D-Days in Detroit

Actually, you don't have to hold your nose, thanks to massive engineering efforts underway in Detroit today to clean up the emissions spewing from diesel tail pipes —and to clean up the less-than-stellar image those cars have among American drivers.

Armed with an arsenal of studies showing the fuel savings and power potential of diesels, all three U.S. automakers have zeroed in on that technology as one of their principal weapons in the battle to produce cars that sip rather than guzzle fuel. While they continue to work on fuel cells—which many believe are the ultimate energy savers—industry experts say they won't be practical for every-day transportation for at least another ten years. Gasoline-electric hybrids? They have potential too, industry experts assert. "But the battery is a major cost issue," says John B. Heywood, director of the Sloan Automotive Lab at the Massachusetts Institute of Technology (MIT) and a noted expert on internal combustion engines.

Diesels, on the other hand, are here today.

"Diesel is the only technology that gets us fuel savings in the short to midterm," says Jim Weidenbach, DaimlerChrysler's manager of small diesel applications. Indeed, DaimlerChrysler will be the first U.S.-based carmaker out of the gate with a diesel for the domestic market: It plans to bring the diesel Cherokee it sells in Europe to U.S. shores in 2004 and market it here under the Jeep Liberty name plate. (Its sister company, Mercedes-Benz, will also send the diesel E320 sedan to the the U.S. in 2004, and Volkswagen will market a diesel car or two here as well.)

While Ford has no definite plans to bring out a diesel passenger car or light-duty vehicle in the U.S., it's pursuing an extensive research program. Its technical staff has been testing two different diesel Focus models—one of them their European model—to build awareness while checking out some new emissions technology.

GM too is investing time, talent, and dollars in diesel technology, mindful not to repeat mistakes made in the late 1970s. During that decade's oil crisis, GM introduced a well-intentioned diesel Oldsmobile to gas-starved U.S. consumers that turned out to be one of the more legendary marketing stinkers in recent automotive history. It appeared then diesels were an idea whose time had not come.

The Right Time

"But, the time is getting right now for diesel passenger vehicles in the U.S.," says Dick Baker, Ford's corporate specialist on combustion and emissions issues. The reason, he says: Diesel's 30 to 40% fuel-efficiency advantage over gasoline engines should appeal to U.S. consumers who are finally getting more sensitive to energy issues.

Thousands of energy-conscious drivers are already piloting diesels on wide highways and narrow city streets. But most of them live in Europe, which has much higher gas prices and different standards for clean air than the U.S. All the U.S. automakers successfully sell diesel models on the European side of the pond. In fact, about 40% of the passenger cars in Europe are diesels, and that number climbs to about 70% in France—which, says DaimlerChrysler's Weidenbach, shows that when it comes to the advantages of diesels, "the rest of the world gets it."

And what they "get" that many Americans haven't grasped yet is this: Diesels pack punch. They zip while they only sip fuel. "They have great power and torque," says Charlie Freese, executive director for diesel engines at GM. For example, Robert Bosch, Inc. (www.bosch.com), which supplies engine and other systems to automakers worldwide, reports that a 2002 BMW 530d (diesel) produces 302 lb/ft of torque at 1,750 rpm vs 221 lb/ft at 3,500 rpm for the gasoline-engine version of that car. Horsepower ratings are, respectively, 193 at 4,000 rpm vs. 231 at 5,900 rpm. Of course, hybrids can be peppy off the starting line too, but MIT's Heywood says diesels would quickly catch and pass them.

Future block: Diesel engines similar to this one from Ford could become more popular among U.S. drivers as a result of majore research and develoment activities in Detroit. The engines already zip while they sip fuel. Now, engineers are cleaning up their emissions.

Diesel's power comes partly from the fact that a gallon of diesel fuel is denser and has a higher carbon content than gasoline, and therefore a higher energy density. But the added oomph is also due to the nature of the technology itself. Diesel engines compress only air, not the fuel/air mixture that gasoline engines compress. That makes their compression ratio higher (within a range of 16:1 to 20.1 vs. a range of 8:1 to 11:1 for gasoline engines). That higher compression ratio alone generates more power. Europeans understand that. "In Europe, 80% of luxury cars are diesels, and it's not because those car owners worry about fuel-cost savings," opines Weidenbach.

