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This paper describes the development of a transient engine test facility for drive cycle simulation and emissions and performance testing. Results are presented to demonstrate correlation with vehicle tests performed on chassis rolls. The tools and techniques developed in the work are discussed.

This paper presents engine performance and emission results that demonstrate a high degree of correlation between tests performed on a transient engine dynamometer with simulated vehicle characteristics, and test performed on a chassis rolls with a vehicle. The transient testing methodology that has been developed is being used to underpin the transfer of vehicle calibration activity to the testbed.

This paper describes the continued development of the Navistar 7.3 litre V8 CNG engine. The project background, objectives and preliminary results have already been described (1). Development results show that U.S. 1994 emissions standards can be comfortably met without the use of electronic air fuel ratio control or an oxidation catalyst. Transient cycle emissions of 1.7 g/bhph NOx + NMHC have been obtained from de-rated engines to be used in field demonstration vehicles. Electronic control will allow 2.5 g/bhph NOx + NMHC to be achieved without de-rating. Further emissions reduction without aftertreatment will depend on aftercooling, which also offers the potential for an increased rating.

This paper describes the first phase of a project to develop a medium duty engine to run on compressed natural gas (CNG) as an alternative fuel for vehicles such as school buses and medium trucks. The engine uses a lean burn, open chamber design featuring the Nebula combustion system. Mechanical air-fuel ratio control and a mapped high energy ignition system, combined with a wastegated turbocharger, will contribute to the low emissions. The CNG engine will have the maximum commonality with the existing diesel engine and will use the same production tooling wherever possible. The initial build of CNG engine is intended to avoid the expense and complication of an intercooler and catalyst. Future potential for even lower emissions and higher pressure could be achieved by the use of electronic air-fuel ratio control and the addition of intercooling and an oxidation catalyst.