Diesel engine technology has come a long way since diesel engines were introduced as an alternative to gasoline-powered engines. If you have ever sat next to a diesel-powered pickup truck at a stop light and had diesel fumes and soot blown in your face from a four inch exhaust pipe, you know what I'm talking about. Traditional diesel engines are about as eco-friendly as a smoke belching coal-fired steam engine from yesteryear.
But diesel engine technology has advanced considerably in recent years. The latest renditions on Otto's compression ignition engine bear little similarity to the black soot belchers of a decade ago. Common rail high pressure direct injection systems with sophisticated electronic controls have finally tamed the diesel, and made it a more eco-friendly alternative to gasoline-powered engines for passenger cars as well as light and medium-duty trucks. It can deliver better fuel economy with minimal emissions. But the move to Clean Diesel Technology has not been without controversy (scroll down to see the latest updates toward the bottom of this article). Emission cheating scandals have damaged the image of clean diesel technology.
Currently, diesel power-powered cars and light trucks account for less than four percent of the North American vehicle population. The German auto makers are the only ones selling diesel-powered cars in the U.S. Yet in Europe, diesel-powered cars account for nearly 60 percent of the vehicle population.
Why, you ask? Because diesels are up to 30 percent or more fuel efficient than a comparable gasoline engine of the same displacement and horsepower rating. Diesel engines get better mileage because they burn their fuel more efficiently. A diesel engine has a much higher static compression ratio than a gasoline engine, so it achieves more thermal efficiency from the fuel it burns. In other words, it produces less waste heat that goes into the cooling system and out the tailpipe compared to a gasoline-powered engine.
So if we all want better fuel economy, why aren't all the auto makers offering diesel-powered cars? Emission regulations have hampered the sale of diesel-powered cars in the U.S. But now that we have ultra low sulfur diesel fuel available, and new electronic diesel injection technology and after treatment systems, diesels can meet the toughest tailpipe emission standards.
Since 1988, Clean Diesel technology has reduced oxides of nitrogen (NOx) emissions 99 percent, and reduced particulate matter (soot) in the exhaust 98 percent! These are HUGE gains as well as proof of how clean today's diesel engines can actually run.
Green Car of the Year Tour
I recently attended a Clean Diesel technology event at the Argonne National Laboratory near Chicago, IL. The event was part of the 2010 Green Car of the Year Tour sponsored by the Green Car Journal magazine. The tour included several diesel-powered Volkswagen Jettas TDI models, and the Green Car of the Year winner, the 2010 Audi A3. The Audi A3 gets 42 mpg on the highway with a 2.0L turbodiesel engine, which is 50 percent better than the exact same car with a gasoline engine. All of the vehicles were available for journalists to test drive. My impression? All of the diesel-powered cars started right up, idled smoothly and quietly, and ran great.. .
If you've never driven one of these state-of-the-art Clean Diesel German cars, I would suggest you do so. You can't tell them from their gasoline -powered counterparts. There's no traditional diesel rattle, no clatter when you step down on the accelerator, no black soot in the exhaust. Just clean, smooth power with lots of low end torque.
A couple of years ago, I also attended an event sponsored by Bosch in Detroit that was promoting their Clean Diesel injection technology. They had a number of European Mercedes and BMW models, some of which were gasoline-powered and some of which were diesel-powered. The badges had been removed from the cars so the journalists couldn't tell which type of engine was powering the vehicle they were driving. I couldn't distinguish any noticeable difference in noise, smell or performance between the diesel-powered cars and the gasoline-powered cars -- which was exactly the point of the demonstration.
Now that Clean Diesel technology is truly available, we will probably see more and more of these vehicles on the road in the years ahead. Proponents of Clean Diesel technology say it can be just as fuel efficient and much more cost effective than hybrid technology.
Argonne is the U.S Dept of Energy's lead laboratory for researching and testing advanced vehicle technologies, including Clean Diesel engines, alternative fuels, hybrid and electric vehicles. The scientists at Argonne are studying and evaluating lots of new technologies to find out how they work, which ones work the best, and what type of fuels offer the best results.
