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Bench tests are often less expensive and faster than vehicle tests. However, correlation between bench tests and the engine needs to be proven, otherwise bench tests may be misleading. This investigation explored the relationships between bench wear test results and engine results from short-trip driving tests for a variety of conditions: fresh vs. used oil, different methods for assessing wear, and chemical effects such as oil contamination and differences in the fuel. There was a negative correlation between bench tests with fresh oil compared to vehicle test results with used oil, which suggests that bench wear characteristics of fresh engine oil should not be used to determine engine wear rates under the conditions tested here. Statistical analysis of bench test wear rates with used engine oil, compared to engine wear measurements, indicated that the trends were in an appropriate direction, with some scatter in the results.

The extent to which the stress history of a component is non-proportional and out-of-phase can strongly influence the accuracy of the fatigue-life prediction. Phenomenological multiaxial fatigue models are more or less accurate depending upon the extent to which the stress or strain history is non-proportional and out-of-phase. Herein, scalar measures are introduced for characterizing the non-proportional and out-of-phase extent of any stress or strain history. These scalar measures are used to characterize the stress history of a an overhead-cam cylinder-head when subjected to severe cyclic operating thermal loads.

Implementation of engine turnoff at idle is desirable to gain improvements in vehicle fuel economy. There are a number of alternatives for implementation of the restarting function, including the existing cranking motor, a 12V or 36V belt-starter, a crankshaft integrated-starter-generator (ISG), and other, more complex hybrid powertrain architectures. Of these options, the 12V belt-alternator-starter (BAS) offers strong potential for fast, quiet starting at a lower system cost and complexity than higher-power 36V alternatives. Two challenges are 1) the need to accelerate a large engine to idle speed quickly, and 2) dynamic torque control during the start for smoothness. In the absence of a higher power electrical machine to accomplish these tasks, combustion-assisted starting has been studied as a potential method of aiding a 12V accessory drive belt-alternator-starter in the starting process on larger engines.

Aromatics, cetane number, density, and lubricity of a large number of retail diesel fuel samples were compared before, during, and after the switch from low sulfur to ultra low sulfur diesel fuel. Also, sulfur and nitrogen speciation was done on a small set of samples to determine the changes in heterocyclic compounds as refiners made the switch. For ultra low sulfur fuel, total aromatics decreased substantially, density decreased slightly, cetane number increased by about 1 - 2 numbers, and lubricity (wear scar) improved slightly relative to low sulfur diesel fuel. Speciation results showed that hydrotreating eliminated thiophenes and benzothiophenes from the fuel. The only sulfur species remaining were dibenzothiophenes, and these were present at very low part per million levels. Nitrogen compounds in the form of carbazoles were either eliminated or reduced to low part per million levels.

American Society for Testing and Materials (ASTM) Sequence III Engine Oil Certification Tests have been used for the past forty-five years to evaluate lubricant performance characteristics for valvetrain wear, viscosity increase, and piston deposit formation. Minimum performance standards for passenger car light duty gasoline engine oil categories are set by the International Lubricants Standardization and Approval Committee (ILSAC) (1) and the American Petroleum Institute (API) (2). This paper describes the development of the new ASTM Sequence IIIG Engine Oil Certification Test for use in evaluating the performance characteristics of engine oils meeting the next generation, low sulfur, low phosphorus, ILSAC GF-4 and API licensing requirements.

The objective of this paper is to propose that the automotive engineering “legacy” approach of assuming that vehicle electrical return paths using conductive structural components have zero (0) ohms of impedance, needs to be reviewed. The process in this review consists of the development of an equivalent circuit composed of both real (“resistive”) and reactive elements (due to inductance and capacitance). This issue needs to be addressed due to the increased complexity of electrical and electronics systems in vehicles and the use of the vehicle structural (such as chassis, frame, or bracket) components to provide a path for the return of electrical power and/or signals as a way to eliminate additional wiring manufacturing issues, cost, and weight contribution to a vehicle.

An integrated approach to modeling end of useful life of an automatic transmission fluid (ATF) has been developed. The flexible fluid life model allows either predictive or real-time calculations of the end of useful fluid life under different transmission design strategies and customer driver behaviors as reflected in operating temperatures, shift characteristics, fluid volume and fluid distribution throughout the transmission. An estimation of remaining useful fluid life is monitored using two metrics, namely bulk oxidation, as a general indicator of fluid quality, and frictional degradation, as an indicator of shift quality. As operating conditions increase in severity, ATF is subjected to conditions that may shorten its life. Using the developed technique, ATF useful life can be better predicted.

Zinc dithiophosphate, or ZDP, for over 60 years has been used as an additive in engine oils to provide wear protection and oxidation stability in an efficient and cost effective manner. Unfortunately, ZDP contains phosphorus, and phosphorus is a widely known and accepted poison of automotive catalysts and other emissions system components. Because of this, phosphorus (and ZDP) levels in automotive engine oils have been gradually reduced by about 35% over the last 10-15 years, and further reductions are likely in the future. This paper traces the history of ZDP use in automotive engine oils, and addresses the issue of how much (if any) ZDP is actually required to provide wear protection in today's, as well as yesterday's, engines. The focus in the paper is on wear (including scuffing) protection, and not on the other aspects of ZDP performance, such as providing oxidation stability of the oil.

Principal Component Analysis (PCA) is a powerful statistical technique used for understanding variation in the observed data and decomposing variation along eigenvectors, known as Principal Components (PCs), by considering variance-covariance structure of the data. Traditionally, eigenvectors that contain most of the variation or information are selected to reduce variables in data reduction. Eigenvalues of low magnitude are considered to be noise and often, not included in the dataset to accomplish dimensional reduction. Analogously, in Principal Component Regression (PCR), PCs with large eigenvalues are selected without considering correlation between the source variables and the dependent response. This inherent deficiency may lead to inferior regression modelling. While addressing this issue, an alternative to PCR is developed and proposed in this paper. In this method, a principal component associated with zero eigenvalue is termed Trivial Principal Component (TPC).

Using standard industry tests, the oxidation stability of General Motors current factory-fill automatic transmission fluid (ATF) was compared to that of a proposed factory-fill ATF to be introduced for the 1995 Model Year. Full-scale transmission tests and Aluminum Beaker Oxidation Tests run at various temperatures showed that a proposed factory-fill fluid is substantially more resistant to oxidation than the current factory-fill ATF. Using Total Acid Number increase (Δ-TAN) as the measure of oxidation, a minimum of 35% improvement was obtained with a proposed factory fill. This improvement at least doubles the time to “perceived fluid failure” (Δ-TAN = 2.5).