual transmissions of car, gearshift system requires high performance with particular emphasis on low effort, minimal travel and positive feel. To meet these targets, a high capacity multi cone synchronizers along with higher co-efficient of friction material used for lower gears. The design of synchronizer with these specifications is influenced by torsional fluctuations from engine. Excessive torsional vibrations leads to wobbling of synchro rings within the peripheral clearances with surrounding parts. Wobbling leads to abrasion wear of frictional area of synchro ring causing grating or crashing noise of gears during shifting. This paper presents the optimization of the multiple cone synchronizer design exposed to excessive torsional vibrations and validation of the same on test bench during development stage instead vehicle level validation.

The engine compartment of passenger car application contains various source which radiates the produced heat and raises the temperature level of the compartment. The rise in compartment temperature increases the body temperature of individual component. The rise in body temperature of critical components can endanger the durability or functionality of the specific component or a system in which it operates. The aim of this paper is to strategize thermal protection of the rear mounted engine and its components of a vehicle having radiator and cooling fan mounted in front. An additional ventilation fan with speed sensor is fitted alongside rear mounted engine and a unique monitoring technique framed in the EMS ECU to protect critical components like HT cables, alternators, ECUs, wiring harness etc. from thermal damage. The EMS continuously monitors the engine speed, vehicle speed and the PWM signal of ventilation fan to ensure the intended operation of the ventilation fan.

In case of new generation of commercial vehicles, three shaft transmissions are designed with press fitted gears on counter shaft. It allows user to save the cost of transmission manufacturing by considerable amount. In case of heavy commercial vehicles, which are being used in abusive conditions such as mining and off-road applications, it becomes absolutely necessary to ensure that the gears press fit should withstand the continuous loads and impact loads. There are design guidelines available to ensure proper fit and torque carrying capacity between the mating parts. Still, there are gear slippage, shaft and gear breakage failures in the field. In this scenario, there is a need to develop bench test procedure which will capture such failures in the prototype stage. Looking at the failures in the field, it is necessary to capture all above hidden failures in design validation phase.

The changing mobility landscape of India reveals that the erstwhile transport modes of the 20th century i.e., railways and road buses are making way for airlines, personal vehicles, shared mobility, metro rails. Rapid technological changes, stricter regulations, new transport cultures autonomous, connected, electric and shared (ACES), state-of-the-art and environmental concerns are shaping up the eco-system for automobiles. Despite these challenges roadways and automobiles will continue to be most prominent solution in India for future. But for that, the automobile sector should be agile, innovative, and adaptable to changing eco-system, vigilant to thwart threat of alternate mobility solutions and must provide sustainable solutions for the future. The purpose of this paper to evaluate various mobility solutions, ascertain prominence of upcoming automobile solutions and their sustainability for future in India.

Clutch engagement judder is a phenomenon wherein the driver experiences vibrations on seat during the clutch engagement process for the vehicle launch. Clutch engagement judder is one of the critical vehicle attributes as a part of overall vehicle NHV. Torsional oscillations, specifically originating from clutch in the driveline during clutch engagement, are referred as clutch engagement judder. Judder is a phenomenon wherein friction induced torsional vibrations are generated in the driveline because of sliding contact between clutch and flywheel, during engagement. These resulting oscillations inherit the first resonance frequency of the driveline. The engagement judder not only affects the dynamics of transmission system but also the vehicle, because of excitations being transferred to body via suspensions and mounts. Passengers experience these oscillations as vibrations during vehicle launch. If excitation level is high then it may cause discomfort to passengers.

In the recent years steering feel characteristics have emerged as one of the important brand image attributes of automotive OEMs. Since past few decades, the hydraulic assisted steering system (HPAS) on which lot of research was done to tune the steering feel has been taken over by electric power assisted steering (EPAS) system. The EPAS primarily uses an electric motor controlled by an electronic control unit to assist the driver in maneuvering the vehicle. The next big leap in the steering system advancement is steer-by-wire (SbW) technology where the mechanical linkage between the steering wheel and the road wheels is eliminated. The advantages of this system are ease to use, elimination of noise-vibration-harshness of steering system caused by road forces, modularly of steering system for packaging, improved visibility to front-end displays and road ahead and a fun to drive concept.

