Diesel: In it for the long haul

Jan. 1, 2020
The diesel market is in the midst of a revolution. Years had passed with little innovation, but now there is an explosion of spectacular sophistication and enhancements that are increasing engine power and torque, lowering emissions and enhancing fue

The diesel market is in the midst of a revolution. Years had passed with little innovation, but now there is an explosion of spectacular sophistication and enhancements that are increasing engine power and torque, lowering emissions and enhancing fuel economy (from 20 to 40 percent), creating a new, cleaner diesel vehicle much more enticing to U.S. consumers, especially in the wake of high gas prices.

Many industry experts suggest these new diesel engines have surpassed gasoline vehicles in terms of performance and technology, and that if diesels enter the light-duty market at the rate some sources are anticipating, the landscape of aftermarket parts and service will surely change.

Some say North America’s newfound interest in diesel vehicles is coming from the growth in Europe, where diesels now make up close to half of the vehicles on the road, according to information collected by Bosch. Market share as high as 70 percent exists in Austria, Belgium and France.

“Hopefully this trend will cross over to the U.S. as well, where the diesel’s fuel economy along with lots of torque, horsepower and driveability would appeal to the American motorist who travels long distances,” says Al Krenz, director of aftermarket service, Automotive and Diesel Products, for Robert Bosch Corp.

Original equipment manufacturers have been extremely successful at developing diesel passenger cars, sport sedans and light-duty trucks and SUVs that perform remarkably well. Popular European models include the BMW 740D, Audi A8 TDI Quattro, Mercedes-Benz E320 EDI, Volkswagen Touareg V10 TDI and Jeep Grand Cherokee 2.7 CRD. Lexus just launched its first ever diesel in Europe — the 2006 IS compact sport sedan. By 2010, the automaker anticipates a three- to four-fold increase in sales.

A trend revs up

As for the U.S. diesel market, it has long been dominated by full-size and heavy-duty diesel pickups. But that is all about to change since companies like Daimler-Chrysler and Mercedes-Benz have entered into the U.S. light-duty market with the Jeep Liberty CRD and the E320 EDI. VW is also a big, yet very quiet, player in the diesel market. They have diesel versions of the Golf, New Beetle, Jetta, Jetta Wagon and the Passat. And coming soon is the Audi Q7 diesel SUV, among others.  

According to the Diesel Technology Forum, R.L. Polk & Co. data show that the registration of diesel passenger vehicles in the U.S. has grown by almost 56 percent since 2000. Five years ago, 301,000 diesels were sold in the passenger car category. In 2004, there were nearly 470,000. For the popular medium-duty truck segment, which includes the Silverado, Dodge Ram, Ford F-Series and GMC Sierra trucks, nearly 60 percent of consumers chose the diesel option in 2004.

Based on a 2003 JD Power & Associates Clean Diesel Market Assessment Study, if given a choice between a traditional gasoline, clean diesel or hybrid electric engine in their next vehicle, 27 percent of consumers said they would select a clean diesel. Given a scenario where fuel prices rise above $2.50 per gallon, which is fairly close to today’s fluctuating prices, 56 percent  claimed they would select a clean diesel-powered vehicle; 38 percent chose hybrid.

“We are kind of the oddball in the world,” says Allen Schaeffer, executive director of the Diesel Technology Forum, a nonprofit educational association promoting clean diesel technology. “Most other markets push diesel engines whereas we are predominately gasoline.” That growth overseas has certainly led to the technology making a comeback here, he asserts.

JD Power expects diesel cars and trucks to comprise as much as 16 percent of new light-vehicle sales in North America by 2015. Diesels made up 4.5 percent of car and light truck sales in North America in 2002.

A technology transformation

Modern diesel vehicles are stocked with new technologies that enable optimum performance. “When you boil it all down, it’s the coming together of the electronics, fuel system and turbocharging. The revolution that has taken place allowed the industry to have a much higher output per volume and at the same time meet emissions standards,” says Jim Weidenbach, manager of small diesel applications for DaimlerChrysler.

The days of old, dirty, noisy diesels that accelerate at painfully low speeds are gone. “Electronics have really been a major force in making the diesel more palatable,” says Krenz, adding that, “We can call diesel systems engine management systems because they are all electronically controlled. They take information from various sensors on the vehicle and convert that into a signal that drives the injector.”

