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Automotive engines are regularly utilized in the material handling market where LPG is often the primary fuel used. When compared to gasoline, the use of gaseous fuels (LPG and CNG) as well as alcohol based fuels, often result in significant increases in valve seat insert (VSI) and valve face wear. This phenomenon is widely recognized and the engine manufacturer is tasked to identify and incorporate appropriate valvetrain material and design features that can meet the ever increasing life expectations of the end-user. Alternate materials are often developed based on laboratory testing – testing that may not represent real world usage. The ultimate goal of the product engineer is to utilize accelerated lab test procedures that can be correlated to field life and field failure mechanisms, and then select appropriate materials/design features that meet the targeted life requirements.

Recently, a new technology, termed 2-way SCR/DPF by the authors, has been developed by several catalyst suppliers for diesel exhaust emission control. Unlike a conventional emission control system consisting of an SCR catalyst followed by a catalyzed DPF, a wall-flow filter is coated with SCR catalysts for controlling both NOx and PM emissions in a single catalytic converter, thus reducing the overall system volume and cost. In this work, the potential and limitations of the Cu/Zeolite-based SCR/DPF technology for meeting future emission standards were evaluated on a pick-up truck equipped with a prototype light-duty diesel engine.

A fully flexible valve actuation (FFVA) system was developed for a single cylinder research engine to investigate high efficiency clean combustion (HECC) in a diesel engine. The main objectives of the study were to examine the emissions, performance, and combustion characteristics of the engine using late intake valve closing (LIVC) to determine the benefits and limitations of this strategy to meet Tier 2 Bin 5 NOx requirements without after-treatment. The most significant benefit of LIVC is a reduction in particulates due to the longer ignition delay time and a subsequent reduction in local fuel rich combustion zones. More than a 95% reduction in particulates was observed at some operating conditions. Combustion noise was also reduced at low and medium loads due to slower heat release. Although it is difficult to assess the fuel economy benefits of LIVC using a single cylinder engine, LIVC shows the potential to improve the fuel economy through several approaches.

Global environmental and economic concerns regarding increasing fuel consumption and greenhouse gas emission are driving changes to legislative regulations and consumer demand. As regulations become more stringent, advanced engine technologies must be developed and implemented to realize desired benefits. Discrete variable valve lift technology is a targeted means to achieve improved fuel economy in gasoline engines. By limiting intake air flow with an engine valve, as opposed to standard throttling, road-load pumping losses are reduced resulting in improved fuel economy. This paper focuses on the design and development of a switching roller finger follower system which enables two mode discrete variable valve lift on end pivot roller finger follower valvetrains. The system configuration presented includes a four-cylinder passenger car engine with an electro-hydraulic oil control valve, dual feed hydraulic lash adjuster, and switching roller finger follower.

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.

Fully flexible valve actuation (FFVA) system, often referred to as camless valvetrain, employs electronically controlled actuators to drive the intake and/or exhaust valves. This technology enables the engine controller to tailor the valve event according to the engine operating condition in real-time to improve fuel economy, emissions and performance. At GM Research and Development Center, we have developed laboratory electro-hydraulic FFVA systems for single cylinder gasoline engines. The objective of this work is to develop a FFVA system for advanced diesel combustion research. There are three major differences between gasoline and diesel engines in terms of applying the FFVA systems. First, the orientation of the diesel engine valves and the location of the fuel injection system complicate the packaging issue. Second, the clearance between the valves and the piston for diesel engines are extremely small.

Homogeneous Charge Compression Ignition (HCCI) is a combustion concept which has the potential for efficiency comparable to a DI Diesel engine with low NOx and soot emissions. However, HCCI is difficult to control, especially at low speeds and loads. One way to assist with combustion control and to extend operation to low speed and loads is to close the exhaust valve before TDC of the exhaust stroke, trapping and recompressing some of the hot residual. Further advantages can be attained by injecting the fuel into this trapped, recompressed mixture, where chemical reactions occur that improve ignitability of the subsequent combustion cycle. Even further improvement in the subsequent combustion cycle can be achieved by applying a spark, leading to a spark-assisted HCCI combustion concept.

This paper describes the development of a mean value model for a turbocharged diesel engine. The objective is to develop a fast-running engine model with sufficient accuracy over a wide range of operating conditions for efficient evaluation of control algorithms and control strategies. The mean value engine model was derived from a detailed 1D engine model, using the Design of Experiments (DOE) and hybrid Radial Basis Functions (RBF) to approximate the simulation results of the detailed model for cylinder quantities (e.g., the engine volumetric efficiency, the indicated efficiency, and the energy fraction of the exhaust gas). Furthermore, the intake and exhaust systems (especially intake and exhaust manifolds) were completely simplified by lumping flow components together. In addition, to compare with hybrid RBF, neural networks were also used to approximate the simulation results of the detailed engine model.

This paper illustrates a methodology in which complete material-manufacturing process cases for closure panels, reinforcements, and assembly are modeled and compared in order to identify the preferred option for a lightweight closure design. First, process-based cost models are used to predict the cost of lightweighting the closure set of a sample midsized sports utility vehicle (SUV) via material and process substitution. Weight savings are then analyzed using a powertrain simulation to understand the impact of lightweighting on fuel economy. The results are evaluated in the context of production volume and total mass change.

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.

