How to Choose the Right Automotive SCR Solenoid Valve, Detailed Version
Selecting an automotive SCR solenoid valve entails making several very important decisions. Since the valve will operate in tough environmental conditions and exposed to the corrosive urea solution (AdBlue) and temperature extremes ranging from freezing to the heat produced by exhaust, proper selection is vital for durability and efficiency. Here’s a detailed explanation of the five key aspects you need to consider when choosing your valve.
1. Fluid compatibility (AdBlue challenge)
This parameter is responsible for most of the failures. Being a highly corrosive liquid, AdBlue (urea solution) will attack common metals like zinc and carbon steel. Therefore, it is important to pay attention to the material your valve is made of.
– Body material: Select brass or stainless steel valves to ensure proper protection from AdBlue’s corrosive properties. Don’t consider cast iron and aluminum valves for urea service;
– Sealing material: It should withstand contact with urea. Consider elastomers like EPDM (cold resistant and good with urea) and FKM/Viton (heat resistant).
2. Electrical parameters (voltage and connectors)
It is crucial to understand that there’s no single voltage and connection type that would apply across all vehicles. You should know what your vehicle uses.
– Voltage: Most cars (including SUVs and trucks) have 12-volt electrical systems. Commercial vehicles with SCR systems usually operate on 24V;
– Protection level: The valve needs to be protected from splashes, rain, dust, etc. Aim for an ingress protection of IP67 and above;
– Connectors: Different manufacturers use different automotive wiring standards. Pay attention to the type of valve connector to make sure it’s compatible with your harness (Deutsch, AMP, etc.)
3. Pressure and flow requirements
Proper atomization depends on the fluid flow rate and pressure.
– Supply pressure: Unlike in the industrial applications, diesel SCR operates at certain pressure levels. Typically, the valve needs to resist a supply pressure of up to 9 Bar (130 psi);
– Dosing: Depending on your engine size, the urea dosing is measured in grams per hour or liters per minute. Make sure your valve’s Kv equals the fluid flow rate in your SCR setup.
4. Temperature range (frost protection)
In cold weather, AdBlue freezes at -11°C (12°F). Once it’s frozen, the standard valve can fail catastrophically.
– Heater presence: Most modern valves feature an embedded heating system or are made specifically for operation together with heated lines, supply modules, and other components aimed to unfreeze the urea before injection.
– Operational temperature range: The valve needs to withstand ambient temperatures between -40°C and +85°C for the solenoid coil and up to 100°C and more for the return line hot fluid.
5. Valve type
There are two main types of valves for SCR systems: dosing valves and heating valves. You should clearly understand which of these you need.
– Dosing valve (injection valve): The valve positioned directly in the exhaust pipe of the engine. High-frequency valve used to spray AdBlue in the form of a fine mist into the exhaust;
– Heating valve (coolant side valve): Placed in the engine coolant line. Open and closed valves used to let hot engine coolant enter the urea tank.
Selection checklist (shortened)
– Fluid type: AdBlue → Brass or Stainless Steel body and seals made of EPDM or FKM;
– Voltage: 12V in cars and 24V in trucks;
– Pressure: At least 9 Bar;
– Temperatures: Resistant to both cold ambient and engine exhaust temperature and able to withstand fluid up to 100+°C;
– Valve type: either dosing valve for exhaust injection or heating valve for coolant side operation.
Important note on Industry standards
For replacement of the valve installed in a modern diesel vehicle equipped with Bosch Denoxtronic, Cummins Ecofit, or any other SCR system, it is recommended to choose an OEM-specific replacement part. In such modern systems, the Engine Control Unit (ECU) carefully controls operation and the valve needs to perfectly match in flow rate and Ohm value to avoid the malfunction and Check Engine warning lights.