All that extra power should make diesels an easy sell to U.S. drivers who want jack-rabbit-quick starts when the traffic light turns green—which is to say virtually everyone here. Indeed, many automotive engineers feel it's that performance advantage—which gasoline-electric hybrids can't claim—that will win hearts and minds in the U.S. more than the energy savings.

There's evidence already that the victory is getting closer. In a 2002 J.D. Power and Associates study, nearly two-thirds of the respondents—all from the U.S.—said they would definitely or probably consider purchasing a new vehicle with a clean diesel engine that provides comparable performace, noise and vibration elimination, and visable exhaust to a gasoline engine. And that percentage could increase if legislation filed by U.S. Representative John D. Dingell is approved by Congress. Dingell, who hails from Ford's hometown of Dearborn, MI, has proposed a Federal income tax credit to consumers who spend the extra $1,500-2000 for a fuel-efficient clean-diesel car between January 2005 and December 2010.

Diesels unplugged: Cleaning up emissions from diesel engines requires new filter technology. In this view, a coated particulate filter forces exhaust flow through its wall where a catalyst cleans the particulates.

There's just one not-so-tiny problem dropping acid rain on the diesel parade: emissions. Current diesel engines don't meet planned U.S. Environmental Protection Agency standards for particulate (read that as "soot") and nitrogen oxide emissions from passenger cars and light-duty vehicles. That's where automakers are putting many of their diesel dollars now. "We have to prove to ourselves that we can meet the emissions challenges," says Ford's Baker.

But in the process of proving it, engineers are running into a classic case of balancing tradeoffs. GM's Freese says that often technology that cuts nitrogen oxide increases particulates. And Baker says the jury is still out on whether emissions-control solutions will adversely impact the twin diesel benefits of fuel economy and performance. Engineers don't think there will be any compromises there, but they're not sure. Nor are they absolutely, positively sure there will be a market when they do lick the emissions problems, though all indications look positive. "We're still in the inventing stage," says Baker. "The tech guys have to take a cold shower now and then."

Perceptions and Misperceptions

So do many U.S. consumers over the age of 40, legions of whom remember the dirty, balky, loud diesels of their youth. Diesel-engine technology has come a long way in the last 30 years. So, any discussion of diesel technology for passenger cars and light-duty vehicles has to begin with a look at the perception vs. the reality of diesel today.

• Perception One:Diesels are difficult to start in the cold. Well, they used to be, but not so much anymore. Unlike gasoline engines, which use a spark to ignite the compressed fuel-air mixture, diesels compress just the air, then inject the fuel into it, relying on the heat of the compressed air to ignite the fuel. When the diesel engine is cold, the compression process might not warm the air up enough to ignite the fuel. Glow plugs—electrically heated wires—help, as does common-rail technology that injects fuel at extremely high pressure, but we'll discuss that a little later. In any event, DaimlerChrysler, for one, tests its diesels for starting at a respectable -15F with a standard battery, and, says Weidenbach, may start testing to an even colder standard. By the way, he reminds inquisitors, gasoline engines don't always start so easily in extreme cold either.

• Perception Two:Diesels are finicky. Guilty as charged, says MIT's Heywood. "Serious repairs could be expensive," he says. Engineers are working to correct that.

• Perception Three:Diesels are noisy. Yes, but truthfully you almost need electronic instrumentation to detect the difference in noise level in modern diesels from that of gasoline engines. Says GM's Freese: "The barking, clattering diesel is gone." The clatter was the ringing of the engine block during combustion ignition, but the precise metering of fuel enabled by common-rail technology has largely done away with that. Still, diesels do sound different, if not appreciably louder. If they were vocalists they would be baritones, where gasoline engines would be tenors. Europeans, who buy diesels by the droves, apparently like that lower tone. Automakers think there's a chance Americans could learn to like it too.

