A large number of problems for which solutions must be found have come to the surface recently in regards to heavy duty diesel engines. These begin with the strict emission regulations, and also include the questions of improved fuel econoray, better engine output and lower noise levels. One indispensable element in the solution to these problems is an improvement in engine combustion, a factor which must include modifications in the fuel injection system. Another critical question is that of improving engine and vehicle control technology. The improvement of fuel injection performance-which must include control performance as well-is hence extremely important to the purification of diesel engine emissions, and research in this area roust progress at ever increasing rates.