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Meeting the California Medium-Duty truck emissions standards presents a significant challenge to automotive engineers due to the combination of sustained high temperature exhaust conditions, high flow rates and relatively high engine out emissions. A successful catalyst for an exhaust treatment system must be resistant to high temperature deactivation, maintain cold start performance and display high three-way conversion efficiencies under most operating conditions. This paper describes a catalyst technology and precious metal loading study targeting a California Medium-Duty truck LEV (MDV2) application. At the same time a direction is presented for optimizing toward the Federal Tier 1 standard through reduction of precious metal use. The paper identifies catalytic formulations for a twin substrate, 1.23 L medium-coupled converter. Two are used per vehicle, mounted 45 cm downstream of each manifold on a 5.7 L V8 engine.

A practical methodology is presented for the synthesis of Chassis Systems and their integration into a vehicle design to achieve a specified vehicle dynamic performance. By focusing on the fundamental performance requirements of gain, response time, and stability in midrange handling and the higher level design parameters of front and rear cornering compliance it is possible to find optimum values for these design parameters. The balancing of these higher level design parameters, in the context of overall vehicle performance, determines primary system requirements for the front suspension, rear suspension, tires, and steering system which may in turn be met by a variety of specific hardware designs.

CFD (Computational Fluid Dynamics) has been used to analyze vehicle air flow. In cross wind conditions an asymmetrical flow field around the vehicle is present. Under these circumstances, in addition to the forces present with symmetric air flow (drag and lift forces and pitching moment), side forces and moments (rolling and yawing) occur. Issues related to fuel economy, driveability, sealing effects (caused by suction exerted on the door), structural integrity (sun roof, spoiler), water management (rain deposit), and dirt deposit (shear stress) have been investigated. Due to the software developments and computer hardware improvements, results can be obtained within a reasonable time frame with excellent accuracy (both geometry and analytical solution). The flow velocity, streamlines, pressure field, and component forces can be extracted from the analysis results through visualization to identify potential improvement areas.

A requirement for larger trucks and higher operating speed is indicated. The present report presents wind tunnel data on drag of a Chevrolet truck-trailer combination. Possible means of drag reduction are examined. Although side force and yawing moment data are presented, their effect on directional stability are not, at present analyzed.

Splash and spray conditions created by tractor-trailer combinations operating on the Federal highway system have been studied and tested for many years with mixed results. Past events are reviewed briefly in this paper. In additional testing during 1983, using new state-of- the-art splash/spray suppressant devices, some encouragement was provided that these devices could work. The 1984 Motor Vehicle Manufacturers Association (MVMA) test program was designed to develop practicable and reliable test procedures to measure effectiveness of splash and spray reduction methods applied to tractor-trailer combination vehicles. Over 40 different combinations of splash/spray suppression devices on five different tractors and three van trailer types were tested. The spray-cloud densities for some 400 test runs were measured by laser transmissometers and also recorded by still photography, motion pictures, and videotape. On-site observers made subjective ratings of spray density.

Diesel exhaust gas dilution and odor intensity were measured in the immediate vicinity of a transit bus equipped with a rear-mounted horizontal exhaust pipe, a rear-mounted vertical exhaust pipe, and a roof-top diffusion system. Exhaust dilution ratios were measured indoors during vehicle idle operation, using propane added to the exhaust gas as a tracer. Exhaust odor intensities were measured also indoors during vehicle idle operation by a human panel, using a threshold odor measurement technique. On the average, the dilution of the exhaust gas around the bus with the vertical exhaust pipe was about eight times greater than it was with the horizontal pipe. Odor intensity, as measured by the threshold response distance, was about 35% less with the vertical pipe than with the horizontal pipe. The roof-top diffuser was not as effective as the vertical exhaust pipe in increasing exhaust gas dilution or in reducing exhaust odor intensity.

For model year 2003, the General Motors Corporation is introducing new medium duty trucks - the Chevrolet Kodiak and GMC TopKick. These new trucks replace the previous versions of the Kodiak and TopKick medium duty trucks that were introduced in 1989 and the Chevrolet and GMC 3500HD that debuted in the 1991 model year. This new series of trucks marks a clear change in General Motors' strategy in the medium duty marketplace. It emphasizes General Motors' strong commitment to the medium duty market, as well as a strong focus on customer needs, vehicle quality and reliability. This paper describes the General Motors strategy in the medium duty market, along with the history of the design and development of these new products. Finally, this paper will discuss performance to program objectives.

This paper describes some methods for greatly reducing or possibly eliminating subjective tuning of suspension parts for ride and handling. Laptop computers can now be used in the vehicle to guide the tuning process. The same tools can be used to select solutions that reduce sensitivity to production and environmental variations. OBJECTIVE Reduce or eliminate time required for tuning of suspension parts for ride characteristics. Improve the robustness of ride performance relative to variations in ambient temperature and production tolerances. PROBLEM REQUIRING SOLUTION AND METHOD OF APPROACH Traditional development programs for new vehicles include time-consuming subjective ride evaluations. One example is shock absorber tuning. Even if sophisticated models define force-velocity curves, numerous hardware iterations are needed to find valvings that will reproduce the curves. Many evaluation rides are needed to modify the valvings to meet performance targets.

The more noise and vibration improvements are incorporated into our vehicles, the more customers notice squeaks and rattles (S&R). Customers increasingly perceive S&R as a direct indicator of vehicle build quality and durability. The high profile nature of S&R has the automotive industry striving to develop the understanding and technology of how to improve the S&R performance in the vehicle. Squeaks and itches make up a significant amount of Squeak and Rattle complaints found in today's vehicles. Squeaks and itches are the result of stick slip behavior between two interacting surfaces. Squeak itch behavior is dependent upon a large number of parameters including but not limited to: the material itself, temperature, humidity, normal load, system compliance, part geometry, velocity, surface roughness, wear, contaminants, etc. This paper will describe the analysis of sound data and friction data and the relationship between them.

