Effects of VGT and Injection Parameters on Performance of HSDI Diesel Engine with Common Rail FIE System

Recently, high speed direct injection (HSDI) diesel engines are rapidly expanding their application to passenger cars and light duty commercial vehicles in western European market and other countries such as Korea and Japan. These movements are strongly backed by the technological innovations in the area of air charging and high pressure fuel injection systems. Variable geometry turbine (VGT) turbocharger, which could overcome the typical weak point of the existing turbocharged engine, and the common rail fuel injection system, which extended the flexibility of fuel injection capability, became two of the most frequently referred keywords in recent HSDI technology. In this paper some aspects of VGT potential as a full load torque and power modulator will be discussed. Possibility to utilize the portion of full load potential in favor of part load emissions and fuel economy will be investigated. A strategy of boost pressure control will be suggested as an attempt to fully utilize the flexibility of VGT in optimizing combustion efficiency. In the later part, the impact of fuel injection parameters such as rail pressure, main and pilot injection timing and their separation, and the pilot injection quantity on part load emissions and combustion efficiency will be investigated.