This url should explain why diesel engines don't get messed up at idle:
http://www.sh015a7585.pwp.blueyonder.co.uk/diesel.htm
The pertaining quote comes from the url above for those who don't bother to read the whole thing:
Quote:
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Apart from injecting fuel according to the operator's demand for torque, the diesel fuel system must perform a secondary function, that of governing the engine. The pumping inefficiencies in a petrol engine increase with speed, imposing an upper limit on the latter and stabilizing idling. If the idle speed drops the pumping torque reduces, causing the engine to speed up again, and vice versa. Because this effect is not nearly so pronounced in the diesel, it has a natural tendancy to stall at low speeds and, if no load is applied when fuel is injected, to accelerate up to speeds which can destroy the engine. Thus, instruments known as governors are attached to the fuel control device in pumps or injectors, in order to achieve a stable idle speed by adjustment of the fuelling level, and to cut off fuelling over the maximum safe speed. Traditionally, governors consisted of mechanisms using fly-weights, levers and springs or pneumatic or hydraulic valves. However, the low cost and enormous flexibility of digital electronics combined with increasingly demanding emissions limits, fuel economy and drivability targets, mean that electronic control is now predominating.
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Hope this explains how the diesel engines don't self-destruct at idle.
Sanosuke!
Return to Japan - Spring 2004 (Bonus: Singapore)