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What is the role of the valve in the engine

Update:01 Dec 2021

The engine valve is located in the cylinder head. The m […]

The engine valve is located in the cylinder head. The main function of the engine valve is to let air in and out of the cylinder. Air is used to help ignite the fuel, which pushes the piston up and down. There are two types of engine valves: intake valve and exhaust valve. Of course, the intake valve lets air in, and the exhaust valve lets air out. The more air is sucked and discharged, the efficiency of the engine is higher, which generates power. This is why engine valves play a key role in engine performance. The piston moves up and down in the cylinder. At the top of the piston stroke is the valve. Depending on the manufacturer, the number of valves is also different.

Since the piston is at the bottom of the cylinder, the intake valve opens to allow air in, and then closes to make the cylinder airtight to establish compression. Once the piston has passed the compression and ignition strokes, the exhaust valve will open to exhaust. Then it closed. But you may ask how does the valve open and close? There is one shaft that can drive all valves, called a camshaft. For more information about the camshaft, be sure to check the camshaft connecting rod. The valve itself consists of a round head connected to a long stem. The valve stem runs in the valve tube to ensure that the valve can only move up and down, not left and right.

The valve consists of two parts, and then they are welded together. The head is usually made of stainless steel, and the valve stem is made of high carbon steel. Valves are mostly made of hardened steel or more exotic materials, such as titanium in high-performance engines. When the valve is closed, it touches the surface around the orifice. The surface on which the valve is located is called the valve seat. The valve seat must be smooth because it provides a sealing surface, and the maximum contact between the valve and the valve seat ensures that the cylinder head absorbs heat from the valve. For cast iron heads, the valve seat will be machined directly into the head, while for softer aluminum heads that are not resistant to exhaust gas corrosion, the valve seat will be made of stronger metal and pressed into the head.

The intake and exhaust valves can be very hot during operation. This heat must be dissipated mainly through the valve surface, valve seat and cylinder head, and be taken away by the flowing coolant. The heat also rises along the valve stem and enters the valve head through the valve conduit. Some well-performing valve stems are filled with sodium, which melts and shakes inside the valve stem to improve heat transfer. The exhaust valve has a longer service life than the intake valve and is exposed to higher temperatures due to hot exhaust gas flowing around and behind the exhaust valve. Their working life is in close contact with high temperature and corrosive exhaust gas, so they are made of particularly durable, heat-resistant, and corrosion-resistant materials.

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