The German Clean Diesel technology engines are designed to run on ultra low sulfur diesel fuel, but can also run on B5 (a five percent blend of Biodiesel with diesel fuel). Research is being done to determine the suitability of higher biodiesel blends, different types of biofuels, and also diesel-ethanol blends, and diesel-butanol blends (butanol is a different type of alcohol that can also be made from corn, and has less affinity for water, making it better suited for transport through pipelines than ethanol). For more information about butanol, Click Here.
Argonne's scientists are also investigating the possibility of running diesel engines on low octane gasoline as well as other alternative fuels such as natural gas and hydrogen. Agronne's advanced combustion research is looking into the processes that occur inside a diesel combustion chamber when the fuel is injected, mixes with air and ignites. Argonne was the first to document the presence of shock waves that occur during the injection event, which is helping scientists figure out how to optimize combustion efficiency while minimizing the formation of particulate particles (soot).
One of the more advanced fuel projects Argonne is working on is the development of diesel nanofluids. Tiny nanoparticles of metals, oxides, carbides, nitrides or nanotubes are added to diesel fuel to change the way the fuel burns so it will release more heat and energy to improve fuel economy.
Argonne also played a key role in evaluating a number of vehicles that were competing for the Automotive X-prize, the goal of which is to achieve 100 miles per gallon with a production-capable three or four-wheeled car. Is that cool or what?
Here are some major news events in the history of Clean Diesel technology since it's development in 1988:October 2011
No one can predict the future, but industry insiders say diesel and hybrid vehicles will continue to experience a growing market share of overall car and light truck sales. The pie chart below was part of a presentation by Bosch on the future growth projections for Clean Diesel engines. Bosch says that the 2013 model year will be a big one for the introduction of many new Clean Diesel powered vehicles in both Europe and North America.
The latest generation of Clean Diesel cars and trucks are using a three -stage exhaust aftertreatment process to reduce oxides of nitrogen and soot emissions. The first stage in the exhaust system is a Diesel Particulate Filter to trap soot. The second stage is a urea injection manifold that sprays Diesel Exhaust Fluid (DEF) into the exhaust to convert oxides of nitrogen into ammonia. The final stage is a catalytic converter that converts the remaining pollutants into carbon dioxide (CO2) and water vapor (H2O). The net result of all this added plumbing is that exhaust pollutants are reduced to almost nothing. The only drawbacks are the added cost of the aftertreatment system, the need to regenerate the particulate filter periodically (which normally occurs during highway driving), and to maintain the fluid level in the DEF reservoir.
Here's a short video that explains how the exhaust aftertreatment setup works on an Audi Clean Diesel car: Audi Clean Diesel Video.
Chrysler introduced a diesel-powered Jeep Grand Cherokee, and said it would offer more diesel models in the future depending on sales and public demand.
That same year, General Motors launched a diesel-powered Cadillac, and a diesel Chevy Cruze.
Audi began selling a TDI turbo diesel Audi A8 TDI in 2013, as well as a diesel powered Porsche Cayenne.
The diesel-powered Volkswagen Passat (Motor Trend Car of the Year in 2012), continued to sell well.
The diesel-powered Mercedes S350 BlueTEC returned to the U.S. market in 2012 after a 17-year absence.
Mazda become the first Asian car manufacturer to sell diesel cars in the U.S. when it introduced its SKYACTIV-D 2.2-liter clean diesel engine.
Seventy-five years ago, Bosch introduced their first diesel injection systems for cars. Over the past 14 years, Bosch has made 75 million common-rail diesel injection systems for Clean Diesel cars and trucks, making Bosch the world's leading supplier of common-rail diesel injection systems."Automobile diesel engines were previously seen as economical and robust, but noisy. The modern common-rail diesel is just as efficient and durable, but it is also quiet, powerful, and eco-friendly. Common-rail high-pressure injection, in conjunction with turbocharging, has revolutionized the diesel engine," said Ross Sandercock, Director, Product Management for Bosch.
As efficient as today's automotive diesels are, continuous improvements by Bosch will make diesel engines even more efficient in the future. For instance, by 2015 diesel-powered compact cars are set to consume as much as 30 percent less fuel than they do currently. And the use of hybrid technology can bring fuel consumption down by as much as 40 percent.
The first customers for common-rail systems in 1997 were Alfa Romeo, for its 156 JTD model, and Mercedes, for the C220 CDI. Unit sales of common-rail systems grew rapidly in the following years. By 2001, three million Bosch common-rail systems were in use, by 2002 the figure had already grown to ten million, and by the start of 2009 it was 50 million.