Bosch is heavily involved in the electronic fuel management system now seen in many diesels. Krenz explains that with common rail injection technology, electronic sensors are used to control the pressure and amount of diesel fuel delivered to the injectors. In the latest systems, these injectors deliver fuel in multiple pulses (vs. one big shot) to highly compressed air in the engine combustion chamber, leading to a more complete combustion and more even fuel distribution per cylinder. “This helps with noise and emissions,” says Krenz. “Injectors were previously triggered by pressure…that’s when you got the diesel rattle. Now, they’re almost as quiet as gasoline cars.”

One truth shared by many is that diesel vehicles could not be as advanced without turbochargers. “There is no such thing as a diesel engine without a turbocharger,” says Dr. Syed M. Shahed, vice president of advanced technology for Honeywell Turbo Technologies. He tells us that conventional turbochargers weren’t able to adjust the speed of the exhaust going into the turbine housing like today’s new variable geometry turbochargers.

“Diesel engines were seen as dirty dogs — smoky, heavy, slow off the curb — but variable geometry has taken care of all that. Today’s turbochargers make good use of exhaust energy that might otherwise be wasted,” explains Shahed. 

Turbochargers are tuned for each vehicle and the variable geometry mechanism calibrated to meet the requirements of that vehicle, but it’s “one of the main reasons [diesels] are becoming cleaner, quieter, more driveable.” Honeywell works with the majority of heavy-duty diesel manufacturers in the U.S. and is involved in the passenger vehicle market in Europe and the United States.

The piezo injector, developed by Siemens VDO, is one of the newest diesel technologies. Current common rail systems use solenoid-driven injector actuators, which are slower in their ability to lower combustion noise and reduce emissions. The actuation of the injector, the most important parameter in a diesel engine combustion process, is what distinguishes the piezo system from other common rail systems in production today. 

The Siemens VDO piezo electronic actuators are four times faster than solenoid actuated systems, which makes it possible to achieve optimized injection control during the combustion process.

Even glow plugs, which take the place of spark plugs, are seeing advancements. Serving as electrical heating devices that help ignite the fuel when the compression pressure is too low, innovations have allowed for the placement of sensors on the end of the plug in order to monitor combustion directly in the cylinder.

New fuel for a new age

The discussion of diesels would not be complete without delving into the importance of ultra-low sulfur fuel, which will be made available in phases starting in September 2007. According to information from the Diesel Technology Forum, “Ultra-low diesel fuel is a specially refined diesel fuel that has dramatically lower sulfur content than regular on-highway diesel and can be used in any diesel engine just like regular on-highway diesel fuel.”

The report says that our current diesel fuel has a maximum of 500 parts per million (PPM) of sulfur. The new fuel is required to have no more than 15 PPM sulfur. This new fuel will dramatically reduce the amount of emissions emitted by diesel engines and will enable the use of emission-reduction equipment, such as particulate filters and exhaust gas recirculation, which traps nitrogen oxides, deemed to be a serious pollutant by the EPA.

Reports suggest that this low sulfur fuel is essential for the new diesel vehicle’s success, and automakers are pushing to ensure the cleaner-burning fuel regulations are enforced. An article from Automotive News suggests that the oil industry challenged the rule on a federal level in May 2002 and very recently sought flexibility in the implementation from the EPA. Interviews from Automotive News suggest oil companies are concerned that the new fuel can become contaminated during pipeline transmission and are looking for flexibility with the 15 PPM requirement.

Under the hood

As for the newest additions to the North American diesel family, the Jeep Liberty CRD features a state-of-the-art common rail diesel system, which is standard in most new “clean diesel” products.

“An accumulator allows you to store fuel at high pressure for use when you need it,” explains Weidenbach. “The higher injection allows for better fuel atomization, better emissions and output in terms of torque.” The acceleration of the four-cylinder diesel vehicle is comparable to that of a V6 gas engine, and its torque output to a gasoline V8. Gas mileage improvements are 30 percent better than the Liberty’s comparable 3.7-liter V6 gasoline model. It also offers a 20-percent reduction in greenhouse gas emissions.

DaimlerChrysler, which has been building and selling light-duty diesels in Europe since 1992, has sold about 1,000 Liberties so far and another 1,500 are at dealerships awaiting purchase. “They are not lasting in dealerships very long,” claims Weidenbach, pointing out that the CRD model is actually selling quicker than its gasoline counterpart.

Mercedes-Benz returned to the U.S. diesel market in 2004, after a five-year hiatus, by launching the only diesel luxury car on the market, the E320 CDI. They sold 4,100 units last year alone. The turbocharged six-cylinder outperforms its gasoline-powered sibling, according to Cox News Service. “Horsepower is a mere 201, but the turbo-six whips out 369 pounds-feet of torque at only 1,800 rpm (the engine red-lines at 4,500 rpm),” the author reports.

