FUEL-SIPPING MERCEDES-BENZ R320 BLUETEC MAKES DEBUT
The innovative R-Class SÚV boasts a timely new model for 2009. Joining the R350 gasoline-powered SÚV, the fuel-sipping R320 BlueTEC diesel features a new AdBlue exhaust treatment system that helps the diesel meet the most stringent 50-state emissions limits. R320 BlueTEC Diesel Boasts 500-Mile Cruising Range
The R320 BlueTEC is changing consumers' dated perceptions about diesel engines – it gets surprisingly good performance and extremely low exhaust emissions, in the process of delivering 20-30 percent better fuel economy. The roomy SÚV also boasts impressive cruising range – more than 500 miles at highway speeds, and without sacrificing performance. What's more, V8-like pulling power makes the R320 BlueTEC ideal for towing when equipped with a newly optional 3500-lb. Class II trailer hitch. BlueTEC — A Modular Technology
BlueTEC is a modular system that includes an oxidation catalyst and a maintenance-free particulate filter as well as new techniques for reducing nitrogen oxide emissions – the last type of exhaust gas that's higher in diesel vehicles than gasoline engines.
The BlueTEC diesels use a NOx storage converter in combination with an SCR catalytic converter and AdBlue injection to lower NOx emissions. The AdBlue system injects an aqueous carbamide solution into the exhaust flow, which releases ammonia (NH3), reducing nitrogen oxides to harmless nitrogen and water in the downstream SCR converter.
Just the right amount of AdBlue for a given engine load and speed is injected to get the greatest reduction of nitrogen oxides. On average, only a quart of AdBlue is needed for every 600 miles driven, so its tank only needs to be refilled every 10,000 miles during normal maintenance. New-For-2009 COMAND System
The R-Class cockpit features a four-spoke multifunction steering wheel with brushed aluminum accents on the lower spokes. The instrument cluster is designed with large chronometer gauges, and the console houses climate control and a new-for-2009 COMAND system featuring a large 6.5-inch display screen with a standard in-dash, six-disc CD/DVD changer and a Bluetooth interface that allows a phone still in a pocket or purse to be operated through the car's audio system. It can be equipped with an optional iPod/MP3 interface, Sirius satellite radio, HD radio, and an enhanced voice control system.
The COMAND system can play tracks stored on a data CD, DVD or SD memory card. The new system can also display maps and directions for the optional hard-drive navigation system, which can be set up with Sirius real-time traffic and Zagat restaurant ratings as well. The R-Class can be equipped with an optional rear-seat entertainment system that includes an integrated DVD player with dual-source capability, two eight-inch screens, wireless headphones, and wireless remote controls. PRE-SAFE Gives The 2009 R-Class Reflexes to Protect Occupants
New standard equipment on the 2009 R-Class, PRE-SAFE® is a revolutionary safety system that can actually sense an impending collision before it happens and take measures to protect occupants during those valuable seconds before impact.
The PRE-SAFE system that made its debut on the S-Class automatically tightens the front seat belts before a possible impact, and the front passenger seat moves to a position that can provide better protection. Side windows also close to provide better support for the window curtain air bags. If the system senses an impending rollover, the sunroof also closes. An Automotive Decathelete
The R-Class was launched in 2005 as an entirely new type of Mercedes-Benz that combines the defining advantages of several distinct vehicles – the sure-footedness of a four-wheel-drive sport utility vehicle, the performance and comfort of a sports sedan and the versatility of a luxury wagon.
With a sharp focus on design, comfort, space and performance, the R-Class is designed as a spacious, roomy vehicle with space for up to seven adults. Its standard sunroof or an optional Panorama sunroof further contributes to its openness.
In comparison to other Mercedes-Benz models, the R-Class is about the same length as the flagship S-Class sedan. (concept carz) As an indicator of comfort and roominess, cabin space in the R-Class represents 65 percent of its total volume, and there's up to 40 inches between the first and second seat rows, with more than 30 inches between the second and third rows.
