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What is the difference between SCR and DEF?

2025-12-26

The difference between SCR and DEF lies in their roles in diesel emission control: SCR (Selective Catalytic Reduction) is the system that reduces NOx emissions, while DEF (Diesel Exhaust Fluid) is the consumable liquid used in the SCR process to facilitate the chemical reaction.‌

‌1. SCR (Selective Catalytic Reduction)‌

‌Definition‌: A system designed to reduce nitrogen oxides (NOx) in diesel engine exhaust.
‌Function‌: Converts NOx into harmless nitrogen (N₂) and water (H₂O) through a chemical reaction.
‌Components‌: Includes a catalyst, DEF injector, and control unit.

‌2. DEF (Diesel Exhaust Fluid)‌

‌Definition‌: A non-hazardous, high-purity urea solution (32.5% urea and 67.5% deionized water).
‌Function‌: Stored in a separate tank and injected into the SCR system, where it decomposes into ammonia (NH₃) to react with NOx.
‌Usage‌: Consumed during vehicle operation, with usage rates varying by driving conditions.

‌3. Key Differences‌

‌Aspect‌	‌SCR‌	‌DEF‌
‌Type‌	Emission control system	Consumable liquid
‌Role‌	Reduces NOx emissions	Provides ammonia for NOx reduction
‌Composition‌	Catalyst, injector, control unit	Urea and deionized water
‌Maintenance‌	Requires periodic inspection	Needs regular refilling

‌4. Summary‌

SCR is the system that actively reduces NOx, while DEF is the essential liquid that enables the chemical reaction. Both are critical for meeting emission standards in diesel vehicles.

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What is the difference between SCR and DEF?

2025-12-26

‌1. SCR (Selective Catalytic Reduction)‌

‌Definition‌: A system designed to reduce nitrogen oxides (NOx) in diesel engine exhaust.
‌Function‌: Converts NOx into harmless nitrogen (N₂) and water (H₂O) through a chemical reaction.
‌Components‌: Includes a catalyst, DEF injector, and control unit.

‌2. DEF (Diesel Exhaust Fluid)‌

‌Definition‌: A non-hazardous, high-purity urea solution (32.5% urea and 67.5% deionized water).
‌Function‌: Stored in a separate tank and injected into the SCR system, where it decomposes into ammonia (NH₃) to react with NOx.
‌Usage‌: Consumed during vehicle operation, with usage rates varying by driving conditions.

‌3. Key Differences‌

‌Aspect‌	‌SCR‌	‌DEF‌
‌Type‌	Emission control system	Consumable liquid
‌Role‌	Reduces NOx emissions	Provides ammonia for NOx reduction
‌Composition‌	Catalyst, injector, control unit	Urea and deionized water
‌Maintenance‌	Requires periodic inspection	Needs regular refilling

‌4. Summary‌

SCR is the system that actively reduces NOx, while DEF is the essential liquid that enables the chemical reaction. Both are critical for meeting emission standards in diesel vehicles.

Engine NOx Sensor

Car NOx Sensor

Nitrogen Oxide NOx Sensor

Truck Blower Motor

Urea Doser Pump

DEF Sensor

PM Sensor

Truck ABS Sensor

Exhaust Temperature Sensor

Crankshaft Position Sensor

Truck Pressure Sensor

Power Window Switch

VGT turbo actuator

Engine NOx Sensor

Car NOx Sensor

Nitrogen Oxide NOx Sensor

Truck Blower Motor

Urea Doser Pump

DEF Sensor

PM Sensor

Truck ABS Sensor

Exhaust Temperature Sensor

Crankshaft Position Sensor

Truck Pressure Sensor

Power Window Switch

VGT turbo actuator

News Details

Company news about What is the difference between SCR and DEF?

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Cases

What is the difference between SCR and DEF?

‌1. SCR (Selective Catalytic Reduction)‌

‌2. DEF (Diesel Exhaust Fluid)‌

‌3. Key Differences‌

‌4. Summary‌

Company news about-What is the difference between SCR and DEF?

News

Cases

What is the difference between SCR and DEF?

‌1. SCR (Selective Catalytic Reduction)‌

‌2. DEF (Diesel Exhaust Fluid)‌

‌3. Key Differences‌

‌4. Summary‌