Join Date: Aug 2005
Location: North Central NJ
Thanked 151 Times in 105 Posts
Your question is a good one. I always used to think smoke meant wasted fuel, which meant less power, but I gave it some thought after reading your post. Imagine things at the molecular scale. And this is a huge over simplification, but it might help explain things (really, we need a diesel combustion expert that knows the theory of combustion wave propagation, etc....but for now its just us chickens).
For a certain engine set up (turbo, IC, etc.) and ambient conditions, you get a certain air charge per stroke. If you shoot just the stoichiometric amount of fuel, we can simplify that to be a table with equal numbers of white balls (oxygen) and black balls (fuel). To get combustion, a black ball and a white ball have to meet. Since your rate limiting ingredient is oxygen, to guarantee you burn every last molecule, by adding an excess of black balls (diesel), you further guarantee that each white ball will strike a black ball. That is, some additional power is possible with an excess of fuel. There are penalties though, like high EGT's, etc. How important this is, I don't know. Might be a 1% gain, in which case it is not worth the smoke and heat and pollution. But maybe it is 10-20%...in that case, for pure performance, it is probably worth it.
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