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Four multigrade engine oils, containing the same base oil plus SE additive package but VI improvers of differing shear stability, were evaluated in 80 000 km of high-speed, high-temperature vehicle service. Bearing, piston ring and valve guide wear, as well as oil consumption, oil filter plugging and engine cleanliness were all worse for the engines operated on the low-shear stability oils. The wear differences were traced to differences in high-shear-rate viscosity, while the cleanliness, filter plugging and oil consumption differences occurred because of excessive wear or polymer shear degradation. These results suggest that engine oil viscosity should be specified under high-shear-rate conditions.

The strain-life approach is now commonly used for fatigue life analysis and predictions in the ground vehicle industry. This approach requires the use of material properties obtained from strain-controlled uniaxial fatigue tests. These properties include fatigue strength coefficient (σf′), fatigue strength exponent (b), fatigue ductility coefficient (εf′), fatigue ductility exponent (c), cyclic strength coefficient (K′), and cyclic strain hardening exponent (n′). To obtain the aforementioned properties for the material, raw data from stable cyclic stress-strain loops are fitted in log-log scale. These data include total, elastic and plastic strain amplitudes, stress amplitude, and fatigue life. Values of the low cycle fatigue properties (σf′, b, εf′, c) determined from the raw data depend on the method of measurement and fitting. This paper examines the merits and influence of using different measurement and fitting methods on the obtained properties.

The development of systems and components for control of exterior noise has traditionally been done through an iterative process of on road testing. Frequently, road testing of vehicle modifications are delayed due to ambient environmental changes that prevent testing. Vehicle dynamometers used for powertrain development often had limited space preventing far field measurements. Recently, several European vehicle manufacturers constructed facilities that provided adequate space for simulation of the road test. This paper describes the first implementation of that technology in the U.S.. The facility is typical of those used world wide, but it is important to recognize some of the challenges to effective utilization of the technique to correlate this measurement to on road certification.

This study evaluated multi-layer steel and composite head gaskets of various thicknesses (0.43 to 1.5 mm) and fire-ring diameters to determine the influence of head gasket crevices on engine-out hydrocarbon (HC) emissions. The upper limit in the percent reduction in HC emissions from gasket-design modifications is estimated to be about 15%. At part-load conditions, the lowest HC emissions were measured for head-gasket thickness of about 1 mm. Significantly smaller thicknesses of the order of 0.4 mm result in an increase in HC emissions. Substantial hydrocarbon-emissions advantage may be realized by minimizing the gasket-to-cylinder bore offset.

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.

The bulge test in hydroforming is a simple fundamental experiment used to obtain basic knowledge in tube expansion. The results can be used to assist design and manufacturing of hydroformed automotive parts. It also can be used to develop a failure criterion for tubes in hydroforming. For these purposes, a section of a long unsupported tube with fixed ends was simulated numerically to obtain the mechanical states of the tube subjected to internal pressure. Steel and aluminum tubes are used. For the bulge tests, the internal pressure reaches a maximum and then decreases in value without failure while the stress, strain and volume of the tube keep increasing. A failure criterion for the bursting of a tube is proposed based on the stress-strain curve of the material.

This paper describes the major electrical characteristics of the automotive power supply system. It is a compilation of existing data and new information that will be helpful to both the electrical component and electronic assembly designers. Previously available battery/alternator data is organized to be useful to the designer. New dynamic information on battery impedance is displayed along with “cogging” transients, regulation limits and load dump characteristics.

In order to engineer Squeak & Rattle (S&R) free vehicles it is essential to develop an objective measurement method to compare and correlate with customer satisfaction and subjective S&R assessments. Three methods for exciting S&Rs -type surfaces. Excitation methods evaluated were road tests over S&R surfaces, road simulators, and direct body excitation (DBE). The principle of DBE involves using electromagnetic shakers to induce controlled, road-measured vibration into the body, bypassing the tire patch and suspension. DBE is a promising technology for making objective measurements because it is extremely quiet (test equipment noise does not mask S&Rs), while meeting other project goals. While DBE is limited in exposing S&Rs caused by body twist and suspension noises, advantages include higher frequency energy owing to electro-dynamic shakers, continuous random excitation, lower capital cost, mobility, and safety.

This paper describes the design, synthesis-analysis and development of the unique vehicle structure architecture for the fifth generation Chevrolet Corvette, ‘C5’, which starts in the 1997 model year. The innovative structural layout of the ‘C5’ enables torsional rigidity in an open roof vehicle which exceeds that of all current production open roof vehicles by a wide margin. The first structural mode of the ‘C5’ in open roof configuration approaches typical values measured in similar size fixed roof vehicles. Extensive use of CAE and a systems methodology of benchmarking and requirements rolldown were employed to develop the ‘C5’ vehicle architecture. Simple computer models coupled with numerical optimization were used early in the design process to evaluate every design concept and alternative iteration for mass and structural efficiency.

