So you went and got that new 3.0 liter diesel and now it needs DEF. To help answer all of uncle Bart’s def questions, let’s dive into what DEF is, how it works, and its importance in emission control.

What is Diesel Exhaust Fluid (DEF)?

Diesel Exhaust Fluid, commonly known as DEF, is a non-toxic, colorless, and odorless solution comprised of 32.5% urea and 67.5% deionized water. It is used in selective catalytic reduction (SCR) systems to reduce nitrogen oxide (NOx) emissions produced by diesel engines. DEF is injected into the exhaust stream, where it undergoes a chemical reaction to convert harmful NOx emissions into harmless nitrogen and water vapor. That’s right…nitrogen and water vapor.

How Does DEF Work?

The operation of DEF in reducing emissions can be summarized in the following steps:

1. Injection into Exhaust Stream: DEF is stored in a separate onboard tank in diesel vehicles and is injected into the exhaust system before it reaches the SCR catalyst.

2. Chemical Reaction: Upon contact with the hot exhaust gases, DEF vaporizes and decomposes into ammonia (NH₃) and carbon dioxide (CO₂). The ammonia then reacts with NOx over the SCR catalyst to form nitrogen (N₂) and water vapor (H₂O), both of which are harmless components of the atmosphere.

3. Conversion Efficiency: The efficiency of NOx reduction depends on various factors, including the temperature of the exhaust gases, the concentration of DEF injected, and the design of the SCR system. Optimal operation typically occurs at temperatures between 200°C to 500°C.

Importance in Emissions Control

The use of DEF plays a crucial role in reducing NOx emissions from diesel engines, thereby mitigating their impact on air quality and human health. NOx emissions contribute to the formation of smog, acid rain, and particulate matter, which can have adverse effects on respiratory health and the environment.

In conclusion, Diesel Exhaust Fluid (DEF) is an essential component in modern diesel engines’ efforts to reduce harmful emissions. Through selective catalytic reduction (SCR) technology, DEF facilitates the conversion of nitrogen oxide (NOx) emissions into harmless nitrogen and water vapor, thereby improving air quality and environmental sustainability. As emissions regulations continue to evolve, the use of DEF is poised to remain a key strategy in mitigating the environmental impact of diesel-powered vehicles and equipment.

For more information, Capital Reman has an interesting post about DEF, found here. 20 Facts you need to know about DEF