Therefore, incorporating EGR systems into the design of a car is important with regards to lowering harmful emissions to save the environment and have a positive impact on human health. The majority of modern vehicles incorporate EGR valves into their design to reduce NOx emissions and therefore meet stringent emissions regulations. EGR systems recycle a portion of the exhaust gas back into the combustion chamber, where it combines with fresh intake air.
This lowers the amount of Oxygen and increases the water vapour content to the combustion mixture which reduces the peak combustion temperature. Because more NOx is created as peak combustion temperature rises, the EGR valve effectively reduces the amount of NOx produced by the engine.
The EGR valve begins working once the engine has started, attained the correct operating temperature and the vehicle's speed increases. Gradually, the EGR valve regulates the flow of exhaust gases.
Once the vehicle slows down and the engine stops, the EGR valve will return to its closed position and prevent the flow of exhaust gases. A frequent problem with the EGR valve is sticking due to a build up of carbon deposits. In worst cases, the EGR valve and EGR passages can be completely blocked, preventing the process of recirculating the exhaust gases.
Clogged EGRs are often the cause of black smoke escaping the exhaust, in addition to increased fuel consumption or reduced performance. On several occasions, small scale EGR applications occurred earlier than indicated in the table, typically driven by various voluntary incentive programs. Light-Duty Engines. The introduction of EGR technology to diesel passenger cars in the s went almost unnoticed and was not considered a major breakthrough for several reasons. Typical passenger car engines operate mostly at part load conditions where temperatures are relatively low.
Heavy-Duty Engines. The wide scale launch of cooled EGR on heavy-duty engines that attracted a lot of attention to the technology took place in late in the North American market. High pressure loop cooled EGR was the most expedient in-cylinder NOx reduction technology that could achieve this emission level [].
There was a considerable apprehension in the field regarding the performance, fuel economy, and the durability of these new engines. While initial statements from fleet managers appeared to praise the new technology [] , some users have complained of the increase in fuel consumption. For EPA , the 0. Navistar—the only manufacturer to temporarily use EGR without aftertreatment for EPA —was able to do so only by certifying engines to 0. However, the use of EGR was often minimized and in some cases, restricted to certain low load conditions with no EGR used at higher load operating conditions such as highway cruise.
Examples of the later approach are the Volvo D11 and D13 engines launched in that utilized uncooled EGR to control NOx and increase the exhaust temperature for the SCR catalyst at low engine loads.
Since the release of the initial Euro VI product lines, systems with over The advantages of eliminating EGR include weight, cost and complexity reduction. On the negative side, SCR-only engines have higher urea consumption and require a larger urea tank. The on-board diagnostic OBD detection threshold requirements could also be a significant challenge in some markets if very high SCR conversion efficiencies are required to meet regulatory limits—a very small decrease in SCR conversion efficiency would need to be detected.
Nonroad Engines. EGR technology was also adopted by nonroad engines. These engines used high pressure loop cooled EGR and a variable geometry turbocharger. This could be caused when the EGR is either constantly closed or open. However, it is worth noting that usually the EGR valve starts to degrade before it fails completely and the engine management system may not pick up on it until it actually fails. Therefore it is worthwhile looking out for the other signs and symptoms mentioned.
As aforementioned if the valve is stuck open the temperature is lowered which prevents all the fuel from burning. This means an increased flow of unburned hydrocarbon gases coming out of the tailpipe. While if your valve is always closed the high temperatures in the combustion chamber allows excessive formation of NOx gases. Knocking noises from the engine can be caused if the EGR is constantly closed. This is because at low rpm the fuel ignites early when it meets the high temperature. Detonations are also common as a second ignition can occur after the normal ignition.
Some of the same engine performance problems which are indicative of an EGR valve failure can also indicate problems in other parts of the system. This can include the likes of faulty spark plugs, spark plug wires, fuel filters, fuel pump regulator or engine sensors. Increased hydrocarbon emissions can be a result of a leaking fuel injector, bad injection timing, bad cylinder compression or a bad oxygen sensor.
An increase in NOx could be caused by a vacuum leak, a clogged fuel injector, low fuel pressure or a leaking head gasket. Rough idle can also be a result of a faulty ignition coil, a vacuum leak or a problem with the ignition system. If your car is displaying any of the EGR valve symptoms mentioned and you suspect that you have a faulty EGR valve then it is advisable to get your vehicle checked out by a qualified mechanic.
EGR faults can be easily diagnosed using the correct diagnostic equipment. At Stoneacre we have all the latest diagnostic tools and equipment, as well as a team of highly trained technicians, making us well-placed to diagnose and treat any EGR valve problems.
Some manufacturers may recommend changing an EGR valve at pre-determined intervals. This information, if provided by the manufacturers will be included in your cars manual, and should be adhered to in order to keep your car running at its best! Advice Centre. Lisa Simm. Share On Share. Book your Service Quickly arrange for your existing car to be seen by our manufacturer-trained technicians.
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