Diesel engines clean up their act

Sophisticated electronic controls and fuel systems improve combustion efficiency and substantially cut emissions. Sophisticated electronic controls and fuel systems improve combustion efficiency and substantially cut emissions. Caterpillar's 330C L hydraulic excavator is powered by the Cat C-9 engine. It features electronic engine control and a hydraulically actuated fuel system for quick response, high efficiency, and low emissions. Cummins meets Tier 2 emissions standards with both mechanical and electronic versions of its B and C Series off-highway engines. The 275-hp 6068H PowerTech engine from John Deere has four valves per cylinder and an electronically controlled high-pressure common-rail fuel system. The 47.5-hp 4TNV88 engine from Yanmar Diesel features reentranttype combustion chambers with high-efficiency swirl and higher injection pressures than previous models. This improves combustion, minimizing emissions and optimizing fuel efficiency. Citing growing evidence that dieselengine exhaust can cause serious health problems, the U.S. Environmental Protection Agency has issued regulations that will dramatically reduce emissions from off-highway diesel vehicles. The EPA considers these engines a major source of harmful particulate matter, as well as NO , hydrocarbons, and other ozone-forming compounds. The standards cover diesel engines used in a range of construction and agricultural equipment, such as excavators, bulldozers, logging equipment, and farm tractors. The regulations are structured in three decreasing levels, with each Tier involving a phase-in, by horsepower rating, over several years. The first Federal standards for off-road diesel engines were adopted in 1994 and were phased in from 1996 to 2000. Tier 2 standards take effect from 2001 to 2006, and more stringent Tier 3 standards phase in starting in 2005. As just one point of comparison, Tier 1 standards mandate maximum NO levels of 9.2 gm/kW-hr for engines over 300 hp, while Tier 2 and 3 levels for combined NO and HC are 6.4 and 4.0 gm/kW-hr, respectively — nearly a 60% reduction. The standards have forced engine manufacturers to take a close look at the nuances of diesel combustion. As a result, they are increasingly turning to sophisticated