The fuel economy of heavy commercial vehicles can be significantly improved by reducing the rolling resistance of tires. To reduce the rolling resistance of 6×4 tractor, the super single tires instead of rear dual wheel tires are tried. Though the field trials showed a significant increase in fuel economy by using super single tires, it posed a concern of road safety when these tires blowout during operation. Physical testing of tire blowout on vehicle is very unsafe, time consuming and expensive. Hence, a full vehicle simulation of super single tire blowout is carried out. The mechanical properties of tires such as cornering stiffness, radial stiffness and rolling resistance changes during the tire blowout; this change is incorporated in simulation using series of events that apply different gains to these mechanical properties.

As automotive technology has evolved, gear rattle has become a prominent contributor for cabin noise as the masking from the engine noise has decreased. The market and customer expectation make the rattle noise a question to be addressed as early as possible in the vehicle development process. However, to simulate rattle, it calls for a detailed modeling of different complex subsystems of driveline to represent their true characteristics. Thus, the paper adopts an FE based elastic multi body dynamics model to predict gear rattle. The approach involves modeling of a complete flexible driveline using condensed FE models from Nastran in AVL Excite Powerunit/Transmission module. It includes combustion pressure as input excitations to crankshaft and then predicts parameters like gear teeth impacts, gear normal meshing force, dynamic mesh stiffness & overall contact state in transient and frequency domain. The output parameters are then analyzed to evaluate the rattle index.

In today's scenario, most of the OEMs use manual transmissions with synchronizer gear shifting system for ease of gear shifting. It gives very high fuel efficiency. Gear shifting is a customer touch point, hence it is very important to select adequate synchronizer capacity so that it will perform in better and last longer. To test the synchronizers, there are many test methods which give the idea about life of synchronizer and its performance, in different conditions. Regular synchronizer rig tests consume lot of time in deriving the results. So it is very important to find out a way which will give same results within short time period. To carry out the short time test or accelerated test, we need to understand the effect of various factors like reflected inertia, drag torque, differential speed, synchronizing time, and gear shifting force on synchronizer capacity.

Nowadays, a higher amount of time is being spent inside the vehicles on account of varied reasons like traffic, longer distances being travelled and leisure rides. As a result, better comfort and convenience features are added to make the driver and passenger feel at ease. Thermal comfort and acoustic isolation are the primary parameters looked at by both the customers and the original equipment manufacturers. Seats are one of the primary touch points inside the vehicle. Perspiration caused at the contact patch areas between the seats and passengers leads to high thermal discomfort. A ventilated seat, with or without an air-conditioning system, is one such attribute offered to improve passenger thermal comfort. Ventilation becomes even more essential for front-row seats, as these are more likely to be exposed to external solar loading through the front windshield.

The authors of this technical paper conceptualize and illustrate a powertrain architecture for a hybrid electric vehicle coupled with a unique strategy to reduce a real life problem of driving in snail paced traffic. This architecture utilizes a relatively low powered hybrid electric prime mover that is generally used in mild hybrid vehicles, in an arrangement similar to a parallel hybrid system. Here, the electric machine is mounted on the input shaft of the gearbox and the clutch is actuated automatically through an Automated Manual Transmission (AMT) system. Therefore, it is possible to completely disengage the engine from the driveline and drive the vehicle independently through an appropriately sized electric prime mover. The high gear ratio between the drivetrain and the electric prime mover at lower gears can be leveraged to provide low velocity electric creep mode during which the vehicle can function as a pure Electric Vehicle (EV) while engine remains off.

