Investigations of injector deposits formation in a GDI flex-fuel engine

Abstract

In the last few decades, several innovations have been implemented in internal combustion engines to meet stricter emissions legislation and challenging targets related to energy efficiency. In this context, gasoline direct injection (GDI) engines adoption has been growing in the market as an economical and technically feasible route. These engines run on accurate fuel injection strategies, including multiple high pressure in-cylinder injections that improve mixture formation, expanding the possibilities for lean burn operation. In general, these strategies contribute to reduce fuel consumption and emissions. GDI fuel injectors have smaller mechanical tolerances and injection orifices diameters than those of PFI engines, which can lead to a higher sensitivity for obstruction by deposits. The GDI engine release in Brazil is relatively new, but included flex-fuel version innovations, allowing the use of Brazilian gasoline (25–27% v/v of anhydrous ethanol), hydrous ethanol, or any mixture of these fuels. Due to Brazilian market characteristics and the lack of information available in the literature, it is important to evaluate flex-fuel GDI injectors deposit formation. This investigation used an in-house patented engine test methodology, and the results showed the good quality of the Brazilian gasoline regarding low levels of injector deposits formation, under different engine operating conditions and, also, under critical fuel storage conditions (quality stress). The higher ethanol content in the gasoline, the fuel quality stress, the use of an in-house patented engine test methodology and the adoption of a flex-fuel engine in different operating conditions, including soak periods, contribute to this work novelty compared to the available literature. The paper also shows preliminary investigations of the deposit’s physicochemical nature, aiming to identify their characteristics and sources. Further research is recommended to improve knowledge in this area.