Katerina Swanson
The impact of EGR on fuel economy is a widely discussed topic, with varying opinions and experiences shared online. Some people claim that deleting the EGR system in their diesel vehicles has resulted in improved fuel economy, particularly in diesel pickup trucks. However, others argue that a properly functioning EGR system should enhance fuel economy by reducing nitrogen oxide (NOx) emissions and improving combustion efficiency. A malfunctioning or clogged EGR can lead to increased fuel consumption and engine performance issues. Cleaning the EGR system can help maintain fuel efficiency, as it ensures the system functions optimally and prevents soot buildup, which can impact performance and fuel usage. The design of the engine and EGR system also plays a role in the overall fuel economy, and some engines may be more susceptible to the effects of EGR deletion or malfunctions.
| Characteristics | Values |
|---|---|
| EGR impact on fuel economy | EGR improves fuel economy by reducing NOx emissions and making the cylinder virtually smaller. |
| EGR function | EGR recirculates burned gases back into the cylinders, allowing more advancing timing and lowering cylinder temperature. |
| Impact of malfunctioning EGR | A malfunctioning or blocked EGR can worsen fuel economy, increase diesel knock, and cause engine performance issues. |
| Impact of deleting EGR | Deleting EGR may worsen MPG as it recycles exhaust and burns remaining fuel, but it can also reduce HP and torque. |
| Impact of cleaning EGR | Cleaning EGR can potentially improve MPG by allowing more efficient recirculation of exhaust gases. |
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What You'll Learn
EGR reduces NOx emissions
Exhaust gas recirculation (EGR) is an effective strategy to control and reduce NOx emissions from diesel engines. EGR works by recirculating part of the burned exhaust gases back into the cylinders, making the cylinder virtually smaller. This process also allows for more advanced timing and lowers the cylinder temperature, which reduces NOx emissions.
The EGR system reduces NOx emissions by lowering the oxygen concentration in the combustion chamber and through heat absorption. The temperature of the EGR impacts the intake mixture temperature and, therefore, NOx emissions. Cooling the EGR stream can further reduce NOx emissions.
EGR is crucial for mitigating NOx emissions in diesel engines, and its application for NOx reduction is the most common reason for its use in modern commercial diesel engines. However, it is not the only technology used to reduce NOx emissions. Other technologies, such as selective catalytic reduction (SCR) and close-coupled selective catalytic reduction (ccSCR), are also employed to achieve ultra-low NOx emissions.
While EGR is effective at reducing NOx emissions, it has drawbacks, including increased fuel consumption, increased emissions of PM, HC, and CO, engine wear, and reduced engine durability. To address these issues, engine manufacturers have adopted additional technological changes and improvements to strike a balance for overall engine economy and performance.
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EGR recycles exhaust gas
Exhaust Gas Recirculation (EGR) is a proven technique for reducing pollution emitted from on-road diesel engines. EGR recycles exhaust gas by diverting exhaust gases from the exhaust manifold to the inlet manifold via the EGR valve unit. This recirculates a portion of the engine's exhaust gas back to the engine cylinders, displacing atmospheric air and reducing the oxygen in the combustion chamber.
EGR valves work to reduce combustion temperature and lower the level of nitrogen oxide (NOx) emitted through the exhaust system. NOx is produced by high-temperature mixtures of atmospheric nitrogen and oxygen, which usually occurs at cylinder peak pressure. By reducing the amount of oxygen, EGR reduces the amount of fuel that can burn in the cylinder, thereby reducing peak in-cylinder temperatures.
In a gasoline engine, the inert exhaust displaces some of the combustible charge in the cylinder, effectively reducing the quantity of charge available for combustion without affecting the air-fuel ratio. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. The lower combustion chamber temperatures caused by EGR reduce the amount of NOx generated.
EGR can theoretically increase the efficiency of gasoline engines via several mechanisms. Firstly, it reduces throttle losses by increasing inlet manifold pressure and reducing throttling losses. Secondly, it reduces heat rejection by lowering peak combustion temperatures, which also reduces the formation of NOx. Finally, it reduces chemical dissociation by keeping more of the released energy as sensible energy near Top Dead Center (TDC).
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EGR improves fuel economy when malfunctioning
The Exhaust Gas Recirculation (EGR) valve is an integral part of a vehicle's engine management system. It recirculates finely metered quantities of exhaust gas to the engine intake system, which increases engine efficiency, improves fuel economy, and reduces fuel consumption and harmful NOx emissions.
When the EGR malfunctions, the vehicle's air-fuel ratio is disrupted, causing engine performance issues such as reduced power, poor acceleration, and rough idling. However, counterintuitively, a malfunctioning EGR may also improve fuel economy. This is because the EGR system recirculates burned gases back into the cylinders, making the cylinders virtually smaller, allowing more advancing timing, and lowering cylinder temperatures. This, in turn, improves fuel economy.