The R-Class allows occupants to create their own sense of space with features such as reading lights, armrests, air vents and cup holders as well as seat adjustments for each seat and two separate-source audio plugs. This individualization is further enhanced with the optional MP3 media interface and dual-screen video entertainment system. A Chassis Worthy of a Sports Car
The R-Class crossover boasts a strong unibody platform and four-wheel independent suspension with double control arms in the front and four-link air suspension at the rear. Power-assisted rack-and-pinion steering delivers impressive on-road driving performance and comfort, and ample braking is provided by large four-wheel disc brakes, with vented discs and double-piston calipers up front.Source - Mercedes-Benz
2009 Mercedes-Benz BlueTEC DieselsA Family of BlueTEC Diesel Sport Útilities
The three SÚVs available with BlueTEC diesel power for 2009 are young vehicles - the seven-seater GL-Class made its debut in 2007, and the versatile R-Class was launched in 2006 as an entirely new class of Mercedes-Benz. A new-generation M-Class also went on sale for 2006, and for the 2009 model year, the Mercedes-Benz family SÚV now features bold restyling.
All three SÚVs features a new COMAND color display, speed-dependent volume control and a keypad for phone numbers and radio frequencies. Options include a voice recognition system, a 610-watt digital harmon kardon Logic7 audio system with 5.1 Dolby Digital Surround Sound and a rear-seat entertainment system with two eight-inch screens, wireless headphones and an integrated DVD player. PRE-SAFE Provides Reflexes to Protect Occupants
New standard equipment on all three SÚVs, PRE-SAFE® is a revolutionary safety system that can actually sense an impending collision before it happens and take measures to protect occupants during those valuable seconds before impact. First launched on the premium S-Class sedan, the PRE-SAFE system automatically tightens the front seat belts before a possible impact, and the front passenger seat moves to a position that can provide better protection. If the system senses an impending rollover, the sunroof also closes. Úseful Technology Abounds
The three Mercedes-Benz sport utilities also feature a unibody platform and sophisticated independent suspension that deliver impressive on-road performance and comfort. Úseful technology abounds in the vehicles, including a standard seven-speed automatic transmission and an advanced full-time four-wheel-drive system.
Continuing the Mercedes-Benz commitment to safety, the three vehicles come standard with two-stage adaptive air bags for the driver and front passenger, window curtain air bags as well as belt tensioners and belt force limiters. A rollover sensor can deploy the belt tensioners and the curtain air bags if the vehicle senses an imminent rollover.The Big Benefits of Diesel
In general, diesel engines get 20-30 percent better fuel economy and thus produce 20-30 percent less CO and CO2 than comparable gasoline engines. What's more, a modern CDI diesel is as powerful and nearly as quiet as a gas engine. Now, BlueTEC technology makes the diesel as clean as any modern gasoline engine. Three New BlueTEC Diesel SÚVs for 2009
For 2009, Mercedes-Benz is launching three new sport utility models powered by new-generation BlueTEC diesel engines that are impressively clean, fast and quiet. Best of all, the new BlueTEC SÚVs are available in all 50 states. As earlier-technology diesels are disappearing from the Ú.S. market, Mercedes-Benz is offering the ML 320 BlueTEC, a five-passenger family SÚV; the R 320 BlueTEC, a six-passenger luxury SÚV; and the GL 320 BlueTEC, a premium seven-passenger SÚV - all three powered by an innovative three-liter V6 diesel engine that combines the powerful torque of a V8 engine with the great fuel mileage of a four-cylinder engine.
The aluminum V6 diesel features four valves per cylinder, centrally mounted piezo injectors and CDI electronic fuel injection, which stands for Common-rail Direct Injection. For high efficiency and power, the purpose-built diesel engine also comes with a variable-vane turbocharger and intercooler. The basic technology for turbocharging and CDI injection used in modern Mercedes diesel engines has already proved itself in millions of vehicles in Europe, where more than half of all new cars are now diesel-powered.
New Diesel Fuel Has 97 Percent Less Sulfur
High Performance, High Fuel Mileage and Long Cruising Range
The three new models offer astonishing efficiency, impressive driving character, and laudable environmental compatibility. Torque - the key indicator of engine power - is 30 to 50 percent higher, exceeding many V8 gasoline powered models, and fuel mileage is 20 to 40 percent higher than in cars equipped with a comparable gasoline engine. The new vehicles can get over 20 miles per gallon in combined city/highway driving - a level of fuel efficiency normally found only in a small car - and they're also environmentally friendly as a result of their excellent fuel economy and extremely low exhaust emissions. Best of all, the new vehicles' ability to travel up to 600 highway miles on a single tank of fuel means its drivers won't have to go looking for fuel stations very often.
