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This paper presents a theoretical study of nitric oxide emissions from an unthrottled stratified charge, spark ignition engine. This investigation was undertaken to determine the nitric oxide production when an ideal rich-lean stratification is present and to determine the effects of introducing an intermediate stoichiometric region. In order to study this problem a three-region (generally rich, stoichiometric, and lean) combustion model was used, and the effects of the following variables were studied: 1. Excess air number of the rich mixture. 2. Percentage of the total fuel in the rich-mixture region. 3. Percentage of fuel burned stoichiometrically. 4. Exhaust gas recirculation, percentage and distribution. Comparisons are made to both experimental results from a throttled engine and calculated results for an unthrottled engine with a homogeneous mixture. For illustrative purposes, an application of the model to a particular geometrical form of charge distribution is analyzed.

Various homogeneous charge and stratified charge engine configurations were studied at wide-open throttle conditions, using simplified computer models. An order-of-magnitude parametric study was performed to find those combinations of variables which predicted a low nitric oxide level. Extreme values of variables were studied for a homogeneous charge engine configuration, which could be difficult to do in a real engine. As expected, these calculations indicated that for practical engine operation the equivalence ratio of the mixture must either be very rich or very lean for a resultant low nitric oxide level. Two extremes of stratified charge engine operation were investigated analytically, in other words, immediate mixing of newly formed products of rich combustion with excess air (instantaneous mixing) and a period of rich combustion followed by air addition to the rich products (delayed mixing). Comparisons of power, efficiency, and specific NOx are presented.

The Volkswagen prechamber injection stratified charge concept has a divided combustion chamber with part of the fuel injected into the prechamber and the intake manifold. Various combustion chamber configurations have been investigated in single-cylinder engine tests, and their applicability to the four-cylinder engine is discussed. The development of the third-generation 1.61 air-cooled opposed cylinder engine, along with its mechanical fuel injection system, is described. Engine maps of the prechamber injection engine are discussed, and engine performance data are specified. Test results on the dynamometer show very low nitrogen oxide emissions with fuel economy not impaired; however, hydrocarbon emissions without aftertreatment are still unsatisfactory.

Charge stratification has long been considered the best feasible means of burning overall weak mixtures. This offers the attractions of fuel economy and relatively low levels of pollutants emitted from the engine. In this paper, two idealised models of charge stratification are considered theoretically, with the emphasis on nitric oxide emissions. The first model represents a linear variation of fuel-air equivalence ratio, from a fuel rich mixture of the first element to burn, to a fuel weak mixture of the last element to burn. The effects of the slope of the equivalence ratio to mass fraction burned and the mean value of the equivalence ratio on nitric oxide emissions are analysed and discussed. The second model represents a step variation in the equivalence ratio, with two different zones each having a constant value of the equivalence ratio, and each being homogeneous within itself.

This paper describes the results of a three year field study into the crash performance of three basic designs of steering assembly, fitted to British cars. These systems have evolved to comply with current European and United States safety standards. While one design, involving a large-area, self-aligning steering wheel mounted on a conventional column, appeared from the field data to be highly effective in preventing serious chest and abdominal injury, the two systems utilizing axial-collapse steering columns proved to be essentially ineffective in practice. This finding is based on a field accident sample of 108 cases, so sampled as to be representative of the severe end of the collision speed and injury spectra. A test program was undertaken to examine the procedures currently used to evaluate steering assemblies. It was found that tests carried out in compliance with FMVSS 203 failed to differentiate between the safe and unsafe systems described above.

To clarify to what extent the results gained from known automobile-pedestrian impact experiments may be applied to actual accidents, comparisons with the analysis of actual accidents and comparable experiments were made with particular attention to the pattern of damage and the throw distances of the pedestrians. These results produced parameters that should be of additional use in forensic practice for defining the location of collision on the roadway. The injury patterns sustained by pedestrians involved in traffic accidents were related to vehicle damage and classified with respect to impact geometry. From the conclusions drawn from the pedestrians' motions, impact stress, and tolerance, experimental results may well be applied to the reconstruction of actual automobile-pedestrian collisions. However, this is true only within distinct classes of impact geometry, characterized by automobile front-end design, pedestrian size, and impact position.

This paper describes the results of a program to develop advanced cantilevered transit bus seats. The Department of Transportation's Urban Mass Transportation Administration funded the $26 million Transbus Program. The paper is divided into two parts. The first part describes the results of a detailed analysis of passenger accidents on-board current transit buses. The second part describes the results of sled tests that evaluated the safety of three new cantilevered seat/sidewall section designs proposed for Transbus relative to the safety of current transit buses. The testing facilities and procedures are described, along with a summary of the results of 16 sled test runs that employed four different sizes of anthropometric dummies. The results clearly indicate that the new seats have safety characteristics superior to current transit bus seats, especially in severe crash situations.

