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During the automotive brake system design and development process, a large number of performance characteristics must be comprehended, assessed, and balanced against each other and, at times, competing performance objectives for the vehicle under development. One area in brake development that is critical to customer acceptance due to its impact on a vehicle's perceived quality is brake pedal feel. While a number of papers have focused on the specification, quantification and modeling of brake pedal feel and the various subsystem characteristics that affect it, few papers have focused specifically on brake corner hoses and their effect on pedal feel, in particular, during race-track conditions. Specifically, the effects of brake hose fluid consumption pedal travel and brake system response is not well comprehended during the brake development process.

Variation in vehicle noise, vibration and harshness (NVH) response can be caused by variability in design (e.g. tolerance), material, manufacturing, or other sources of variation. Such variation in the vehicle response causes a higher percentage of produced vehicles with higher levels (out of specifications) of NVH leading to higher number of warranty claims and loss of customer satisfaction, which are proven costly. Measures must be taken to ensure less warranty claims and higher levels of customer satisfaction. As a result, original equipment manufacturers have implemented design for variation in the design process to secure an acceptable (or within specification) response. This paper focuses on aspects of design variations that should be considered in the design process of drivelines. Variations due to imbalance and runout in rotating components can be unavoidable or costly to control.

This paper discusses an analytical technique for computing the failure rate of steel springs used in automotive part applications. Preliminary computations may be performed and used to predict spring failure rates quickly at a very early stage of a product development cycle and to establish program reliability impact before commitment. The analytical method is essentially a combination of various existing procedures that are logically sequenced to compute a spring probability of failure under various operational conditions. Fatigue life of a mechanical component can be computed from its S-N curve. For steels, the S-N curve can be approximated by formulae which describe the fatigue life as a function of its endurance limit and its alternating stress. Most springs in service are preloaded and the actual stress fluctuates about a mean level. In order to compute an equivalent alternating stress with zero mean, an analytical method based on the Goodman Diagram is used.

As a result of raised awareness regarding the proliferation of individual OEM recommended ATFs, and discussion in various forums regarding the possibility of ‘universal’ service fill fluids, it was decided to study how divergent individual OEM requirements actually are by comparing the fluids performance in industry standard tests. A bench-mark study was carried out to compare the performance of various OEM automatic transmission fluids in selected industry standard tests. All of the fluids evaluated in the study are used by certain OEMs for both factory and service fill. The areas evaluated included friction durability, oxidation resistance, viscosity stability, aeration and foam control. The results of this study are discussed in this paper. Based on the results, one can conclude that each ATF is uniquely formulated to specific OEM requirements.

This paper describes the application of Statistical Energy Analysis (SEA) and Experimental SEA (ESEA) to calculating the transmission of air-borne and structure-borne noise in a mid-sized sedan. SEA can be applied rapidly in the early stages of vehicle design where the degree of geometric detail is relatively low. It is well suited to the analysis of multiple paths of vibrational energy flow from multiple sources into the passenger compartment at mid to high frequencies. However, the application of SEA is made difficult by the geometry of the vehicle's subsystems and joints. Experience with current unibody vehicles leads to distinct modeling strategies for the various frequency ranges in which airborne or structure-borne noise predominates. The theory and application of ESEA to structure-borne noise is discussed. ESEA yields loss factors and input powers which are combined with an analytical SEA model to yield a single hybrid model.

Variable valve actuation has become a very popular feature in today's engines. With many of these systems being hydraulically actuated, the engine lubrication system requires enhancement to support their function. To expand the system's operational range with respect to speed and temperature, a traditional solution has been to increase oil pressure by increasing pump displacement. To better optimize the system, a variable displacement vane pump has been adapted to the engine lube oil system. Based on existing transmission pump technology, a pivoting cam ring design is employed that is able to vary the pump's displacement as a function of pump regulating oil pressure which in-turn provides a net reduction in its drive torque. While others have addressed this issue using complex and expensive pressure regulating systems, this passive solution requires no valves or additional hardware.

Since 1997, General Motors Body Manufacturing Engineering - Die Engineering Services (BME-DES) has been working jointly with our software vendor to develop and implement a parallel version of stamping simulation software for mass production analysis applications. The evolution of this technology and the insight gained through the implementation of DMP/MPP technology as well as performance benchmarks are discussed in this publication.