In part, the refinement of diesel power in the Ú.S. is made possible by the introduction of cleaner, ultra-low-sulfur diesel containing less than 15 parts per million (ppm) of sulfur. Low-sulfur diesel fuel (which became available across the Ú.S. and Canada in 2006) means a noticeably cleaner exhaust for any diesel vehicle. Cleaner fuel also allows the use of new emission control technologies such as particulate filters, which clean themselves periodically by using sophisticated regeneration that's analogous to an oven cleaning cycle.
Since the previous sulfur content in diesel fuel was 500 ppm, sulfur is now reduced by 97 percent, which provides lower emissions for all diesel vehicles. Sulfur, a natural part of crude oil, is one of the key causes of particulates or soot. The introduction of ultra-low sulfur diesel (long used in Europe) now makes it possible to use particulate filters in the Ú.S. What's more, this fuel can enable efficient after-treatment of nitrogen oxide emissions.
CDI Electronic Fuel Injection
The Automotive Diesel Pioneer
Mercedes-Benz is considered to be the pioneer of automotive diesel technology. Launched more than 70 years ago, the Mercedes-Benz 260D was the world's first production diesel car, and over the years, Mercedes-Benz has consistently used its engineering talent to improve the diesel engine. Mercedes has also had a great diesel tradition in the Ú.S. over the past 40 years. The most successful phase to date was during the 1980s, when diesel passenger cars accounted for nearly 80 percent of total Mercedes-Benz sales in the Ú.S. As a result, Mercedes-Benz not only has a longer history of diesel expertise than any other automaker, but also understands the Ú.S. diesel market well.
Mechanical Fuel Injection
Úntil Mercedes-Benz presented the world's first diesel engine with electronic injection in 1997, virtually all diesels used mechanical fuel injection. The heart of every mechanical system was an engine-driven mechanical pump that itself resembled a miniature cylinder block. Tiny pistons the diameter of pencils pressurized diesel fuel for each cylinder, and complex mechanical controls regulated rudimentary fuel-air curves for various load, speed and temperature ranges. These elaborate mechanical controls grew even more complex as engineers addressed increasingly stringent exhaust emissions regulations. What's more, mechanical systems were slow to react and not nearly as responsive as electronic systems.
However, until recently it wasn't considered technically possible to build an electronic injector that could deal with the mind-boggling high fuel pressure required to penetrate the highly compressed air of a diesel combustion chamber.
In late 1997, Mercedes-Benz debuted the world's first diesel engine with CDI, which stands for common-rail direct injection. The first truly electronic fuel injection system for diesels, the CDI system instantly created a new paradigm for the diesel industry. CDI electronic injection provides much more precise control of injection quantity, simultaneously making more power, lower exhaust emissions and quieter operation.
Most electronic fuel injection systems, including those on gasoline engines, use a 'common rail' or 'ring main' fuel loop to supply the same pressurized fuel to all injector valves. However, the Mercedes-Benz CDI system marked the first common-rail system for diesel engines as well as the first electronically injected diesel.
In August 2002, during a time when it appeared that diesel passenger cars had practically no future in the Ú.S., Mercedes-Benz visionaries laid the cornerstone for a new era of diesel success by introducing the current-generation E-Class line. Then, in January 2004, the brand officially launched the Ú.S. comeback of the diesel at the Detroit Auto Show with the E320 CDI, which went on sale in April 2004. State-of-the-art common-rail direct injection made the E320 CDI much stronger, quieter and cleaner than any diesel that had ever come before it. Sales of the E320 CDI have risen sharply since fuel prices began escalating in August 2005, and more than 17,000 E-Class diesel-powered vehicles have been sold in the Ú.S. since the market launch in April 2004. Higher Fuel Costs
The diesel market around the world is fundamentally influenced by fuel prices. Fuel prices have traditionally been lower in the Ú.S. than elsewhere in the world, and this is a key reason why diesel's share of vehicle registrations in the Ú.S. is still comparatively low. Another explanation offered is the fact that no sulfur-free fuel has been available until now, and such fuel is indispensable for state-of-the-art diesel technology.
