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Technical Paper

Air Charge Estimation in Camless Engines

2001-03-05
2001-01-0581
An electromechanically driven valve train offers unprecedented flexibility to optimize engine operation for each speed load point individually. One of the main benefits is the increased fuel economy resulting from unthrottled operation. The absence of a restriction at the entrance of the intake manifold leads to wave propagation in the intake system and makes a direct measurement of air flow with a hot wire air meter unreliable. To deliver the right amount of fuel for a desired air-fuel ratio, we therefore need an open loop estimate of the air flow based on measureable or commanded signals or quantities. This paper investigates various expressions for air charge in camless engines based on quasi-static assumptions for heat transfer and pressure.
Technical Paper

Overall Results: Phase I Ad Hoc Diesel Fuel Test Program

2001-03-05
2001-01-0151
The future of diesel-engine-powered passenger cars and light-duty vehicles in the United States depends on their ability to meet Federal Tier 2 and California LEV2 tailpipe emission standards. The experimental purpose of this work was to examine the potential role of fuels; specifically, to determine the sensitivity of engine-out NOx and particulate matter (PM) to gross changes in fuel formulation. The fuels studied were a market-average California baseline fuel and three advanced low sulfur fuels (<2 ppm). The advanced fuels were a low-sulfur-highly-hydrocracked diesel (LSHC), a neat (100%) Fischer-Tropsch (FT100) and 15% DMM (dimethoxy methane) blended into LSHC (DMM15). The fuels were tested on modern, turbocharged, common-rail, direct-injection diesel engines at DaimlerChrysler, Ford and General Motors. The engines were tested at five speed/load conditions with injection timing set to minimize fuel consumption.
Technical Paper

Evaluation of Idle Combustion Stability Using Flywheel Acceleration

2003-05-05
2003-01-1673
Vehicle idle quality has become an increasing quality concern for car manufacturers because of its impact on customer satisfaction. To get better fuel economy the overall trend is to reduce idle speed at both drive and neutral idles. This typically has adverse impact on vehicle idle quality. Lowering the idle rpm generally degrades the engine combustion stability and also makes the engine driving forces more likely to align with vehicle sensitivities (Powertrain rigid body modes, body modes, etc.). To better understand the contribution to the idle quality from different factors and carry out well-planned improvement measures, a quick and easy way to assess engine combustion stability is required.
Technical Paper

Simulation of Hybrid Electric Vehicles with Emphasis on Fuel Economy Estimation

1998-02-23
981132
This paper describes SHEV, a computer program created to simulate hybrid electric vehicles. SHEV employs the time-stepping technique in order to evaluate energy flow in series hybrids, and makes use of a unique method in order to speed up the fuel economy estimation. This estimation method is a refinement of the “state of charge matching” method and is explained in detail. The graphic user interfaces employed in SHEV make it easy to use and give it a look similar to regular Windows‚ applications. This paper also gives some examples of the screens created by the program, depicts its main flowchart, and describes a battery model optimized for this application.
Technical Paper

Stratified-Charge Engine Fuel Economy and Emission Characteristics

1998-10-19
982704
Data from two engines with distinct stratified-charge combustion systems are presented. One uses an air-forced injection system with a bowl-in-piston combustion chamber. The other is a liquid-only, high-pressure injection system which uses fluid dynamics coupled with a shaped piston to achieve stratification. The fuel economy and emission characteristics were very similar despite significant hardware differences. The contributions of indicated thermal efficiency, mechanical friction, and pumping work to fuel economy are investigated to elucidate where the efficiency gains exist and in which categories further improvements are possible. Emissions patterns and combustion phasing characteristics of stratified-charge combustion are also discussed.
Technical Paper

Sequence VIB Engine Test for Evaluation of Fuel Efficiency of Engine Oils - Part II. Stage Selection and Time Factor Determination

