Sep 28, 2024
"In all internal combustion engines, undesirable nitrogen oxides (NOₓ) are formed when combustion takes place at high temperatures with excess air. These gases can be largely avoided, however, through the use of exhaust gas recirculation (EGR), EGR returns a high proportion of the exhaust gas to the combustion chambers. This reduces the amount of fresh, oxygen-rich air in the chambers. The exhaust gas also inhibits the chemical reactions taking place in the combustion chamber. Both of these effects cause combustion temperatures to fall, thereby significantly reducing the amount of NOₓ produced. To increase efficiency, water-cooled EGR systems are used on all engines today. On its way back to the engine, the exhaust gas flows through a water cooler with a map-controlled cooling capacity. This additional cooling of the exhaust gas allows a greater amount of exhaust gas to be recirculated, while also reducing the initial temperature in the combustion chamber. manufactures have significantly increased efficiency in this area of technology, for example, the separate low-temperature cooler has been eliminated, along with its pump drive. Modern engine have a dedicated high- and low-temperature circuit that does an excellent job supplying the EGR cooler. The efficiency of the entire cooling system has increased significantly.
Despite the emissions benefits, EGR systems can encounter issues. Here are some common faults:
1. **EGR Valve Malfunction**: Sticky or clogged valves can restrict exhaust gas flow, leading to performance issues or increased emissions. The build up of carbon and oil which is in the exhaust gasses clog up the valve which stops it from working correctly. Sometimes the valve can be cleaned but also they can seize solid and replacement is needed. Some valves are electronically operated or vacuum operated. A seized valve can damage the vacuum diaphragm or electric solenoid or motor.
2. **EGR Cooler Failures**: Leaks or blockages in the cooler can cause overheating and reduced efficiency. It can be quite common to have a coolant leak from the EGR cooler.
3. **Sensor Failures**: Faulty sensors can misinform the ECU, disrupting the EGR process and potentially causing engine knock or poor fuel economy, or increased smoke.
4. **Carbon Build-Up**: Over time, carbon deposits can accumulate on the EGR valve and cooler, reducing their effectiveness."
Hi guys, welcome back to Garry's Tech. In this video I'll take a look at the exhaust gas
recirculation system or EGR. I'll explain the design principles, how it works and common
faults. Exhaust gas recirculation or EGR is a technique used in internal combustion engines
to reduce nitrogen oxide emissions. Harmful NOx emissions occur when there are high temperatures
By recirculating a proportion of the exhaust gases back into the engine's intake manifold,
EGR lowers the combustion temperature and excess oxygen, thus minimizing the formation of NOx.
EGR systems are used in both petrol and diesel engines and on light passenger cars and heavy
duty vehicles and even in industrial engines. The EGR system comprises of valves and pipes
which directs a proportion of the exhaust gases back into the intake manifold. Usually this
consists of a metal pipe connected to the exhaust manifold so a proportion of the exhaust gases can
be directed back into the intake system. These gases pass through an EGR valve and then typically
an EGR cooler. On modern engines the recirculated exhaust gases are cooled before entering the
intake manifold to prevent knocking and ensure a smooth engine operation. There is a valve within
the cooler to bypass this when the engine is cold so the warmer exhaust gases help warm the engine
to operating temperature more quickly. The cooled exhaust gases are then introduced back into the
intake manifold mixing with the fresh air fuel mixture. The presence of the recirculated exhaust
gases lowers the combustion temperature reducing NOx emissions. The engine control unit ECU monitors
exhaust gas emissions and temperature and adjusts the flow of exhaust gases based on engine
temperature load and speed. Despite the emission benefits EGR systems can encounter issues. Here
are some common faults. EGR valve malfunction so a sticky or clogged valve can restrict exhaust gas
flow leading to performance issues or increased emissions. The buildup of carbon and oil which is
in the exhaust gases clog up the valve which stop it from working correctly. Sometimes the valves can
be cleaned but also they can seize solid and replacement is needed. Some valves are electronically
operated or vacuum operated. A seized valve can damage the vacuum diaphragm or electric solenoid
or motor. Leaks or blockages in the cooler can cause overheating or reduced efficiency
and can be quite common to have a coolant leak from the EGR cooler. Faulty sensors can misinform
the ECU disrupting the EGR process and potentially cause engine knock, poor fuel economy or increased
smoke. But over time the biggest fault tends to be carbon deposit buildup and this can accumulate
on the EGR valve and cooler reducing their effectiveness. So to sum it up exhaust gas
recirculation is a critical technology for reducing NOx emissions in internal combustion engines.
By understanding its design principle operations and common faults I'm sure we can appreciate the
complexity and importance of the EGR system in modern engines. As always thank you for watching
and if you've enjoyed this video give it a thumbs up and hit the subscribe button. If you have any
automotive questions or related comments to this video put it in the comments section below
and I'll get back to you soon. Thanks, take care.
