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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.

Homogenous Charge Compression Ignition (HCCI) combustion offers significant efficiency improvements compared to conventional gasoline engines. However, due to the nature of HCCI combustion, traditional HCCI engines show some degree of sensitivity to in-cylinder thermal conditions; thus higher cylinder-to-cylinder variation was observed especially at low load and high load operating conditions due to different injector characteristics, different amount of reforming as well as non-uniform EGR distribution. To address these issues, a cylinder balancing control strategy was developed for a multi-cylinder engine. In particular, the cylinder balancing control strategy balances CA50 and AF ratio at high load and low load conditions, respectively. Combustion noise was significantly reduced at high load while combustion stability was improved at low load with the cylinder balancing control.

Two-stage turbochargers are a recent solution to improve engine performance, reducing the turbo-lag phenomenon and improving the matching. However, the definition of the control system is particularly complex, as the presence of two turbochargers that can be in part operated independently requires effort in terms of analysis and optimization. This work documents a characterization study of two-stage turbocharger systems. The study relies on a mean-value model of a Diesel engine equipped with a two-stage turbocharger, validated on experimental data. The turbocharger is characterized by a VGT actuator and a bypass valve (BPV), both located on the high-pressure turbine. This model structure is representative of a “virtual engine”, which can be effectively utilized for applications related to analysis and control. Using this tool, a complete characterization was conducted considering key operating conditions representative of FTP driving cycle operations.

Engine cylinder deactivation is used to save engine pumping loss but raises oil consumption concerns for the deactivated cylinders. In this paper, general mechanisms of oil transport via piston rings are reviewed. The characteristic of oil transport and oil accumulation in a cylinder deactivation mode through the piston ring path are analyzed. Suggestions to reduce the oil transport to the combustion chamber in a deactivated cylinder are discussed. In a deactivated cylinder, the amount of oil brought into the combustion chamber by the top ring up-scraping due to the ring/bore conformability difference between intake stroke and compression stroke is much less compared to a firing cylinder. However, compared to a firing cylinder, a deactivated cylinder has more oil entering the combustion chamber through the top ring end gap and ring groove as a result of the lower cylinder gas pressure, lower ring temperature and more frequent top ring axial movements.

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 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.

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.

Brake squeal has been analyzed by finite elements for some time. Among several methods, complex eigenvalue analysis is proving useful in the design process. It requires hardware verification and it falls into a simulation process. However, it is fast and it can provide guidance for resolving engineering problems. There are successes as well as frustrations in implementing this analysis tool. Its capability, robustness and reliability are closely examined in many companies. Generally, the low frequency squealing mechanism is a rotor axial direction mode that couples the pads, rotor, and other components; while higher frequency squeal mainly exhibits a rotor tangential mode. Design modifications such as selection of rotor design, insulator, chamfer, and lining materials are aimed specifically to cure these noise-generating mechanisms. In GM, complex eigenvalue analysis is used for brake noise analysis and noise reduction. Finite element models are validated with component modal testing.

This paper documents a joint development process between General Motors and Dow Automotive to improve primary body structure frequencies on the GM family of midsize vans by utilizing cavity-filling structural foam. Optimum foam locations, foam quantity, and foam density within the body structure were determined by employing both math-based modeling and vehicle hardware testing techniques. Finite element analysis (FEA) simulations of the Body-In-White (BIW) and “trimmed body” were used to predict the global body structure modes and associated resonant frequencies with and without structural foam. The objective of the FEA activity was to quantify frequency improvements to the primary body structure modes of matchboxing, bending, and torsion when using structural foam. Comprehensive hardware testing on the vehicle was also executed to validate the frequency improvements observed in the FEA results.

A gasoline direct injection fuel spray was observed using a fired, optical access, square cross-section single cylinder research engine and high-speed video imaging. Spray interaction with the piston is described qualitatively, and the results are compared with Computational Fluid Dynamics (CFD) simulation results using KIVA-3V version 2. CFD simulations predicted that within the operating window for stratified charge operation, between 1% and 4% of the injected fuel would remain on the piston as a liquid film, dependent primarily on piston temperature. The experimental results support the CFD simulations qualitatively, but the amount of fuel film remaining on the piston appears to be under-predicted. High-speed video footage shows a vigorous spray impingement on the piston crown, resulting in vapor production.

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.

The approaches used to develop an NVH package for a vehicle have changed dramatically over the last several years. New noise and vibration control strategies have been introduced, new materials have been developed, advanced testing techniques have been implemented, and sophisticated computer modeling has been applied. These approaches help design NVH solutions that are optimized for cost, performance, and weight. This paper explains the NVH practices available for use in designing vehicles for the new millennium.

FIGURE 1 The 200 HP high performance 4.3L Vortec V6 engine has been developed to satisfy the need for a fuel efficient performance powerplant in the General Motors small truck platforms. Marketing requirements included strong low and mid range torque, relatively high specific power, smoothness and noise comparable to the best competitive six cylinder engines, excellent driveability, and a new technology image. Maintaining the 4.3L engine record of high reliability and customer satisfaction was an absolute requirement. Fuel economy and exhaust emission performance had to meet expected customer and legislated requirements in the mid 1990's.

General Motors Powertrain Division has developed a new V-8 engine for Cadillac vehicles in the 1990s. The Northstar engine incorporates the use of aluminum for both the cylinder block and head and other lightweight materials throughout. The valve train incorporates direct acting hydraulic lifters actuating the four valves per cylinder through dual overhead camshafts. The primary focus of the project has been to produce an engine of unquestioned reliability and exceptional value which is pleasing to the customer throughout the range of loads and speeds. The engine was designed with a light weight valve train, low valve overlap and moderate lift, resulting in a very pleasing combination of smooth idle and a broad range of power. The use of analytical methods early in the design stage enabled systems to be engineered to optimize reliability, pleaseability and value by reducing frictional losses, noise, and potential leak paths, while increasing efficiency and ease of manufacture.

Several factors have influenced the size and design of domestic passenger cars over the past 30 years. Of most significance has been the influx of imported cars, initially from Europe, later from Japan. Interspersed within the fabric of this influx have been two energy crises and several recessions, and the onset of safety, emission, and energy regulations. These factors have led to various responses by domestic manufacturers as indicated by the types of products and vehicle systems that they have introduced during this period. This paper chronicles both the events as well as the responses.

Higher horsepower per liter engines have put more demand on the crankshaft, often requiring the use of forged steel. This paper examines cost reduction opportunities to offset the penalties associated with forged steel, with raw material and machinability being the primary factors evaluated. A cost model for crankshaft processing is utilized in this paper as a design tool to select the lowest cost material grade. This model is supported by fatigue and machinability data for various steel grades. Materials considered are medium carbon, low alloy, and microalloy steels; the effects of sulfur as a machining enhancer is also studied.

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.

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 primary objective of Central Port Fuel Injection is to be a low cost multi-point fuel injection system with the additional attributes of compactness, packaging flexibility, and reliability. Performance of this fuel system closely resembles that of a simultaneous multi-point fuel injection system in flow control, dynamic range, cylinder-to-cylinder distribution, idle quality, transient response, and emissions. The system provides significantly improved performance in the areas of hot fuel handling, cold startability, vacuum and voltage sensitivity and system noise. This performance comes at a significant cost savings and greater packaging and targeting flexibility over a conventional multi-point fuel injection system.

An OEM Natural Gas Vehicle (NGV) has been developed to address recently enacted Clean-Fuel Vehicle legislation. The NGV incorporates advanced fuel storage and fuel metering technologies to produce very low emissions and to provide superior customer value compared to aftermarket conversion units.