1998-10-19
982624
The newly developed Sequence VIB engine dynamometer test for measuring the ability of engine oils to improve engine fuel efficiency was designed as an improvement on its predecessor, the Sequence VIA test. The Sequence VIB test features an additional, extended oil aging to correspond to aging of engine oils in certification vehicles and in customer use, and a new set of boundary/mixed and hydrodynamic lubrication stages to better represent a wider range of engines. Five fuel economy measurement stages were chosen for the Sequence VIB test from a larger set of prototype stages, based on extensive friction modeling of engines, analysis of Sequence VIA data on reference oils, and operational considerations. Time factors for these stages were derived based on a mini-mapping of engines considering engine operating conditions in the Metro/Highway Federal fuel economy test procedure (FTP M/H) and the estimated market volume of each engine-vehicle.
Technical Paper

Sequence VIB Engine Test for Evaluation of Fuel Efficiency of Engine Oils - Part I. Aging Procedure for Determination of Fuel Efficiency Retention

1998-10-19
982623
Development of the Sequence VIB dynamometer engine test procedure for evaluating the fuel efficiency benefits of engine oils has recently been completed. This test was designed as an improvement over its predecessor, the Sequence VIA test. It evaluates fuel economy using a range of boundary/mixed and hydrodynamic lubrication stages selected to better represent a wider range of engines. In addition to determining “fresh oil” fuel economy, the new test determines fuel efficiency retention after a second oil aging stage that corresponds to 6437 - 9674 km (4,000 - 6,000 miles) of pre-certification aging of engine oils in vehicles and is representative of customer use. This paper describes the selection of aging conditions and length.
Technical Paper

Engine and Aftertreatment Modeling for Gasoline Direct Injection

1998-10-19
982596
Engine and aftertreatment models have been developed in support of gasoline direct injection (GDI) engine development and aftertreatment system design. A brief overview of the engine models that were used to project emissions and fuel economy performance for the GDI engine is presented. Additionally, the construction and validation of a NOx trap aftertreatment model is described in considerable detail. The insights and increased understanding which have been gained regarding the trade-offs between engine out emission targets, aftertreatment performance, and emission constrained fuel economy benefits for direct injection gasoline engines are reviewed and discussed.
Technical Paper

Life Cycle Assessment of a Transmission Case: Magnesium vs. Aluminum

1998-02-23
980470
This paper describes a Life Cycle Assessment (LCA) done to evaluate the relative environmental performance of magnesium (Mg) and aluminum (Al) automatic transmission cases. Magnesium is considered a lighter weight substitute for aluminum in this application. Light weighting of vehicles increases fuel economy and is an important vehicle design metric. The objective of this LCA is to quantify energy and other environmental trade-offs associated with each alternative for material production, manufacturing, use, and end-of-life management stages. Key features of the inventory modeling and the data collection and analysis methods are included in this paper along with life cycle inventory profiles of aluminum and magnesium alternatives. The life cycle inventory (LCI) was interpreted using a set of environmental metrics and areas needing further research were identified. A qualitative cost assessment was done in conjunction with this LCA to highlight potential cost drivers.
Technical Paper

Parametric Simulation of Significant Design and Operating Alternatives Affecting the Fuel Economy and Emissions of Spark-Ignited Engines

1978-02-01
780943
A fundamental thermodynamic model of the complete spark-ignited, homogeneous charge engine cycle has been used in several parametric analyses to predict the effects of engine design and operating alternatives on fuel consumption and emissions of NOx and unburned hydrocarbons (HC). The simulation includes sub-models for wall heat transfer, NOx and HC emissions, and the engine breathing processes. This work demonstrates the power and utility of a comprehensive engine simulation by presenting several independent parametric studies that were carried out in response to genuine engine design and/or operating strategy questions. Included in this compilation are the effects of cycle heat loss, exhaust port heat loss, combustion duration, and charge dilution (EGR and/or lean air-fuel ratio). In addition, the influence of the design variables associated with bore-stroke ratio, intake and exhaust valve lift, and cam timing are considered.
Technical Paper