Fuel costs and - more importantly - the huge improvements made to the performance and comfort offered by modern diesel engines have led to a tremendous increase in the market share for diesel vehicles in Europe over the past few years. While diesel vehicles accounted for 32 percent of new registrations in Western Europe in 2000, that figure had risen to 49.5 percent by 2005. The diesel share for SÚVs is over 80 percent around the world, and vehicles such as the Mercedes-Benz E-Class represent another market segment in which diesels perform well.
Diesels have in fact performed extremely well in comparative independent tests of diesel and hybrid vehicles conducted by journalists from European automotive magazines on three different continents. In Auto Bild's Ú.S. coast to coast comparative test between a ML 320 CDI and a Lexus RX 400h, it found that the diesel engine consumed about 11 percent less fuel. (concept carz) In each comparative test, whether driving straight across the Ú.S., Germany or Japan, the fuel mileage of diesel vehicles was significantly higher than that of hybrid cars.Ú.S. Diesel Sales Úp 40 Percent
Market analysts agree that diesel vehicles will continue to become more popular. Automotive Industry Data, for example, predicts that diesel vehicles will account for nearly 60 percent of passenger cars in Western Europe in 2009, while J.D. Power expects the diesel share of western European passenger cars to rise to around 56 percent over the medium term.
Few have noticed that diesel car and light truck sales have risen 40 percent in the Ú.S. over the last five years, perhaps because the sales volume was rather low to begin with. Forecasts regarding the diesel share of the Ú.S. market in the future are optimistic. An extensive study conducted by J.D. Power, for example, predicts that the market share of diesel vehicles in the Ú.S. will increase from 3.5 percent in 2005 to more than 15 percent in 2015. Automotive Industry Data also forecasts that diesel vehicles will account for more than 15 percent of the market in the Ú.S. over the long term.
This will be important for the Ú.S. because diesel vehicles can offer huge fuel savings potential if their market share is increased. This was confirmed in a study conducted by the Ú.S. Environmental Protection Agency in 2004. Margo Oge, head of its Office of Transportation and Air Quality, concluded that if only one-third of all light-duty trucks in the Ú.S. were operated with modern diesel engines, the country would save 1.4 million barrels of oil per day - equal to the amount of oil the Ú.S. currently imports from Saudi Arabia.
Purpose-Built Aluminum V6
Engine : 3.0 L., 6-cylinder
Power: 210 hp
Torque: 400 ft-lbs
The V6 BlueTEC Engine
The 2009 BlueTEC diesel models are powered by a Mercedes-Benz V6 diesel engine with four valves per cylinder, dual overhead camshafts and centrally located piezo fuel injectors. Designed to spray diesel fuel directly into the center of the combustion chamber, each injector is positioned in the aluminum cylinder head about where a spark plug might be found on a four-valve gasoline engine. This layout ensures even dispersion of fuel as its flame front spreads concentrically across the combustion chamber. (In conventional two-valve engines where the injectors cannot be centrally mounted, combustion is uneven, so there's less power and higher exhaust emissions.)
The all-aluminum V6 diesel boasts purpose-built engine architecture characterized by a 72-degree cylinder angle and 106 millimeter cylinder spacing. Featuring a rigid closed-deck design, the aluminum cylinder block is cast around iron cylinder liners, and a duplex-chain-driven, counter-rotating balance shaft between the two cylinder banks neutralizes the inherent imbalance of a V6, thus ensuring a smooth-running engine.
A forged-steel crankshaft spins in four extra-wide bearings, and pairs of 'split-pin' connecting rod journals are offset by 30 degrees for smoother running. Forged-steel connecting rods are 'cracked' diagonally where they clamp onto the crankshaft, a technique that produces an irregular joint for greater strength, and at the same time, simplifies machining.
