It's a powertrain engineer's equivalent of a Chinese finger prison. U.S. consumers crave big vehicles with powerful engines, while regulators prod automakers to improve fuel economy.
In a bid to balance those competing demands, a higher level of technology is finding its way into pickups and sport-utilities: overhead-camshaft engines with variable valve technology, five- and six-speed transmissions and a growing use of lightweight materials such as aluminum and plastic.
Yet one technology that offers power and fuel economy remains in the background: the diesel engine.
In Europe, where taxes dramatically increase the cost of fuel, diesels command about a third of the market. But in America, where gasoline is cheaper than bottled water, most drivers have no idea how smooth, clean and quiet today's diesel engine is.
A new look
It probably will be a few more years before they find out. But advances in fuel-system technology and better exhaust-filtering devices, plus government-mandated low-sulfur fuel that will be available in 2006, is prompting automakers to take another look at the energy-efficient powerplant for use in more than just heavy-duty pickups and jumbo sport-utilities.
'Until a few months ago this was a cold market for diesels,' says David Ladd, spokesman for Siemens Automotive of Auburn Hills, Mich., a leading supplier of fuel injectors and engine electronics. Now, he says, the buzz from automakers is that diesel engines are being examined seriously.
Though no automaker has revealed plans to introduce a new diesel-powered car or light truck in the United States, the diesel engine is an option they can't ignore, says Greg Dana, vice president for environmental affairs for the Alliance of Automobile Manufacturers.
'It's one of the tools they want to have in their hip pocket,' Dana says. 'Obviously, companies are going to look at diesels and diesel-hybrids.'
But upcoming Tier 2 emissions regulations, which go into effect in 2004 and aim to cut tailpipe emissions in cars and light trucks by 95 percent from today's limits, could delay the arrival of diesels until 2006, Dana says. That's when cleaner diesel fuel will be available.
Key ruling on sulfur
Last December, the EPA enacted regulations that call for the removal of most of the sulfur from diesel fuel. The rule, scheduled to go into effect in 2006, requires oil companies to reduce sulfur in diesel by 97 percent, from 500 parts per million today to just 15 ppm. That cleaner fuel must be available to 80 percent of the nation's drivers. The change is important because sulfur fouls catalytic converters and hinders the emission-control equipment.
Because diesels typically deliver 25 percent to 35 percent greater fuel economy than a similar-sized gasoline engine, automakers view diesels as a way to boost their Corporate Average Fuel Economy figures. This is true particularly for light trucks, where the popularity of pickups and sport-utilities has DaimlerChrysler, Ford Motor Co. and General Motors facing the prospect of fines for missing CAFE targets.
In late February, the auto industry signaled it has abandoned efforts to keep the government from raising fuel-economy standards, currently 27.5 mpg for cars and 20,7 mpg for trucks.
'We are very enthusiastic about the possibilities for diesel,' said Bryan Wallace, Washington public affairs manager for Daimler-Chrysler. 'People in the auto industry, in our company and in the government are looking at ways to improve fuel economy. The diesel is a great way to do that. We are already building PT Cruisers and Cherokees with diesel engines in Europe, and we'd love to bring them over here,' he said.
Still, diesels carry a lot of baggage in America. No matter how clean and refined diesels become, it will be an uphill struggle to make them appealing in mainstream vehicles.
Many of the gains in diesel engine performance and emissions in the past few years are the result of changes in the fuel injectors and fuel delivery system.
The common-rail fuel system uses a high-pressure pump to deliver the fuel to the injectors. Direct injection squirts the fuel directly into the combustion chamber, allowing for precise placement to reduce noise and emissions. Most diesel systems also use pre-injection - a small squirt of fuel to start the combustion before the bulk of the fuel is injected. In addition to assisting combustion, it also reduces noise and emissions.
The heart of the direct injection diesel system is the sophisticated, electronically controlled fuel injectors and the control module.
Siemens Automotive believes its new line of piezohydraulic injectors will lower emissions even further, increase fuel economy, cut noise and improve performance.
The new injector has a small actuator that responds to electronic impulses from the engine management system in 0.1 milliseconds - four times faster than the injectors used on most of today's diesel engines, according to Siemens.
That means the injector can fire at precisely the right moment and can deliver the perfect amount of fuel for a clean and efficient burn.
Trucks lead the way
Makers of diesel engines used in heavy-duty trucks are helping drive technology advancements that make diesels viable for light trucks.
Among them is International Truck and Engine Corp., which is developing a camless diesel engine that uses electronics to operate the valves instead of the usual camshaft, lifters and pushrods.
International, working with catalyst companies, is developing catalysts that can trap soot. International executives demonstrate the effectiveness of their clean diesels by holding a handkerchief over the tailpipe to show how the cloth remains clean.
