NASHVILLE, Tenn. – The latest model year of heavy-duty engines has met tightened emission standards without measurable drops in fuel economy. Manufacturers, however, are looking nervously to October 2002, when even-tighter standards will force dramatic changes in engine designs.
“It (the deadline) is going to be on us before we know it,” said Cummins’ field service engineering director Tim Thompson, speaking during a panel session of the Maintenance Council of the American Trucking Associations.
“The 1999 and 2000 emission standards are essentially the same,” said Chuck Blake of Detroit Diesel. But those extending oil drain intervals need to keep a close eye on their oil analysis results because of the higher soot levels that come with changes to injection timing.
By the end of this year, manufacturers will have enough low-NOx rebuild kits available to outfit engines built between 1993 and 1998 (some engines aren’t affected until 1994 model years). Those engines have to be upgraded when users replace or recondition more than one major cylinder component in more than half the cylinders, Thompson added. At best, heavy-duty engines won’t require the work until they reach 290,000 miles, while the limit for medium-duty equipment is 185,000 miles.
The rebuild kits include some pistons, rings and liners, new calibrations for ECMs and a label confirming that the engine has been upgraded.
Engine makers are paying the bill for the program that has to remain in place for 10 years.
The remaining questions relate to how engines will reach 2002 targets, although the addition of Exhaust Gas Recirculation (EGR) equipment seems to be emerging as the ultimate way to meet tightening emission requirements that were originally planned for 2004.
Plans for EGR offer the best hope for lowering NOx, said Mack’s Chris Smith. Through the systems, exhaust gases are cooled, mixed with fresh air and fed back into the combustion process. But first the gases start out at 1,200 F before they are cooled to between 300 and 500 F. That means more equipment such as a valve, piping, cooling system and electronics need to be added on engines. And with the cooling of EGR comes more heat that has to be handled by the radiator, meaning some changes in that equipment.
“We will still be using the coolants we are using today,” he assured the crowd. “We’ll still be using a radiator.”
But so too will there be new issues of higher soot and sulfuric acid levels in engines.
“We’re evaluating enhanced filtration,” he said, noting that oil manufacturers are also being pushed to develop new formulas. “Our target will be to maintain current oil drain intervals.”
Some other technology will include new injector rate shaping, the use of multiple injections and modified combustion chambers, said Smith. “But that’s already part of our typical engine development process.”
In terms of turbochargers, some wastegate models are already appearing on the latest generation of clean enignes, while variable geometry turbochargers are available on medium-duty engines in Europe. Then there’s the option of twin turbos and multi-wheel turbos to increase the supply of air.
Plans for NOx aftertreatment devices simply aren’t viable in time for 2002, Smith says. “Their technologies are not mature yet.” But once they do appear, they could be anything from a urea-based de-NOx catalyst, to a NOx-absorbing variety or a plasma-assisted catalyst. So too could aftertreatments emerge to control particulate matter, with an oxidation catalyst or regenerating particulate filter. n
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