Turbocharging Ford's 2.3 Liter Spark Ignition Engine

1979-02-01
790312
Ford's new 2.3 Litre I-4 Turbocharged Engine and Powertrain was specifically developed to match the new 1979 Mustang/ Capri. This engine/vehicle combination was developed to provide the customer excellent vehicle performance, good fuel economy and driveability. Extensive vehicle and dynamometer work was done to match the turbocharger to the engine and optimize in-vehicle mid-range to high end performance. The relatively high compression ratio (9.0:1) was retained from the naturally aspirated engine to preserve low end manual transmission vehicle performance before turbocharger boost. Revisions to basic engine components and structures to insure durability will be discussed.
Technical Paper

The Influence of Cooling System Variables

1978-02-01
780595
A vehicle fleet test has been conducted to determine if octane advantages due to selected cooling system variables persist with stabilized deposits. The variables tested were reduced coolant temperatures, a direct substitution of aluminum for the iron cylinder head and an aluminum head with Unique Cooling. Octane requirements, octane requirement increase (ORI), emissions and fuel economy results are presented and discussed. Engine tests to determine the sensitivity of octane to independently controlled engine temperatures confirmed the primary dependence upon coolant temperature. Additional tests identified some of the variables which cause octane differences among the cylinders of one engine and between engine families.
Technical Paper

50,000 Mile Vehicle Road Test of Three-Way and NOx Reduction Catalyst Systems

1978-02-01
780608
The performance of three way and NOx catalysts was evaluated on vehicles utilizing non-feedback fuel control and electronic feedback fuel control. The vehicles accumulated 80,450 km (50,000 miles) using fuels representing the extremes in hydrogen-carbon ratio available for commercial use. Feedback carburetion compared to non-feedback carburetion improved highway fuel economy by about 0.4 km/l (1 mpg) and reduced deterioration of NOx with mileage accumulation. NOx emissions were higher with the low H/C fuel in the three way catalyst system; feedback reduced the fuel effect on NOx in these cars by improving conversion efficiency with the low H/C fuel. Feedback had no measureable effect on HC and CO catalyst efficiency. Hydrocarbon emissions were lower with the low H/C fuel in all cars. Unleaded gasoline octane improver, MMT, at 0.015g Mn/l (0.06 g/gal) increased tailpipe hydrocarbon emissions by 0.05 g/km (0.08 g/mile).
Technical Paper

Control of Gear Ratio and Slip in Continuously Variable Transmissions: A Model Predictive Control Approach

2017-03-28
2017-01-1104
The efficiency of power transmission through a Van Doorne type Continuously Variable Transmission (CVT) can be improved by allowing a small amount of relative slip between the engine and driveline side pulleys. However, excessive slip must be avoided to prevent transmission wear and damage. To enable fuel economy improvements without compromising drivability, a CVT control system must ensure accurate tracking of the gear ratio set-point while satisfying pointwise-in-time constraints on the slip, enforcing limits on the pulley forces, and counteracting driveline side and engine side disturbances. In this paper, the CVT control problem is approached from the perspective of Model Predictive Control (MPC). To develop an MPC controller, a low order nonlinear model of the CVT is established. This model is linearized at a selected operating point, and the resulting linear model is extended with extra states to ensure zero steady-state error when tracking constant set-points.
Technical Paper

Ting Noise Generation in Automotive Applications

2017-03-28
2017-01-1121
Automobile customers are looking for higher performance and quieter comfortable rides. The driveline of a vehicle can be a substantial source of NVH issues. This paper provides an understanding of a driveline noise issue which can affect any variant of driveline architecture (FWD, AWD, RWD and 4X4). This metallic noise is mostly present during the take-off and appropriately termed as ting noise. This noise was not prevalent in the past. For higher fuel economy, OEMs started integrating several components for lighter subsystems. This in effect made the system more sensitive to the excitation. At present the issue is addressed by adding a ting washer in the interface of the wheel hub bearings and the halfshafts. This paper explains the physics behind the excitation and defines the parameters that influence the excitation. The halfshaft and the wheel hub are assembled with a specified hub nut torque.
Technical Paper

Factors Influencing Liquid over Air Cooling of High Voltage Battery Packs in an Electrified Vehicle

