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The current figure of Diesel market share in Europe of about 50% indicates a high market penetration of the HSDI Diesel engine. Due to increasing fuel prices and limited crude oil resources the worldwide demand for Diesel engines for the passenger car sector is increasing - even in typical gasoline markets like the united States. The key factors for the further success of the HSDI Diesel engine are the fulfillment of future worldwide emission legislation and that the production costs of the technologies necessary to do so, do not make it uncompetitive in comparison to the various gasoline engine concepts. Heavy SUVs with relatively small engines will therefore have to face the biggest challenge.

HSDI diesel engines have become increasingly popular in Europe over the last 20 years to the extent that market penetration now exceeds 40%. The situation is very different in the US where diesel accounts for only 4.5% of the light vehicle total at present. This paper provides a perspective on the technological, economic and societal issues associated with the large scale introduction of passenger vehicle diesels to the US.

The worldwide trend to increasingly stringent exhaust emissions standards, together with consumer requirements, are forcing both vehicle and engine manufacturers, as well as manufacturers of ancilliary equipment, to introduce new and often novel technology in order to produce clean, quiet and socially acceptable transport at affordable prices. The combustion process lies at the heart of the engine and the quality of the combustion determines the acceptability of the product to a very large extent. The fuel injection system plays a large role in the combustion process and in consequence, the fuel system type and capabilities strongly influence the performance of the combustion system. There has never been such a range of fuel injection systems available at one time as there is today. High pressure hydraulically actuated systems /1/ compete with cam driven fuel injection systems /2/ to deliver the injection requirements demanded by the vehicles both of today and in the future.

This paper reports on research and development work conducted at AVL to determine the NOx-reduction potential of in-cylinder charge conditions, fuel injection system parameters, exhaust gas recirculation, fuel formulation, and exhaust gas aftertreatment by catalyst. Based on these findings, development options are derived and assigned to the various future emission standards in USA, Europe and Japan.

This paper reports on research conducted at AVL on swirl supported and quiescent combustion systems on heavy-duty and medium-duty direct injection diesel engines towards defining the most appropriate combustion system technologies which will enable the EPA 1991 HD diesel emissions standards to be met without the use of exhaust after-treatment devices and with good prospects for meeting the 1994 standards. Based on both theoretical work and development efforts on a variety of engines, an analysis is conducted of the various aspects of swirl and fuel injection with regard to their effect on the formation of combustible mixtures and on particulate formation. Particular reference is given to the lube oil particulate fractions and to the dry soot fraction, recognized as the main contributors to total particulates. Based on this analysis, the main features of a low emission combustion system are derived, and a strategy to satisfy the 1991 and 1994 standards is presented.