There has been immense focus on Gear Shift Quality as it is seen as an important factor for subjective evaluation of driving comfort of a vehicle with manual transmission. Synchronizer and driveline stiffness optimization is often the only area of focus for gear shift quality during early design stage. Proven Simulation models are already available for predicting the effect of synchronizer and driveline stiffness. Though Gear shift cable also has a significant effect on gear shift quality, neither design guidelines nor simulation models are available for predicting gear shift cable performance. Designers have relied on physical approach to establish cable routing, since cable routing cannot be predicted on virtual vehicle. In design phase cable routing is imagined and modeled in CAD using constrained curve geometry and later on established by physical trials on vehicle with various cable lengths, routing paths and clamp positions.

Vehicle floor vibration is the resultant of different road inputs damped through various transfer paths. Seat comfort, which depends on these floor vibrations, can be evaluated with a single input signal “Pink noise”; which constitutes various road inputs. Transmissibility of seat structure on a vibration shaker with pink noise input includes all possible responses of road inputs. Still, transmissibility profile at vehicle end and component level varies. This is due to the utilization of “dummy” on component level testing on vibration shaker, which acts as a dead weight with dissimilar damping characteristics of human. A transmissibility correlation between human and dummy is attained by replacing the dummy in place of human and actuating it to find the difference in contribution between them for different class of vehicles. This contribution extrapolation from the damping effects of human and dummy is applied on dummy transmissibility.

Traditionally, vehicle ride and comfort is evaluated, subjectively as well as objectively. Based on the outcome of subjective and objective tests, it is refined by optimizing primary suspension system, secondary suspension system, seating system, rubber bushings, frame and BIW for mass, stiffness, damping, geometry etc. Many a time subjective assessment results stands in contradiction to the objective assessment results; emphasizing need for having good correlation between subjective and objective test results. In such cases, it is ambiguous to decide suitable design refinement action and can lead to no improvement situation. Hence, it is essential to have concurring test procedures for subjective and objective ride evaluation. This paper describes a novel methodology to address the above said challenge. There are defined set of test events and measurement data points to be used in subjective and objective testing.

With the advent of BS VI regulations, automotive manufacturers are required to innovate the powertrains, fuel systems, exhaust and its after treatment systems to meet the regulatory requirements. The exhaust regulations can be met either by reducing the exhaust gases being generated by the engine (attacking the source) or by treating the exhaust gases in after treatment devices. The choice of the opted system varies with the manufacturer. The after-treatment devices such as catalytic converters are generally mounted in the engine compartment to take advantage of high temperature of exhaust gases to yield the reactions. Such an arrangement imposes a lot of thermal load on the peripheral components such as gearshift cables, bearings, oil seals, driveshafts etc. Thermal shields or thermal sleeve are used to address thermal issue and to protect transmission components.

Passenger utility vehicles like car, SUVs, MPVs are used in wide application all over the world. Luxuries are becoming essential features of product mix along with comfort and ergonomics. Customer desires best shift quality with emerging technologies like AT, DCT, CVT, etc. and every OEM is working hard to achieve it. It is very difficult to satisfy the customer desire because of diversities in demographics and geographic. Gear shift quality (GSQ) is very crucial touch point in overall drive feel of vehicle. It consist of various parameters like mode selection feel, precision, comfort, select Noise, etc. It demands tradeoff practices among various parameters as stated. In this paper, external mode selection system of automatic transmission is explained. Various contributing parameters are explained with practical design approach for detent profile, mode selection mechanism, cable & dampers, etc.

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.

Exhaust Noise attenuation is one of the important functions of exhaust muffler. Transmission Loss (TL) is a measure of noise attenuation used in designing exhaust mufflers for NVH. TL is a logarithmic difference between inlet and outlet pressures for unit velocity input at inlet of the muffler and anechoic termination at outlet of the muffler as boundary conditions. TL amplitude and its frequency tuning depends on a combination of various muffler design parameters like volume, length, muffler cross section, pipe cross sections, pipe perforations, number of chambers, baffle perforations, etc. Achieving the desired TL performance with no valleys over a wide frequency range is very challenging. Manual design iterations with large numbers of permutations and combinations of design variables are difficult and time-consuming. It also needs a highly experienced professional to balance TL performance, design variables and design constraints.