Bill Rutecki, director of diesel products for Robert Bosch GmbH, believes the diesel can meet new emissions standards now that the sulfur content in fuel has been set.
'We view that as an enabler. Had that not been done, we would have a huge challenge before us,' Rutecki says.
Rutecki says there has been great interest recently on the part of diesel engine manufacturers to develop a small displacement diesel for light trucks. But he believes that the diesel won't reach the mainstream until consumers' perception of the diesel catches up with reality. 'There's a lot of misunderstanding out there, a host of issues,' he said.
Gas is cheap
The low cost of gasoline in the United States, in comparison to Europe, is a major obstacle.
'Consumers don't care about fuel economy. They keep buying sport-utilities and trucks,' says the Alliance of Automobile Manufacturers' Dana.
Consumers won't warm up to diesels, he predicts, until there is significant pressure on their wallets in the form of sharply higher fuel prices.
But even if fuel prices rise and engineers can make the diesel engine perform nearly as well as a gasoline engine, American buyers will still have to be convinced. That could be the most daunting task of all.
Says Wallace of Daimler-Chrysler: 'When you say diesel, people think back to the old stinky GM diesels spewing clouds of black smoke,' says Wallace of DaimlerChrysler. 'But there are plenty of smooth, quiet modern diesels available now in Europe. If we could get a few of them over here, I think those old stereotypes would go by the wayside very quickly.'
The GM factor
No matter how much diesel engines are improved, many car buyers likely will never trust them again because of the problem-plagued diesels General Motors built between 1978 and 1983. That, more than anything, many say, destroyed the reputation of the diesel engine in America.
'That was the dagger through the heart of the diesel passenger car market in the United States,' says Ladd of Siemens Automotive. 'That still hasn't healed. It comes up everywhere.'
GM converted its V-6 and V-8 gasoline engines to run on diesel fuel. But the engines suffered from badly designed fuel pumps. The higher compression and extra stress caused the engines to overheat. Serpentine fan belts flew off. GM customers couldn't get their cars fixed. The press lambasted GM, and many customers who bought a diesel lost so much money that they never forgave GM.
At one point, any GM diesel-engine car carried a $3,000 deduction in used-vehicle price guides.
Ironically, GM for years has built one of the toughest and most dependable diesels for use in the Hummer all-terrain vehicle and its military counterpart, the Humvee.
Gaining in trucks
In 2000, GM introduced the new Ohio-built Duramax turbocharged V-8 diesel. The 6.6-liter, 300-hp engine was developed with Isuzu, GM's Japanese partner. The engine is available in GM's new line of heavy-duty pickups.
With no advertising except word of mouth, the Duramax has been a sellout as GM slowly cranks up production. GM sold all 10,000 Duramax diesels it built in 2000, says Dave Roman, a spokesman for GM Powertrain. At full production, GM can build 100,000 units a year.
Ford and Dodge are also enjoying healthy sales of their diesel-powered trucks. Ford uses a big diesel V-8 built by Navistar International. The Power Stroke, as Ford calls it, has become so popular that an 11,000-strong owners club has formed and is growing at the rate of 4,000 new members per year.
Dodge has aligned itself with Cummins and uses an inline six-cylinder diesel, one of the loudest motors on the market, in its Ram trucks. Dodge fans like the big-rig sound of the Cummins diesel in their brawny Rams, and there are no plans to change that, said Dodge General Manager Jim Julow.
But can GM - or any automaker - transfer the popularity of diesels in pickups to cars and sport-utilities? Probably not, at least as long as gasoline remains inexpensive.
'We are not building anything for production yet,' says Jim Kerekes, GM's chief engineer for diesel engines at GM Powertrain. 'But we are monitoring the market, and if there's a need, we'll be ready. We are always looking.'
Ford also won't be moving into the diesel market anytime soon.
'If you don't have diesel applications in Europe, you might as well call it a day and go home. You won't be competitive,' says George Pipas, Ford's spokesman for sales analysis and forecasting. 'With gasoline at about $1.50 per gallon, there's no pressing need at this point. But today's diesels are a lot better than they were a few years ago.'
Kevin Ridell, a forecasting specialist for J.D. Power and Associates' Detroit office, also doesn't see the diesel making inroads in the near future. He says proposed emissions regulations and the relatively low cost of gasoline will keep the diesel in trucks and big sport-utilities.
'Automakers are looking at the fact that the EPA is taking a hard stance against diesels because of pollution,' he said. 'Particulate matter has been found to cause cancer. I think technology could solve that, but growth in the diesel market is just not there.'
Perhaps the best thing that could happen to the diesel is another fuel crisis.
Richard Truett is a staff reporter at Automotive News