Older diesels didn't have the emissions requirements, so black smoke was not prohibited (to a point).

I agree with others, that the diesel will run lean most of the time, it has all of the air it needs with no throttle on the air supply.

To increase power, you increase heat. To increase heat, you increase fuel. Fuel is air + diesel fuel, the air is already there so you turn up the fuel.

When diesels were allowed to smoke a little, it was common practice to overfuel at full-throttle. Even though the excess fuel isn't burning completely (thus the smoke), it is creating a little more heat = a little more power. You can overfuel to a great degree and get more power, ever watch a tractor pull? Diesels at a drag race? The efficiency isn't there, you're getting less energy per gallon of diesel, but you will get more energy with more fuel to a point. It also will create lots of smoke and too much heat for the engine to last, but it is a cheap and simple way to increase power.

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Gone to the dark side

- Jeff