EGR Valve (Exhaust Gas Recirculation)
The main function of the EGR valve is to control the emissions in exhaust gases in both petrol and diesel engines it plays a major role in maintaining the health of your vehicle's engine and exhaust system.
Nearly 80 percent of the air we breathe is nitrogen. However, when it is exposed to the extremely high temperatures in the combustion chamber, plus 1370°C, the normally inert gas becomes reactive, creating harmful oxides of nitrogen or NOx, which are then passed through the exhaust system into the atmosphere.
To help minimize this, the EGR valve allows a precise quantity of exhaust gas to re-enter the intake system, effectively changing the chemical makeup of the air entering the engine. With less oxygen, the now diluted mixture burns slower, lowering temperatures in the combustion chamber by almost 150°C, and reducing NOx production for a cleaner, more efficient exhaust.
The EGR valve has two primary settings: open and closed, although the position can vary anywhere in between. The EGR valve is closed when the engine is starting up. During idle and at low speeds, only a small amount of power is required, and therefore only a small amount of oxygen, so the valve gradually opens – it can be up to 90% open at idle. However as more torque and power is required, for example during full acceleration, the EGR valve closes to ensure as much oxygen enters the cylinder.
As well are reducing NOx, the EGR valve can be used in downsized GDi engines to reduce pumping losses and improve both combustion efficiency and knock tolerance. In diesel, it can also help to reduce diesel knock at idle.
EGR Cooler (Exhaust Gas Recirculation Cooler)
An EGR cooler is a heat exchanger which exchanges heat from the exhaust air to the engine coolant. Its purpose is to cool down the exhaust gas before they are returned into the engine to reduce the NOx values. (Meets the new EURO 6 standards).
With growing pressures to reduce the emissions the EGR valve will play an increasingly important role in helping to deal with that.
When the EGR cooler has any issues, it can cause problems with the functionality of the EGR system.
This can lead to performance issues and even problems with passing emissions standards for states where they are required. Usually, a bad or failing EGR cooler will produce a few symptoms that can alert the driver of a potential problem that should be serviced.
1. Engine overheating.
One of the first symptoms of a potential problem with the EGR cooler is engine overheating. If the EGR cooler has any issues that restrict the flow of exhaust gases through the cooler it can cause the engine to overheat. Over time, carbon can build up on the inside of the EGR cooler and restrict flow through the cooler. This can cause the unit to overheat, at which point it will not be able to cool the exhaust gases, and the engine will overheat as a result. Engine overheating can lead to knock or ping from the engine, and even serious damage, if the issue is left unattended.
2. Exhaust leak.
Another issue of problem with the EGR cooler is the exhaust leaks. If the EGR cooler gaskets fail, or the cooler gets damaged for any reason, it can cause an exhaust leak. An exhaust leak may be heard as a hissing or tapping sound coming from the front of the vehicle. This will reduce the efficiency of the EGR system, and affect the engine's performance.
3. Check Engine Light comes on.
Another symptom of a bad or failing EGR cooler is a Check Engine Light. If the computer detects a problem with the EGR system, such as insufficient flow or exhaust, it will set off the Check Engine Light to alert the driver of the issue. A Check Engine Light can also be set off by a wide variety of other issues, so having the computer scanned for trouble codes is highly recommended. EGR coolers are not found on all vehicles, but for the vehicles that are equipped with them, they are critical to the performance and drivability of the vehicle. Any problems with the EGR cooler can also lead to increased emissions, which will be a problem for states that require emissions testing for all of their vehicles.
A glowplug is a heating device used to help start diesel engines. In cold weather, diesel engines can be difficult to start because the mass of the cylinder block and cylinder head absorb the heat of compression, preventing the car from starting.
A glowplug is a pencil-shaped piece of metal with a heating element at the tip. This heating element, when electrified, heats due to electrical resistance and begins to emit light in the visible spectrum, hence the term glowplug. The visual effect is similar to the heating element in a toaster. The fuel injector spray pattern then impinges directly upon the hot tip of the glow plug during the injection of fuel at the top dead center. This ignites the fuel even when the engine is insufficiently hot for normal operation, which reduces the cranking time required to start the engine.
As the main source of power in any petrol engine, a spark plug performs an essential function: It is responsible for igniting the air-fuel mixture in the combustion chamber of petrol engines. This combustion process creates power, ultimately setting the vehicle in motion.
To make sure the combustion process runs smoothly, the spark delivered by the spark plug must ignite just before the piston reaches its highest point and the compression is at its greatest. The quality of this ignition influences several factors which are of great importance for both the driving operation and the environment, including smooth running, performance and efficiency of the engine as well as harmful emissions.