Historically, the long development time required to produce a new automobile has meant that the electronics in that vehicle might lag the state-of-the-art by several years. For traditional vehicle electronics, this was certainly an appropriate delay, ensuring through extensive testing and qualification that the quality and reliability of the electronic systems met rigorous standards. However, with the growing consumer-oriented electronics content in today's vehicles, it is becoming more difficult for the automotive manufacturers to meet consumers' expectations with older technology. Couple this with the fast-paced consumer product cycle, typically nine to eighteen and the result is increasing pressure on the vehicle manufacturers from after-market electronics suppliers, who can update their product lines as fast as the component manufacturers can produce new models.

The use of regrind acrylonitrile-butadiene-styrene (ABS) for automotive parts and components results in two types of financial savings. The first is the shared monetary savings between General Motors and the molder for the difference in the virgin resin price versus price of the ABS regrind. The second is a societal energy savings seen in the life cycle of virgin ABS versus reground ABS. An added benefit is the preservation of natural resources used to produce virgin ABS.

A Cyber-Physical System (CPS) facilitates the embedding of computational intelligence, communication, control, and new mechanisms for sensing and actuation into physical systems, such as the transportation infrastructure. They are a combination of computation and physical processes each affecting the outcome of the other. The wireless networked CPS sensors are envisaged to provide rapid response capabilities such as real time analysis, distributed coordination, classify events, condition based maintenance etc, to make critical decisions in networked transportation systems. To achieve the above it is required to fuse data from multiple heterogeneous sensors data. However, such ability is currently impeded by a lack of expressive and standardized syntactic and semantic models for the sensors data for proper exchange of information with the cyber and physical applications.

General Motors introduced a family of small front wheel drive six speed automatic transmissions for the 2008 model year. The family currently has two variants: 6T40 and 6T45, which cover a range of vehicles from small & compact cars to small SUVs and handle engines torque capacities up to 240 Nm Gas(280 Nm Diesel) & 315 Nm Gas (380 Nm Diesel) respectively. The 6T40/45 transmissions replace GM traditional four speed automatic wrap around transmissions 4T40/45. The wrap around transmissions have Torque Converter, Pump & Controls on the engine axis and the rest of the transmission content on the output axis. The 6T40/45 have an on-axis architecture with majority of the transmission content on the engine axis and final drive & differential on the output axis. The 4T40/45 have input chain transfer whereas the 6T40/45 have an output chain transfer.

Homogenous Charge Compression Ignition (HCCI) combustion offers significant efficiency improvements compared to conventional gasoline engines. However, due to the nature of HCCI combustion, traditional HCCI engines show some degree of sensitivity to in-cylinder thermal conditions; thus higher cylinder-to-cylinder variation was observed especially at low load and high load operating conditions due to different injector characteristics, different amount of reforming as well as non-uniform EGR distribution. To address these issues, a cylinder balancing control strategy was developed for a multi-cylinder engine. In particular, the cylinder balancing control strategy balances CA50 and AF ratio at high load and low load conditions, respectively. Combustion noise was significantly reduced at high load while combustion stability was improved at low load with the cylinder balancing control.

This paper studies the dynamics and noise of timing belt. A comprehensive theoretical contact dynamics model for belt tooth-sprocket tooth pair is developed. The general belt dynamics model in conjunction with the contact model is used to quantify the impact-sliding process of belt tooth. The effect of tooth meshing process is illustrated which results in the vibrations of belt span and tooth vibrations. The structural borne noise consists of structural impact portion and friction-induced portion. The relationship between system parameters and noise is quantified. The air borne noise due to air-pumping is investigated based on Lighthill's equation. A comprehensive model is developed and the spectrum signatures of the air-pumping noise are illustrated.

Two-stage turbochargers are a recent solution to improve engine performance, reducing the turbo-lag phenomenon and improving the matching. However, the definition of the control system is particularly complex, as the presence of two turbochargers that can be in part operated independently requires effort in terms of analysis and optimization. This work documents a characterization study of two-stage turbocharger systems. The study relies on a mean-value model of a Diesel engine equipped with a two-stage turbocharger, validated on experimental data. The turbocharger is characterized by a VGT actuator and a bypass valve (BPV), both located on the high-pressure turbine. This model structure is representative of a “virtual engine”, which can be effectively utilized for applications related to analysis and control. Using this tool, a complete characterization was conducted considering key operating conditions representative of FTP driving cycle operations.