EPA figures for the gasoline E320 are 19 mpg city and 27 mpg highway, while the CDI is delivering 27 mpg and 37 mpg city and highway, respectively.

Volkswagen (VW), which utilizes a different engine technology, actually sells several diesel models, the most recent being the Touareg V10 TDI. The engineers at VW say that controlling the mist into the cylinder is the most important aspect of TDI technology. “The electronic control of this injection directly into the cylinder allows for a more precise, high-pressure fuel spray that is beneficial to the combustion process that creates the power,” explains Tony Fouladpour, press relations manager for VW — Americas. This allows for fewer tailpipe emissions, promotes better fuel economy and the engine performs better.

Fouladpour says they’ve been selling generations of the TDI since 1995. As for sales in the U.S., VW sold slightly more than 30,000 diesel vehicles in 2004 out of a total of 256,111 vehicles. About 50 percent of their vehicles in Europe are diesel, though the Touareg’s diesel version dominates. About 65 percent of consumers in Europe choose the  diesel Touareg over the gasoline model. Fouladpour told Aftermarket Business that VW has actually been offering diesel vehicles in the U.S. since 1979 and has remained a strong proponent of diesel technology.

An emissions mission

“Southern California Air Quality Management, CARB (California Air Resources Board), environmental groups and the EPA used to be very opposed to the concept of diesel engines. Over time, they have actually seen what the technology has done for Europe,” says Shahed.

Diesel vehicles have a number of environmental advantages over other types of internal combustion engines. Of the five major emissions — carbon monoxide, hydrocarbons, carbon dioxide, particulate matter (PM) and nitrogen oxide (NOx) — diesels emit small amounts of the first three. However, when it comes to the latter two, exhaust emissions get more complicated. 

The entire diesel industry has accepted the challenge of reducing PM and NOx emissions and has made great strides. Explains Krenz: “Particulate emissions will go away by 2007. We’ve reduced overall emissions by over 90 percent in the past 10 years.” NOx emissions too have been minimized over the last several years.

Despite these accomplishments and advantages, new, ever more stringent emissions standards are making it increasingly complicated for OEMs to keep up. Many are using special devices and additives to make the vehicles meet standards, but new laws are being passed regularly.

Currently, Volkswagen’s Touareg V10 TDI, boasted as having the largest and most powerful direct-injection diesel engine in an SUV, had to suspend sales in the U.S. for 2005. The EPA would like more tests conducted on a liquid additive that VW uses in its exhaust treatment system to reduce emissions. “This additive has been successfully used in Europe with good result, however, the EPA determined it needed to conduct its own testing,” a statement read. Though VW considers this a setback, they’re determined to bring the “most advanced and cleanest diesels to this market.”

DaimlerChrysler’s Jeep Liberty CRD and Mercedes-Benz’s E320 CDI do not meet the LEVII emissions standards that became effective this year in California and therefore cannot sell their vehicles in the Golden State or in the four other states that have adopted the same standards (Massachusetts, Maine, New York and Vermont).

Rob Moran, manager of Product and Technology Public Relations for Mercedes-Benz, says this is one of their biggest obstacles right now. But, he suggests that when the new low sulfur fuel hits, “we’ll see more diesels enter the market.” He explains the new fuel will be vital in developing diesels that meet the new standards, though particulate filters and gas recirculation technology will also play an enormous role in the future of diesels.

Cooled exhaust gas recirculation (EGR) is being used to reduce NOx emissions. The use of EGR tends to increase particulate emissions.

In today’s engines, an EGR takes about 10 to 15 percent of the exhaust gas that would otherwise be emitted through the exhaust pipe and redirects them through a cooler, bringing them gases to about 350 degrees F, and injecting them back into the intake system.

“These gases don’t have any oxygen in them so they aren’t going to burn,” says Gary Parsons, global OEM and industry liaison manager for Chevron Oronite Company. They sit in the cylinder and absorb heat, which helps reduce the peak temperature and pressure of combustion. The amount of NOx in the exhaust stream is directly related to the peak combustion temperature. “As (with) everything, there is a trade-off,” says Parsons. “As you inject more EGR gases into the combustion chamber, you tend to increase particulate emissions. And in 2007, the particulate matter specifications will become tight enough that they can no longer do it without a filter on the exhaust system.”

Particulate filters collect particulate matter as the exhaust gas passes through and can reduce particulate emissions by 80 and 90 percent. Mercedes-Benz said it will be the world’s first automaker to equip all of its diesel passenger cars with a particulate filter as standard, initially starting with vehicles sold in Germany, Austria, the Netherlands and Switzerland. A total of 30 different models will be involved.