• Perception Four:Diesels are dirty. Okay, now the discussion gets interesting. In general, says Allen Schaeffer, executive director of the Diesel Technology Forum, diesel engines actually emit less hydrocarbons, carbon monoxide, and carbon dioxide than gasoline engines. In fact, the $4 million 1998 Northern Front Range Air Quality Study performed by Colorado State University concluded that it was gasoline engines, not diesels, making the biggest contribution to pollution problems in the Front Range of the Rockies. So, on at least one level, diesel engines are relatively clean. "We're testing diesels in the GM labs that won't soil a white handkerchief," says Freese.

Squirt Gun: When voltage hits piezo crystals in a common-rai module, the crystals expand, moving injector needles and squirting diesel fuel into the combustion chamber at about 30,000 PSI. The result is more precise dosing and atomization of the fuel.

The problem with diesels is in those sooty, carbonaceous particulates and the nitrogen oxide, both of which, quite literally, poison the air we breathe. The Union of Concerned Scientists says that studies show diesel exhaust causes cancer in rats and could be a human carcinogen. The nitrogen oxide also contributes to ozone formation, the major ingredient in smog. Obviously, these pollutants are a big problem, and the automakers and their suppliers are tossing a lot of R&D money into efforts to solve it.

Actually, they have to if they want to sell diesels to the U.S. passenger-car and light-duty-vehicle market. So-called Tier II regulations emanating from the U.S. Environmental Protection Agency require about a 77% reduction in nitrogen oxide from all such vehicles—gasoline and diesel-powered alike—by 2004. Meeting that goal for diesels will take a prodigious effort, given that the U.S. Department of Energy admits there has already been a 90% cut since 1980.

The particulates are the easier of the two problems to solve. "It's a fluid mechanics job," says Ford's Baker. Working with such suppliers as Corning, Johnson & Mathey, and others, engineers are developing filters that collect the carbon particulates. But carbon trapped in the filters builds up back pressure, which makes the engines work harder. Ceramic filters can tolerate the high temperatures needed to burn out the carbon and relieve the back pressure. "We collect the carbon on the filter and a couple of times per tank of fuel we force heat through it as if we were lighting briquettes on a grill," Baker says.

It's also possible to add a catalyst material to get the chemical reaction going at a lower temperature. For example, placing a small amount of platinum on a ceramic honeycomb substrate causes the oxidation of hydrocarbons and carbon monoxide to be completed in the engine exhaust if it wasn't completed in the combustion chamber.

NOX Killer: One strategy for lowering nitrogen oxide emissions is to inject urea into the exhaust stream under a system called selective catalytic reduction. The urea releases ammonia, which in turn reduces nitrogen oxide to nitrogen dioxide and water. But the urea must be separate from the diesel fuel. Ford, in its experiments, used a two-fluid nozzle for injecting urea and diesel fuel, something the company admits may be impractical.

Sticky Wicket

The nitrogen oxide problem is stickier, which is ironic since gasoline engines actually produce more nitrogen oxide than diesel engines. But the catalysts in gasoline engines are super efficient and cut about 90% of the nitrogen oxide from the exhaust. Those catalysts don't work as well for diesel engines. Catalysts for diesel engines cut only about 20% of the nitrogen oxide.

Engineers are experimenting with nitrogen oxide traps, which include a special catalyst that contains barium in addition to platinum and rhodium. In a complicated process that marries chemical and mechanical engineering, the nitrogen oxide reaches the trap under lean air/fuel conditions (excess oxygen), gets oxidized to NO³, and is trapped by the barium as barium nitrate. At that point, the engine would switch the air/fuel ratio to rich (less oxygen) by varying fuel-injection timing, among other things, and the barium would release the nitrate. Hydrogen would reduce the nitrate to nitrogen dioxide and water, which would go out with the exhaust. The reduction step would take only a few seconds, and then the engine would switch back to the lean-mixture mode. For that system to work properly, says Baker, engineers have to develop a combustion process that goes from lean to rich back to lean quickly. They don't have the process yet.

Quick Shot: Common-rai technology delivers diesel fuel to cylinders via computer-controlled injections. The figure on the right is a cutaway of an injector that uses piezo crystals. The crystals expand when hit with a a voltage and move the needle to inject fuel into the combustion chamber.

