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A comprehensive test program was conducted to correlate aerodynamic drag measurements from the General Motors Aerodynamics Laboratory with coastdown results. An improved method of coastdown testing was used to minimize the sources of error in determining aerodynamic drag. Several vehicles were tested, covering a large range of aerodynamic drag values, representative of current and future production vehicles. Wind tunnel and coastdown results were determined to be in good agreement, with an average drag coefficient difference of only. 008 (2%).

The application of crash durable structural adhesives in modern cars design, to improve the driving durability, the overall vehicle stiffness, the crash resistance and to make real light weight constructions feasible is significantly gaining in importance. 1-component systems are already introduced in the market and used in automotive industries. Usually the use of these bonds in automotive industries is limited by a relatively low wash off resistance in the pre-treatment tanks of the paint shop. If no additional actions are taken, there is a severe risk of wash off of the adhesives up to the partial loss in functionality. Respectively contamination of the pre-treatment tanks and aftereffects damage the surface of the coated cars. To avoid wash off a thermal process (oven) to pre-gel the adhesive in the flanges of the Body-In-White (BIW)- bodies before entering the pre-treatment utility is necessary. This is a save but cost intensive solution.

AS a basis for the analyses of this symposium, a hypothetical car has been used to evaluate the engine power distribution in performance. Effects of fuel,-engine accessories, and certain car accessories are evaluated. The role of the transmission in making engine power useful at normal car speeds is also discussed. Variables encountered in wind and rolling resistance determinations are reevaluated by improved test techniques. Net horsepower of the car in terms of acceleration, passing ability and grade capability are also summarized.

The search for improvements in occupant protection under vehicle impact is hampered by a real lack of reliable biomechanical data. To help fill this void, General Motors has initiated joint research with independent researchers such as the School of Medicine, U. C. L. A. – in this case to study localized head and facial trauma — and has developed such unique laboratory tools as “Tramasaf,” a human-simulating headform, and “MetNet,” a pressure-sensitive metal foam. Research applied directly to product design also has culminated in developments such as the Side-Guard Beam for side impact protection.

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.

To meet automotive legal, consumer and insurance test requirements, the process for designing energy absorption countermeasures usually comprises Finite Element simulations of the specified test. Finite element simulations are used first to see if there is a need for an Energy Absorption countermeasure at all and if so, what type, material and shape. A widely used class of energy absorption countermeasures in automotive interior applications is honeycomb extruded polypropylene foams (HXPP). Under compression, these foams exhibit a constant plateau stress until late densification. This enables these foams to minimize packaging space for a given amount of energy to be absorbed or maximize energy absorption for a given packaging space. Robust and easy to use isotropic CAE material models have been developed for HXPP, however the true material properties are anisotropic and such a material model could be necessary in some cases.

A detailed description of the oxidative stability of GM's DEXRON®-VI Factory Fill Automatic Transmission Fluid (ATF) is provided, which can be integrated into a working algorithm to estimate the end of useful oxidative life of the fluid. As described previously, an algorithm to determine the end of useful life of an automatic transmission fluid exists and is composed of two simultaneous counters, one monitoring bulk oxidation and the other monitoring friction degradation [1]. When either the bulk oxidation model or the friction model reach the specified limit, a signal can be triggered to alert the driver that an ATF change is required. The data presented in this report can be used to develop the bulk oxidation model. The bulk oxidation model is built from a large series of bench oxidation tests. These data can also be used independent of a vehicle to show the relative oxidation resistance of this fluid, at various temperatures, compared to other common lubricants.

This paper describes the methodology used to achieve optimum aerodynamic performance of the 1992 through 1995 Oldsmobile Cutlass Supreme IMSA GT race car and will demonstrate the continuous improvements successfully used to respond to rule changes and competition. The concerted effort by the sanctioning body to limit the aerodynamic performance of IMSA GT race cars for the 1995 season required a rigorous wind tunnel test program backed by track validation to maintain the necessary aerodynamic balance, cooling flows, engine induction flow, and overall competitive parity. The specific modifications that were evaluated to accommodate these rules changes will be detailed in this paper. Special test methodologies developed to better understand specific aerodynamics questions such as the effects of vehicle attitude, internal cooling flows, underbody treatments, and engine air inlet performance will also be discussed.

HOW well are multigrade oils performing at low temperatures? An investigation has shown that the low-tem perature properties of mulrigrade oils are often not equivalent to the single-grade oils-lOW in a mulrigrade oil may actually be 20W. One phase of this investigation, a full-scale cranking study using commercial 10W and 10W-30 oils in cars at 0 F, is discussed in detail in this paper.

The work presented here builds on the practical and effective spot weld fatigue life prediction method, the structural stress method (SSM), that was developed at Stanford University. Constant amplitude loading tests for various spot weld joint configurations have been conducted and the SSM has been shown to accurately predict fatigue life. In this paper refinements to the structural stress approach are first presented, including a variable amplitude fatigue life prediction method based on the SSM and Palmgren-Miner's rule. A test matrix was designed to study the fatigue behavior of spot welds under tensile shear loading conditions. Constant amplitude tests under different R-ratios were performed first to obtain the necessary material properties. Variable amplitude tests were then performed for specimens containing single and multiple welds.

