About SCR System
The SCR system is an exhaust gas aftertreatment system that utilizes a urea solution for neutralization.
In European countries, the environmental standard Euro 4 has been in effect since 2004, followed by Euro 5 from September 2009. These standards aim to reduce the amount of harmful emissions released into the atmosphere to the following levels: particulate matter (PM) to 0.05 g/km, carbon monoxide (CO) to 0.8 g/km, and nitrogen oxides (NOx) to 0.06 g/km. To achieve these requirements, manufacturers of commercial vehicles employ two systems: EGR (Exhaust Gas Recirculation) and SCR (Selective Catalytic Reduction). Let’s delve into each of them.
EGR is an exhaust gas recirculation system. Most leading manufacturers do not equip vehicles sold in the market with EGR systems. This is primarily due to the quality of fuel, which contains three times more sulfur compared to the Euro 4 fuel standard. The increased sulfur content places additional stress on the engine’s piston group, leading to premature engine failure. This prevents the manufacturer from fulfilling warranty obligations.
An alternative to the EGR system is Selective Catalytic Reduction (SCR). Unlike the EGR system, SCR does not affect the engine’s performance. Nevertheless, it also presents numerous challenges for drivers and owners of commercial vehicles.
SCR is a complex and expensive system to repair and maintain. In Europe, alongside diesel fuel, it is possible to purchase a solution called Adblue (urea) at refueling stations. It is poured into a special tank, the volume of which is usually proportional to the fuel tank capacity. The consumption of urea is approximately 4-8% of the fuel consumption. From the tank, the solution is pumped to a dosing module and then injected under 5 bar pressure into the catalytic converter, which is heated to 200 degrees Celsius. Hydrolysis occurs, resulting in the formation of ammonia. This is followed by a reduction reaction that produces the original components: nitrogen and water.
The amount of injected urea constantly varies and is calculated in real time by the dosing unit. Several factors influence this amount, including the temperature of the catalyst and the surrounding environment, engine load, and crankshaft rotational speed.
During idle engine operation, no urea injection occurs, but the system maintains pressure.
Our engineers have developed a device (Emulator) that fully replicates all the operational processes of a fully functional dosing system, including temperature modes of the catalyst. This allows for maintaining fuel consumption at the same level as with a fully operational dosing system. The Emulator receives all the necessary data via the CAN bus from the engine control unit, performs calculations of all the required operational parameters (from 10 to 50 parameters) using complex mathematical models, and feeds them back to the engine control unit. This enables the removal of the entire dosing system when necessary.
It is worth noting that the Adblue solution needs to be at a temperature ranging from 11 to 40 degrees Celsius for the system to function.
What Is Adblue Removal?
Disabling urea or, alternatively, disabling Adblue refers to a set of actions aimed at deactivating the SCR (Selective Catalytic Reduction) system. The SCR system is responsible for controlling the exhaust system in modern trucks, buses, or other vehicles that utilize a urea solution.
Let’s take a closer look at the SCR system:
Selective Catalytic Reduction (SCR) is a device that reduces the emission of nitrogen oxides (NOx) in the engine’s exhaust gases. The core of the SCR catalytic converter is typically made of ceramic material (titanium oxide) and is coated with oxides of metals such as tungsten, vanadium, molybdenum, and other precious or rare metals. However, to perform the necessary reduction reaction, the SCR system requires an additional reagent. This can be an anhydrous ammonia solution, aqueous ammonia, or a urea solution. The additional component is referred to as DEF (Diesel Exhaust Fluid). The most commonly used solution in the market is AdBlue. That’s why SCR system emulators are often called AdBlue emulators.
Principle of operation of the SCR system (diesel engines)
Adblue solution is injected into the chamber of the catalytic converter, where its vapor mixes with the exhaust gases, resulting in a reduction of the harmful substance (NOx) emissions. It’s important to note that the SCR system operates effectively when the engine reaches the required temperature range (360-450 °C) before the NOx reduction process begins. The SCR system has a temperature sensor for the exhaust gases, which sends temperature data to the Engine Control Unit (ECU).