Another option under study is selective catalytic reduction (SCR). According to the Diesel Technology Forum's Schaeffer, SCR involves injecting urea into the exhaust stream as a reductant to drive down the concentration of nitrogen oxide. Urea dissolves in water and decomposes to release ammonia when heated. Ammonia can reduce nitrogen oxides to nitrogen dioxide and water.

Ford has used a urea system in its experimental diesel Focus and found it worked well, says Baker. The problem was getting the urea on board. Engineers needed a two-fluid nozzle to keep the urea separate from the diesel fuel. The implication there is that the nation's infrastructure would have to change to incorporate two nozzles at gas-station diesel pumps. "It may not be the technology of the future," Baker says.

Recognizing the engineering difficulties of reducing nitrogen oxide, the EPA has mandated that refiners make ultra-low-sulfur fuel available at the pump by 2006. Sulfur is the nasty culprit that causes pollution problems with diesel fuel. The EPA says it wants refiners to get the sulfur content down to 15 parts per million (ppm). That's quite a drop considering that low-sulfur diesel fuel, as opposed to ultra-low-sulfur, contains 500 ppm of sulfur. But it's a critical part of the diesel strategy. "It's the key enabler," says DaimlerChrysler's Weidenbach. Without it, others say, emissions technologies won't work well enough to pass muster.

Actually, at least one refiner is already making ultra-low-sulfur diesel fuel: BP. In fact, BP (www.bp.com) has that fuel at its ARCO retail stations in California now. The technology for lowering the sulfur content isn't black magic, but it is expensive, says BP Principal Engineer Ken Kimura. If it's not hard, why not take the sulfur content down to zero? Kimura says theoretically that's possible, but practically it's a non-starter. The problem is in the common-carrier pipeline that moves the fuel from the refinery to the consumer.

There are other high-sulfur products in that pipeline such as jet fuel, which contains about 3,000 ppm of sulfur. "A small quantity of jet fuel would make the diesel go off spec," he says. Of course, refiners could just build a separate system for carrying the diesel fuel, but that would be prohibitively expensive, Kimura asserts. So why not just lower the sulfur content of jet fuel? That, says Kimura, would require close cooperation between refiners and the aviation industry to ensure that the reliability of jet engines isn't compromised by the change. Besides, Kimura adds, "we don't know of any technology that absolutely requires 0 ppm of sulfur." In other words, there would be little gain for a lot of effort.

Veggie Cars

There is, of course, another alternative on the fuel side of the diesel question: biodiesel. It's liquid produced from renewable sources such as vegetable oils and animal fats, and U.S. government scientists have approved it as an alternative fuel for Energy Policy Act programs.

Biodiesel runs on the same principle as regular diesel and doesn't require any engine modifications, though, according to the U.S. Department of Energy, it may require special hoses and gaskets. Also, so-called B-20 blends (20% biodiesel blended with 80% conventional diesel) can slightly increase nitrogen oxide emissions, according to an EPA study.

Environmental groups like biodiesel and see it as a natural way to break away from dependence on foreign oil. Automotive companies are more cautious. Ford, for example, cites the EPA study and a few other concerns as reasons why it isn't enthusiastic about biodiesel, though it does approve of use of 5% blends in its engines.

In the end, the key to increased use of diesel cars in the U.S., bio or otherwise, could come down to old-fashioned marketing. Efforts in the 1970s to introduce diesels to the U.S. passenger car market gave the industry and the technology a big black eye. But, engineers are confident they can clean up the emissions sufficiently to meet federal regulations, and they know that Americans will like the way diesels perform if they only give them a chance. "Once people get accustomed to them, they'll like the aggressive low-end torque," says GM's Freese. The trick, then, is to get people into showrooms to do test drives. Perhaps the way to do that is for the automakers to videotape a testimonial from racecar-driving champion (and Infineon spokesman) Mario Andretti, who says he almost always rents them when he travels to Europe. "You can hardly tell you're driving a diesel anymore, and you can drive all day without giving anything away," he says.

Still, says the Diesel Technology Forum's Schaeffer, for the technology to truly win wide acceptance, you must see no, hear no, smell no diesel. "Customers who will make diesels a success are those who were only in diapers, or maybe not born, in the 70s and 80s", he says.

National Editor Paul E. Teague can be reached atteague@reedbusiness.com.