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A broad range of diesel, kerosene, and gasoline-like fuels has been tested in a single-cylinder diesel engine optimized for advanced combustion performance. These fuels were selected in order to better understand the effects of ignition quality, volatility, and molecular composition on engine-out emissions, performance, and noise levels. Low-level biofuel blends, both biodiesel (FAME) and ethanol, were included in the fuel set in order to test for short-term advantages or disadvantages. The diesel engine optimized in Part 1 of this study included cumulative engine hardware enhancements that are likely to be used to meet Euro 6 emissions limits and beyond, in part by operating under conditions of Homogeneous Charge Compression Ignition (HCCI), at least over some portions of the speed and load map.

Two single-cylinder diesel engines were optimised for advanced combustion performance by means of practical and cumulative hardware enhancements that are likely to be used to meet Euro 5 and 6 emissions limits and beyond. These enhancements included high fuel injection pressures, high EGR levels and charge cooling, increased swirl, and a fixed combustion phasing, providing low engine-out emissions of NOx and PM with engine efficiencies equivalent to today's diesel engines. These combustion conditions approach those of Homogeneous Charge Compression Ignition (HCCI), especially at the lower part-load operating points. Four fuels exhibiting a range of ignition quality, volatility, and aromatics contents were used to evaluate the performance of these hardware enhancements on engine-out emissions, performance, and noise levels.

Recent years have seen dramatic reductions in gasoline and diesel sulfur concentrations in the United States, Europe, Japan and other countries. Many developing countries are evaluating the appropriate sulfur levels to choose for the future. This paper examines the current state of knowledge concerning the impact of fuel sulfur on exhaust emissions, and the sensitivity of exhaust aftertreatment technology to fuel sulfur. Gasoline vehicles achieve very low emissions through use of three-way catalysts. These systems are relatively insensitive to sulfur, being able to operate on levels of up to 500 ppm. Further reduction in sulfur will produce additional, small emission reductions. Diesel emissions may be reduced significantly using engine modifications, oxidation catalysts or exhaust gas recirculation, which may require sulfur levels of 500 ppm.

Particle emissions from vehicles are currently under close scrutiny with respect to their contribution to ambient air quality relative to other sources. Small particles, less than 10 μm, referred to as PM10, have been linked to various health issues. In this study, tests have been performed on European diesel light duty vehicles using a range of production diesel fuels. Tests were also performed on two gasoline passenger cars for comparison. Measurements were made of exhaust particle size distribution and number, as well as mass emissions using the legislated filter paper method. The results showed that most of the particles emitted were very small, with median size of the order 100 nanometres (nm). The median particle size was insensitive to changes in fuel, vehicle or operating condition. Measurements of particle number broadly correlated with particle mass emissions, and ranked fuels and vehicle types in the same order.

The results for the light duty and heavy duty diesel studies in the EPEFE have been compared, and areas of similarity and differences explored. Consistent with the intent to choose the widest possible range of engine technologies and vehicle configurations, the impact of the vehicle and engine sets on emissions was larger than that of the matrix of fuel properties. Vehicles showed a wide range in response to the fuel properties investigated. In some cases, the effects of fuel changes on emissions from the LD vehicle and HD engine sets were similar, but in other cases emissions changed in opposite directions in the two sets for the same fuel change. However, fuel changes that were beneficial for PM in LD vehicles were also positive for NOx and PM in HD engines. Differences between engine design features and test cycles were examined to investigate the reasons for these results. Fuel effects were generally larger in percentage terms for Light Duty Vehicles than for Heavy Duty Engines.

A consortium of CONCAWE, EUCAR and the EU Commission's JRC carried out a Well-to-Wheels analysis of a wide range of automotive fuels and powertrains. The study gives an assessment of the energy consumption and greenhouse gas emissions for each pathway. It also considers macroeconomic costs and the market potential of alternative fuels.