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General Motors' 3.6L DOHC 4V V6 engine has been upgraded to provide substantial improvements in performance, fuel economy, and emissions for the 2008 model year Cadillac CTS and STS. The fundamental change was a switch from traditional manifold-port fuel injection (MPFI) to spark ignition direct injection (SIDI). Additional modifications include enhanced cylinder head and intake manifold air flow capacities, optimized camshaft profiles, and increased compression ratio. The SIDI fuel system presented the greatest opportunities for system development and optimization in order to maximize improvements in performance, fuel economy, and emissions. In particular, the injector flow rate, orifice geometry, and spray pattern were selected to provide the optimum balance of high power and torque, low fuel consumption, stable combustion, low smoke emissions, and robust tolerance to injector plugging.

The work presented in this paper outlines the design and development of a compliant sprocket for balancer drives in an effort to reduce the noise levels related to chain-sprocket meshing. An experimental observation of a severe chain noise around a resonant engine speed with the Dual-Mass Flywheel (DMF) and standard build solid (fixed) balancer drive sprocket. Torsional oscillation at the crankshaft nose at full load is induced by uneven running of crankshaft with a dual-mass flywheel system. This results in an increase of the undesirable impact noise caused by the meshing between the chain-links and the engagement/disengagement regions of sprockets, and the clatter noise from the interaction between the vibrating chain and the guides. This paper evaluates and discusses the benefits that the compliant sprocket design provided. A multi-body dynamics system (MBS) model of the balancer chain drive has been developed, validated, and used to investigate the chain noise.

This work provides an effective engineering method of building a part-load engine simulation model from a wide-open throttle (WOT) engine model and available dynamometer data. It shows how to perform part-load engine simulation using optimizer for targeted manifold absolute air pressure (MAP) on a basic matrix of engine speed and MAP. Key combustion parameters were estimated to cover the entire part-load region based on affordable assumptions and limitations. Engine rubbing friction and pumping friction were combined to compare against the motoring torque. The emission data from GM dynamometer laboratory were used to compare against engine simulation results after attaching the RLT sensor to record emission data in the engine simulation model.

The new regulations to reduce emissions have resulted in the development of new techniques to maintain or enhance competitive performance. A requirement for the manifold is to help meet the reduction in cold start emissions, particularly during the transient conditions from start to 100 seconds following the Federal Test Procedures for vehicle emissions. Finite element computer models were developed to predict inner and outer wall temperatures, and to determine structural soundness. Tests were performed to assure that noise levels were minimized. Dynamometer lab and field tests were performed to verify that the manifold would meet the design requirements. From the results of these tests and analyses, modifications were made to the weld and manufacturing techniques to improve product life and reduce noise. Dual wall manifolds have proven durability to meet high exhaust gas temperatures up to 1650°F (900°C), while meeting the performance, noise, and weight reduction goals.

Development and integration of the cooling system for an automotive vehicle requires a balancing act between several performance and styling objectives. The cooling system needs to provide sufficient air for heat rejection with minimal impact on the aerodynamic drag, styling requirements and other criteria. An optimization of various design parameters is needed to develop a design to meet these objectives in a short amount of time. Increase in the accuracy of the numerical predictions and reduction in the turn-around time has made it possible for Computational Fluid Dynamics (CFD) to be used early in the design phase of the vehicle development. This study shows application of the CFD for robust design of the engine cooling system.

During a new engine development program, or the adaptation of an existing engine to new platform architectures, testing is performed to determine the durability characteristics of the basic engine structure. Such testing helps to uncover High Cycle durability-related issues that can occur at the bulkhead walls as well as cap bolt thread areas in an aluminum cylinder block. When this class of issues occurs, an Elastohydrodynamic (EHD) bearing simulation capability is required. In this study, analytical methods and processes are established to calculate the localized distributed load on the bulkhead. The complexity in performing a system analysis is due to the nonlinear coupling between the bearing hydrodynamic pressure distribution and the crankshaft and block deformation. A system approach for studying the crankshaft-block interaction requires a crankshaft flexible body dynamics model, an engine block assembly flexible body dynamics model and a main bearing lubrication model.

This paper presents a comprehensive Matlab/Simulink-based framework that affords a rapid, systematic, and efficient engine control system development process including automated code generation. The proposed framework hinges on three essential pillars: 1 ) an accurate model for the target engine, 2) a toolset for systematic control design, and 3) a modular system architecture that enhances feature reusability and rapid algorithm deployment. The proposed framework promotes systematic model-based algorithm development and validation in virtual reality. Within this context, the framework affords integration and evaluation of the entire control system at an early development stage, seamless transitions across inherently incompatible product development stages, and rapid code generation for production target hardware.