In 2011 alone, Bosch produced some nine million common-rail systems, which were fitted in passenger cars, commercial vehicles, in the off-highway segment, and also in large diesel engines such as those found in ships.
Higher pressure in future common-rail Clean Diesel engines
The name "common rail" is a reference to the pressure accumulator from which fuel is injected at high pressure into the cylinders via the injectors connected to it. The possibility of multiple injections that this allows makes engines quieter and reduces fuel consumption, as well as cutting emissions of CO2 and other pollutants. The first generation of common-rail systems operates at a pressure of 1,350 bar (19,580 PSI), but today's CRS2 achieves up to 2,000 bar (29,007 PSI), with some Bosch systems at 2,500 bar (36,259 PSI).
Fuel is precisely metered by solenoid valves that allow up to eight single injections per power cycle. CRS2 can be used around the world in all passenger car classes as well as in light commercial vehicles and the off-highway segment. Bosch also offers CRS3 with piezo injectors for the most demanding applications. This makes it possible to meter the tiniest amounts of fuel even more precisely for pre- and post-injection, which serves to further reduce NOx emissions and make the engine operate even more quietly. In this system, the injection pressure is as high as 2,200 bar (31,905 PSI).
The diesel engine is well equipped for the future. In conjunction with NOx exhaust gas treatment such as Bosch Denoxtronic, common-rail Clean Diesel technology makes it possible to meet the strictest emissions regulations, including Tier 2 Bin 5 in the United States or Euro 6 in Europe from 2014.
Allen Schaeffer, Executive Director of the Diesel Technology Forum (www.dieselforum.org) issued the following statement for Earth Day 2012 regarding the historic environmental advances that new clean diesel technology is achieving:
"While the national conversation about the energy future talks a lot about promising and potential technologies, hope for eventual acceptance and success, clean diesel power is delivering our energy future today. There is no other technology that can claim to powering 94 percent of all global trade, powering more than two-thirds of the all farm and construction equipment, the majority of emergency back-up electrical power generators and a growing number of passenger cars. There is no other technology that comes close to delivering what clean diesel technology does today in the form of advanced, low-emissions, fuel-efficient technology that drives economic growth with the record of environmental achievement.
- 98% Reduction in Emissions from New Commercial Trucks: Emissions of nitrogen oxides and particulate matter have been reduced by 98 percent in commercial diesel trucks over the past five years, now making them near-zero emissions. At the same time, the new clean diesel technology has made these new engines five to 10 percent more fuel efficient. More than 25 percent of all heavy-duty Class 8 commercial trucks on the road today are 2007 and later model year clean diesel powered.
- 90% Reduction in Emissions from New Farm and Construction Equipment: Farm tractors, harvesters, construction machines and industrial equipment are well on their way to fully implementing the new "Tier 4" clean diesel technology, which will cut emissions of particulate matter by 90 percent and half of all nitrogen oxide emissions compared to 2009 models.
- 97% Reduction in Sulfur Emissions in New Diesel Fuel: The new ultra-low sulfur diesel (ULSD) for automobiles has reduced sulfur emissions by 97 percent since its introduction for highway uses in 2006. The transition to the ULSD for all diesel fuel applications for highway vehicles was completed December 1, 2010, and the majority of fuel supplied for non-road, marine and locomotive was substantially completed on January 1, 2012.
"All around us we see first-hand the growing recognition of clean diesel technology. Whether it be in the growing success of the new generation of passenger cars and trucks, the remarkable fuel-efficiency gains of heavy-duty commercial vehicles or the productivity and efficiency gains from farm tractors and construction equipment, marine work boats or railroad locomotives. All of these sectors are embracing clean diesel technology.
"Today the newest generation of clean diesel technology for off-road engines and equipment known as "Tier 4" is making its way into our farm fields and construction and industrial sites. These new engines will revolutionize construction and agricultural productivity and efficiency. Tier 4 regulations require that manufacturers reduce the level of particulate matter and oxides of nitrogen to a level that is 50 to 96 percent lower than the existing generation of diesel engines.
"Advanced renewable diesel fuels made from a variety of feedstocks are another promising aspect of diesel technology that have the potential to further reduce CO2 emissions and reliance on imported oil.
