Combined Fuel and Lubricant Effects on Low Speed Pre-Ignition 2018-01-1669
Many studies on low speed pre-ignition have been published to investigate the impact of fuel properties and of lubricant properties. Fuels with high aromatic content or higher distillation temperatures have been shown to increase LSPI activity. The results have also shown that oil additives such as calcium sulfonate tend to increase the occurrence of LSPI while others such as magnesium sulfonate tend to decrease the occurrence. Very few studies have varied the fuel and oil properties at the same time. This approach is useful in isolating only the impact of the oil or the fuel, but both fluids impact the LSPI behavior of the engine simultaneously.
To understand how the lubricant and fuel impacts on LSPI interact, a series of LSPI tests were performed with a matrix which combined fuels and lubricants with a range of LSPI activity. This study was intended to determine if a low activity lubricant could suppress the increased LSPI from a high activity fuel, and vice versa. The results showed that a low activity fuel was insensitive to the lubricant used in the test, while a high activity fuel could be moderated by a low activity lubricant. The combination of a high activity fuel and high activity lubricant, as expected, yielded a large number of LSPI events.
These results help to understand how formulation changes to the lubricant or to the fuel may impact the other fluid, particularly with respect to regional variations in fuel specification and in lubricant additive standards.