The Influence of High Pressure Fuel injection on Performance and Exhaust Emissions of a High Speed Direct injection Diesel Engine 890438

Conventional direct injection diesel engines for cars or light duty trucks, equipped with injection pumps of conventional types, such as distributor injection pumps and inline injection pumps, and operating at compression ratios of 18-19, are capable of offering a fuel consumption benefit of some 15% compared to chamber diesel engines. In terms of noise and exhaust emissions, and also black smoke characteristics, however, they are significantly inferior to the prechamber engine. In addition, they have a specific rated output which is some 20% lower. Only through the use of a compression ratio of 21 and high injection pressures it is possible to measurably diminish the drawbacks in respect of exhaust emissions and, to some extent, in respect of soot emissions. This in no way enhances the noise behaviour, though. For this reason, it is essential to employ measures such as injection rate shaping or split-injection. Satisfactory engine characteristics are best achieved if a pilot- injection is used, which can be controlled as need to be, independently of load and engine speed. Such a pilot-injection is only feasible, however, with an electronically controlled unit injector.