Modernizing & Cleaning Up Older Diesel Engines: "The Diesel Emissions Reduction Act"
"Environmental and clean air progress is not limited to just new technology. This year we are continuing our bipartisan effort with our coalition of more than 400 environmental, health, industry and labor organizations to continue federal funding for the DERA program. Though the Administration�s budget provides for only $15 million in funding for the modernizing and upgrading of existing diesel engines, based on our past efforts, those investments will be leveraged by more than 2:1. And we know this program works; EPA has found that the Diesel Emissions Reduction Act (DERA) has delivered $13 in benefits for every $1 invested in reducing emissions from some of America�s 11 million older diesel engines.
According to a report issued by the Diesel Technology Forum, clean diesel sales in the U.S. jumped 44 percent in September, the largest gain of any month in 2012. Overall, clean diesel sales are up 25.6 for the year (compared to an overall increase in auto sales of 13.8 percent for 2012).
Diesel sales have increased in 26 of the past 27 months, with 23 of these months showing double-digit increases. One of the reasons for the growth in clean diesel sales is that the price differential between diesel and gasoline has been narrowing. With diesel's higher operating efficiency, the payback for buying a clean diesel-powered vehicle is faster than before.
Another reason for the dramatic growth is that there are now more clean diesel powered vehicles available to U.S. consumers. There are currently 14 clean diesel autos and SUVs available in car dealerships in the U.S. and the number increases to 31 when light duty trucks and vans are added in. What's more, the number of new diesel-powered vehicles will almost double over the next 18 months, which should stimulate clean diesel sales even more.
According to Pike Research, sales of clean diesel vehicles should increase from 9.1 million in 2012 to 12.1 million annually by 2018, with clean diesels representing 12.4 percent of all light-duty vehicle sales by the end of that period.
US and Asian auto makers will soon be offering more diesel engine options in their 2014 models. Diesel engines provide high mileage (30% better than most gasoline engines) and a significant cost advantage over hybrids, and with Clean Diesel technology the diesel clatter, soot and smell are history.
Chevrolet will have a turbo diesel option for the Cruze, and Nissan will have a 5.0L Cummins turbo diesel option available in their Titan pickup truck. GM and Chrysler will also offer more diesel options in certain truck lines as well, and Audi is expanding their list of models that will have diesel engines available.
Diesel sales were up 24 percent in 2013, and are expected to grow at an even faster clip in 2014. Although passenger cars and light trucks with diesel engines still account for only about 3 percent of the US vehicle fleet, the percentage of diesels is predited to grow to as much as 8 to 10 percent of the vehicle population over the next five years.
According to the Diesel Technology Forum, one of the true environmental success stories of the past two decades has been the emergence of clean diesel technology and fuel. After billions of dollars to research and development, truck, car, bus and off-road manufacturers are now producing clean diesel engines and equipment that have near zero emissions.
The United States has experienced a truly remarkable transition with the development of new clean diesel technology. New diesel truck, car and off-road engines have reduced particulate matter and nitrogen oxide emissions by more than 90 percent in the past two decades. The emergence of new clean diesel technology is a true environmental success story.
Clean diesel technology has achieved a 98 percent Reduction in Emissions from New Commercial Diesel Trucks: Emissions of nitrogen oxides and particulate matter have been reduced by 98 percent in commercial diesel trucks making them near-zero emissions. At the same time, the new clean diesel technology has made these new engines five to 10 percent more fuel efficient. More than one-third of all heavy-duty Class 8 commercial trucks on the road today are 2007 and later model year clean diesel powered.
To learn more go to https://www.dieselforum.org/index.cfm?objectid=3A4CE710-9375-11E0-98E9000C296BA163
A 90% Reduction in Emissions from New Farm and Construction Equipment: Farm tractors, harvesters, construction machines and industrial equipment have fully implementing the new Tier 4 Final clean diesel technology, which has cut emissions of particulate matter by more than 90 percent and half of all nitrogen oxide emissions.
To learn more go to https://www.dieselforum.org/meet-the-leaders/conexpo-tier-4
A 97 percent Reduction in Sulfur in New Diesel Fuel: The new ultra-low sulfur diesel (ULSD) for all diesel vehicles has reduced the sulfur content 97 percent since its introduction for highway uses in 2006. The transition to the ULSD for all diesel fuel applications for highway vehicles was completed December 1, 2010, and the majority of fuel supplied for non-road, marine and locomotive was substantially completed on January 1, 2012.
