What is the normal ignition advance angle of a normal automobile engine?

In theory, the minimum ignition advance angle is 0 degrees, but in order to prevent the mixture from being ignited during the power stroke (which will cause power loss), it is often set to more than 5 degrees, which is also the angle required for starting the speed. The maximum ignition advance angle should not be too large, generally not more than 60 degrees, otherwise the problems of vibration and temperature rise will be highlighted and the efficiency will be reduced. In fact, the speed of crankshaft structure is limited.

There is a time process from ignition, combustion to burnout, and the best ignition advance angle is to maximize the gas expansion trend in the downward stroke of piston under various working conditions. This has the highest efficiency, the least vibration and the lowest temperature rise. In order to make the highest combustion pressure in the engine cylinder appear at 18 to 15 degrees after compression, and to maximize the combustion power of the mixture, it is necessary to ignite at an appropriate time before compression.

Adjust the foundation

The best ignition advance angle is mainly related to engine speed, load and fuel type (such as gasoline brand).

1, when the engine throttle is fixed, it is necessary to increase the ignition advance angle with the increase of the rotational speed, but when the rotational speed reaches a certain value, the increase speed of the optimal ignition advance angle slows down instead of keeping the same increase speed.

2. When the engine speed is constant, with the increase of load, the throttle opening increases, so it is necessary to reduce the ignition advance angle appropriately. On the contrary, when the engine load decreases, the ignition advance angle should be increased appropriately.

3. Fuel type: different gasoline brands have different octane numbers, and the octane number indicates the antiknock performance of gasoline. When using gasoline with higher octane number, that is, better antiknock performance, the ignition advance angle should be increased.

Other factors: some other factors in the engine will affect the combustion speed of the mixture, and these factors will have a certain impact on the ignition advance angle, such as the shape of the combustion chamber, the temperature in the combustion chamber, the air-fuel ratio, the atmospheric pressure, the cooling water temperature, etc.