Starting January, 2010, the U.S. Environmental Protection Agency (EPA) will require all engine manufacturers to produce engines that meet the 2010 near-zero emissions criteria, which includes emissions of no more than .2 grams nitrogen oxide (NOx) and .01 grams particulate matter. Columbus, Ind.-based Cummins Inc. has updated and customized its engines to meet these new standards — without losing fuel efficiency or performance — by integrating subsystems.
Cummins displayed these newly tailored ISB Hybrid and ISL Diesel engines as well as its ISL G gas product at the APTA EXPO in San Diego. Cummins’ Tom Hodek, general manager, worldwide bus business, says that the company has made some reliability and efficiency improvements to the engines — mostly internal — without any architectural changes. “It’s the 2007 system plus a Selective Catalytic Reduction (SCR) system. It’s not a big tear-up and redesign. We’re taking the reliability from 2007 and improving upon it for 2010, and [will continue to] improve upon it from there.”
In order to adjust to the 2010 near-zero-emission standard criteria, engine manufacturers have had to change from allowing about four grams of nitrous oxide (NOx) and .1 gram particulate matter in emissions in 1998, down to .2 grams of NOx and .01 grams of particulate matter in 2010.
“The emissions reductions are substantial. We’ve had to meet these hurdles about every three years now. So, the investment in the technology, the effort we’ve had to put forth, the development curve we’ve been on is very steep. We’ve been able to manage to retain that advantage primarily due to the integration of all the subsystems,” Hodek says.
Engine efficiency improved
The ISB Hybrid engine, used with hybrid technologies in the BAE- and Allison-equipped buses on display, was part of technology that allows the hybrid system to recover braking energy, which can be used to drive the bus. The ISB Hybrid is a diesel engine, just like the ISL diesel, and they both operate like diesel engines. However, the ISB Hybrid engine has been tailored in its calibration and electronic controls to work more efficiently with a hybrid system, as opposed to a standard automatic or manual transmission. “We work with hybrid manufacturers, including BAE, Allison and Eaton, and have adapted our engines to work efficiently with their systems,” Hodek says.
The ISL, a diesel product, is Cummins’ highest-volume product right now for transit buses. It will be available in 2010 with its current horsepower and some hybrid ratings. Hodek describes it as “a building block emissions change for us, in that we made a lot of changes in 2007 to the engine, and added aftertreatment. In 2010, the engine changes are focused on reliability and efficiency improvements.” The ISL G, a natural gas product, is in production today, and currently meets the 2010 emissions standards. “It’s ahead of its time, so to speak,” he says.
While the EPA may not be taking certifications yet for 2010, if the product could be certified at present, it would meet the standard. The gas product has been well-received in the marketplace and is a much-improved product, according to Hodek, and may be an optimal product for a municipality that has the appropriate infrastructure.
On the SCR system in the new engines, there is an injector that sends diesel exhaust fluid (DEF) into the exhaust stream to clean it and, on that line, will be a filter that the DEF passes through prior to injection. The filter needs to be changed — similar to an oil filter — approximately every 200,000 miles. The hour translation, Hodek estimates, would be about every 5,000 hours of operation. “Given the changing of the system, and the amount of emissions reduction we’re gaining, that maintenance change is negligible,” says Hodek.