Noise tests were conducted on new and retreaded truck tires of a wide variety of patterns using three different procedures. Single tires on the test wheel and 2-tire sets on the road were correlated with the standard 4-tire sets in accordance with the Recommended Practice SAE J57 Procedure. The correlation was analyzed and the conversion techniques were discussed with the conclusions that it is possible to convert test wheel data to equivalent road test data. The results show that retreaded truck tires are not noisier than new tires of similar construction and tread design.

This paper explains how structural properties of radial and bias ply truck tires affect tire and vehicle performance. The author concludes that a knowledgeable evaluation of the pros and cons of both bias and radial ply truck tires be based on individual operational evaluations and the compromise of tire characteristics which best satisfy needs. Neither radial nor bias ply truck tires can be generalized as the superior choice since each type has areas of superiority.

A simple method based on bevameter soil values enables the engineer to evaluate the motion resistance of a pneumatic tire, in the given soil, and to perform parametric analyses of design and performance. The parameters measured include, besides soil parameters, the following characteristics of the tire: width, diameter, inflation pressure, carcass stiffness, and load. An inexpensive electronic desk calculator assures accuracy of prediction that is more than satisfactory.

This paper discusses equipment and procedures required to retread radial tires, emphasizing truck tires; reviews retreading process for conventional tires; and notes changes required for radials. In exploring the most extensive problem, inability to properly contract and expand radials to provide curing pressure, the paper indicates the need for an elastic matrix and supports use of precured tread systems.

Tire traction test data has shown empirically that peak skid number dry pavement traction performance of bias ply tires is inversely proportional to the dynamic instantaneous tire load and is a function of inflation pressure. A modification to classical braking theory, which assumes constant traction coefficients at the tire-road interface, is therefore required to obtain maximum theoretical unlocked wheel vehicle deceleration. Optimum brake proportioning between front and rear axles is dictated by the maximum braking force which, with respect to each axle, can be generated at the tire-road interface. The inclusion of peak traction coefficient normal load sensitivity significantly modifies classical theory and changes the selection of brake force balance required to attain maximum theoretical deceleration capability. The importance of the effects of tire traction load sensitivity on the requirements of FMVSS 105-75 is discussed in this paper.

A mobile dynamometer has been constructed for measurement of the longitudinal force/slip characteristics of truck tires. The application of this apparatus in testing of a preliminary sample of tires has indicated that the shear force production properties of truck tires differ in many respects from the corresponding behavior of passenger car tires. These differences are discussed in terms of shear force sensitivity to a number of operating variables. The inadequacy of current semi-empirical tire models in representing truck tire traction is noted.

A comprehensive structural performance standard for school bus superstructures is being developed by a special task force on school bus safety organized by the School Bus Manufacturers Institute. This paper presents a progress report on the standard. Included is a review of the main features: the basic philosophy that the bus body must be capable of safe, controlled energy absorption in the event of a crash; the establishment of a statically equivalent test through the use of energy absorption as a simulation parameter; and detailed specifications for simulated crash modes. As a specific example, the rollover simulation test specification is presented in its entirety and a critical assessment is provided.

This paper outlines several specifications for heavy-duty truck wiring, especially wire and harness assemblies, and low-tension electrical wire. Emphasized are avoidance of substandard wiring and components, identification of circuits, grounding techniques, and construction. It is noted that improved specifications will result in reduced maintenance costs.

Obtaining and maintaining a stratified charge in a practical engine is a difficult problem. Consequently, many approaches have been proposed and reported in the scientific and patent literature. In attempting to assess the most profitable approach for future development work, it is important to group together similar approaches so that one can study their performance as a group. Making such a classification has the additional advantage of helping to standardize terminology used by different investigators. With this thought in mind, a literature study was made and a proposed classification chart prepared for the different engine combustion systems reported in the literature. For the sake of completeness, the finally proposed classification chart includes homogeneous combustion engines as well as heterogeneous combustion engines. Because of their similarity of combustion, rotary engines such as the Wankel engine are considered as “reciprocating” although gas turbines are not included.

A new concept in school bus body construction, the Wayne Lifeguard bus, provides solutions to specific problems cited by critics of school bus safety. This report chronicles development of the Lifeguard bus from conception through production and compares it with traditionally built buses.

In this paper, the experimental results concerning the effect of the geometrical and operating factors of the CVCC engine on NOx emission, taking into consideration the fuel economy, are described with respect to a specific engine configuration, and they are compared with the results calculated by means of the mixture formation model. Furthermore the relationship between the NOx emission level and specific fuel consumption has been explained, and then it has been shown that the controlled combustion obtained with the CVCC engine is very effective for eliminating fuel economy penalty and reducing emissions.

Vehicle systems utilizing a stratified charge engine have been evaluated for their emission potential. They have shown the ability to meet the 2.0 gm/mi NOx emission standard without EGR at low mileage, but require some form of aftertreatment device to simultaneously achieve emission levels of 0.41 gm/mi HC and 3.4 gm/mi CO. The system hardware required in conjunction with the stratified charge engine is described.

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.