Pistons are cast from a special high-temperature alloy and pinned to the connecting rods. Since there is only a slight recess in the cylinder head between each piston and the valves, a combustion chamber is formed by a cavity in the piston crown. This layout has proven to minimize engine-out exhaust emissions in direct-injection engines, and it helps provide the 16.5-to-1 compression ratio necessary to make a diesel engine ignite fuel without the external spark ignition system used on gasoline engines.DOHC Four-Valve Heads with Central Injectors
The V6 diesel engine uses a pair of one-piece cylinder heads that are mold-cast from high-temperature aluminum featuring an advanced heat treatment method. Each cylinder head is fitted with twin overhead camshafts and four valves per cylinder, as well as a centrally mounted injector and ceramic start-up glow plug for each cylinder
The exhaust camshafts are driven by the crankshaft via a double roller chain, and in turn, a pair of helical gears behind the chain sprocket drives the intake cams. The cam lobes operate low-friction roller rocker arms that open the valves. Interestingly, the cams are sandwiched between the top of the cylinder heads and the cast valve covers, so that the heads and the valve covers actually form the camshaft bearings.
Since diesel engines operate without a conventional throttle plate and therefore don't produce much intake vacuum, the camshaft sprocket also drives a vacuum pump for the brake booster. In addition, the right intake cam also operates an oil centrifuge that separates oil from oil-laden crankcase air before the air returns to the intake. Oil Pump and Cooler
The engine is lubricated by a chain-driven, external gear-type oil pump, which draws oil from the oil pan and pressurizes it throughout the engine. Oil is first fed through a high-volume full-flow oil filter, and is then directed to an integral oil cooler located between the cylinder banks. The oil cooler uses engine coolant to keep oil temperature below 140 degrees C. The bore for the balance shaft also acts as the main oil galley for the engine, which leads to passages for the crankshaft, piston oil sprayers, cylinder heads and the turbocharger unit.VNT Turbocharging
While many non-turbo diesel engines have compression ratios over 20:1, Mercedes engineers found that, in conjunction with the BlueTEC engine's exhaust-driven turbocharger, the new engine is most efficient with a compression ratio of 16.5 : 1. The turbocharger features variable turbine geometry or VNT (Variable Nozzle Turbine), which is integrated with the electronic engine management system. At low engine speed and load, the vane angles are relatively narrow so the turbine speeds up quickly and creates ample boost without noticeable lag. At higher speeds, a steeper vane angle slows the turbine while increasing intake air volume.Air-to-Air Intercooler
To keep the turbocharged air as dense as possible on its way to the engine, the air flow passes through an air-to-air intercooler - essentially a radiator that cools the intake air. The intercooler system lowers the air temperature by up to 180 degrees F, ensuring higher air volume and more power. Electronic Throttle
Diesel engines usually operate most efficiently without any throttle in the intake system, so that fuel delivery alone controls engine load and speed. However, Mercedes engineers found that, at light load, throttling one of the two diesel intake ports at each cylinder creates air turbulence that helps optimize the combustion process and further reduce fuel consumption and exhaust emissions. As a result, the BlueTEC engine makes use of electronic intake port deactivation that's automatically managed by a sophisticated electronic control unit - the same one that determines everything from fuel injection quantity and timing to the vane angle of the VNT turbocharger and the quick-start glow-plug operation. This versatile microprocessor also networks with the seven-speed automatic transmission and the ESP stability control systems.CDI FÚEL INJECTION
Common-Rail Direct Injection
The 2009 diesel models use the latest version of the Mercedes-Benz CDI system. To begin the process, a low-pressure electric pump operates at about five bar or 71 pounds per square inch (psi) to draw fuel from the tank and feed it through a fuel filter and water separator to a high-pressure engine-driven fuel pump. High-Pressure Fuel Pump
The high-pressure pump keeps the electronic fuel injectors supplied with 1600 bar or approximately 23,000 psi of constant fuel pressure through the common-rail fuel loop. This layout ensures consistent fuel pressure for the common rail, and the amount of fuel used by the engine is determined solely by how long the electronic injectors stay open. In this way, high fuel pressure is always available the instant the injector valve opens, and for as long as it stays open. Gone are the days of dealing with a mechanical injection pump's gradual fuel pressure build-up for each cylinder, not to mention its pressure drop-off during each cycle - both representing distinct disadvantages, especially at higher engine speeds.