Diesel Particulate Filter (DPF):
The Diesel Particulate Filter (DPF) is a device designed to reduce the emission of solid particles or soot that are formed during the combustion of diesel fuel.
Possible causes of soot and solid particle formation:
- Incomplete fuel combustion
- Incorrect injector installation
- Injector leakage
- Low cetane number of the fuel
- Excessive coolant entering the combustion chamber
- Lack of pressure or airflow due to turbocharger damage or clogged intake channels
- Poor fuel quality, engine oil, and other factors
Diesel particulate matter is considered one of the most harmful pollutants. All EURO 6 exhaust systems must have DPF systems. Some DPF filters are disposable, while others are capable of regeneration under certain conditions. Regeneration is achieved by burning a greater amount of fuel and increasing the exhaust system temperature, which allows for the combustion of accumulated soot in the filter. DPF regeneration is controlled by the vehicle’s Engine Control Unit (ECU) and is performed when the necessary conditions are met (exhaust temperature, fuel tank level, vehicle speed, and engine RPM).
SCR and DPF errors
The most common issues encountered during the operation of modern vehicles are related to failures in the SCR (Selective Catalytic Reduction) or DPF (Diesel Particulate Filter) systems. In the event of such a malfunction, the vehicle’s control will be significantly hindered due to the Limp mode activated by the Engine Control Unit (ECU). Limp mode is an emergency engine operation mode that reduces power (torque) by 40%. This mode is activated when active fault codes related to the emission control system (SCR) indicate a malfunction in the exhaust gas after-treatment system. By entering this mode, the ECU reduces the amount of fuel injected into the cylinders and decreases the volume of exhaust gases, thereby protecting the environment from pollution.
Operating a commercial vehicle with a faulty SCR or DPF system is practically impossible, and it can cause significant problems for a freight company. Delivery schedules may be disrupted, increased fuel consumption (due to reduced power) can raise the cost per kilometer, and the repair cost of any emission control system is typically high.
The causes of SCR and DPF system failures can vary, but one of the most common reasons, particularly in regions like India, is the use of low-quality AdBlue solution. Such a solution may contain various petroleum products (diesel fuel, oils), and the presence of such impurities can quickly lead to the failure of SCR system components such as the pump, dosing valve, or catalytic elements.
It’s worth noting that there are many countries outside of CIS and the EU that do not require compliance with EURO 6, EURO 5, or even EURO 4 standards for SCR or DPF systems. This makes operating and servicing these systems in such countries disadvantageous and, in addition, unnecessary.
What should you do if you want to repair the SCR system or completely disable it (saving a lot of money)?
We can highlight three options:
- Seek professional repair services (recommended if your vehicle is frequently used in the EU). The cost of the service is high, but your transportation will be guaranteed to comply with the EURO standards.
- Disable the SCR system by reprogramming the Engine Control Unit (ECU). This method is relatively simple for a specialist, but if you change your mind and want to restore the SCR system, it can be costly. If you update your vehicle’s software, the reprogramming will be nullified after each firmware update (meaning the vehicle will once again use the SCR system). Additionally, this approach may cause issues if you decide to sell the truck with modified software.
- Lastly, you can choose the fastest, easiest, and cheapest option – installing an Adblue emulator. It is safe to use, easy to install (even if you don’t have extensive knowledge of automotive electronics), and you can disable or remove the emulator at any time within a few minutes. Furthermore, you can resell the Adblue emulator if you no longer need it.
An AdBlue emulator is a device that can simulate a fully functional SCR system in a vehicle. The emulator gathers data on the engine’s operating modes, temperatures, and torque, calculates these parameters, and generates signals that mimic a working SCR system. By doing so, it prevents the occurrence of errors in the system. The Engine Control Unit (ECU) receives all the necessary information about a properly functioning emission control system, while the actual SCR system may be absent from the vehicle. There are different types of AdBlue emulators available, which are adapted to specific truck models or engines.
An AdBlue emulator can help operate your vehicle in normal engine mode even if the SCR system is faulty. However, the main reason why many trucks are equipped with AdBlue emulators is to save money on AdBlue fluid and the maintenance of the SCR system.