Mercedes-Benz Commercial Vehicle Engines to Meet Worldwide Environmental Requirements

Tighter emission regulations are leading engine development to high innovation rates at ever shorter time intervals. Mercedes- Benz revised its engines of the model series 300 and 400 to comply with Euro 2 limits valid as of October 1996. Comprehensive further developments of the combustion process, turbocharging and the overall injection system made it possible to meet emission limits at the best possible fuel economy. The new multi-hole nozzles with very small injection holes result in high injection pressures which are required for low particulate emissions. To optimize fuel consumption of series 400 engines, an electronically controlled variable pre-stroke injection pump is used to allow optimum adaptation of the start of injection depending on load, engine speed and temperature without the use of a mechanical injection timing device. The high rated series 300 engines are equipped with a waste gate turbocharger in order to optimize starting-off characteristics and to obtain favorable torque characteristics in the low speed range of the engine. Stringent American limits valid as of model year 1994 have been complied with by further developing the series 300 and the series 400 in-line engines. The various cycle-specific development strategies available to meet the European and American limits have been compared with one another and evaluated. CNG engines (Series 300 and Series 400) are available for special applications.