Abstract: Apparatus for controlling dual fuel supply to a fuel injected engine having an electronic engine management system (1) that supplies a primary injector control signal (8) to each of primary fuel injectors (2), the apparatus comprising an emulator (11) that emulates the electrical characteristics of a primary injector, a fuel control switch (10) that switches the primary injector control signal (8) from the primary injector (2) to the emulator (11) when an alternative mode is selected, a monitor (16) that monitors the primary injector control signal (8) to produce a monitor signal, and a controller (4) that processes the monitor signal to derive an alternative control signal which is used to control the primary fuel supply or a mixture of the primary fuel and a secondary fuel such as LPG, to the engine. Preferably the primary fuel supply is modulated by controlling injector control pulses. A secondary fuel may also be injected (3) and controlled by the controller (4).

Abstract: A compression ignition engine is supplied with a first fuel in a flow of air and a second fuel is injected into the combustion chamber. The first fuel comprises a more volatile fuel than diesel such as ethanol, LPG or other combustible gas; the second fuel comprises diesel or biodiesel; and the second fuel is injected in multiple pulses in each ignition cycle with the first pulse acting as a pilot pulse to trigger ignition, and the timing of the second pulse being such as to modify the temperature through evaporation of the second fuel and thereby reduce the combustion temperature and mitigate knock susceptibility. Preferably the pilot pulse is followed by a single further pulse of the second fuel in the ignition cycle.