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Technical Paper

Oil Transport Analysis of a Cylinder Deactivation Engine

2010-04-12
2010-01-1098
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.
Technical Paper

Diagnosis of Off-Brake Performance Issues with Low Range Pressure Distribution Sensors

2010-04-12
2010-01-0073
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.
Technical Paper

General Motors Small Front Wheel Drive Six speed Automatic Transmission Family

2010-04-12
2010-01-0857
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.
Technical Paper

Improvement on Cylinder-to-Cylinder Variation Using a Cylinder Balancing Control Strategy in Gasoline HCCI Engines

2010-04-12
2010-01-0848
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.
Technical Paper

Model-Based Characterization and Analysis of Diesel Engines with Two-Stage Turbochargers

2010-04-12
2010-01-1220
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.
Technical Paper

Electro-Hydraulic Fully Flexible Valve Actuation System for Engine Test Cell

2010-04-12
2010-01-1200
Fully Flexible Valve Actuation (FFVA) systems provide maximum flexibility to adjust lift profiles of engine intake and exhaust valves. A research grade electro-hydraulic servo valve based FFVA system was designed to be used with an engine in a test cell to precisely follow desired lift profiles. Repetitive control was chosen as the control strategy. Crank angle instead of time is used to trigger execution to ensure repeatability. A single control is used for different engine speeds even though the period for one revolution changes with engine speeds. The paper also discusses lift profile extension, instantaneous lift profile switching capability and built-in safety features.
Journal Article

Automotive Brake Hose Fluid Consumption Characteristics and Its Effects on Brake System Pedal Feel

2010-04-12
2010-01-0082
During the automotive brake system design and development process, a large number of performance characteristics must be comprehended, assessed, and balanced against each other and, at times, competing performance objectives for the vehicle under development. One area in brake development that is critical to customer acceptance due to its impact on a vehicle's perceived quality is brake pedal feel. While a number of papers have focused on the specification, quantification and modeling of brake pedal feel and the various subsystem characteristics that affect it, few papers have focused specifically on brake corner hoses and their effect on pedal feel, in particular, during race-track conditions. Specifically, the effects of brake hose fluid consumption pedal travel and brake system response is not well comprehended during the brake development process.
Technical Paper

Comparison of OEM Automatic Transmission Fluids in Industry Standard Tests

2007-10-29
2007-01-3987
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.
Technical Paper

Combining DFSS and Multi-body Dynamics for Vehicle Ride Tuning

2007-04-16
2007-01-0586
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.
Technical Paper

Adaptation of a Variable Displacement Vane Pump to Engine Lube Oil Applications

2007-04-16
2007-01-1567
Variable valve actuation has become a very popular feature in today's engines. With many of these systems being hydraulically actuated, the engine lubrication system requires enhancement to support their function. To expand the system's operational range with respect to speed and temperature, a traditional solution has been to increase oil pressure by increasing pump displacement. To better optimize the system, a variable displacement vane pump has been adapted to the engine lube oil system. Based on existing transmission pump technology, a pivoting cam ring design is employed that is able to vary the pump's displacement as a function of pump regulating oil pressure which in-turn provides a net reduction in its drive torque. While others have addressed this issue using complex and expensive pressure regulating systems, this passive solution requires no valves or additional hardware.
Technical Paper

General Motors DEXRON®-VI Global Service-Fill Specification

2006-10-16
2006-01-3242
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].
Technical Paper

The Oxidative Stability of GM's DEXRON®-VI Global Factory Fill ATF

2006-10-16
2006-01-3241
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.
Technical Paper

Chemiluminescence Measurements of Homogeneous Charge Compression Ignition (HCCI) Combustion

2006-04-03
2006-01-1520
A spectroscopic diagnostic system was designed to study the effects of different engine parameters on the chemiluminescence characteristic of HCCI combustion. The engine parameters studied in this work were intake temperature, fuel delivery method, fueling rate (load), air-fuel ratio, and the effect of partial fuel reforming due to intake charge preheating. At each data point, a set of time-resolved spectra were obtained along with the cylinder pressure and exhaust emissions data. It was determined that different engine parameters affect the ignition timing of HCCI combustion without altering the reaction pathways of the fuel after the combustion has started. The chemiluminescence spectra of HCCI combustion appear as several distinct peaks corresponding to emission from CHO, HCHO, CH, and OH superimposed on top of a CO-O continuum. A strong correlation was found between the chemiluminescence light intensity and the rate of heat release.
Technical Paper

Emissions of Toxicologically Relevant Compounds Using Dibutyl Maleate and Tripropylene Glycol Monomethyl Ether Diesel Fuel Additives to Lower NOx Emissions