The fierce competition and shifting consumer demands require automotive companies to be more efficient in all aspects of vehicle development and specifically in the area of embedded engine control system development. In order to reduce development cost, shorten time-to-market, and meet more stringent emission regulations without sacrificing quality, the increasingly complex control algorithms must be transportable and reusable. Within an efficient development process it is necessary that the algorithms can be seamlessly moved throughout different development stages and that they can be easily reused for different applications. In this paper, we propose a flexible engine control architecture that greatly boosts development efficiency.

Power-hop is a self-excited and potential locally unstable torsional vibration of a vehicle's driveline, caused by stick and slip of the tire. It is especially prevalent in high-powered cars and trucks, under heavy acceleration. Torque arms have been used to reduce power-hop for many solid axle suspension vehicles, mostly trucks and old rear wheel drive sports cars. It has long been known that the shortest torque arm easily reduces power-hop, but will increase hop under braking (braking-hop). The fundamental mechanism of torque arm effects on solid axle suspension vehicles, however, has not yet been fully explained. This study explains the stability of solid axle, torque arm suspension vehicles under heavy acceleration and braking. Analytical techniques utilize conventional linear analysis and a non-linear coupling force in a 4 degree of freedom dynamic model.

When pickup trucks are driven on concrete paved freeways, freeway hop shake is a major complaint. Freeway hop shake occurs when the vehicle passes over the concrete joints of the freeway which impose in-phase harmonic road inputs. These road inputs excite vehicle modes that degrade ride comfort. The worst shake level occurs when the vehicle speed is such that the road input excites the vehicle 1st bending mode and/or the rear wheel hop mode. The hop and bending mode are very close in frequency. This phenomenon is called freeway hop shake. Automotive manufacturers are searching for ways to mitigate freeway hop shake. There are several ways to reduce the shake amplitude. This paper documents a new approach using hydraulic body mounts to reduce the shake. A full vehicle analytical model was used to determine the root cause of the freeway hop shake.

Homogeneous Charge Compression Ignition (HCCI) combustion shows a high potential of reducing both fuel consumption and exhaust gas emissions. Many works have been devoted to extend the HCCI operation range in order to maximize its fuel economy benefit. Among them, fuel injection strategies that use fuel reforming to increase the cylinder charge temperature to facilitate HCCI combustion at low engine loads have been proposed. However, to estimate and control an optimal amount of fuel reforming in the cylinder of an HCCI engine proves to be challenging because the fuel reforming process depends on many engine variables. It is conceivable that the amount of fuel reforming can be estimated since it correlates with the combustion phasing which in turn can be measured using a cylinder pressure sensor.

General Motors recently demonstrated two driveable test vehicles powered by a Homogeneous Charge Compression Ignition (HCCI) engine. HCCI combustion has the potential of a significant fuel economy benefit with reduced after-treatment cost. However, the biggest challenge of realizing HCCI in vehicle applications is controlling the combustion process. Without a direct trigger mechanism for HCCI's flameless combustion, the in-cylinder mixture composition and temperature must be tightly controlled in order to achieve robust HCCI combustion. The control architecture and strategy that was implemented in the demo vehicles is presented in this paper. Both demo vehicles, one with automatic transmission and the other one with manual transmission, are powered by a 2.2-liter HCCI engine that features a central direct-injection system, variable valve lift on both intake and exhaust valves, dual electric camshaft phasers and individual cylinder pressure transducers.

Model-based design is a collection of practices in which a system model is at the center of the development process, from requirements definition and system design to implementation and testing. This approach provides a number of benefits such as reducing development time and cost, improving product quality, and generating a more reliable final product through the use of computer models for system verification and testing. Model-based design is particularly useful in automotive control applications where ease of calibration and reliability are critical parameters. A novel application of the model-based design approach is demonstrated by The Ohio State University (OSU) student team as part of the Challenge X advanced vehicle development competition. In 2008, the team participated in the final year of the competition with a highly refined hybrid-electric vehicle (HEV) that uses a through-the-road parallel architecture.

CFD method for the calculation of flow rate and air re-circulation at vehicle idle conditions is described. A small velocity is added to the ambient airflow in order to improve the numerical stability. The flow rate passing through the heat exchangers is insensitive to the ambient velocity, since the flow rate is largely determined by the fan operation. The air re-circulation, however, is quite sensitive to the ambient air velocity. The ambient velocity of U=-1m/s was found to be the more critical case, and is recommended for the air re-circulation analysis. The CFD analysis can also lead to design modifications improving the air re-circulation.

