December 5, 2023

To Cut Smog, Navistar Blazes Risky Path of Its Own

One measurement — for nitrogen oxide emissions, or NOx — is of particular concern to Navistar. From 2010 onward, all new truck engines must achieve tough, near-zero limits for NOx, a chief ingredient of smog. Virtually every truck maker besides Navistar chose to use an add-on system to their existing engines that uses a fluid cocktail to help neutralize the pollutant as it makes its way out of the exhaust.

Navistar went a different route, deciding to invest hundreds of millions of dollars to refine an engine that produces minimal NOx in the first place. At the same time, the company attacked the competing systems, suing federal air quality regulators and claiming that the add-on technology was so flawed that it failed to meet the clean-air requirements.

If Navistar’s engine works — the company recently submitted test results for the latest version to the Environmental Protection Agency for certification — it could be the simplest, most elegant solution to the vexing engineering problem of how to reduce smog created by diesel truck exhaust.

But the company would also have to persuade skeptical fleet owners to buy the engines. If those owners do not see a clear advantage in operating costs and fuel efficiency, Navistar could find itself stuck as the only engine maker promoting an alternative technology to the rest of the industry’s E.P.A.-approved approach.

The company has already paid a price for choosing the road less traveled. While its engines have been in development, its share of the United States market for the heaviest trucks fell to 20.2 percent this year, down from 28.5 percent in 2009, according to researchers at JPMorgan.

Many of Navistar’s fellow truck makers and some environmental groups have dismissed the company’s complaints as the desperate grumblings of a truck builder that painted itself into a corner with a system that some have written off as impractical — the Betamax of pollution control technology.

Navistar says its approach to NOx reduction will ultimately be justified.

“We didn’t make this decision lightly,” said Jack Allen, the president of the company’s North American Truck Group. “We’ve been making diesel engines for 75-plus years, and we evaluated every alternative that was out there. We’re confident that our solution is what customers will want.”

Operators of truck fleets say they are keeping an open mind.

But so far, the add-on systems made by other truck companies offer the best combination of “fuel performance, upfront purchase price and running costs,” said Art Vallely, senior vice president of rental and vehicle management for Penske Truck Leasing, which operates 200,000 vehicles.

Diesel engines in the nation’s 18-wheelers, buses and other heavy-duty vehicles power less than 10 percent of all vehicle traffic in the United States, but they account for an outsize portion of the haze of pollution that hangs over many American cities — as much as 25 percent by some estimates.

Reducing those emissions is an engineering challenge in which every tweak has consequences. Reducing the temperature of combustion, for example, is an easy way to reduce NOx emissions. But it also generates more soot — the black smoke coming out of a diesel engine. The soot levels can be reduced by altering the timing of combustion, but that raises fuel consumption.

Standing on the floor of Navistar’s engine facility here, Luis C. Cattani, a chief engineer with the company, recalled that he was discouraged by colleagues from joining Navistar after a career designing high-performance engines in Detroit. “They said, ‘Oh, you’ll be so bored,’ ” Mr. Cattani said. “But as an engineer, you really love this sort of challenge.”

Recognizing the complexity of the issue, the E.P.A. gave truck makers a decade to engineer a solution when it issued new NOx limits in 2001. Navistar was an early proponent of a technique called exhaust gas recirculation, or E.G.R., a well-established process in which burned gases from the engine exhaust are routed back to the cylinder, diluting the mixture and lowering the temperature of combustion, which in turn reduces the amount of NOx formed.

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