Paper 4: Induction System Development for High-Performance Direct-Injection Diesel Engines

Abstract

This paper describes some of the techniques employed by the author's company in the development of induction systems for direct-injection engines. Emphasis is placed upon those methods amenable to use during the day-to-day performance development of several engine types simultaneously. The induction system has two functions to perform: ( a) to provide maximum gravimetric aspiration, and ( b) to generate optimum and consistent swirl. These requirements are investigated using digital computers, air flow and swirl rigs, and engine experimental results. The effects of port size, port shape, valve timing, engine speed, and heat transfer on volumetric efficiency are presented in simplified theoretical and experimental forms. The behaviour of ports is discussed and a method of correlation of air swirl rig and engine results is presented. Experimental data is included, demonstrating the importance of correct swirl match. Fully machined inlet ports are discussed together with reasons for their adoption. The principles of induction pulse tuning are briefly enumerated and typical results included. Iso-fuel consumption curves are included to show the present level of d.i. engine performance. The paper concludes with a tentative hypothesis to explain engine swirl response, and suggests the general level of performance improvement likely during the next few years.