DESCRIBED here is a 250-hp free-piston gasifier-turbine engine that has actually been installed in an automobile. A unique feature of this Hyprex engine is that it is a siamesed unit. The overall design has been selected, according to the author, to secure a compact, light-weight machine with improved thermal efficiency and with a reduction in general noise. Although the engine is still in the experimental stage, the author reports that analysis and results indicate it will be a serious contender for powering automotive vehicles.

Dynamic conditions of automotive type valve trains have been investigated by means of digital computers. It has been possible to include the effect of such nonlinearities as valve lash, linkage separation, valve seating, and valve spring surge. Comparison with experimental results has shown that computer solutions are realistic. The advantage of being able to simulate and predict performance of any proposed type of valve train is obvious. This paper presents methods of approach for analyzing valve dynamics, correlation of computed results with experimental values, and examples of application of interrelated methods. Included in this paper are: (1) Methods of approach for analyzing valve dynamics, (2) Correlation of computed results with experimental values and, (3) Examples of application of interrelated methods.

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.

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.

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.

This paper discusses four general attributes which quantify the character of an impulsive sound event. These attributes include the time duration, amplitude and frequency content of the impulsive noise. A three dimensional plot relating time, frequency and amplitude have been developed for the presentation of the measured data. This format allows graphic illustration of the noise event, providing fast interpretation and communication of the measured sound. Application of this methodology to the sound of an automotive door closing event is presented here. Representative door closing sound events are analyzed, with correlation presented between the attributes above to dynamic events of the physical hardware within the door and vehicle systems. Modifications of the door-in-white, internal door hardware, seal systems and additional content are investigated for their effect on the sound quality of the door closing event. Finally, recommended values for these attributes are presented.

In order to meet progressively stringent regulations on particulate emission from diesel engines, GM has developed and tested a variety of trap oxidizer systems over the years. A particulate trap system for a light duty diesel engine has been selected and developed based on this experience, with particular emphasis on production feasibility. The system components have been designed and developed in collaboration with potential suppliers, to the extent possible. The technical performance of this system has been demonstrated by successful system durability testing in the test cell and vehicle experience in computer controlled automatic operation mode. Although the system shows promise, its production readiness will require more development and extensive vehicle validation under all operating conditions.

The application of Statistical Energy Analysis (SEA) to vehicle development is discussed, with a new technique to implement noise path analysis within a SEA model to enable efficient solution and optimization of acoustic trim. A whole vehicle Performance-Based SEA model is used, in which Sound Transmission Loss (STL) and acoustic absorption coefficient characterize subsystem performance. In such a model, the net contribution from each body panel/path, such as the floor, to a specific interior subsystem, such as the driver's head space, is extremely important for vehicle interior noise development. First, it helps to identify the critical path to root-cause potential problems. Second, it is necessary in order to perform balancing of path contributions. With current software, the power based noise contribution analysis is for direct paths/adjacent subsystems.

A running loss test procedure has been developed which integrates a point-source collection method to measure fuel evaporative running loss from vehicles during their operation on the chassis dynamometer. The point-source method is part of a complete running loss test procedure which employs the combination of site-specific collection devices on the vehicle, and a sampling pump with sampling lines. Fugitive fuel vapor is drawn into these collectors which have been matched to characteristics of the vehicle and the test cell. The composite vapor sample is routed to a collection bag through an adaptation of the ordinary constant volume dilution system typically used for vehicle exhaust gas sampling. Analysis of the contents of such bags provides an accurate measure of the mass and species of running loss collected during each of three LA-4* driving cycles. Other running loss sampling methods were considered by the Auto-Oil Air Quality Improvement Research Program (AQIRP or Program).

The function of the inlet header of a catalytic converter is to diffuse the inlet exhaust flow, decreasing its velocity and increasing its static pressure with as little loss in total pressure as possible. In practice, very little diffusion takes place in most catalytic converter inlet headers because the flow separates at the interface of the pipe and the tapered section leading to the substrate. This leads to increased converter pressure loss and flow maldistribution. An improved inlet-header design called the Enhanced Diffusion Header (EDH) was developed which combines a short, shallow-angle diffuser with a more abrupt expansion to the substrate cross section. Tests conducted in room air (cold flow) and engine exhaust showed that improved inlet-jet diffusion leads to substantial reductions in converter restriction. EDH performance was not compromised by the presence of a right-angle bend upstream of the converter.

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.