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. This eliminates the well-known cloud of black smoke emitted when starting a warm engine and considerably improves smoke emission when accelerating at low engine speeds.
A burner starting aid of simple design and fully automatic operation is described, which has been newly developed and is used to suppress, or even to eliminate, the emission of white and blue smoke during cold start and warm-up.