Search Results

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.

An energy-absorbing restraint system that limits the accelerations of a passenger in a forward auto crash to 20 g's is presented. The device absorbs energy through the continuous bending of a steel wire. Results of an elastic-plastic analysis of the device indicate that it closely approximates a constant force energy absorber; the force is only a weak function of velocity. Preliminary results from drop tests and high-speed impact tests to 100 mph indicate that the absorber can limit acceleration to a specified value. The results of two tests in which the device was used to restrain a volunteer during a head-on crash are presented. In each crash a vehicle driven at 50 mph impacted a parked vehicle. The results show that the restraint system protects a man in a forward crash by limiting his accelerations to a level below the threshold of injury for the vital organs.