6 April 2011 | updated 15 April 2011

Navistar International Corporation announced that it has received a certification from the US Environmental Protection Agency (EPA) for its 2011 MaxxForce® DT mid-range diesel engine with in-cylinder NOx reduction technology. The NOx family emission limit (FEL) was 0.39 g/bhp-hr and the FTP certification level 0.30 g/bhp-hr. The certification “demonstrates progress to achieving the 0.20 g/bhp-hr standard through base engine and in-cylinder optimization”, said Navistar.

In 2010, Navistar certified one engine family (ANVXH04660GA) for the DT that covered the range from 215-300 hp. The NOx FEL was 0.50 g and the certification level was 0.42 g. In 2011, the DT model was split into two families: the BNVXH0660GA covered the 245-300 hp ratings while BNVXH0660GC covered the 215 and 230 hp models. Both families had a NOx FEL of 0.50 g. As certification NOx levels generally scale with engine output, the higher power ...GA family cert level was 0.46 g while the lower power ...GC family cert level was 0.30 g.

After the initial 0.5 g certification, the FEL of the lower power ...GC family was brought down in two steps. On March 22, 2011, it came down to 0.45 g and on April 7, 2011 to 0.39 g. Thus, it appears that the lower NOx certification for DT engines with lower power output was made possible through restructuring the DT engine family definitions. Lowering the FEL—especially for engine models with higher sales volume—allows Navistar to extend their NOx credits.

The FEL is an emission limit chosen by a manufacturer for use in the EPA emissions averaging, banking and trading program. In effect, the FEL replaces the emission standard—in this case 0.20 g/bhp-hr NOx—for emission certification of a given engine family. If the FEL is lower than the emission standard, the manufacturer accumulates emission credits. If it is higher, the excessive emissions must be offset by emission credits accumulated in the past.

As their emission credits run out, Navistar intends to phase-in its engines at progressively lower NOx emissions levels—0.4 g NOx, 0.35 g NOx, 0.3 g NOx, 0.25 g NOx, etc.—in the years ahead. Presumably, these figures represent a sequence of FELs to be targeted by Navistar for future certifications.

Compared to the urea-SCR technology chosen by other engine manufacturers, the in-cylinder NOx control approach carries a fuel economy penalty. According to JPMorgan figures, as quoted by the New York Times, Navistar’s share of the United States market for the heaviest trucks fell to 20.2% this year, down from 28.5% in 2009.

Navistar also announced that it recently submitted the MaxxForce 13 for EPA certification at 0.20 g NOx.

Source: Navistar