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Driveline clunk during static engagements on vehicles with automatic transmissions is a phenomenon that can adversely affect customer perception of vehicle quality. Tuning a vehicle's static engagement characteristics for superior shift quality demands a good understanding of the inputs to the vehicle driveline, the response of the driveline, and the sensitivity of the vehicle to such inputs. This paper describes a case study conducted on a rear wheel drive vehicle with an automatic transmission and independent rear suspension to understand and reduce the severity of driveline engagement clunk to acceptable levels. Finally, the results of the study are used to develop guidelines for such vehicles to ensure superior shift quality during static engagements.

The sound quality and performance of an automotive engine are both significantly influenced by the “air-to-air” system, i.e., the intake system, the exhaust system, and the engine gas dynamics. Only a full systems approach can result in an optimized air-to-air system, which fulfills engine performance requirements, overall sound pressure level targets for airborne vehicle noise, as well as sound quality demands. This paper describes an approach, which considers the intake system, engine, and exhaust system within one CAE model that can be utilized for engine performance calculations as well as acoustic simulations. Examples comparing simulated and measured sound are discussed. Finally, the simulated sound (e.g., at the tailpipe of the exhaust system) is combined with an interior noise simulation technique to evaluate its influence inside the vehicle's interior.

The shifter lever is one of the main customer contact points in the vehicle. Vibration levels at this contact point have an effect on perceived vehicle quality. For this reason, shifter lever vibration and the corresponding transfer paths from the transmission to the shifter lever need to be considered during vehicle development. On a recent program, experimental measurements identified the shifter cable to be a significant transfer path for shifter lever vibration. An integrated Computer Aided Engineering (CAE) and experimental effort was undertaken to model and optimize the shifter lever and cable assembly for reduced vibration. Experimental data was used to better understand the vibration phenomenon, set boundary conditions for the CAE modeling, and for correlation. The CAE model contains the shifter lever assembly and a detailed cable assembly model.

Based on the TurboDISI engine presented earlier [1], [2], a new Spray Guided Turbo (SGT) concept with enhanced engine performance was developed. The turbocharged engine was modified towards utilizing a spray-guided combustion system with a central piezo injector location. Higher specific power and torque levels were achieved by applying specific design and cooling solutions. The engine was developed utilizing a state-of-the-art newly developed charge motion design (CMD) process in combination with single cylinder investigations. The engine control unit has a modular basis and is realized using rapid prototyping hardware. Additional fuel consumption potentials can be achieved with high load EGR, use of alternative fuels and a hybrid powertrain. The CO2 targets of the EU (120 g/km by 2012 in the NEDC) can be obtained with a mid-size vehicle applying the technologies presented within this paper.

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions. Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined.

With rising gasoline prices in the US the need for increasingly fuel efficient powertrain concepts has never been more critical. Evaluation of the market on the other hand shows that the vehicle-buying consumer is unwilling to compromise engine power output for this needed fuel efficiency. Boosted, direct-injected gasoline engines with high specific output and low end torque seem to be the most logical path to satisfying both good part load fuel economy and generous power and torque characteristics. Turbo lag and subsequent lack of torque during transient acceleration (with low initial engine speeds) are characteristics of current turbocharged gasoline engines. These phenomena have prevented successful penetration of these boosted powertrains into the marketplace. Larger displacement, naturally aspirated gasoline engines have been the preferred choice.

The combustion process in an IC engine is of significant importance for its noise and vibration characteristics in the vehicle. Describing the combustion process with thermodynamic metrics typically demands extensive instrumentation of the engine to obtain the cylinder pressure from the combustion chamber. This time consuming task often requires, that the engine be removed from the vehicle, instrumented with pressure transducers, and then either reinstalled in the vehicle and tested or installed in a test cell and evaluated. This paper describes a new relatively simple approach towards examining important combustion parameters. The technique is based on statistical analysis of the crankshaft's speed fluctuation. This approach requires relatively simple instrumentation of the engine and is therefore more applicable for vehicle level investigations.

Increasing fuel costs, the need to reduce dependence on foreign oil as well as the high efficiency and the desire for superior durability have caused the diesel engine to again become a prime target for light-duty vehicle applications in the United States. In support of this the U.S. Department of Energy (DOE) has engaged in a test project under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity to develop a passenger car with the capability to demonstrate compliance with Tier 2 Bin 5 emission targets with a fresh emission control catalyst system. In order to achieve this goal, a prototype engine was installed in a passenger car and optimized to provide the lowest practical level of engine-out emissions.

The aggressive reduction of future diesel engine NOx emission limits forces the heavy- and light-duty diesel engine manufacturers to develop means to comply with stringent legislation. As a result, different exhaust emission control technologies applicable to NOx have been the subject of many investigations. One of these systems is the NOx adsorber catalyst, which has shown high NOx conversion rates during previous investigations with acceptable fuel consumption penalties. In addition, the NOx adsorber catalyst does not require a secondary on-board reductant. However, the NOx adsorber catalyst also represents the most sulfur sensitive emissions control device currently under investigation for advanced NOx control. To remove the sulfur introduced into the system through the diesel fuel and stored on the catalyst sites during operation, specific regeneration strategies and boundary conditions were investigated and developed.

The U.S. Tier 2 emission regulations require sophisticated exhaust aftertreatment technologies for diesel engines. One of the projects under the U.S. Department of Energy's (DOE's) Advanced Petroleum Based Fuels - Diesel Emission Controls (APBF-DEC) activity focused on the development of a light-duty passenger car with an integrated NOx (oxides of nitrogen) adsorber catalyst (NAC) and diesel particle filter (DPF) technology. Vehicle emissions tests on this platform showed the great potential of the system, achieving the Tier 2 Bin 5 emission standards with new, but degreened emission control systems. The platform development and control strategies for this project were presented in 2004-01-0581 [1]. The main disadvantage of the NOx adsorber technology is its susceptibility to sulfur poisoning. The fuel- and lubrication oil-borne sulfur is converted into sulfur dioxide (SO2) in the combustion process and is adsorbed by the active sites of the NAC.