Recently, automotive engineers have been looking at rigid polyurethane foam systems for the advantages their application brings to vehicle design and performance. The benefits range from NVH management achieved through effective body cavity sealing and improved structural dynamics, to enhanced vehicle crashworthiness. These benefits can be realized through application of polyurethane foam systems designed for energy management. These systems offer multifunctional, low cost solutions to traditional approaches and can be modeled early in the vehicle design stage. In many cases, the overall vehicle mass is reduced as reinforcements are eliminated and/or sheet metal thickness is decreased. Dow Automotive has developed a family of water blown polyurethane foams specifically for these applications. Development has focused on foam systems designed for impact optimization, allowing OEM's to optimize the body structure content.

The application of two-component polyurethane (PU) foam materials for acoustical and structural performance enhancements in vehicle structures have increased significantly in the past ten years. The benefits include NVH management (through effective cavity sealing), body stiffness improvements and energy management in crash applications. These PU foams can either be pumped into body cavities in the OEM assembly plants (bulk applied) or can be pre-molded into Structural Foam Inserts (SFI) and installed in the body-shop prior to full frame assembly. The choice of application type depends on vehicle-specific requirements and assembly plant criteria. The chemistry, plant application and benefits associated with bulk PU foam has already been cited in previous work.1, 2, 3 This paper showcases BETAFOAM™ SFI technology developed by Dow Automotive that complements traditional bulk foam technology.

Low density polyurethane foam, applied in general assembly, is being used as a replacement for rubber-based heat reactive baffles in automobile cavities to inhibit noise transmittance. Most chemically reactive urethane foam systems used in barrier applications are MDI-based (diphenylmethane diisocyanate). The use of classical MDI-based technology in assembly plants typically requires substantial levels of ventilation [1]. High capital and operating expenses associated with plant ventilation systems have hindered the growth of polyurethane technology. This paper describes benefits of using a low MDI polyurethane foam system in place of classical two-component MDI-based foam systems and conventional rubber-based heat reactive baffles. Severe industrial hygiene testing has indicated that ventilation requirements to use the low MDI foam system in assembly plants may be greatly reduced.

During early 2005 General Motors released a newly developed ATF for the factory fill of all GM Powertrain stepped gear automatic transmissions. The new fluid provided significantly improved performance in terms of friction durability, viscosity stability, aeration and foam control and oxidation resistance. In addition, the fluid has the potential to enable improved fuel economy and extended drain intervals. Since the performance of the new fluid far exceeded that of the DEXRON®-III service fill fluids available at the time it became necessary to upgrade the DEXRON® service fill specification in order to ensure that similar fluids were available in the market for service and repair situations. This latest upgrade to the service fill specification is designated DEXRON®-VI [1].

The potential of bake hardenable steel as a substitute for SAE 1008 steel to reduce gage and improve dent resistance is investigated in this report. Outer body panels in particular are susceptible to palm printing and other forms of denting. Conventional SAE 1008 steel and a developmental continuous annealed bake hardenable steel from Inland Steel Company are compared for dent performance properties. Bake hardenable (BH) steel is a medium strength (200-350 MPa) steel that receives an increase in yield strength during the heating of the paint bake cycle. An increase in yield strength would result in an increase in dent resistance. The increase in dent resistance is more quantitatively evaluated by comparing the BH steel with the current production material (SAE 1008) of a rear compartment lid outer.

Dow Automotive has developed an ACM DPF substrate, characterized with light-weight, low pressure-drop, rapid regeneration, and excellent chemical resistance at high temperature. An uncatalyzed DPF was tested on a 2.0L common-rail diesel engine for over 100 soot loading and regeneration cycles, which included a combination of controlled regenerations, uncontrolled regenerations and incomplete regenerations. The DPF demonstrated high filtration efficiency and physical integrity throughout the entire test. The ACM DPF has also demonstrated excellent catalyst coating capability and performance. An ACM DPF with a total volume of three-liter and coated with the same catalyst formulation as the original catalyzed DPF, was used to replace the OEM four-liter catalyzed SiC DPF on a 2005 model-year 1.9L European diesel passenger car. It was demonstrated that the ACM DPF has lower pressure drop and faster regeneration than that of the OEM DPF.

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.

The use of two-component polyurethane foam materials to improve sealing, stiffness, and crash performance in vehicle structures has increased significantly in the past 10 years. The proven cost and performance advantages associated with polyurethane chemistry, along with recent development efforts by Dow Automotive to minimize industrial hygiene concerns traditionally associated with polyurethane use [1], have resulted in increased activities associated with design, application development, and launch of foam systems in the automotive industry. This paper describes the key considerations that must be addressed to successfully incorporate polyurethane foams into vehicle structures from design, application development, and launch perspectives.

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.

The results of comparative aerodynamic force measurements on a full-scale notchback-type vehicle, performed between 6 European companies operating full-scale automotive wind tunnels, were published in the SAE Paper 800140. Correlation tests with the same vehicle have been extended to 2 further European and 3 North American wind tunnels. First the geometry, the design and the flow data of the different wind tunnels is compared. The facilities compared include wind tunnels with open-test-sections, closed-test-sections and one tunnel with slotted side walls. The comparison of results, especially for drag coefficients, show that the correlation between the differently designed wind tunnels is reasonable. Problems of blockage correction are briefly discussed. The comparison tests furthermore revealed that careful design of the wheel pads and blockage corrections for lift seem to be very influential in achieving reasonable lift correlations. Six-component measurements show similar problems.