It is important to note that this improvement in fuel economy comes at a cost. The malfunction can cause turbo boost pressure leaks, making the turbo work harder. Additionally, the higher temperatures and increased NOx emissions may result in increased detonation or "engine knock," which can be heard as knocking noises in the engine.
While a malfunctioning EGR may provide a temporary boost in fuel economy, it is not advisable to rely on this as it can lead to other engine issues and increased wear and tear. It is always best to follow the troubleshooting procedures detailed in the service manual and seek professional help when needed.
Overall, while a malfunctioning EGR may provide a short-term improvement in fuel economy, it is essential to address the issue to ensure the long-term health and optimal performance of the vehicle.
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EGR reduces diesel knock
Exhaust gas recirculation (EGR) is a technology that has been used in diesel engines since the 1970s. It works by recirculating finely metered quantities of exhaust gas back into the engine intake system. This reduces the amount of oxygen in the cylinder, which in turn reduces the production of harmful nitrogen oxides (NOx) and improves fuel efficiency.
While EGR technology can improve fuel efficiency, it is not the primary mechanism for doing so. The recirculation of exhaust gas can worsen the fuel and air mix, which reduces horsepower and torque. This can lead to a loss of overall efficiency over time. Thus, the only way fuel economy improves is if the EGR is malfunctioning or deleted.
However, EGR technology can help to reduce diesel knock at idle. Knock, or engine knock, refers to the knocking noises that can occur in an engine due to increased detonation. This is often caused by higher temperatures and increased NOx emissions. By recirculating exhaust gas, EGR valves help to lower cylinder temperatures and reduce NOx emissions, thereby reducing the occurrence of engine knock.
There are several types of EGR valves, including vacuum-operated valves and electronically controlled valves. Diesel high-pressure EGR valves divert high-flow, high-soot exhaust gas before it enters the diesel particulate filter, while low-pressure EGR valves divert exhaust gas after it has passed through the filter. The gas is then passed back to the inlet manifold, reducing the oxygen content in the cylinder and helping to prevent engine knock.
In summary, while EGR technology may have a minor impact on fuel efficiency, its primary function is to reduce NOx emissions and engine knock in diesel engines. By recirculating exhaust gas, EGR valves help to lower cylinder temperatures and reduce the occurrence of engine knock, particularly at idle.
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EGR reduces engine performance
Exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol, gasoline, diesel engines, and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust gas back into the engine cylinders. The exhaust gas replaces the excess oxygen in the pre-combustion mixture, thereby reducing the amount of oxygen available to burn fuel in the cylinder. This, in turn, reduces the peak in-cylinder temperatures.
While EGR is an effective strategy to control NOx emissions, it does have some drawbacks. One of the main drawbacks is that it can lead to increased fuel consumption. This is because the recirculated exhaust gas contains water vapour and carbon dioxide, which have lower heat capacity ratios than air. As a result, adding exhaust gas reduces pressure and temperature during the isentropic compression in the cylinder, which lowers the adiabatic flame temperature. This leads to a slower combustion process, which can impact engine performance.
Additionally, EGR can cause engine performance issues if the valve gets stuck in the open position. This disrupts the vehicle's air-fuel ratio, resulting in reduced power, poor acceleration, and rough idling. It can also cause turbo boost pressure leaks, making the turbo work harder. Furthermore, if the EGR valve remains shut, the high temperatures in the combustion chamber can lead to increased NOx emissions and reduced fuel efficiency.
Another issue with EGR, specifically in diesel engines, is the buildup of soot and oil in the intake system over time. This buildup can impact the engine's performance and fuel economy. In some cases, deleting the EGR system in diesel engines has been reported to improve fuel economy, possibly due to the removal of the soot and oil buildup. However, this may also be due to the engine operating outside of its programmed parameters, which can have other negative consequences.
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Frequently asked questions
Yes, EGR can increase fuel economy in diesel engines. A fully functioning EGR system should reduce diesel knock and improve fuel economy by recirculating burned gases back into the cylinders, making the cylinder virtually smaller.
EGR recycles exhaust gas, which is largely carbon dioxide and water vapour, and has a higher specific heat than air. This lowers peak combustion temperatures, aiding the diesel engine's efficiency by reducing heat rejection and dissociation.
A malfunctioning or clogged EGR can lead to increased fuel consumption, engine performance issues, and excess soot in the exhaust. This can be caused by a build-up of soot and oil in the intake, which is common in turbo diesel engines.
Cleaning the EGR can potentially improve fuel economy by removing any blockages and allowing the system to function optimally. However, results may vary depending on the engine and EGR design, and other factors such as driving habits.
