How to correctly set the ignition timing

Before proceeding to an operation such as setting the ignition, you need to read some definitions. For example, the ignition timing. It is known that at the time when the piston passes the compression stroke, the crankshaft makes half a turn, it turns 180 degrees. This applies not only to the compression stroke, but to all others, so the full cycle of the 4-stroke engine is two revolutions, or 720 degrees.

There is such a thing as the octane number of gasoline. We will not go into details about how it is measured, it is important that it is different. So, for gasoline with a different octane number, the rate of ignition is very different. If the ignition timing is set exactly when the piston is at the top dead center, ignition will occur even when it goes down under the action of the flywheel inertia.

To prevent this from happening, and the explosion of the mixture occurred exactly at the top dead center, the ignition timing is set. For example, if the VAZ-2106 piston does not reach the VMT. 4-5 mm, then the crankshaft to the full 180 will not be missed 10 degrees. If the first value is reduced to 2-3 mm, then the second will be reduced to 5 degrees. These are the most common angles that are used when using AI-80 and AI-92, respectively.

Now about the ignition. Consider this procedure using the example of a contactless system to eliminate problems with the gap in the contacts. First, you need to determine the compression stroke in the first cylinder. This is done with the help of cotton wool, which plugs the spark plug in the head, after which the crankshaft turns slowly behind the ratchet. If in the cylinders a good compression, the fleece should fly out at the beginning of the tact.

As a rule, there are labels on the crankshaft pulley and on the front cover. This is the ignition advance angle. They correspond to the above angles, as well as the VMT. In turn, along the rotation. The last label usually sets the ignition for AI-95 or AI-98, so the use of this tag is quite rare.

After putting the crankshaft in the right position, the tags on the ignition distributor are combined , they differ in different brands and models, and the trampler is inserted into the landing socket, and then fixed.

But I must say, the initially exposed corner of the ignition advance may not be final.

A more thorough adjustment of the ignition is carried out after starting the engine, its warming up to normal operating temperature, and also after correct adjustment of the carburettor at idle. For this, the speed is 35-40 km / h in the third gear, after which the fourth gear is switched on. After this, there should be a short-term detonation, which disappears for five seconds. If it remains for a long time, then it is necessary to turn the distributor body in the direction of rotation of the roller, or vice versa, if there was no detonation at all.

In conclusion, it should be said that an incorrect lead angle, especially too early, leads to serious damage to the crankshaft-piston group, such as, for example, loosening the piston in the upper connecting rod head or the crankshaft neck at the bottom.