The aptly named Diesel Forecast is reporting on a diesel technology discussion involving BMW, Volvo, Audi, and Bosch, and the path that each may take to address the increasingly-stringent emission requirements in the U.S. and in Europe.

BMW, for its part, does not envision bringing over diesels to the US before calendar year 2008. The automaker wants to introduce a 50-state solution, and feels that selective catalyst reduction (SCR) will be the way to go to meet California's requirements - said to be the toughest diesel emissions standards in the world. Audi will also be exploring the use of SCR, and plans to use what it learns in developing a 50-state diesel to meet upcoming European requirements.  Volvo basically doesn't know when it'll offer diesel in the US, as it feels that it is not in a position to shape the market. Too bad, because many would say that a small OEM is in the best position to shake up this segment of the market right now.

Mega-supplier Bosch, for its part, sees clean diesel as facing serious competition from gasoline homogenous charge compression ignition (HCCI) in the long term. In the shorter term, SCR and urea injection will work together with increasingly complex combustion-management techniques in diesel, but the supplier seems to feel that the rate of diesel technology improvement may be approaching the point of diminishing returns after the last decade of significant advancements.