Fleets Must Adjust Upkeep for New Engines
hese recommendations from engine manufacturers could not be repeated enough at The Maintenance Council conference in mid-March.
The repetition was needed to emphasize changes fleets might have to make in their maintenance schedules to ensure the best performance and fuel mileage from 1999 model diesel engines in the wake of the consent decrees with the federal government.
In October, the six major manufacturers of diesel engines in the United States signed settlements with the Environmental Protection Agency to end a dispute over alleged violations of the Clean Air Act. The agreements required the companies to lower nitrogen oxide emissions in new engines and to pay millions in fines.
Under the decree, the manufacturers agreed to lower NOx emissions to 6.0 grams/per brake horsepower hour beginning with 1999 models used in heavy-duty over-the-road applications. Emission levels must be reduced to 2.5 g/bhp-hr by Oct. 1, 2002.
The engine manufacturers were able to meet the near-term emission levels by changing some of the operating characteristics of the engines, most notably by retarding the timing.
Instead of igniting the fuel at the dead center of the cylinder’s stroke, it is ignited a fraction of a second later. The result of this delayed combustion is a slightly lower temperature and lower NOx emissions.
However, the new combustion cycle produces more soot than before. The larger amounts of soot and their effect on engines is new territory for the manufacturers and fleets.
“We’re still learning about it and what might happen when there is too much soot,” said Charles Blake, applications engineer with Detroit Diesel.
There was consensus, however, that reliance on the quality of the engine oil and the need for more frequent oil changes have increased.
The oil must be formulated to keep enough soot suspended between oil changes to prevent air filter clogging and sludge buildup. Currently, the highest quality oil for heavy-duty engines is graded CH-4 by the American Petroleum Institute.
Although a relatively recent introduction, this oil grade was formulated before the consent decree and before the engines were adjusted to meet the lower emissions standards. The engines running with this combustion cycle will build up soot faster than this oil was formulated to handle.
For the full story, see the March 29 print edition of Transport Topics. Subscribe today.