The introduction of the new emission standards in 2002/04 for heavy-duty diesel engines requires a substantial reduction of the NOx emissions while the particulate emissions remain on a constant level. The application of cooled EGR appears to be the most common approach in order to achieve the required target, although other means such as advanced combustion systems and the application of emission control devices to reduce NOx emissions have to be taken into account as well. The purpose of this study is to investigate the potential of such alternative solutions in comparison with cooled EGR to meet the upcoming emission standards.

The HSDI Diesel engine contributes substantially to the decrease of fleet fuel consumption thus to the reduction of CO2 emissions. This results in the rising market acceptance which is supported by desirable driving performance as well as greatly improved NVH behavior. In addition to the above mentioned requirements on driving performance, fuel economy and NVH behavior, continuously increasing demands on emissions performance have to be met. From today's view the Diesel particulate trap presents a safe technology to achieve the required reduction of the particle emission of more than 95%. However, according to today's knowledge a further, substantial NOx engine-out emission reduction for the Diesel engine is counteracts with the other goal of reduced fuel consumption. To comply with current and future emission standards, Diesel engines will require DeNOx technologies.

Internal combustion engine noise is primarily composed of combustion and mechanical noise shares. Mechanical noise contributions in engines have increased relevance at low load conditions when combustion related noise is not significant. Current literature on mechanical noise in engines includes: piston pin ticking, piston secondary motion, and valvetrain impacts. A mechanical noise source from excitation of piston tertiary motion is described here in the form of a case study on an engine exhibiting a cold start “clatter” noise. Targeted experimental measurements were initially used to rule out potential mechanisms such as impacts resulting from piston pin ticking and piston secondary motion. Experimental modification studies and piston load and kinematics modeling led to discovery of instability of the piston which is understood to excite tertiary motion of the piston and result in impulsive “clatter” noise under certain low load/speed conditions.

A customer's perception of vehicle quality very closely parallels the noise vibration and harshness (NVH) characteristics of the vehicle. Consequently, automotive manufacturers are investing significant resources into optimizing the NVH performance of their vehicles. Automatic transmission shift quality is one of a number of attributes where NVH optimization is critical towards providing customers with a pleasant driving experience. This paper addresses various aspects of understanding, quantifying and optimizing a vehicle's shift quality characteristics. Following an introductory treatment of automatic transmission planetary gear systems, the interaction between the engine/transmission system during shifts is summarized. Various shift quality metrics used to quantify a vehicle's response and its sensitivity to transient inputs are provided. Approaches to manage the engine torque output during the shifts are discussed.

NVH refinement is an important aspect of the powertrain development process. Powertrain NVH refinement is influenced by overall sound levels as well as sound quality. The sound quality and hence the level of powertrain NVH refinement can be negatively affected by the presence of excessive impulsive noise. This paper describes a process used to develop an understanding of impulsive powertrain noise. The paper begins with an introductory discussion of various sources of impulsive noise in an automotive powertrain. Following this, the paper outlines a process for identifying the source of the impulsive powertrain noise using examples from case studies. The remainder of the paper focuses on certain examples of impulsive noise such as Diesel knocking noise, injector ticking, impulsive cranktrain noise, and gear rattle. For these examples, the development of key objective metrics, optimization measures, and improvement potential are examined.

Optimization of the interface between the powerplant and vehicle frame/body is critical to obtaining superior interior structureborne noise and vibration characteristics in the vehicle. This paper demonstrates the combination of new and existing simulation/experimental methodologies for powerplant integration, including results from case studies. Multi-body simulation based methodologies are used to optimize the location, number, and type of powerplant mounts on a vehicle, taking into account the input forcing from the engine and frequency-dependent mount properties. Upon obtaining the first prototype vehicle, a procedure to evaluate the effectiveness of the powerplant mounts using a vibrational power flow technique, is described. The influence of mount bracket resonances on interior vehicle sound is shown and a new procedure to optimize mount brackets, provided.

Customer requirements for quiet and more comfortable vehicles have steadily increased. Requirements for lightweight vehicle designs and the need for more fuel efficient engines are often contradictory to the customer expectations for NVH refinement. The driveline can be a significant source of NVH issues in the vehicle. The increasing complexity of modern driveline systems as well as the existence of several variants in the driveline architecture (front wheel, rear wheel and four-wheel/all-wheel drive, automatic-, manual-, automatic-shifted manual transmission, etc.) can make the driveline integration task very challenging. Due to the multitude of driveline components and potential driveline excitations sources, several driveline-related noise and vibration problems within different frequency ranges have to be understood and controlled to ensure a well refined vehicle.

In a gasoline engine, the unswept in-cylinder residual gas and introduction of external EGR is one of the important means of controlling engine raw NOx emissions and improving part load fuel economy via reduction of pumping losses. Since the trapped in-cylinder Residual Gas Fraction (RGF, comprised of both internal, and external) significantly affects the combustion process, on-line diagnosis and monitoring of in-cylinder RGF is very important to the understanding of the in-cylinder dilution condition. This is critical during the combustion system development testing and calibration processes. However, on-line measurement of in-cylinder RGF is difficult and requires an expensive exhaust gas analyzer, making it impractical for every application. Other existing methods, based on measured intake and exhaust pressures (steady state or dynamic traces) to calculate gas mass flowrate across the cylinder ports, provide a fast and economical solution to this problem.