Ford claims it has developed a system that will enable its future vehicles to meet even the most stringent emissions standards. The Onboard Reductant Delivery system, as it is called, is an air-assisted reductant injection system that quickly delivers liquid reducing agents, which are needed in almost all diesel after-treatment devices.

In the aftermarket arena

Based on input from the 2003 JD Power and Associates study, consumers expressed some concerns about clean diesels, including limited availability of fuel and repair locations, along with maintenance costs. Clearly, the aftermarket will be commissioned to help combat these concerns should diesels make a major impact.

“If diesels are accepted, there will certainly be an impact in the aftermarket,” says Weidenbach. “They are a bit different and do require different parts...there will be a learning curve on working on these vehicles,” he explains. Diesels will require some of the same diagnostic analysis as gasoline engines due to their electronics.

Shahed from Honeywell reports that diesel engines have “a reputation to last longer. Some [heavy-duty models] can do half a million miles before they need to be rebuilt.” It seems as if diesels may increase the average age of vehicles on the road, a good sign for the aftermarket community.

Krenz from Bosch thinks that servicing diesels will “pretty much be like servicing a gas vehicle,” in that they will require technicians to connect a scan tool and read a fault code. “Both have a fuel pump, rail, injector and sensors. The main difference is the pressures,” he says, adding that, “we need to have more drive-in facilities for the anticipated work that will be coming our way when the diesel market expands.”

Bosch has several authorized training programs in the U.S. that include hotlines, tech support and service information.

SEMA’s 2004/2005 Diesel Market Study points out that the light truck diesel segment already represents a growing market — as demand for engine parts alone will likely reach $375 million by 2007. Distributors will need to stock more products specific to diesel vehicles, and that can include everything from glow plugs (though these are more typical on older model diesels) and common rail system components to diesel motor oil and special filtration components.

And with different components, there will be different service and maintenance routines. Parsons notes that the diesel “is a more expensive piece of equipment and is less forgiving” than a gasoline engine, adding that tolerance is much lower and precision is crucial during repairs. For example, “if you get any air in a diesel fuel system, then it just won’t operate properly. With a gasoline engine, you don’t need to worry about it that much,” he says.

Also, when it comes to the particulate filters, though it hasn’t been established fully yet, “there is a high likelihood that these traps will need to be exchanged or cleaned,” suggests Parsons, who explains that the repair shop may just take the cartridge out and clean it or send it to a central facility and get an exchange.

Chemicals, like antifreeze/coolant and motor oil along with their service intervals, will also be vastly different for diesels. “The pressures and temperatures in a diesel are higher than a comparable gasoline engine,” says Parsons. Diesel engine oils have more anti-oxidants and higher levels of detergents and dispersants because these oils need to fight off acid and other contaminants that can get into the oil as a result of the combustion process. And diesel engines typically have larger crankcase capacities than gasoline engines since its engine oil is subjected to more severe conditions. According to Parsons, it is important to follow the recommendations in the owner’s manual for proper drain intervals.

A forecast for the future

The diesel Liberty is “a toe in the water, so to speak, to see if the diesel has some acceptance in the light-duty market,” Weidenbach told Aftermarket Business. He thinks the entire industry is viewing the market in the same way. 

Mercedes-Benz’s Moran says they too are still determining what the acceptance is. He does think that a lot of what happens  will be based on legislation, though he is confident that diesels will see some positive growth, just as they did in the 1980s when “diesels accounted for close to 80 percent of our sales in the U.S,” he says. Will it peak and then decline like it did then? Based on the technology, it seems as if the sure answer is no. Based on the stringent emissions standards, time will tell.

“Exhaust treatment technology needs to be brought to maturity,” says Shahed. “It’s well along in Europe, but we have more strict urban emissions [standards], but it can be done. It’s just a matter of working on it.”

Allen Schaeffer, executive director for the Diesel Technology Forum says there are three issues that need to be resolved:

1. Getting vehicles to meet 2007 emissions standards. “These new standards are quite significant.” From 2002 to 2004, there was a 50-percent reduction. The new standards will require another 40- and 45-percent reduction in particulate matter and nitrogen oxide, respectively, from today’s standards.

2. Getting the market in shape. “Consumers need to be willing to buy [diesels],” though “we are seeing some positive trends.” But part of this involves getting the U.S. to accept the higher premium.

3. Establishing a business case for diesels. Schaeffer says, “It’s an expensive proposition to bring in light-duty diesels or any vehicles for that matter.”

He happily reports, however, that all three initiatives are no doubt in motion.