One of the manufacturers or importers has to offer one or more of their ALCo Diesel-Electric Locomotives which has the feature of an engine that puffs out black smoke.
Real black carbon powder would work. The puffing of the carbon powder would need to be synchronized with the change in speed and diesel sounds.
Black smoke is a realistic feature that is missing from the O gauge ALCo diesels.
Thank you.
Andrew
Falcon Service