When developing diesel fuel formulations, it is important to ensure that existing engines in the market place start and continue to run satisfactorily at low temperatures. The objective of this project, carried out jointly by Statoil and Ricardo Consulting Engineers Ltd, was to develop a test technique capable of discriminating between different fuels and to apply the technique to a range of experimental fuels tested in six diesel engines.
The engines were selected to represent the technologies available in the current vehicle parc, ranging from indirect injection diesel engines used in passenger cars to highly-rated, direct injection engines found in commercial vehicles. These engines were instrumented to measure crankshaft position and speed, in-cylinder pressure and exhaust emissions. Cold start testing was carried out at -16°C and -24°C in Ricardo's cold chamber and data were recorded during the cold starts by analogue recorders and a high speed digital data logger.
The fuels matrix comprised fuels of varying composition with and without an ignition improving additive. In total, the test programme consisted of 90 engine and fuel combinations.
This paper describes the test methods and data analysis techniques which were developed to evaluate the effects of the fuels on cold startability.
The effect of fuel composition is compared with that of the engine design.