Take the working principle of four-stroke engine and two-stroke engine as an example:
The four-stroke engine has a wide range of applications. The four-stroke engine means that the cylinder ignites once every four times the piston reciprocates. The specific working principle is as follows:
1. Intake: At this time, the intake valve opens, the piston descends, and the mixture of gasoline and air is sucked into the cylinder.
2. Compression: At this time, the intake valve and exhaust valve are closed at the same time, the piston moves up, and the mixture is compressed.
3. Combustion: When the mixer is compressed to a minimum, the spark plug ignites the mixed gas, and the pressure generated by the combustion pushes the piston down and drives the crankshaft to rotate.
4. Exhaust: When the piston descends to the lowest point, the exhaust valve opens, exhaust gas is discharged, and the piston continues to move upward to discharge the excess exhaust gas.
The working principle of a two-stroke engine, as the name implies, a two-stroke engine is that the piston moves up and down for two strokes, and the spark plug ignites once. The intake process of a two-stroke engine is completely different from that of a four-stroke engine. A two-stroke engine undergoes two compressions. On a two-stroke engine, the mixture first flows into the crankcase and then into the cylinder. To be precise, it should flow into the combustion chamber. , And the mixed gas of the four-stroke engine flows directly into the cylinder. The crankcase of the four-stroke engine is used to store the oil. The two-stroke engine cannot store the oil because the crankcase is used to store the mixed gas, so the oil for the two-stroke engine cannot Burning oil for recycling.
The working process of the two-stroke engine is as follows:
1. The piston moves upward and the mixed air flows into the crankcase.
2. The piston moves down to transfer the mixed air pressure to the combustion chamber to complete the first compression.
3. After the mixed gas reaches the cylinder, the piston moves upward to close the intake and exhaust ports. When the piston compresses the gas to the minimum volume (this is the second compression), the spark plug ignites.
4. The pressure of combustion pushes the piston down. When the piston descends to a certain position, the exhaust port opens first, the exhaust gas is discharged and then the intake port opens. The new mixed gas enters the cylinder to squeeze out the remaining exhaust gas.
Because the two-stroke engine burns once more than the four-stroke engine at the same speed, the power is large, and the two-stroke engine is much lighter than the four-stroke engine of the same displacement, so the two-stroke car has an overwhelming advantage in racing. However, since the intake and exhaust of the two-stroke engine are carried out at the same time, when the engine speed is low, because the exhaust port is opened for too long, a part of the fresh mixture will be discharged from the exhaust port together with the exhaust gas. The power is not high at the bottom speed. The new two-stroke engine has added some parts to improve this problem, such as YAMAHA's YPVS, HONDA's ATAC SUZUKID's SAEC. Due to the carbon deposits produced by burning engine oil and the intake and exhaust holes on the cylinder wall, the wear and tear of the two-stroke engine is much faster than that of the four-stroke engine.