Clean air rules improve tractor fuel performance

Tuesday, November 1, 2011

Tests show that some models have boosted fuel efficiency by up to 10 per cent, especially those using selective catalytic reduction technology

by MIKE MULHERN

The high-horsepower tractor you could buy in 2010 is not the same as the high-horsepower tractor you can buy in 2011. The newest tractors have to meet Interim Tier 4 emissions regulations that drastically reduce nitrogen oxides (NOx) and particulate matter (PM) coming from tractor engines of 174 horsepower or higher. As part of the bargain many of the cleaner burning engines deliver improved fuel efficiency.

The U.S. Environmental Protection Agency (EPA) has been mandating reduced emissions from off-road diesels since the 1990s through a tier system. The end game is to reduce emissions by 2014 to the point where the air coming out of the engine is about as clean as the air going in.

Interim Tier 4 regulations that took effect Jan. 1, 2011, called for a 90 per cent reduction in PM and a 50 per cent reduction in NOx over emissions levels for Tier 3 mandated in 2006. Final Tier 4 emissions will take those levels to near zero when they come into effect in 2014.

Since 2000, Canadian regulations have been in lockstep with EPA rules for Tier 2 and Tier 3. Alignment with U.S. Tier 4 rules is expected. However, even without those regulations in place at the moment, tractor manufacturers are treating the Canada/U.S. market the same and delivering Tier 4 tractors into our market.

John Schmeiser, executive vice-president of the Canada West Equipment Dealers Association, says his association is encouraging the Canadian government to follow the U.S. lead on Tier 4 regulations.

"We understand that manufacturers are only going to make one tractor for North America," Schmeiser says. "There is a lot of equipment movement across the border between Canada and the United States, so our dealers asked us to communicate the message to Ottawa" that they would like the same standards here so that equipment could move easily between the two countries.

Rachelle Thibert, manager of marketing planning for John Deere, echoed those comments.

Manufacturers all have to hit the emissions targets set by the EPA. but they don't all use the same technology to do it. One method is selective catalytic reduction (SCR) along with a diesel oxidation catalyst (DOC). The SCR system lowers NOx while the diesel oxidation catalyst reduces PM. A second method is cooled exhaust gas recirculation (EGR) used with an exhaust filter. EGR lowers NOx and the filter collects particles.

Diesels that use SCR run at a higher temperature and produce less smoke. Higher combustion temperatures, however, create more NOx, so a diesel exhaust fluid (urea) is injected into the exhaust stream. NOx is broken down into nitrogen gas and water vapour that goes out through the exhaust pipe.

While most manufacturers point to the increased fuel efficiency of their cleaner engines, Thibert says that even high fuel prices have not moved fuel efficiency to the top of the buyer priority list.

"For some, it's the No. 1 priority, for other people it's way down the list," she says. She notes that tractor buyers have a list of priorities that influence their buying decisions, among them creature comforts in the cab.

The Nebraska Tractor Test Laboratory at the University of Nebraska in Lincoln is the official U.S. tractor-testing station. It tests power takeoff and drawbar performance and it measures fuel consumption.

Brent Sampson, a test engineer at the facility, says a number of manufacturers are showing improved fuel ratings for their Tier 4 tractors, singling out those using the SCR technology.

"The ones from Case New Holland," he says, "are probably about 10 per cent better than they were on Tier 3." He says some AGCO tractors showed a Tier 4 improvement of about eight per cent.

Test results for all tractors are available at the test lab website: http://tractortestlab.unl.edu/testreports.htm BF