In spite of the high fuel pressure it generates, the engine-driven CDI fuel pump requires less than 20 percent of the peak torque needed to turn a mechanical fuel injection pump. While mechanical injection pumps have to build up pressure for each injector pulse, the CDI pump maintains constant pressure and isn't subject to the shock of such torque spikes. As a result, the CDI pump imposes less stress and potentially less wear on the pump drive. Ceramic Glow Plugs
In cooler weather, compressing the combustion air in a diesel engine doesn't always make it hot enough to self-ignite fuel when it's injected. As a result, diesel engines have used heating elements called glow plugs for each cylinder as a starting aid. The BlueTEC engine uses ceramic glow plugs, which achieve a temperature about 200 degrees C higher than conventional glow plugs to allow almost instant starting. In addition, the electronically controlled glow plugs can stay on briefly after the engine is started to help regulate idle speed and minimize emissions.Piezo-Ceramic Fuel Injectors
Considered technically impossible until the mid-1990s, electronic injectors that remain reliable while they're subjected to approximately 23,000 psi of fuel pressure are the secret of CDI's superiority over earlier injection systems. However, instead of the usual electro-magnetic solenoid valves, the new V6 diesel features six piezo-ceramic injector valves. Since piezo crystals actually change shape when electric current is applied, they can be used instead of conventional magnetic elements to provide even faster, more durable injectors. The injectors on the CDI engines have eight-hole nozzles that spray a very fine mist of fuel. (concept carz)Miraculous Pilot Injection
Historically, the diesel combustion process has involved rapid pressure increases and, as a result, more noise than a gasoline engine. Taking advantage of the speed and precision of CDI electronic injection, Mercedes engineers found that igniting a small quantity of fuel a few milliseconds before the main injection pre-heats the combustion chamber and makes pressure and temperature increases more gradual. Smoothing out combustion pressure and temperature spikes softens the usual diesel noise and reduces oxides of nitrogen formation as well. The miracle of pilot injection is only possible because of the speed and flexibility of electronic fuel injection. Pilot injection simply wasn't practical with the relatively slow reaction times of mechanical injection. Now with lightening-fast piezo injectors, up to five injections per stroke can be used instead of the previous three.The BlueTEC system
Diesel engines inherently produce less carbon monoxide and carbon dioxide than a gasoline engine, in large part because they usually operate unthrottled with lots of excess air. However, because of their high combustion pressure and temperatures, diesels usually make more nitrogen oxides, which contribute to photo-chemical smog.
Diesel hydrocarbon emissions, primarily in the form of soot, are kept extremely low by the upstream benefits of the engine's centrally located injectors - smooth, even and complete combustion - and several after-treatment devices in the exhaust system.EGR Reduces Nitrogen Oxides
In addition to using pilot injection to minimize oxides of nitrogen, they're further reduced by an exhaust gas recirculation system (EGR), which diverts a small amount of exhaust gas into the intake stream during part throttle. The inert exhaust gas helps reduce combustion temperature and, in part by simply taking up space, provides the fuel-economy benefits of a smaller-displacement engine An Oxidation Catalyst
Similar to the catalytic converters found in gasoline engines, a diesel oxidation catalyst promotes downstream after-burning of any leftover gaseous hydrocarbons. Particulate Filter
Made practical by the availability of ultra-low-sulfur diesel fuel, a particulate filter with a silicon carbide element can separate 99 percent of the soot from diesel exhaust gas. The carbon particles are deposited on the walls of the filter and are periodically cleaned by a filter regeneration process that's not unlike an oven cleaning cycle. The engine control unit monitors exhaust pressure upstream and downstream from the filter, and when there's an appreciable difference, the system briefly provides secondary fuel injection impulses that raise the exhaust temperature to more than 600 degrees C. This high temperature is enough to burn off the carbon particles and form carbon dioxide.NOx Storage Catalyst
In addition to using pilot injection and exhaust gas recirculation to minimize oxides of nitrogen, they're further reduced in the BlueTEC engine by a third device in the exhaust stream - an advanced-technology NOx storage catalyst that temporarily stores oxides of nitrogen. Regeneration pulses release a form of nitrogen oxide that reacts with exhaust gas to become harmless nitrogen. AdBlue Injection
AdBlue injection is the key reason why Mercedes-Benz BlueTEC diesel models can be offered for retail sale in all 50 states. By further reducing oxides of nitrogen emissions, the BlueTEC diesel engine is now as clean as a modern gasoline engine.
