CAN Newsletter magazine
In most European countries, the use of Adblue emulators is forbidden or restricted. In other ones, they are allowed. An Adblue emulator simulates the Selective Catalytic Reduction (SCR) system behavior and truck owners can save a lot of money.
This article originally appeared in the June issue of the CAN Newsletter magazine 2019. This is just an excerpt.
The SCR system reduces the quantity of Mono-Nitrogen Oxides (NOx) in engine exhaust gasses. The SCR catalytic converter core is usually made from ceramic (titanium oxide). It is coated with oxides of such metals as tungsten, vanadium, molybdenum, and other precious or rare metals. The reduction reaction is achieved by adding a solution of anhydrous ammonia, aqueous ammonia, or urea. This additive is called Diesel Exhaust Fluid (DEF). The most popular DEF solution on the market is Adblue; this is a registered trademark of the German Association of the Automotive Industry (VDA). DEF is the reducing agent that reacts with NOx to convert the pollutants into nitrogen, water, and tiny amounts of CO2. The DEF can be rapidly broken down to produce the oxidizing ammonia in the exhaust stream. SCR technology alone can achieve NOx reductions up to 90 percent. Most of the SCR systems available on the market use CAN communication based on the J1939 higher-layer protocol and associated Parameter Groups.
The SCR catalytic converter works by injecting Adblue to the exhaust system. DEF is injected before the catalytic converter chamber, where its vapor is mixed with exhaust gasses. It is important that the temperature will reach 360°C to 450 °C otherwise SCR effectiveness is relatively small. It means that it needs some time after the cold engine starts to arrive at the required temperature to start the NOx reduction process effectively. The SCR system has an exhaust temperature sensor, which sends temperature data to the SCR electronic control unit (ECU). All Euro-V and Euro-IV type diesel engines are equipped with SCR systems. European regulation mandates this.
All Euro-VI type engines provide a Diesel Particulate Filter (DPF). This device removes any possible diesel particulate matter (solid particles) or soot from the exhaust gasses before they are exhausted to the atmosphere. Particulate matter is a result of incomplete or improper diesel combustion cycle. There are several reasons, why particles could be produced: Cold engine starts, especially in the ultra low-temperature environment; lack of intake air pressure or flow due to damaged turbo charger or clogged intake channels; reduced compression in cylinders due to damaged engine parts; high engine load or sudden power demand on rapid acceleration; clogged exhaust gas recirculation (EGR) system; or poor fuel quality, engine oil in the combustion chamber of cylinders and other factors. SCR systems are also used in other countries.
For example, in the USA to meet the EPA 2010 diesel engine emission standards for heavy-duty vehicles and the Tier-4 emissions standard for engines found in off-road equipment. Diesel particulate matter particles are considered as one of the most harmful pollutants. Therefore all Euro-IV type exhaust systems must have DPF systems. Some DPF filters are single use, and some of them are capable of regenerating at certain conditions (DPF regeneration).
Recovery is possible by burning more fuel and rising exhaust system temperature, which makes it possible to burn out any contamination from the filter. DPF regeneration controlled by a vehicle ECU and executed when necessary conditions are reached (exhaust temperature, fuel quantity in the tank, vehicle speed, and engine speed).
When the SCR or DPF systems fail, the truck driver is in trouble: In both cases, the central ECU activates the limp mode of the engine. This reduces the engine power to protect the environment from possible highly polluted exhaust gasses. This is done independent, if the engine is capable to work properly. The ride to the next repair shop or garage can be time-consuming. Additionally, repair costs are high. In some northern regions of Europe and Russia, environment temperatures can be low as -40 °C. These ultralow temperatures are way beyond the freezing point of DEF; it freezes if its temperature falls below -11 °C.
Injecting frozen Adblue to the SCR chamber is impossible. Also, it will damage the DEF pump, and the whole SCR system fails. This means, you need to switch-off the SCR system. This could be done by means of so-called Adblue emulators. They can help to drive on the regular engine mode even if the SCR system is faulty. But the main reason why so many trucks equipped with Adblue emulators is the saving of money on a diesel exhaust fluid. Such products were available shortly after introduction of Euro-IV type diesel engines.
The first of such CAN-connectable devices were designed for a dedicated truck. In the meantime, they can support multiple brands. Some of them are configurable by means of DIP-switches, while others implement an USB-to-CAN dongle. The price for such Adblue emulators has come down to 30 euros comprising a USB dongle. This leads to another question: Why generic CAN-to-USB interfaces cost often more than 300 euros? Of course, some of them provide additional features and are tailored for sophisticated diagnostic purposes.
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