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Mercedes-Benz has revised their Series 300 and 400 engines so that they do comply with EURO 2 limits even prior to their coming into force in October 1996. Comprehensive further development of the combustion process, turbocharging and of the entire fuel injection system has made it possible to comply with the exhaust limits while achieving optimal fuel consumption. Multi-hole injection nozzles with small spray cross-section and appropriately matched injection pumps produce the high injection pressures necessary for low particulate emissions. An electronically controlled variable stroke injection pump is used for achieving optimal fuel consumption on the Series 400, enabling the start of injection to be ideally matched to engine load, speed, temperature and operating altitude without the need for a mechanical injection timing device. To remain within the economic remit, the aim in the case of the Series 300 was to meet the emission limits using a mechanically controlled injection pump.

From engine test results, methods can be derived for reducing visible emissions of diesel engines, particularly under such operating conditions which so far are not yet subject to environment protection legislation. It is general practice today when starting diesel engines, to inject excess fuel, i.e. an additional amount of fuel in excess of the full load quantity, independent of ambient and engine temperatures and regardless of whether this is necessary or not. It is demonstrated that excess fuel should only be injected when starting a cold engine at ambient temperatures below freezing point and that the quantity of excess fuel should increase with falling temperature, reaching its maximum at the minimum engine starting temperature. The excess fuel quantity injected can be controlled with the aid of a wax element, so that, when the engine is warm, only the full load fuel quantity is injected.