The progress made in achieving those reductions—progress that is paving the way for the introduction of light-duty diesels into the North American market—has come with a bit of an efficiency penalty, noted Dr. Gerhard Schmidt, Ford’s Vice President for Research and Advanced Engineering.

Resolution of emissions challenges need to be achieved without radical cost and without sacrificing [diesel’s] fuel-economy advantage. Competition is coming from the gasoline engine...new gasoline engine technologies will reduce the fuel economy benefit [of diesel] to about 20%. The gap will close, especially when you talk about volumetric comparisons.

We have to improve the fuel economy [of diesels] further. In the long term, it is not acceptable that we have this disadvantage from the aftertreatment.

—Dr. Gerhardt Schmidt

The need for enhanced efficiency is driven by two primary factors, said John Amdall, Director of Engine R&D at Caterpillar: the uncertainty over the price and supply of oil, and CO₂.

Among the varied scenarios Caterpillar has developed to map out its medium-term R&D work, the one that is “most likely for the next 15 years or so is that we are shifting focus away from...emissions versus the cost of owning and operating to CO₂ versus owning and operating cost. For the next 15 years, CO₂ replaces NO_x and PM.”

Amdall suggested the creation of a new DOE program—Ultra-High Efficiency Engines—to accompany some of the other DOE programs that have been of value to the industry: the heavy-duty truck engine, high-efficiency clean combustion, waste-heat recovery, advanced propulsion materials and advanced petroleum and renewable fuels programs.

Although much progress has been made on diesel-engine emissions reduction for the US, there remain some gaps in making US diesels as clean as advanced gasoline engine vehicles, according to another plenary speaker, Tom Cackette, Chief Deputy Executive Office at the California Air Resources Board.

In terms of urban pollutants (regulated tailpipe and evaporative emissions), light-duty diesels today are at the Bin 8 level and are planned to move to Bin 5, making them compliant with the California LEV 2 standard: the 50-state diesel.

But, Cackette noted, Bin 5 is the entry point to California standards.

The average standard in California is about 45% lower than Bin 5. And by the middle of the next decade, half of new vehicles must meet PZEV (about 75% below Bin 5). In other words, diesels meet the minimum, the challenges are to drop.

—Tom Cackette

California is allowing the diesel industry some latitude in the implementation of regulations for on-board diagnostics (OBD) systems used to ensure the proper functioning of emissions aftertreatment systems. The durability requirement for diesel OBD is lower, and the trigger thresholds are higher. But by 2013, the principal is that diesels have to be as clean as gasoline engines in all categories.