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Misfire diagnostics are required to detect missed combustion events which may cause an increase in emissions and a reduction in performance and fuel economy. If the misfire detection system is based on crankshaft speed measurement, driveline torque variations due to rough road can hinder the diagnosis of misfire. A common method of rough road detection uses the ABS (Anti-Lock Braking System) module to process wheel speed sensor data. This leads to multiple integration issues including complexities in interacting with multiple suppliers, inapplicability in certain markets and lower reliability of wheel speed sensors. This paper describes novel rough road detection concepts based on signal processing and statistical analysis without using wheel speed sensors. These include engine crankshaft and Transmission Output Speed (TOS) sensing information. Algorithms that combine adaptive signal processing and specific statistical analysis of this information are presented.

General Motors introduced a family of small front wheel drive six speed automatic transmissions for the 2008 model year. The family currently has two variants: 6T40 and 6T45, which cover a range of vehicles from small & compact cars to small SUVs and handle engines torque capacities up to 240 Nm Gas(280 Nm Diesel) & 315 Nm Gas (380 Nm Diesel) respectively. The 6T40/45 transmissions replace GM traditional four speed automatic wrap around transmissions 4T40/45. The wrap around transmissions have Torque Converter, Pump & Controls on the engine axis and the rest of the transmission content on the output axis. The 6T40/45 have an on-axis architecture with majority of the transmission content on the engine axis and final drive & differential on the output axis. The 4T40/45 have input chain transfer whereas the 6T40/45 have an output chain transfer.

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.

General Motors has developed a portfolio of advanced propulsion vehicles that has set the standard for optimal fuel economy in full-size utility vehicles. An overview of power electronics used in this portfolio, already available in the market, is presented. These components are key enablers for the strategic products in portfolio. Block diagrams for various configurations are also described to show common power electronics components used in traction and auxiliary systems. Briefly real wheel drive (RWD) and front wheel drive (FWD) vehicle applications are described. Specific analysis and test results are presented from development of Traction Power Inverter used in RWD vehicles. Vehicle-based durability profiles are used in analysis to predict IGBT power modules thermal performance. Using key metrics for volume and mass, benchmarking data is also presented.

In response to the TREAD act of 2002, ASTM F09.30 Aged Tire Durability Task Group was formed with the objective of developing a scientifically valid, short duration aged durability test which correlates to field behavior. The target end-of-test condition was belt edge separation (or related damage). One strategy, driven by that objective, has been a steady state design of experiment investigating aging temperature and duration as well as roadwheel speed, pressure and deflection. The rationale behind investigating a steady state test and selecting these parameters and methodology for setting their initial values is reviewed.

In response to the TREAD act of 2002, ASTM F09.30 Aged Tire Durability Task Group was formed with the objective of developing a scientifically valid, short duration, laboratory aged tire durability test which correlates to field behavior. The target end-of-test condition was belt edge separation (or related damage). Two strategies have been investigated, aged stepped-up load and steady state DOE. Results of the two strategies are compared and contrasted and a test condition from the steady state DOE has been identified as the preferred direction for further validation.

In the work leading to the TREAD Act, some members of Congress expressed the need for some type of aging test on light vehicle tires. Since no industry-wide recommended practice existed, the ASTM F09.30 Aged Tire Durability task group was established in 2002 to develop a scientifically valid, short duration, laboratory aged tire durability test which correlates to in-service aging. The target end-of-test condition was belt edge separation (or related tire conditions). One strategy, driven by that objective, has been a Steady State DOE investigating aging temperature and duration, as well as, roadwheel speed, pressure and deflection. Testing was performed on three tire types, including two where relevant field aging data was publicly available from NHTSA studies. A region of interest, within the design space, was identified where target end-of-test conditions were possible and undesirable (non-target or non-representative of those seen in consumer use) were avoided.

A methodology involving Design for Six Sigma (DFSS) and Multi-body dynamic simulation is employed to tune a body-on-frame vehicle, for improved ride (shake) performance. The design space is limited to four sets of symmetric body mounts for a vehicle. The stiffness and damping characteristics of the mounts are the control factors in the virtual experiment. Variation of these design parameters from the nominal settings, as well as axle size, tire and wheel combinations, tire pressure, shock damping, and vehicle speed constitute the noise factors. This approach proves to be an excellent predictor of the vehicle behavior, by which much insight as to influence of each parameter on vehicle performance is gained. Ultimately, specific recommendations for the control factor settings are provided. Subsequent hardware builds show excellent agreement with the analytical model and suggested tuning.

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].

At certain key stages in the vehicle development process, prototype vehicles are available for NVH testing. This testing fulfills two functions: primarily it is used to assess the status of the vehicle to the program NVH performance targets, but it also provides an opportunity to validate the vehicle SEA model. These single vehicle test events provide a snapshot of the NVH performance but do not provide any understanding of the variability of the NVH performance, which is due to many factors: components, build or assembly and test setup variability. SEA models can be used to estimate the vehicle level variability, if the variability of the interior components is understood, but there is limited data available to confirm the accuracy of these predictions. In this paper we examine the repeatability and reproducibility through a standard gage R&R study of Engine Noise Reduction (engine NR) and Tire NR testing.

