Power system (fuel system). The main differences between gasoline and diesel engines

4.11.2 Fuel for powering gasoline engines

It goes without saying that a gasoline engine requires gasoline to run.

Note
Gasoline is a light fuel oil and is a light liquid, which evaporates in air and is highly flammable.

Volatility, calorific value and antiknock quality are the main properties of gasoline. For the crowd, the defining characteristic is the latter.

Antiknock quality determines the possible value of the engine compression ratio.

Note
Knocking is the combustion of fuel at such a speed that it can be safely called an explosion (2000 m/s and more versus 20-40 m/s in case of normal combustion), which occurs at extremely high temperatures with a sharp increase in pressure in the cylinder. It occurs when using fuel with an inappropriate engine compression ratio and antiknock quality.

In case of detonation combustion of the mixture in the engine, sharp metal knocks and ringing are heard, explained by the impact of high-pressure sound waves on the walls of the combustion chambers, cylinders and piston tops and the occurrence of vibration in parts. At the same time, enhanced heat transfer and an increase in mechanical losses as a result of incomplete fuel combustion. The power and economy of the engine are sharply reduced.

Note
Long-term operation during detonation combustion can lead not only to increased wear of engine parts, but even to their breakdown or the creation of large defects in form of cracks and bending of parts with their subsequent destruction.

Therefore, if during the movement constant resonant metal blows are heard from the engine side, it is better to stop. Otherwise, there will be a possibility of major overhaul of the engine or its replacement.

Note
Knocking can be eliminated by reducing engine load (downshifting) and closing the throttle blade.

Gasoline octane number is an indicator characterizing the antiknock qualities of gasoline. The higher the octane number of gasoline, the less it detonates and the higher the compression ratio can be adopted for the engine.

Gasoline brands that are sold on the fuel market have their own designation. For example, A-95, where "A" tells us that gasoline is "automobile", and the number after the letter denotes the octane number.