Diesel Cars and Pickup Trucks Are 30% More Fuel Efficient: Diesel cars get about 30 percent better fuel economy than a comparable gasoline car. Today diesel cars make up only about three percent of all vehicles on the road. If 30 percent of the cars in the U.S. ran on diesel instead of gasoline, they would reduce the demand for oil by 1.4 million barrels a day - about the amount the U.S. imports from Saudi Arabia.
To learn more go to https://www.dieselforum.org/diesel-at-work/cars-trucks-and-suvs
New Clean Diesel Buses Are Comparable to CNG Buses: An analysis by the Clean Air Task Force comparing emissions from 2012 clean diesel buses to 2012 CNG to 2012 buses found that new clean diesel technology is very competitive with CNG.
According to the analysis: "Both new diesel and new CNG buses have significantly lower emissions of NOx, PM, and HC than the older diesel buses that they replace. According to EPA's MOVES emissions model a 2012 model year diesel bus emits 94% less NOx per mile, 98% less PM, and 89% less HC than a model year 2000 (12-year old) diesel bus. A model year 2012 CNG bus emits 80% less NOx, 99% less PM, and 100% less HC than a model year 2000 diesel bus.�
After researchers at the International Council on Clean Transport and West Virginia University discovered that Oxides of Nitrogen (NOx) tailpipe emissions from certain diesel-powered VW cars under real world driving conditions appeared to be 10 to 40 times than federal emission standards, Volkswagen admitted that some if its TDI "clean" diesels were not so clean after all. VW was faking emission test results so its 2.0L TDI clean diesel engines would meet U.S. diesel standards.
Sources say VW programmed the engine computer so it would recognize when the vehicle was undergoing a tailpipe emissions test on a dyno (front drive wheels spinning at high speed, back wheels motionless and no steering inputs). This would put the engine control system into a special "test mode" that lowered NOx emissions so the engine would pass the tailpipe emissions test. The software would then switch the test mode off for normal driving so the engine would deliver better fuel economy and performance.
By fooling the emission test, VW was able to meet U.S. diesel emission standards for NOx while still delivering excellent fuel economy and performance. Nobody was the wiser until the trick was accidentally discovered by researchers who were investigating clean diesel technology.
Up to 11 million VW vehicles may be involved in the scam, and the problem may not be limited to VW. Other auto makers (Audi, Porsche, BMW, Mercedes, General Motors) may be using similar tricks to pass diesel emissions.
Engines currently involved in the controversy include 2009 to 2015 VW and Audi 2.0L TDI clean diesel engines in VW Jetta, Passat, Golf and Beetle models, and Audi A3. This includes the "EA188" 2.0L TDI engine and the redesigned 2015 "EA288" 2.0L TDI engine.
For now, VW has been prohibited from selling 2015 and 2016 models with diesel engines until a software fix has been approved and installed. VW will likely issue a recall notice to reprogram all of its vehicles with new software so they will be emissions compliant under all driving conditions.
VW is facing emission violation fines and class action lawsuits that may cost the car company billions of dollars. Many are also concerned this may damage the future of clean diesel technology irreparably, causing a decline in diesel engine usage in passenger cars. Time will tell how all of this plays out and what this means for clean diesel engines.
For an update on the Volkswagen diesel emissions scandal and settlement, see the Consumer Reports Guide to VW Emissions Recall (January 2017).
If you want to read up on the technical details of the VW 2.0L TDI engine, Click Here for the VW Training Manual.
VW pleaded guilty in U.S. Court to using secret software to deceive emission test procedures on their diesel-powered TDI engines. The software allowed the TDI engines to produce up to 40 percent more NOx (Oxides of Nitrogen) thaan allowed by current emission standards. The verdict cost VW more than $20 billion dollars in the U.S., which does not include billions lost in unsold vehicles because their engines could not meet emission standards.
