I've read on the internet, in a couple of maintenance books and asked a few buddy mechanics and they all seem to point to the fact that a healthy diesel engine should not produce black smoke and that the common reason why this happens is because of too much fuel to not enough oxygen leading to incomplete combustion.
If the fuel is not completely burnt, then all that fuel is wasted which is not what I would expect in a racing context, so what gives? Why don't they cut on the amount of fuel injected into the engine so as to maintain a proper fuel/air ratio? Or better yet, increase the amount of air being rammed into the engine (at least as long as it wouldn't hurt the power to mass ratio)?
To add more confusion, I took a look at some footage of the Audi R18 TDI and I failed to notice any black smoke, which makes perfect sense, given the nature of the type of contest it is taking part in (efficiency anyone?).
So why are diesel dragsters wasting fuel and producing soot?