2005-04-11
2005-01-0475
A previous paper reported (SAE Paper 2002-01-2884) that it was possible to decrease mode-weighted NOx emissions compared to the OEM calibration with corresponding increases in particulate matter (PM) emissions. These PM emission increases were partially overcome with the use of oxygenated diesel fuel additives. We wanted to know if compounds of toxicological concern were emitted more or less using oxygenated diesel fuel additives that were used in conjunction with a modified engine operating strategy to lower engine-out NOx emissions. Emissions of toxicologically relevant compounds from fuels containing triproplyene glycol monomethyl ether and dibutyl maleate were the same or lower compared to a low sulfur fuel (15 ppm sulfur) even under engine operating conditions designed to lower engine-out NOx emissions.
Technical Paper

Evaluation of a High Speed, High Resolution Gas Chromatography Instrument for Exhaust Hydrocarbon Speciation

2005-04-11
2005-01-0683
The ozone forming potential (OFP) and specific reactivity (SR) of tailpipe exhaust are among the factors that determine the environmental impact of a motor vehicle. OFP and SR measurements require a lengthy determination of about 190 non-methane hydrocarbon species. A rapid gas chromatography (GC) instrument has been constructed to separate both the light (C2 - C4) and the midrange (C5 - C12) hydrocarbons in less than 10 minutes. The limit of detection is about 0.002 parts per million carbon (ppmC). Thirty exhaust samples from natural gas vehicles (NGV's) were analyzed to compare the rapid GC method with the standard GC method, which required 40-minute analyses on two different instruments. In general, evaluation of the commercial prototype from Separation Systems, Inc., indicates that a high speed, high resolution gas chromatograph can meet the need for fast, efficient exhaust hydrocarbon speciation.
Technical Paper

Streamlining Chassis Tuning for Chevrolet and GMC Trucks and Vans

2005-04-11
2005-01-0406
This paper describes some methods for greatly reducing or possibly eliminating subjective tuning of suspension parts for ride and handling. Laptop computers can now be used in the vehicle to guide the tuning process. The same tools can be used to select solutions that reduce sensitivity to production and environmental variations. OBJECTIVE Reduce or eliminate time required for tuning of suspension parts for ride characteristics. Improve the robustness of ride performance relative to variations in ambient temperature and production tolerances. PROBLEM REQUIRING SOLUTION AND METHOD OF APPROACH Traditional development programs for new vehicles include time-consuming subjective ride evaluations. One example is shock absorber tuning. Even if sophisticated models define force-velocity curves, numerous hardware iterations are needed to find valvings that will reproduce the curves. Many evaluation rides are needed to modify the valvings to meet performance targets.
Technical Paper

Multivariate Robust Design

2005-04-11
2005-01-1213
In a complex system, large numbers of design variables and responses are involved in performance analysis. Relationships between design variables and individual responses can be complex, and the outcomes are often competing. In addition, noise from manufacturing processes, environment, and customer misusage causes variation in performance. The proposed method utilizes the two-step optimization process from robust design and performs the optimization on multiple responses using Hotelling's T2 statistic. The application of the T2-statistic allows the use of univariate tools in multiple objective problems. Furthermore, the decomposition of T20 into a location component, T2M and a dispersion component, T2D substitutes a complex multivariate optimization process with the simpler two-step procedure. Finally, using information from the experiment, a multivariate process capability estimates for the design can be made prior to hardware fabrication.
Technical Paper

Life Cycle Analysis Framework; A Comparison of HFC-134a, HFC-134a Enhanced, HFC-152a, R744, R744 Enhanced, and R290 Automotive Refrigerant Systems

2005-04-11
2005-01-1511
The goal of this study is to assess the total Life Cycle Global Warming Impact of the current HFC-134a (R134a) refrigeration system and compare it with the effect of proposed alternatives, HFC-134a Enhanced, HFC-152 (R152a), R744, R744 Enhanced and R290, based on life cycle analysis (LCA). The enhanced systems include control strategies to elevate the compressor suction pressure as the evaporator load is reduced. The hydrofluorocarbons HFC-134a and HFC-152a are greenhouse gases (GHGs) and are subject to the Kyoto Protocol timetables, which when the treaty takes effect will require participating developed countries to reduce their overall CO2 equivalent emissions of six GHGs by at least 5% by 2012 from 1990 levels.
Technical Paper

A Five-Speed Starting Clutch Automatic Transmission Vehicle

2003-03-03
2003-01-0248
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.
Technical Paper

Fuel Economy and Performance Potential of a Five-Speed 4T60-E Starting Clutch Automatic Transmission Vehicle

2003-03-03
2003-01-0246
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.
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