Sluggish eighteen-wheeled behemoths, crawling along the highway belching black toxic smoke. Mention the word “diesel”, and this is what comes to the mind of many individuals who drive to work and back each day in their fuel-efficient, imported grocery-getter. While it may be true that diesel-powered vehicles have been treated leniently in the past when it comes to emissions regulations, at least more so than that of gasoline powered cars, many people do not keep in mind that their non-diesel vehicle produces as much if not more harmful byproducts. The fact that their emissions are not as visible as a black puff of diesel smoke does not mean that they do not exist.
The rules are changing for diesel emissions, just as they are on the gasoline side. In actuality, the progression of change in the diesel arena has most likely dwarfed that of the gasoline world in the past several years. Late model diesels have made vast changes in the area of emissions technology. Newer fuel systems are now utilizing common rails, which feed injectors at pressure rates considered extreme when compared to earlier models. Changes such as this, as well as new equipment to trap and neutralize contaminants, are making for extremely clean running diesels.
OEM modifications to new model vehicles to allow for cleaner operation come in a few different areas. The slightly more obscure processes involve programming and electronics. By changing the pulse width, duration and timing of diesel injected into the cylinders, the burn efficiency can be increased. Each time the injector is fired, it pulses at a high rate of speed under very high pressure. This gives the piston a more atomized and even dose of fuel to burn. The use of direct injection and a centered injector makes a major difference in performance. Late model diesel systems also use four valves per cylinder, with two providing intake and the other two exhausting. Eliminating the pre-combustion chamber that was used on earlier systems has led to more effective use of the fuel.
Onboard computers now control the cylinder firing and pump pressures through constant monitoring and preset maps. Now entering the market is a technology that was pioneered in 1880, and it is known as piezoelectricity. Piezoelectric fuel injectors contain a stack of ceramic elements that expand instantaneously when an electric current is applied to them to allow diesel to pass into the cylinder. This allows a greater volume of fuel to be injected in a shorter time than what would be available with solenoid style injectors. With this ability to precisely place the fuel, efficiency and emission quality are maximized.
With tolerances becoming tighter inside system components such as injectors, and the extreme pressure used to push the diesel through them, making sure that contamination of the fuel does not occur is paramount. Losing a batch of injectors or a main injection pump on today’s diesel can be a costly affair if not covered by warranty.
Effective airflow is important to burn the fuel that enters the system. The latest round of clean-minded diesels are now equipped with variable turbochargers. Instead of the turbo only being effective within a limited range, the computer-controlled veins inside the charger open and close to ensure that positive airflow exists during as much of the on-throttle drive time as possible.
Features previously seen only on California-manufactured vehicles are now found on Federally emissioned units. Catalytic converters are inline on the exhaust system to neutralize carbon monoxide [CO] and unburnt hydrocarbons [UHC]. The honeycomb interior and overall design on these has not changed significantly in recent times, but materials used continue to evolve and create better longevity. A newer feature on late-model diesels is the particulate filter, which works either in place of or in addition to the catalytic converter. These trap soot after it exits the motor and contain it using ceramic or other material elements. Periodically, the temperature of the exhaust is computer controlled to allow it to reach nearly 580 degrees F, which begins a “regeneration” process in the filter. An oxidation process begins to cook off the captured particulate matter and eliminate exhaust odor and hydrocarbons [HC]. This process is able to reduce particulate emission by 85-95%. The harmful exhaust is converted into carbon dioxide and water vapor. In order for this system to be truly effective, the newer style ultra-low sulfur diesel must be used. This helps to ensure the filters do not become excessively clogged.
The use of EGR [Exhaust Gas Recirculation] is not new, but it was primarily related with California emissioned vehicles in previous years. With non-EGR diesels, the motor typically utilizes 75-85% of the fuel that passes through the system. This principal is what allows for fuel economy and power gains by using propane injection which enters the cylinder and catalyses unburnt fuel.
By rerouting exhaust gases back into the intake, some of the otherwise wasted fuel can be burned. For the performance-oriented customer, the EGR system may not be such a welcome sight as it does mean that the motor is operating using a lower percentage of fresh cool air [which typically makes for better power].
