Urea shutdown: what is it?

Turning off urea or, in another way, turning off Adblue is a set of actions aimed at disabling the SCR system (Selective Catalytic Reduction). The SCR system is responsible for controlling the exhaust system on modern trucks, buses or other vehicles using urea solution.

Consider the SCR system in more detail:

A selective catalytic system (SCR) is a device that reduces the amount of nitrogen monoxide (NOx) emissions from engine exhaust gases. The core of the SCR catalytic converter is usually made of ceramics (titanium oxide) and covered with oxides of metals such as tungsten, vanadium, molybdenum and other precious or rare metals. In any case, the SCR system requires an additional reagent to perform the required reduction reaction. This may be a solution of anhydrous ammonia, aqueous ammonia, or a solution of urea. An additional component is called DEF (Diesel Exhaust Fluid). The most popular solution on the market is AdBlue. That is why SCR system emulators are often called AdBlue emulators.

The principle of operation of the SCR system (diesel engines):

Adblue solution is introduced into the catalytic converter chamber, where its vapor is mixed with exhaust gases, thereby reducing the emission of harmful substances (NOx). It should be clarified that the operation of the SCR system will be effective if the engine reaches the required temperature (360-450 ° C) before starting the process of reducing NOx emissions. The SCR system has an exhaust temperature sensor that sends temperature data to an electronic control unit (ECU).

Particulate filter (DPF)

DPF (Diesel Particulate Filter) is a device that is designed to reduce the emission of particulate matter or soot into the atmosphere, which are formed during the combustion of diesel fuel.

Possible causes of soot and particulate matter are:

  • Incomplete combustion
  • Wrong nozzle installation
  • Nozzle leakage
  • Low cetane number of fuel
  • Abundant ingress of coolant into the combustion chamber
  • No pressure or intake air flow due to damage to the turbocharger or clogged intake ducts
  • Poor fuel quality, engine oil and other factors.

Diesel particulate matter is considered one of the most harmful pollutants. All exhaust systems of type EURO 6 must have a DPF system. Some DPF filters are disposable, and some of them are able to regenerate under certain conditions. Recovery is possible by burning more fuel and raising the temperature of the exhaust system, which allows you to burn pollution from the filter. The DPF regeneration is controlled by the vehicle engine control unit (ECU) and is performed when the necessary conditions are reached (exhaust temperature, amount of fuel in the tank, vehicle speed and engine speed).