There is a growing requirement for lightweight high performance engines capable of operation with heavy fuels such as JP5 (F44), JP8 (F34) and diesel fuels as well as maintaining the capability of running on unleaded gasoline. Traditionally heavy fuels are associated with operation in compression ignition engines which exhibit poor power to weight characteristics. Today's engine applications call for much greater mobility and flexibility in use, especially in applications such as outboard engines, motorcycles, All Terrain Vehicles, Light Aircraft and portable generator sets. Compression ignition engines with their poor power to weight and vibration characteristics are less likely to succeed in these applications. These requirements are more likely to be met by the development of a spark ignition engine capable of operating on these heavy fuels.
With the development of Direct Injection technologies it is now possible to achieve sufficient control over the combustion process in spark ignition engines to overcome the poor physical properties of the heavy fuels that to date have prevented good combustion being achieved across the entire speed and load domain of the engine.
This paper explores the development path and results from several conversions of direct injected gasoline engines, both 2 and 4-stroke, to operate as spark ignition heavy fuel engines, thus offering the fuel of choice whilst retaining the weight advantages and the desirable power to weight ratios of the gasoline engines.