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This paper presents a 2.5L V6 aluminum cylinder block engine that has been developed for use in the next HYUNDAI SONATA vehicle. The major objective in developing this new engine was to achieve high power,especially high torque at low to mid speed range, quiet engine operation, reliability and good fuel economy. The basic construction of the engine is characterized by its 60-degree V6 configuration, compact combustion chamber and simple variable intake systems. The new engine has been designed to comply with the tougher TLEV emission standard, OBD-II requirements and California's new evaporative emission standards. This paper will introduce various technologies used in this engine that increased engine performance while reducing emission and improving fuel economy and NVH characteristics, and will discuss the engine construction, principal component parts, major development objects and test results.

Four ports which have slightly different shapes have been applied to 3-valve MPI SI engine to develop Axially Stratified Lean Combustion engine. The purpose of port modification test was to investigate the effects of swirl ratio and direction on engine performance and emissions. In the engine test injection characteristics, i.e. timing, flow rate, direction as well as port design significantly effected on the engine combustion. Especially, it was observed that injection timing was the most important factor for combustion stability, but its effect on performance has some differences in accordance with the port designs. To verify the relationship between port shape and injection timing, in-cylinder gas was sampled by high speed gas sampling device varing injection timing through whole intake and compression,. strokes at spark plug position and analyzed by gas chromatography.

An experiment has been carried out to investigate the combustion process in an operating S.I. engine (MPI and Multi- valve), using in-cylinder high speed gas sampling techniques. Measurements have been made of local air fuel ratios and time-resolved concentrations of combustion gases such as CO, CO2, THC, NOx, and O2, particularly focused on spark plug location. The effects of fuel injection timing, swirl generating air motion, sampling location, spark timing, speed and load have been considered. With the end of fuel injection at 120° ATDC on the intake stroke, A/F ratio at spark plug location has the leanest value for standard inlet port, while it has the richest value for swirl generating inlet port. The initial NOx concentration in the unburned gas region, diluted by the residual gases, has been substantially reduced between 5° BTDC and 15° ATDC crank angle prior to combustion.