Want to find out What is the difference between a gasoline engine and a diesel engine? We need to first understand the difference between gasoline and diesel. The oil refining process mainly uses fractional distillation, which is to first heat the crude oil to obtain different substance vapors, and then cool the vapors. Thereby refining different products. Such as gasoline, diesel, kerosene, lubricating oil, asphalt, etc.

Gasoline has a small molecular weight, so its boiling point is only 20-220°C, but its ignition point is over 400°C. Diesel has a large molecular weight, longer carbon chain, and higher boiling point, but its ignition point is only 220°C. ℃.

This difference in fuel characteristics also leads to a big difference between gasoline engines and diesel engines.

1. Different ignition methods

Since gasoline has a high ignition point, it must pass through the spark plug to ignite after the engine piston is compressed.

Diesel engines do not require spark plugs. They rely on the temperature rise after gas compression to directly cause spontaneous combustion of diesel fuel.

This compression ignition effect also gives diesel engines many advantages. For example, it does not require an ignition system and has a lower failure rate. The compression ignition method allows the compression ratio to be very high. The compression ratio of an ordinary gasoline engine is 13:1, which is already very high. , but a diesel engine can easily do 17:1

By using a longer piston connecting rod, the piston stroke is increased, the engine torque is greatly improved, and the fuel economy of the diesel engine is even better with the same displacement.

2. Engine speed is different

Gasoline engines can pre-mix the gas, which means mixing gasoline and air before injecting it into the cylinder, or direct injection into the cylinder, using a high-pressure injector to atomize the gasoline and compress it while mixing in the cylinder.

When the engine piston is at top dead center, it is ignited by the spark plug. In short, the gasoline and air are mixed first and then burned.

However, diesel has high viscosity and cannot be effectively mixed with air, so the diesel machine first sucks in air, then compresses and heats the air, and then injects diesel when the piston is close to top dead center, using the high-temperature air to ignite the diesel.

The entire combustion process is also divided into a pre-combustion period, a fast combustion period, a slow combustion period and a post-combustion period. This method has an obvious disadvantage, which is that it requires a longer combustion time. The increase in the piston stroke mentioned earlier is also for this purpose.

Therefore, the speed of the diesel engine cannot be set too high. Too high a speed will not only prevent the diesel from being completely burned and emit black smoke like crazy, but also cause torque attenuation.

For example, the largest engine in the world is a diesel engine installed on a ship, with a rated speed of only 102r/min.

The speed of diesel versions of many cars is also much lower than that of gasoline versions.

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