The settlement required VW to pay $2.8 billion in criminal penalties, plus $1.5 billion in civil fines for violating emission laws. VW also agreed to buy back or fix cars involved in the cheating scandal, and to also pay the owners of these vehicles $5,100 to $10,000 depending on the age of the vehicle. To qualify for the payment, owners had to have possession of the vehicle on or before Sept 18, 2015. Owners also have until Sept 1, 2018 to apply for a buy-back on leased vehicles. The total compensation will cost VW another $10 billion!
VW also agreed to also pay another $1.2 to $4 billion to owners of 78,000 VWs with 3.0L diesel engines.
The settlement also requires VW to spend $2.9 billion for "environmental mitigation" and another $2 billion to promote zero-emission vehicles.
Finally, VW also agreed to pay its dealers $1.2 billion to compensate them for damage that resulted from the dirty diesel scandal.
It took several years to get approval, but VW now has a software update that more or less fixes its diesel emission problem. The recall affected 590,000 diesel-powered VW models in the U.S. The recall and subsequent settlement resulted in VW buying back many of the recalled 2009-2014 Jetta, 2010-2014 Golf and 2013-2014 Beetle cars with TDI engines, and 2010-2013 Audi A3 models with TDI engines. VW had to pay simliar software update is also being applied to 2012-2014 Passats.
The new software upgrade allows all of the vehicles to meet a new emission standard similar to the Tier 3 Bin 160 NOx emission rules that allows slightly more NOx emissions at lower speeds, but less NOx emissions at highway speeds. The software update is "one-way" so that vehicles cannot be reprogrammed back to the previous calibration.
Testing has shown that the new software update does not reduce performance or fuel economy. On models that use DEF (Diesel Exhaust Fluid) to reduce NOX, the consumption of DEF is somewhat higher (up to 14 percent says VW) with the new software update.
Research conducted by IHS Markit reveals that for the first time ever, clean diesel engines power HALF of all the commercial diesel vehicles on the road in the U.S. as of December 2021.
The Clean Diesel engines use high pressure common rail injection systems with exhaust particulate filters, oxidation catalysts, and selective catalytic reduction systems to achieve near zero emissions with better fuel efficiency and lower CO2 emissions.
Estimates predict the growing number of trucks using clean diesel technology will eliminate more than 1.3 billion tonnes of CO2 by 2030. What's more, the technology has a solid track record of performance, reliability, and durability.
Another plus for Clean Diesel engines is that they can burn low carbon biofuels from renewable sources (soybeans and other crops). That helps to reduce greenhouse gas (GHG) emissions by 20-80 percent compared to conventional diesel fuel.
Clean Diesel engines have been standard in new commercial trucks since 2011, and farm and construction equipment since 2014. Clean Diesel engines are also used in 58 percent of school buses and 47 percent of urban transit buses. This has allowed more than a 98 percent reduction in nitrogen oxides (NOx) and particulate matter (PM). Since 2011, this has translated into saving more than 20 billion gallons of fuel, as well as eliminating the creation of 202 million metric tons of GHG emissions and 27 million metric tons of NOx emissions.
When it comes to emissions tampering, repair shops or dealerships that remove, disconnect or otherwise render inoperative ANY emissions device are engine in risky business. Midwest Motors or Eureka Missouri was recently caught installing aftermarket parts that defeat the factory diesel exhaust emission control systems on 21 Ford Power Stroke trucks and Dodge Ram Cummins-powered trucks. The penalty for each violation of federal anti-emissions tampering regulations will cost this dealership $315,000 (21 x $15,000 for each violation)!
The EPA says removing or replacing factory exhaust components such as the EGR system, catalytic converter, diesel particulate trap, diesel exhaust aftertreatment (DEA) system, or to modify the electronic controls that operate these systems using a handheld tuner scan tool is against the law. Although such modifications might slightly improve fuel economy, performance and/or towing capabilities, it also significantly increases diesel oxides of nitrogen (NOx) and soot emissions. So if you like "rolling coal" (spewing thick black smoke to show off or make some kind of anti-environmental statement with your diesel-powered truck), it could end up costing you or the shop that made the illegal modifications a lot of money!
The EPA says it has also recently fined auto repair facilities in Iowa, Missouri and Nebraska thousands of dollars for similar violations.
The whole point of having these various emission control systems on diesel engine is to make them clean running. Diesels are notoriously dirty when it comes to NOx and soot emissions, but with the proper emission controls in place and functioning they can run almost as clean as an emission controlled gasoline engine.