A wet multi-plate clutch, designated as the “starting clutch”, and a two-speed simple planetary gearset are used to replace the torque converter in the 4T60-E automatic transmission in order to study the potential improvement of vehicle fuel economy without sacrificing 0 - 60 mph acceleration performance. The starting clutch and the two-speed simple planetary gearset are designed to fit in the torque converter compartment. This paper describes the modified five-speed 4T60-E starting clutch automatic transmission system and provides vehicle test results to demonstrate its fuel economy and 0-60 mph performance potential.

A wet multi-plate clutch, designated as the “starting clutch”, is used to replace the torque converter in the automatic transmission in order to improve vehicle fuel economy. The transmission ratio spread must be increased to compensate for the torque multiplication of the torque converter and avoid penalizing the 0-60 mph acceleration performance. The main challenge of this concept is the control of the starting clutch to ensure acceptable vehicle drivability. This paper describes the system of a five-speed starting clutch automatic transmission vehicle and shows vehicle test results. Vehicle test data show that (i) the fuel economy benefit of the starting clutch is significant, and (ii) a starting clutch transmission can be designed to equal or better the 0-60 mph acceleration performance of a torque converter transmission by proper selection of the gear ratios.

The development and application of a traction control Kodiak and GMC TopKick are explained. Most traction systems use engine management to enable traction control, while the adaptive braking system can provide traction assist for either gas or Diesel powered vehicles from 14,000 lbs. to 33,000 lbs. GVW. The performance driven criteria that established the design requirements and the development of a new product to meet these objectives are discussed. Both the vehicle manufacturer and the traction controller supplier provided these criteria. The basic ABS and traction control hydraulic schematics will be described as they apply to the vehicles. The results of the development program will be compared to the criteria used to establish the goals, and the benefits of the traction control system will be discussed.

This paper describes the recent efforts on developing an automotive climate control system throughout integrating an electrically-controlled variable capacity scroll compressor with a fuzzy logic control-based refrigerant flow management. Applying electrically-controlled variable capacity compressor technology to climate control systems has a significant impact on improving vehicle fuel economy, achieving higher passenger comfort level, and extending air and refrigerant temperature controllability as well. In this regard, it is very important for automotive climate control engineers to layout a system-level temperature control strategy so that the operation of variable capacity compressor can be optimized through integrating the component control schemes into the system-level temperature control. Electronically controlled expansion devices have become widely available in automotive air conditioning (A/C) systems for the future vehicle applications(1, 2, 3 and 4).

CFD (Computational Fluid Dynamics) has been used to analyze vehicle air flow. In cross wind conditions an asymmetrical flow field around the vehicle is present. Under these circumstances, in addition to the forces present with symmetric air flow (drag and lift forces and pitching moment), side forces and moments (rolling and yawing) occur. Issues related to fuel economy, driveability, sealing effects (caused by suction exerted on the door), structural integrity (sun roof, spoiler), water management (rain deposit), and dirt deposit (shear stress) have been investigated. Due to the software developments and computer hardware improvements, results can be obtained within a reasonable time frame with excellent accuracy (both geometry and analytical solution). The flow velocity, streamlines, pressure field, and component forces can be extracted from the analysis results through visualization to identify potential improvement areas.

This paper describes the performance attributes of the all-new front and rear SLA (short-long arm) suspensions, steering system, and tires of the 1997 Corvette. The process by which these subsystem attributes flowed down from vehicle-level requirements for ride and handling performance is briefly described. Additionally, where applicable, specific subsystem attributes are rationalized back to a corresponding vehicle-level performance requirement. Suspension kinematic and compliance characteristics are described and contrasted to those of the previous generation (1984 to 1996 Model Year) Corvette. Both synthesis/analysis activities as well as mule-level vehicle development work are cited for their roles in mapping out specific subsystem attributes and related vehicle performance.

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.

During braking, the ability to utilize available tire-road friction is determined by brake balance. Previous methods for objectively measuring balance require various degrees of vehicle instrumentation and modification. The Road Transducer is a new measurement technique based on instrumented sections of roadway. Individual braking forces developed by each wheel are measured without vehicle instrumentation, modification, or special set up. This facilitates assessment of many vehicles required for statistical analyses. Brake balance data for several hundred vehicles are presented and provide insight to the nominal levels and variability of braking efficiencies found in the field.

An owner survey was conducted to determine the owner-measured in-use fuel economy of 1981 model passenger cars. The in-use fuel economy has been compared to the Environmental Protection Agency's (EPA) fuel economy ratings. Data were analyzed to compare the influence of vehicle design parameters on the difference between in-use fuel economy and the EPA ratings. An analysis was also done to allow comparisons of in-use fuel economy from this survey with the results of a previously reported survey on 1980 models.

The purpose of this paper is to provide an overview of the process of selection, development and approval of General Motors original equipment TPC passenger car tires. We have attempted to minimize detail in each specific area, but intend to provide a general comprehension of the thought processes involved and the procedures used to select the proper tire size and type for a vehicle. We will then describe the tire performance criteria involved in the overall development and approval process and will subsequently consider tire noise requirements in somewhat greater detail. The paper will conclude by describing the General Motors Tire Performance Criteria (TPC) System, which is a documentation of the General Motors Tire Performance requirements and test procedures.