Finite element analysis (FEA) predictions of magnesium beams are compared to load versus displacement test measurements. The beams are made from AM60B die castings, AM30 extrusions and AZ31 sheet. The sheet and die cast beams are built up from two top hat sections joined with toughened epoxy adhesive and structural rivets. LS-DYNA material model MAT_124 predicts the magnesium behavior over a range of strain rates and accommodates different responses in tension and compression. Material test results and FEA experience set the strain to failure limits in the FEA predictions. The boundary conditions in the FEA models closely mimic the loading and constraint conditions in the component testing. Results from quasi-static four-point bend, quasi-static axial compression and high-speed axial compression tests of magnesium beams show the beam's behavior over a range of loadings and test rates. The magnesium beams exhibit significant material cracking and splitting in all the tests.

Magnesium alloy extrusions offer potentially more mass saving compared to magnesium castings. One of the tasks in the United States Automotive Materials Partnership (USAMP) ?Magnesium Front End Research and Development? (MFERD) project is to evaluate magnesium extrusion alloys AM30, AZ31 and AZ61 for automotive body applications. Solid and hollow sections were made by lowcost direct extrusion process. Mechanical properties in tension and compression were tested in extrusion, transverse and 45 degree directions. The tensile properties of the extrusion alloys in the extrusion direction are generally higher than those of conventional die cast alloys. However, significant tension-compression asymmetry and plastic anisotropy need to be understood and captured in the component design.

Magnesium alloys are the lightest structural metal and recently attention has been focused on using them for structural automotive components. Fatigue and durability studies are essential in the design of these load-bearing components. In 2006, a large multinational research effort, Magnesium Front End Research & Development (MFERD), was launched involving researchers from Canada, China and the US. The MFERD project is intended to investigate the applicability of Mg alloys as lightweight materials for automotive body structures. The participating institutions in fatigue and durability studies were the University of Waterloo and Ryerson University from Canada, Institute of Metal Research (IMR) from China, and Mississippi State University, Westmorland, General Motors Corporation, Ford Motor Company and Chrysler Group LLC from the United States.

Engine cylinder deactivation is used to save engine pumping loss but raises oil consumption concerns for the deactivated cylinders. In this paper, general mechanisms of oil transport via piston rings are reviewed. The characteristic of oil transport and oil accumulation in a cylinder deactivation mode through the piston ring path are analyzed. Suggestions to reduce the oil transport to the combustion chamber in a deactivated cylinder are discussed. In a deactivated cylinder, the amount of oil brought into the combustion chamber by the top ring up-scraping due to the ring/bore conformability difference between intake stroke and compression stroke is much less compared to a firing cylinder. However, compared to a firing cylinder, a deactivated cylinder has more oil entering the combustion chamber through the top ring end gap and ring groove as a result of the lower cylinder gas pressure, lower ring temperature and more frequent top ring axial movements.

Fully Flexible Valve Actuation (FFVA) systems provide maximum flexibility to adjust lift profiles of engine intake and exhaust valves. A research grade electro-hydraulic servo valve based FFVA system was designed to be used with an engine in a test cell to precisely follow desired lift profiles. Repetitive control was chosen as the control strategy. Crank angle instead of time is used to trigger execution to ensure repeatability. A single control is used for different engine speeds even though the period for one revolution changes with engine speeds. The paper also discusses lift profile extension, instantaneous lift profile switching capability and built-in safety features.

Brake caliper and corner behavior in the off-brake condition can lead, at times, to brake system performance issues such as residual drag (and related issues such as pulsation, judder, and loss of fuel economy), and caliper pryback during aggressive driving maneuvers. The dynamics in the brake corner can be strikingly complex, with numerous friction interfaces, rubber component and grease dynamics, deflections of multiple components, and significant dependence on usage conditions. Displacements of moving parts are usually small, and the residual forces in the caliper interfaces involved are also small in comparison with other forces acting on the same components, making direct observation very difficult. The present work attempts to illuminate off-brake behavior in two different conditions - residual drag and pryback - through the use of low-range pressure distribution sensors placed in between the caliper (pistons and fingers) and the brake pad pressure plates.