High speed swirl chamber diesel engines having been developed to a high level of performance have always needed starting aids. By optimising both plug temperatures and position, it has been demonstrated that good start-ability can be achieved with plugs having a very low thermal inertia and therefore rapid warm up capability. The design of this new starting aid Lucas CAV (Micronova) which concentrates the heat at the tip of the plug enables good starting to be achieved without the plug having to extend to the centre of the chamber. Removal of the obstruction to swirl presented by conventional sheathed element plugs mounted in a horizontal position or the relocation of the plug in the vertical position have enabled the Ricardo Comet combustion system to be reoptimised giving a significant improvement in fuel economy coupled with very low part load smoke with the obvious benefit of reduced particulate emissions.
This paper describes the development of the unique igniter plug and its contribution to the Advanced Comet chamber concept.