Diesel engines will remain the predominant power source for commercial trucks

In less than a decade, rules mandated by EPA will force diesel engine makers to cut the amount of particulate matter and oxides of nitrogen emitted by their products by 90%. While those numbers seem daunting—and will require some new engine and exhaust aftertreatment technology to achieve—they won’t drive diesel engines out of the trucking industry. Not by a long shot, contends Allen Schaeffer, executive

In less than a decade, rules mandated by EPA will force diesel engine makers to cut the amount of particulate matter and oxides of nitrogen emitted by their products by 90%. While those numbers seem daunting—and will require some new engine and exhaust aftertreatment technology to achieve—they won’t drive diesel engines out of the trucking industry. Not by a long shot, contends Allen Schaeffer, executive director of the Diesel Technology Forum (DTF), Herndon, VA.

“Diesel is inherently the most efficient truck power source, period. No other engine technology can match its power and density,” he says. That’s not just idle talk. According to a report prepared by Charles River Assoc. for DTF called “Diesel Powers America,” diesel engines provide the power to move 94% of all freight in the U.S. and 95% of all transit buses and heavy construction machinery.

And while freight traffic increased nearly 25% over the last decade, the cost of moving it has declined by 4%, which Schaeffer says highlights the efficiency and practicality of diesel engines. Diesels achieve a better level of performance than gasoline engines because they operate using highly compressed air instead of spark plugs to ignite fuel.

It’s also a technology under increasing pressure to decrease emissions—reductions that may, by 2007, make diesels actually run cleaner than natural gas-powered engines. The concern with this new phase of cleaner diesel power is how attaining lower emissions levels will affect the fuel economy, performance and life cycle of diesel engines.

The real challenge posed by the demand for cleaner diesel emissions comes from the engineering changes necessary to reach the levels mandated by EPA. Right now, exhaust gas recirculation (EGR) systems are being used to help burn off particulates by funneling them back through the engine. Some manufacturers are using variable turbochargers to enable that process, while others are using specially designed exhaust system valves to reintroduce the exhaust air.

Meeting 2007 emissions levels, however, will require high-tech systems that treat the exhaust before it gets vented to the outside air. Many industry engineers believe such aftertreatment systems can involve the use of different chemicals that will “change” the exhaust from diesel engines into something cleaner.

Much of the concern, however, centers on the upfront and maintenance costs of such aftertreatment technology. “Exhaust aftertreatment systems being developed to meet 2007 emissions regulations will most likely impact vehicle specifications, parts, maintenance programs, and ultimately resale value,” says Larry Strawhorn, vp-engineering for the American Trucking Assns. “Look at suggested catalytic converters for diesel exhaust. Some may hold up to $3,000 worth of platinum to enable the necessary chemical reactions,” he says. “A maintenance program will be needed to remove residual ash, for starters. Then these devices will have to hang out in harm’s way like mufflers, exposed to damage, etc. Also, theft may be a problem. In an industry that has problems with people stealing $50 replacement tires from under truck trailers, what happens to a catalytic converter with $3,000 worth of platinum in it?”

Christine Vujovich, vp-environmental policy and product strategy for Cummins, puts it even more bluntly. “The last 30 years of diesel engine development have shown we can change and improve our products to meet government standards,” she says. “But the ’07 rules are very, very stringent; this is the toughest challenge we’ve ever faced. And it is the first time I’ve ever come before the EPA without a clear idea of exactly how we’re going to get to those levels.”

The road ahead

The way Vujovich sees it, however, diesel engines won’t disappear because of impending emissions regulations; diesels are too vital a cog in the national economy to be disposed with. Yet the way the diesel engine is viewed by the trucking industry and other users will undergo a fundamental shift.

“First of all, government and society at large do value the contribution the diesel makes to our way of life in the U.S.,” she says. But the trucking industry must realize that the environmental impact of the diesel will be a focal point for the government and the public as the 21st century progresses.

Vujovich says the technology exists to get diesel engines down to the emissions levels demanded by the EPA. “But with greater emissions controls come added cost,” she adds. In the final analysis, Vujovich believes that not only will the diesel survive, but the effects of emissions control efforts could be minimized if fleets work more closely with engine manufacturers and even EPA. “We need more involvement from fleets—to sit down with EPA to discuss emissions reductions, mobile testing, etc.,” she says. “It’s an opportunity for the trucking industry to be a billboard for clean air efforts, yet have technology on hand that will still help them get their primary job—hauling freight—done in a cost-effective manner.”

Detroit Diesel is another engine maker that believes diesel will survive as a viable powerplant for trucks in the future. The company says the negative impact of lower emissions levels can be minimized by using advanced technology.

“Our goal is to continue improving until any difference compared to current ratings is insignificant,” says John Morelli, vp-2002 Engine Program, Detroit Diesel Corp. Currently, the company’s 2002-compliant engines have only a 2%-4% fuel economy penalty.

“Soot loading of engine lubrication oil, once considered by some to be a potential problem, is in line with current production engines,” he adds. “We had to do a lot of work to get where we are and we remain committed to do even more work to make sure our Series 60 engine keeps all of its advantages.”

“Over the past 20 years, there have been continuous concerns that engines built to meet the ever-demanding standards would suffer losses in fuel economy, durability or cost of operation. But when you look at today’s engines compared to those of 20 years ago, there’s really no comparison,” Morelli says. “Today’s engines provide much better fuel economy, and are easier to drive and maintain.”

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