Diesel engine technology has evolved enormously over the past decade to meet emissions legislation requirements and consumer demands. Not only do modern diesel engines produce fewer emissions, but they are also more powerful, quieter and have improved fuel economy. These benefits have been made possible by the introduction of improved fuel injection systems, such as common rail. These systems operate at high pressures and temperatures and can meter precise volumes of fuel into the combustion chamber, forming finely atomized fuel droplets. This makes them more sensitive to deposit formation. When deposits form, there is a noticeable loss of power and increased emissions can result.
In this paper, we examine injector fouling tendency in a range of engine technologies and demonstrate that the new engine technologies differ in deposit severity and appetite not only from older, indirect injection systems, but also among each other. A comparison of test methods for accelerating deposit formation further demonstrates that significant differences in appetite and the character of the deposits can result. Finally, it is shown that while properly formulated, current detergent additives can significantly reduce the level of deposits and the associated performance deterioration in most cases, new detergent additives are in development that provide further performance benefits in these new engine systems.