EGR or exhaust gas recirculation valve is an integral component of your vehicle’s engine management system. EGR valves facilitate increased engine efficiency by recirculating extremely small quantities of exhaust gas into the engine intake system. This helps produce lower NOx emissions and also result in reduced fuel consumption.
It’s all about being green and efficient today, which means there’s a lot of pressure to reduce emissions. With the EGR valve, you can take a huge step towards being sustainable. Not only this, a healthy EGR will contribute towards car engine tuning, meaning you’ll be upping your ride’s performance and adding towards your vehicle’s maintenance.
This is why you need to know what it does, what causes it to fail and how you can replace it.
EGR In Vehicle – How Does It Work?
About 80% of the air we breathe is made up of nitrogen. When this gas is exposed to tremendously high temperatures (1370°+) in the confines of a combustion chamber, this inert gas tends to become reactive. This leads to the creation of harmful oxides of nitrogen known as NOx. This harmful gas is then released into the atmosphere, after passing through the exhaust system.
To help moderate this, the EGR valve acts like a gateway that allows a very precisely calculated quantity of exhaust gas to re-enter the engine intake system, instantly changing the chemical composition of the air entering the confines of your vehicle’s engine.
With lower quantities of oxygen, the diluted version of the gas now burns at a slower rate, which helps lower the temperatures in the combustion chamber by nearly 150°C. This works towards reducing the NOx production and results in a more efficient and cleaner exhaust.
There are two primary settings in the EGR valve – open and closed. When the engine sputters to life, the EGR valve is in a closed position. When your vehicle sits idle or operates at a low speed, it requires a very small amount of power. This tells us that only small amounts of oxygen is consumed which means that the valve opens up gradually. When your vehicle sits idle, up to 90% of the valve could be open.
When your car uses up more power and torque during full acceleration for instance, the EGR valve shuts off to allow as much oxygen to enter the cylinder as possible.
Along with reducing NOx, EGR valves are used to downsize GDI in engines to lessen pumping losses and enhance knock tolerance and combustion efficiency.
EGR Valve Types
There are several types of EGR valves. Older systems used a vacuum-operated valve whereas the newer cars are now electrically powered and controlled. This is why car and engine tuning becomes a whole lot streamlined in newer systems.
Let’s take a look at the main types of EGR below:
- Diesel High Pressure EGR Valves
These help redirect the high-soot, high-pressure exhaust gas before it can enter the diesel particulate filter (DPF). The combination of soot and oil vapour can result in the formation of sludge. The gas produced is then transferred back to the inlet manifold either through internal drillings or a pipe in the head of the cylinder. Another valve is used to form a vacuum in the inlet manifold as this is not included in the diesel engines organically.
- Diesel Low Pressure EGR Valves
This helps reroute the gas once it has passed through the DPF. The gas here has a lower flow comparatively and is nearly clean of any soot. The resulting gas is then passed back via a pipe to the inlet manifold section.
- Gasoline EGR Valves
With this valve, exhaust gases are diverted in a high pressure format. The exhaust gas is drawn in and the flow of the same is moderated with the opening and closing of the EGR valve, thanks to the vacuum created by cylinder depression.
- Vacuum Operated EGR Valves
These use a vacuum solenoid to measure the vacuum to the diaphragm and in turn cause the EGR to open and close. Certain valves come with a feedback sensor that informs the ECU in electronically controlled vehicles of the positions of the valves.
- Digital EGR Valves
This valve features a stepper motor or a solenoid along with a feedback sensor. The EGR receives a pulse width with due modulation signal from the ECU chip to adjust and control the flow of the exhaust gas.
EGR Fails – How Does That Happen?
EGR valves are positioned in extremely hostile and exposed environments, so it is natural and expected that with time, it is bound to experience hefty wear and tear. That said, the primary reason behind EGR failure is due to the buildup of carbon particles from the exhaust gases that block up the EGR opening along with the passages of the intake system.
As more and more time passes, this buildup will end up clogging tubes, channels of the exhaust gas and ultimately the plunger system of the valve resulting in it to either stick open or shut close for good.
Failures can happen due to puncture, leaks or damages to the diaphragm of the valve as well.
EGR Replacement – How to Do It?
- Move the engine’s cover first
- Proceed to loosen up the electrical cable on the valve and get rid of the electrical connections and/or vacuum lines, all the while checking for signs of damage
- Unfasten the screws and look for any valve damage, carbon buildup or corrosion
- Thoroughly clean the EGR valve mounting surface and fit the new gasket and valve. Wipe off any loose carbon from the EGR supply port
- Now proceed to line up the EGR valve with gasket and bolt holes and refasten the housing and setup
- Secure and screw everything in place as per the recommended torque setting
- Once everything is in place, reattach and connect the vacuum lines once again along with all the electrical connections
- Lastly, use a diagnostic scanning tool to re-analyse and reset the engine management light and look for any other errors
- See that the malfunction indicator lamp is extinguished. Once you’re sure, proceed to conduct a road test
Note – As an additional safety precaution, it is required to test and reset the EGR valve under professional scrutiny and adaptation. This will enable the ECU to familiarise itself regarding when to stop at the open and closed points.
If you fail to do this, it can potentially cause the valve to break off and fall into the manifold.
Setup EGR for Your Vehicle Right Away
Now that you have a better understanding of how EGR operates, speak to a professional and get one for your vehicle right away. Ensure that your ride remains well tuned and sustainable for better performance and longevity!
Plus, every step you take towards being green counts and your vehicle is no exception.