An optimum combustion chamber was designed for a reverse-tumble wall-controlled gasoline direct-injection engine by systematically optimizing each design element of the combustion system. The optimization was based on fuel-economy, hydrocarbon, combustion-stability and smoke measurements at a 2000 rev/min test-point representation of road-load operating condition. The combustion-chamber design parameters that were optimized in this study included: piston-bowl depth, piston-bowl opening width, piston-bowl-volume ratio, exhaust-side squish height, bowl-lip draft angle, distance between spark-plug electrode and piston-bowl lip, spark-plug-electrode length, and injector spray-cone angle. No attempt was made to optimize the gross engine parameters such as bore and stroke or the intake system, since this study focused on optimizing a reverse-tumble wall-controlled gasoline direct-injection variant of an existing port-fueled injection engine.

Superior fuel economy was achieved for a small-displacement spark-ignition direct-injection (SIDI) engine by optimizing the stratified combustion operation. The optimization was performed using computational analyses and subsequently testing the most promising configurations experimentally. The fuel economy savings are achieved by the use of a multihole injector with novel spray shape, which allows ultra-lean stratification for a wide range of part-load operating conditions without compromising smoke and hydrocarbon emissions. In this regard, a key challenge for wall-controlled SIDI engines is the minimization of wall wetting to prevent smoke, which may require advanced injection timings, while at the same time minimizing hydrocarbon emissions, which may require retarding injection and thereby preventing over-mixing of the fuel vapor.

Full-load operation of a small-displacement spark-ignition direct-injection (SIDI) engine was thoroughly investigated by means of computational analysis and engine measurements. The performance is affected by many different factors, which can be grouped as those pertaining to volumetric efficiency, to mixing and stratification, and to system issues, respectively. Volumetric efficiency is affected by flow losses, tuning and charge cooling. Charge cooling due to spray vaporization is often touted as the most significant benefit of direct-injection on full-load performance. However, if wall wetting occurs, this benefit may be completely negated or even reversed. The fuel-air mixing is strongly affected by the injection timing and characteristics at lower engine speeds, while at higher engine speeds the intake flow dominates the transport of fuel particles and resultant vapor distribution. A higher injector flow rate enhances mixing especially at higher engine speeds.

An intake manifold produced a distinct whistle noise in a vehicle while driving through high torque conditions. The diagnostic tests in a steady air flow test bench helped reveal that the whistle was occurring due to the shear layer instabilities in the air flow over the sump cavity in the intake manifold which acts as an Helmoltz-like resonator. Joint time-frequency domain signal analysis was applied to detect the peak whistle. A sharp radius and a ramp at the upstream edge of the sump cavity reduced the peak whistle sound pressure level from 106dB to 85dB in the air flow bench and made the whistle inaudible in the vehicle. Tolerance study was performed on this geometry to allow manufacturing variations. A test method, using rapid prototype parts, has been developed in order to identify whistles early in the design cycle.

The US Automotive Materials Partnership (USAMP) and the US Department of Energy launched the Magnesium Powertrain Cast Components Project in 2001 to determine the feasibility and desirability of producing a magnesium-intensive engine; a V6 engine with a magnesium block, bedplate, oil pan, and front cover. In 2003 the Project reached mid-point and accomplished a successful Decision Gate Review for entry into the second half (Phase II) of the Project. Three tasks, comprising Phase I were completed: (1) evaluation of the most promising low-cost, creep-resistant magnesium alloys, (2) design of the engine components using the properties of the optimized alloys and creation of cost model to assess the cost/benefit of the magnesium-intensive engine, and (3) identification and prioritization of scientific research areas deemed by the project team to be critical for the use of magnesium in powertrain applications.

Driveline clunk is a phenomenon that can adversely affect customer perception of vehicle quality. Clunk is created by the impact of two driveline components as they oscillate in response to a torque disturbance in the driveline system. This disturbance is typically initiated by a driver controlled engine torque variation, most severely through a throttle or clutch manipulation. This torque variation excites a torsional response from the driveline, manifested by a variety of mechanisms such as resonances of various shafts, housings and axles, clutch oscillations, and gear impacts. Because automotive drivelines are complex systems composed of many rotating components, difficulty arises in identifying the impacts that cause clunk and evaluating the significant parameters that can positively affect these collisions. This paper will describe the application of analysis and test methods in the investigation of clunk in a rear wheel drive, manual transmission vehicle.