OBDII - Components - Exhaust Gas Recirculation

Exhaust Gas Recirculation

- Last Edited: Aug 27, 2023
- Popularity: 2,796 Views


Exhaust Gas Recirculation (EGR) is an emissions control technology used in internal combustion engines, particularly in gasoline and diesel-powered vehicles. Its primary purpose is to reduce the formation of nitrogen oxides (NOx), which are harmful pollutants that contribute to smog and air quality issues.

Here's how the EGR system works:

Recirculation of Exhaust Gas: A portion of the exhaust gases produced during combustion is redirected back into the engine's intake manifold. This recirculated exhaust gas contains inert gases like carbon dioxide (CO2) and water vapor, which act as a "buffer" to lower the combustion temperature and reduce the formation of nitrogen oxides.

Lowering Combustion Temperature: By introducing the recirculated exhaust gas into the combustion process, the overall oxygen content in the combustion chamber is reduced. This results in a decrease in the combustion temperature, which helps prevent the formation of high levels of nitrogen oxides, which tend to form at high temperatures.

EGR Valve: The EGR system is controlled by an EGR valve that regulates the flow of exhaust gases into the intake manifold. The Engine Control Module (ECM) or Engine Control Unit (ECU) monitors various engine parameters such as engine load, temperature, and speed to determine when and how much exhaust gas should be recirculated.

While EGR is effective at reducing NOx emissions, it can also have some side effects, such as potentially impacting engine efficiency and power output. As a result, modern engines often use more advanced EGR systems that can be precisely controlled to optimize emissions reduction while minimizing any negative impact on performance.

Overall, Exhaust Gas Recirculation is a critical technology in reducing harmful emissions from internal combustion engines and helping vehicles meet increasingly stringent emission regulations.

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