What is the ignition advance angle? What's the effect of ignition too late and too early?

The ignition system provides high-voltage spark to the spark plug to ignite the compressed mixture in the cylinder to do work. This time is the ignition timing. In order to maximize the ignition energy, the ignition timing is generally advanced by a certain amount, so it is ignited at the moment when the piston is about to reach the top dead center, not just when it reaches the top dead center. This advance is called the ignition advance angle.

Impact:

If the ignition is too late, it will be ignited when the piston reaches the top dead center, then the mixture will burn when the piston descends, that is, when the volume increases, thus reducing the in-cylinder pressure and engine power. At the same time, as the contact area between the hot gas and the cylinder wall increases, the heat loss will increase, leading to overheating of the engine and increased fuel consumption.

If the ignition is too early, the combustion will be completely carried out in the compression process, and the pressure in the cylinder will rise sharply, reaching the maximum pressure before the piston reaches the top dead center, which will give great resistance to the rising piston, not only reducing the engine power, increasing fuel consumption, but also causing deflagration.

Extended data

Influencing factors:

The optimal ignition angle is influenced by many factors. If the car is to work in an ideal state, the following factors must be considered:

(1), cylinder temperature and cylinder pressure

The higher the combustion speed, the smaller the ignition advance angle. The factors affecting cylinder temperature and cylinder pressure are:

Engine compression ratio, air temperature, cylinder temperature and load. Because of this, in the season of temperature change, everyone's car has different performances.

(2) Octane number of gasoline

That is, the higher the gasoline brand, the stronger the antiknock ability and the larger the corresponding allowable ignition advance angle.

(3), gas mixing ratio

Too rich and too lean combustion speed is slow, so it is necessary to increase the ignition advance angle. This mainly depends on the throttle opening and altitude.

Baidu encyclopedia-ignition timing

Baidu encyclopedia-ignition advance angle