2017-03-28
2017-01-1171
Automotive vehicle manufactures are implementing electrification technologies in many vehicle line-ups to improve fuel economy and meet emission standards. As a part of electrification, High Voltage (HV) battery packs are integrated alongside internal combustion engines. Recent generation HV batteries allow extensive power usage, by allowing greater charge and discharge currents and broader State of Charge (SOC) ranges. Heat generated during the charge-discharge cycles must be managed effectively to maintain battery cell performance and life. This situation requires a cooling system with higher efficiency than earlier generation electrified powertrains. There are multiple thermal solutions for cooling HV battery packs including forced air, liquid, direct refrigerant, and passive cooling. The most common types of HV battery pack cooling, for production vehicles, are air cooled using cabin interior air and liquid cooled using powertrain cooling systems.
Technical Paper

Improving Range Robustness: Heat Pump Value for Plug-In Electric Vehicles

2017-03-28
2017-01-1161
Integration of a new, complex technology which crosses powertrain system boundaries (and thereby involves multiple organizations), at the optimum cost-attribute balance, is a complex task. An example of such a technology is a Vapor-Compression Heat Pump (VCHP) system. A VCHP system uses a vapor-compression refrigeration cycle to ‘pump’ heat from ambient into the cabin. This system can be used to supplement or replace other less efficient heating systems (e.g. engine, LV-PTC air heater, HV-PTC coolant heater, etc.) - which will improve fuel economy. The use of a heat pump system impacts several primary attributes, including heating, cooling, fuel economy, and electric range. These attributes must be balanced in an ideal fashion against the substantial expense, if a VCHP is to be selected for use in a particular vehicle. This paper walks through the value equation for the VCHP from start to end, addressing potential concerns and opportunities.
Technical Paper

Estimation of the Effects of Auxiliary Electrical Loads on Hybrid Electric Vehicle Fuel Economy

2017-03-28
2017-01-1155
In recent years the fuel efficiency of modern hybrid electric vehicle (HEV) powertrains has progressed to a point where low voltage auxiliary electrical system loads have a pronounced impact on fuel economy (FE). While improving the energy consumption of an individual component may result in minor improvements, the collective optimization of such loads across a complete vehicle system can result in meaningful FE gains. Traditional methods using chassis dynamometer testing alone to quantify the impact of a specific auxiliary load can lead to issues where signal state changes are too small for accurate detection. This presents difficulties in accurately predicting the influence of such loads on FE of next-generation electrified vehicles under development. This paper describes a newly developed method where dynamometer test results are combined with computer simulation analyses to create a practical technique for assessing the impact of small changes in auxiliary load energy consumption.
Technical Paper

Hybrid Powertrain Operation Optimization Considering Cross Attribute Performance Metrics

2017-03-28
2017-01-1145
Hybrid electric vehicles are continuously challenged to meet cross attribute performance while minimizing energy usage and component cost in a very competitive automotive market. As electrified vehicles become more mainstream in the marketplace, hybrid customers are expecting more attribute refinement in combination with the enhanced fuel economy benefits. Minimizing fuel consumption, which tends to drive hybrid powertrain engines to operate under lugging type calibrations, traditionally challenge noise, vibration, and harshness (NVH) metrics. Balancing the design space to satisfy the cost metrics, energy efficiency, noise and vibration & drivability under the hybrid engine lugging conditions can be optimized through the use of multiple CAE tools. This paper describes how achieving NVH metrics can put undesirable boundaries on Powertrain Operation which could affect other performance attributes.
Technical Paper

Piecewise 1st Order Hydraulic Actuator Model for Transient Transmission Simulations

2017-03-28
2017-01-1140
A transmission system model is developed at various complexities in order to capture the transient behaviors in drivability and fuel economy simulations. A large number of model parameters bring more degree of freedom to correlate with vehicular test data. However, in practice, it requires extensive time and effort to tune the parameters to satisfy the model performance requirements. Among the transmission model, a hydraulic clutch actuator plays a critical role in transient shift simulations. It is particularly difficult to tune the actuator model when it is over-parameterized. Therefore, it is of great importance to develop a hydraulic actuator model that is easy to adjust while retaining sufficient complexity for replicating realistic transient behaviors. This paper describes a systematic approach for reducing the hydraulic actuator model into a piecewise 1st order representation based on piston movement.
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