Starting With The Source
In order to affect and clean up the emissions from diesel vehicles, the EPA has started the changeover from standard #2 diesel fuel to ULSD [Ultra-Low Sulfur Diesel]. Starting in June 2006, US refiners and importers were required to run at least 80% ULSD. The new fuel contains 15 parts-per-million [ppm] sulfur content to comply with new emissions equipment. By significantly lowering the sulfur in the fuel, the harmful expectorants are greatly reduced. One worry that consumers have expressed is that the lack of sulfur would now cause lubrication and corrosion issues. The EPA has stated that additives are being mixed into the ULSD “as needed” before it ships to retail customers.
As with earlier #2 diesel, the new fuel can still have issues with “gelling” in very cold conditions. Running anti-gel additives preventatively with each tank of fuel is the best option and resolves any questions about the lubricity level of ULSD. Available additives contain less than 15ppm sulfur content [as opposed to past mixtures of up-to 500ppm], but have other ingredients to ensure longevity of the motor and fuel system. Use of ULSD is required in 2007 and later light-duty passenger diesel vehicles for proper operation. Earlier type fuel can cause issues over time by allowing a high volume of byproduct to build up in the filter systems. Once this has happened, the regenerative process used by the truck is not able to effectively clean the particulates out.
Some manufacturers have also stated that warranties could be voided if testing produces evidence of incorrect fuel usage. ULSD varies somewhat in appearance from its counterpart due to refining procedures and is generally a lighter tinted color. By December 2010, all retail fuel outlets will have switched over to the clean diesel standard. Until that point, owners of brand new trucks can check for specific labels at the pumps where they fill up which specify that they are getting the correct grade of fuel. The EPA predicts that by 2030, [at which point the majority of the HD vehicle fleets in the US will be updated], the reduction in emissions will be equivalent to removing the pollution of 90% of today’s HD trucks and buses.
Diesel fuel costs have skyrocketed as of late due to various factors. In addition to price points set by fuel producers around the world and volatile markets, the cost of producing ULSD is higher than that of the older #2 type. Government testing has shown no noticeable loss of power under normal driving conditions with the new fuel, but it states that economy is diminished due to the removal of sulfur. With limited resources and climbing prices, many diesel owners around the world are looking for a different solution.
Usage of biodiesel is gaining popularity rapidly. Companies that produce alternative fuels, such as Blue Sun Biodiesel [a Colorado-based company], are helping to clean up the environment while reducing dependency on foreign oil. By combining 80% petroleum diesel with 20% Blue Sun Bio [referred to as B20], reductions in harmful emissions and effective lubrication are accomplished. Blue Sun opened an automated B20 terminal to produce their fuel in Alamosa, Colo. in February 2005 [the first such station in the US]. Since B20 and B100 are made from soybean oil and other sources, the fuel is both environment-friendly and renewable. Currently, biodiesel is subject to cold weather gelling, and because it is mixed with regular diesel, also to price fluctuation. As this energy becomes wider spread it could help strengthen the US economy. A common question is whether biodiesel is a step down in performance. It just so happens that the first diesel powered dragster to make a seven-second, quarter-mile pass runs on Blue Sun’s B100.
Does Green = Go, or Whoa!?
Aftermarket performance and emission-conscious diesels don’t always go hand-in-hand. Typically, it is much easier to develop a vehicle with over-amped levels of fuel than to balance the air:fuel ratio. Every corner performance shop sells a chip or programmer to increase fuel rates, but they may not supply supporting components.
This route provides increased power, but it also produces excess amounts of unburnt fuel, which exits the exhaust as a black cloud. With new emissions standards and filtering equipment like particulate filters that could potentially clog, applying additional power cleanly has become more important. Aside from ending up with greatly reduced fuel economy, excessively high EGTs [Exhaust Gas Temperatures] over time will result in damage. With the proper tuning and right upgrades, diesel owners will be able to modify their vehicle for improved drivability, while maintaining critical emissions equipment.
So, will new emissions equipment and leaner fuel spell the end for aftermarket diesel performance? Probably not anytime soon. However, with sensitive integrated systems, which are vital for normal operation and which use complex computer interaction, methods of modification will have to adapt.
Environmental Protection Agency
The Clean Diesel Fuel Alliance Information Center
The Diesel Technology Forum
Blue Sun Biodiesel