[freebeard]

https://www.sandia.gov/news/publicat...injection.html

Nitrogen oxides are also atmospheric pollutants, and the soot/NOx trade-off meant that truck, car and equipment makers couldn’t meet current legislated limits without adding exhaust-gas aftertreatment systems. But remove one of those pollutants almost entirely — like DFI does with soot — and Chuck said you have changed the game.

“Now that we’ve got soot out of the way, there’s no more soot/NOx trade-off,” he said. “So we can add dilution — taking some of the engine exhaust and routing it back to the intake — to get rid of NOx without soot emissions becoming a problem. It’s like a two-for-one deal on reducing pollutants.”
....
Paul Miles, manager of Sandia’s engine research program, said the potential impact of DFI cannot be overstated.

“Breaking the soot/NOx trade-off is the holy grail of diesel engine development,” Paul said.