The difference between the petrol engine and the diesel engine, the principle, and the method of igniting the mixture are different. The diesel engine is compression ignition and the petrol engine is ignited. Petrol engines generally inject gasoline into the intake pipe and mix it with air to become a combustible mixture and then enter the cylinder, and the spark plug ignites and burns to work. It is often referred to as a sparking engine. The diesel engine generally injects diesel fuel directly into the engine cylinder through the fuel injection pump and the fuel injection nozzle, and uniformly mixes the compressed air in the cylinder, and spontaneously ignites under high temperature and high pressure to push the piston to work. This type of engine is often referred to as a compression ignition engine.
Petrol engine cars have high speed (the speed of petrol engines for cars can be as high as 5000-6000 rpm, and the petrol engines for trucks reach 4000 rpm). The quality is light, the noise is small during operation, the starting is easy, and the manufacturing and maintenance costs are low. Therefore, it is widely used in cars and small and medium-sized trucks and military off-road vehicles. The downside is that fuel consumption is high and the fuel economy is poor.
Due to the high compression ratio, the diesel engine has an average fuel consumption of about 30% lower than that of the gasoline engine, so the fuel economy is better. For example, the recently-launched TDI 1.7-liter diesel sedan produced by FAW-Volkswagen can save 2 liters of oil per 100 kilometers compared to a 1.6-liter gasoline car. Most trucks generally use diesel engines. The weakness of the diesel engine is that the rotation speed is lower than that of the petrol engine (the general maximum speed is about 2500-3000 rev/min), the quality is high, and the manufacturing and maintenance costs are high (because the injection pump and the injector have high processing precision).
However, these weaknesses of diesel engines are gradually being overcome, and its application range is expanding to medium and light trucks. Foreign diesel cars have also developed rapidly, with a maximum speed of 5,000 rpm. Typically, diesel engines are 30% more thermally efficient than petrol engines.
Therefore, from the perspective of energy conservation and fuel cost reduction, the promotion and use of diesel engine cars are of great significance. Compared with petrol engines, diesel engines have the characteristics of high power, long life, and good power performance. Its greenhouse emissions are 45% lower than gasoline, carbon monoxide and hydrocarbon emissions are also low, and NOx emissions are slightly larger than petrol engines during the life of the vehicle. The downside of diesel engines is the high emissions of harmful particulate matter.