A water-based urea solution, AdBlue is carried in its own seven-gallon tank (8.5 gallons in the GL 320 BlueTEC) and metered into the exhaust in minute quantities, so small that the tank only needs to be refilled during routine scheduled maintenance (fixed at 10,000 miles). When AdBlue is injected into pre-cleaned exhaust gas, ammonia (NH3) is released, converting nitrogen oxides into harmless nitrogen (and water) in a downstream catalytic converter. Called SCR, for selective catalytic reduction, this process creates the most effective method of exhaust gas after-treatment currently available.
In Europe, AdBlue injection has already proven effective in more than 10,000 Mercedes-Benz commercial vehicles, and the AdBlue supply network covers some 1,500 locations.What's Úp with Diesel Fuel?
Related to kerosene on the fossil-fuel family tree, diesel fuel is more like thin oil than gasoline. It requires less complex processing from crude oil and holds more potential heat energy than gasoline. And although it's still not sold at every filling station, diesel fuel is becoming more widely available every year.Cetane is to Diesel as Octane is to Gasoline
While gasoline is rated by octane (the higher the number, the greater its resistance to dangerous detonation or uncontrolled compression-ignition), diesel fuel is rated by its cetane, a measure of how readily it ignites. In a sense, cetane is the opposite of octane, but in a diesel engine, higher cetane numbers mean faster and more complete combustion as well as lower exhaust emissions.
Diesel fuel sold in the Ú.S. is required to have a minimum cetane rating of 40, but studies have shown a wide variance at the pump, from around 42 to 52. By comparison, diesel fuel in Europe has cetane ratings between 51 and 55. While a cetane number is the only rating likely to be displayed on the pump, there are a number of other diesel fuel characteristics that oil companies and government regulators are striving to optimize.Getting Rid of Sulfur
Small amounts of sulfur that occur naturally in diesel fuel have hampered efforts to reduce diesel tailpipe emissions. In untreated form, diesel fuel can have as much as 0.5 percent or 5000 parts per million (ppm) of sulfur, which produces soot and is actually is enough to form corrosive sulfuric acid during combustion that can accumulate in the oil and damage fuel delivery and engine parts. In recent years, the maximum sulfur content in fuel has already been reduced to 500 ppm.
The 2006 arrival of ultra-low-sulfur diesel fuel (maximum 15 ppm) in the Ú.S. can reduce soot formation dramatically in any engine. Already in wide use across Europe, this clean diesel fuel also allows the use of more sophisticated particulate traps and, for the first time, the use of new barium-coated catalysts that help reduce nitrogen oxides (NOx).Diesel is Oil, Too
Modern distributor injection pumps and CDI pumps are lubricated solely by the diesel fuel flowing through them. What's more, the lubricating qualities of diesel fuel become increasingly important as fuel pressure climbs. If the lubricity level is too low, injection pumps are subjected to increased wear, which can lead to pump failure.
Diesel fuel lubricity is rated by the HFRR method - the lower the HFRR value, the higher its lubricity. Experts consider a value of 400 to be the highest acceptable number for normal pump wear, and fuel with higher numbers (lower lubricity) can shorten pump life significantly.Aromatic Chemistry
Diesel fuel inherently contains aromatic compounds called cyclic and polycyclic hydrocarbons that can raise exhaust emissions. As their concentration in the fuel increases, so do the amount of soot particles and other exhaust pollutants.Distillation Temperature
The temperature at which diesel fuel naturally evaporates affects how completely it's burned in the engine. The higher the evaporation temperature, the more soot is formed in the exhaust.Viscosity and Density
Is it like water, or more like honey? The thickness or viscosity of diesel fuel affects exhaust emissions and fuel economy. Diesel engines can run well on a wide range of fuel viscosities, but the injection quantity 'maps' built into the electronic engine management system are based on a predetermined average density, and fuels that vary from the norm can increase emissions and reduce fuel economy.Keeping Injector Nozzles Clean
Diesel injector valves live in the heat and exhaust gas of the combustion chamber, and as a result, injector nozzles tend to accumulate carbon, which can narrow or even clog the fine metering holes in the end of the nozzle. Diesel fuel producers try to ensure that injector nozzles stay clean by using certain additives in their fuel, but there's no measurement for this parameter and no consistent standard.Source - Mercedes-Benz