Diesel engines offer better fuel economy compared to their gasoline counterpart, but simultaneous control of NOx and particulates is very challenging. The blended 2-way SCR/DPF is recently emerging as a compact and cost-effective technology to reduce NOx and particulates from diesel exhaust using a single aftertreatment device. By coating SCR catalysts on and inside the walls of the conventional wall-flow filter, the 2-way SCR/DPF eliminates the volume and mass of the conventional SCR device. Compared with the conventional diesel aftertreatment system with a SCR and a DPF, the 2-way SCR/DPF technology offers the potential of significant cost saving and packaging flexibility. In this study, an engine dynamometer test cell was set up to repeatedly load and regenerate the SCR/DPF devices to mimic catalyst aging experienced during periodic high-temperature soot regenerations in the real world.

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.

The issue of thermal-velocity coupling is discussed in the context of vehicle thermal system analysis. Temperature variations in the bulk of the fluids caused by the vehicle engine, cooling, and exhaust system lead to variations in the density of the airflow. The density variations impact the velocity field in two ways: by introducing a driving force term explicitly to account for the effect of buoyancy force and by coupling with the other governing equations. The buoyancy force is crucial for buoyancy driven flows such as vehicle under soak condition. The vehicle thermal system analysis based on the coupled approach leads to a 15°C improvement in the prediction of the underhood thermal environment.

The National Research Council (NRC) recently published a report entitled “Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards” intended to help U.S. policymakers in the formulation of CAFE policy. In the Report, the NRC projects fuel consumption reductions from the application of a wide range of engine, transmission, and vehicle technologies. The Report employs a simple multiplicative method to aggregate the effects of multiple technologies on fuel consumption. In this paper, a basic energy balance calculation is used to examine the NRC results against theoretical limits. Theoretical limits are calculated using measured and simulated breakdowns of system energy losses incurred during vehicle operation on EPA driving cycles. This analysis demonstrates the inherently optimistic results produced by simple aggregation methodologies. Methods for enhancing the accuracy of the technology-aggregation process are proposed.

A new generation Northstar DOHC V8 engine has been developed for a new family of rear-wheel-drive (RWD) Cadillac vehicles. The new longitudinal engine architecture includes strategically selected technologies to enable a higher level of performance and refinement. These technologies include four-cam continuously variable valve timing, low restriction intake and exhaust manifolds and cylinder head ports, a steel crankshaft, electronic throttle control, and close-coupled catalysts. Additional design features beyond those required for RWD include optimized block ribbing, improved coolant flow, and a newly developed lubrication and ventilation system for high-speed operation and high lateral acceleration. This new design results in improved performance over the entire operating range, lower emissions, improved fuel economy, improved operating refinement, and reduced noise/vibration/harshness (NVH).

An advanced variable valve actuation (VVA) system is characterized following end-of-life testing to enable fuel economy solutions for passenger car applications. The system consists of a switching roller finger follower (SRFF) combined with a dual feed hydraulic lash adjuster and an oil control valve that are integrated into a four cylinder gasoline engine. The SRFF provides discrete valve lift capability on the intake valves. The motivation for designing this type of VVA system is targeted to improve fuel economy by reducing the air pumping losses during part load engine operation. This paper addresses the durability of a SRFF for meeting passenger car durability requirements. Extensive durability tests were conducted for high speed, low speed, switching, and cold start operation. High engine speed test results show stable valvetrain dynamics above 7000 engine rpm. System wear requirements met end-of-life criteria for the switching, sliding, rolling and torsion spring interfaces.

A system-level, data driven model was developed to predict gas temperature in the exhaust manifolds of naturally aspirated spark ignited engines during vehicle operation. The model is based on data gathered from 67 vehicle tests. The data were collected over the last few years, from a dozen cars and trucks, spanning a range of rated power from 127 to 350 hp, engine displacements from 2 to 8 liters, Line-4, V-6 and V-8 engine configurations, vehicle mass from 1500 to nearly 9000 kg, trailer mass from zero to nearly 4000 kg, different vehicle drive schedules, different vehicle speeds, varying road grades up to a maximum in excess of 9% and ambient temperatures of 40°C. The large number of engine and vehicle design and operational variables that can influence exhaust gas temperature was limited to high-level variables known early in a vehicle development program.

The US Environmental Protection Agency (EPA)’s heavy duty diesel emission standard was tightened beginning from 2007 with the introduction of ultra-low-sulfur diesel fuel. Most heavy duty diesel applications were required to equip Particulate Matter (PM) after-treatment systems to meet the new tighter, emission standard. Systems utilizing Diesel Oxidation Catalyst (DOC) and Catalyzed-Diesel Particulate Filter (DPF) are a mainstream of modern diesel PM after-treatment systems. To ensure appropriate performance of the system, periodic cleaning of the PM trapped in DPF by its oxidation (a process called “regeneration”) is necessary. As a result, of this regeneration, DOC’s and DPF’s can be exposed to hundreds of thermal cycles during their lifetime. Therefore, to understand the thermo-mechanical performance of the DOC and DPF is an essential issue to evaluate the durability of the system.

The hybrid system for the 2007 Model Year Saturn VUE Green Line Hybrid SUV was designed to provide the fuel economy of a compact sedan, while delivering improved acceleration performance over the base vehicle, and maintaining full vehicle utility. Key elements of the hybrid powertrain are a 2.4L DOHC engine with dual cam-phasers, a modified 4-speed automatic transmission, an electric motor-generator connected to the crankshaft through a bi-directional belt-drive system, power electronics to control the motor-generator, and a NiMH battery pack. The VUE's hybrid functionality includes: engine stop-start, regenerative braking, intelligent charge control of the hybrid battery, electric power assist, and electrically motored creep. Methods of improving urban and highway fuel economy via optimal use of the hybrid motor and battery, engine and transmission hardware and controls modifications, and vehicle enhancements, are discussed.