Measurement of gear noise requires accurate measurement of gear mesh harmonic sound levels. The sound signal may include sidebands, such that the frequency bandwidth and computation method of respective “order tracking” analysis will have a profound effect on measured sound levels. A further consideration is the spatial distribution of the sound field inside typical passenger cars and light duty trucks, in which sound levels can change dramatically within small distances. This paper provides a discussion of the data processing and measurement location effects at hand. It explains their influence and provides guidelines for their selection.

This report presents the test methods and results of a study involving lap/shoulder belted dummies in dynamic dolly rollover tests and inverted vehicle drop tests. Data are presented showing dummy neck loadings resulting from head impacts to the vehicle interior as the vehicle contacts the ground. Comparison of the number and magnitude of axial neckloads are presented for rollcaged and production vehicles, as well as an analysis of the factors which influence neckloads under these conditions.

Although rollover crashes represent a small fraction (approximately 3%) of all motor vehicle crashes, they account for roughly one quarter of crash fatalities to occupants of cars, light trucks, and vans (NHTSA Traffic Safety Facts, 2004). Therefore, the National Highway Traffic Safety Administration (NHTSA) has identified rollover injuries as one of its safety priorities. Motor vehicle manufacturers are developing technologies to reduce the risk of injury associated with rollover collisions. This paper describes the development by General Motors Corporation (GM) of a suite of laboratory tests that can be used to develop sensors that can deploy occupant protection devices like roof rail side air bags and pretensioners in a rollover as well as a discussion of the challenges of conducting this suite of tests.

The Auto/Steel Partnership established the Light Truck Frame Project Group in 1996 with two objectives: (a) to develop materials, design and fabrication knowledge that would enable the frames on North American OEM (original equipment manufacturer) light trucks to be reduced in weight, and (b) to improve corrosion resistance of frames on these vehicles, thereby allowing a reduction in the thickness of the components and a reduction in frame weight. To address the issues relating to corrosion, a subgroup of the Light Truck Frame Project Group was formed. The group comprised representatives from the North American automotive companies, test laboratories, frame manufacturers, and steel producers. As part of a comprehensive test program, the Corrosion Subgroup has completed tests on frame coatings. Using coated panels of a low carbon hot rolled and pickled steel sheet and two types of accelerated cyclic corrosion tests, seven frame coatings were tested for corrosion performance.

THIS paper describes the development of a truck automatic transmission, from a statement of broad objectives through the growing pains, to road testing of the final product. Emphasis is placed upon original thinking that led to the decision to undertake such a project, compromises that suggested themselves throughout the various stages, and features tried and found wanting as well as those retained. The finished product is described full though not in detail, stress being placed upon interesting and novel design features.

The complexity of designing and implementing a vehicle electrical control system for ultra fuel-efficient hybrid vehicles is significantly greater than that of a conventional vehicle. To quickly demonstrate and iterate capabilities of these vehicles, an efficient and rapid means for developing requirements, mapping these into an electrical control and communications architecture, and developing prototype systems is needed. The General Motors Precept concept vehicle is an example of an energy- efficient vehicular control system developed using a "requirements to software'' development process and electronic controller infrastructure that demonstrates these attributes. The Precept is General Motors Corporation's technology demonstration concept vehicle developed to address General Motors Corporation's commitment to the Partnership for a New Generation (PNGV) program.

The common occurrence of impulsive sounds in automobiles and the recent emphasis on producing vehicles with a “quality sound” has increased the need for a method for measuring the pitch of impulsive sounds. Using Zwicker’s Loudness Patterns as a basis, a data reduction method was developed which summarizes the frequency content of each pattern. The method yields time varying quantities called Percentile Partial Loudness Frequencies from a time series of Loudness Patterns. Several “simple” impulsive sounds, representing a range of pitches, were investigated using this method. Visual inspection of the results has identified trends which seem to rank the impulsive sounds in agreement with subjective pitch rankings of a listening jury. In addition, the method appears to be capable of ranking the early portion of the impulse as a sharp or dull attack. Further investigations are needed to confirm these observations and refine the technique.

A front suspension laboratory test procedure was developed to reproduce time-correlated fatigue damaging events from a light truck road durability test. Subsequently, the performance of front suspension systems for the GMT 400 light truck program were evaluated in terms of customer reliability. Both prototype and pilot testing, as well as computer modeling, were used in the evaluation.

SPECIFICATIONS of the new Chevrolet Turbo Thrust V-8 engine described in this paper are:

Electro-Motive Division of GM jointly with HRL Laboratories have developed a software tool, called TechPro, which assists in troubleshooting of diesel locomotives. The tool has been tested extensively in the field for the last two years. It has improved significantly the quality of diagnosis of locomotives. The tool is based on Graphical Probabilistic Models and Case Data Bases. We will discuss the design of the tool, its performance and will show its relevance to diagnosis of automobiles.

Allison Gas Turbine Division of General Motors is performing the first phase of a multiphase development project aimed at demonstrating an electric vehicle based on a proton exchange membrane (PEM) fuel cell. This work is sponsored by the Office of Transportation Technologies of the U.S. Department of Energy (DoE) through the DoE's Chicago Field Office (Contract No. DE-AC02-90CH10435). This work complements major efforts under way to produce electric vehicles for reducing pollution in key urban areas. Battery powered vehicles will initially satisfy niche markets where limited range vehicles can meet commuter needs. The PEM fuel cell/battery hybrid using methanol as fuel potentially offers an extremely attractive option to increasing the range, payload, and/or performance of battery powered vehicles.