Ignition timing: features, rules and recommendations

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Ignition advance is a very important parameter on which the stability and correct operation of injection and carburetor engines operating on gasoline or gas directly depend. Let's look at what the ignition timing is, what it affects, how to determine and set it up, including on gas equipment.

What is POP

This is the point at which the air/fuel mixture inside the combustion chambers ignites as the piston approaches its top dead center.

The ignition timing must be set correctly. After all, it directly affects the operation of the motor. The thing is that the efficiency and efficiency of the motor directly depends on this angle. Depending on whether the ignition is early or late, the pressure of the gases inside the system is different.

Gases press on the piston. And the force of their pressure should reach its maximum when the elementwill start moving down after passing top dead center.

If the ignition is early, the air-fuel mixture will ignite when the piston is at the beginning or middle of its journey to TDC. As a result, the efficiency of the engine is significantly reduced. The gas pressure will push the piston down. The latter is trying to move to TDC.

If the ignition is later, then the spark is supplied at the moment when the piston moves down. In this case, efficiency is also lost, the motor power is reduced.

Combustion Doctrine

Ignition and burning it is more than just a chemical process. This is a whole section of theory. For example, if you delve a little into this area of science, it becomes known that from a small spark discharge on a candle, a flame front begins and spreads to the combustion chambers. It is known that the duration of the spark is no more than one meter per second. During this time, temperatures can reach up to ten thousand degrees. The volume of the mixture that ignites is destroyed in an instant.

It has been proven that the burning rate is actually slow. However, as the flame increases, the burning rate also increases by 70-80 times. Residues of the mixture, which are not completely removed due to the fact that they are located near the rather cold walls of the cylinder, burn more slowly. In this case, the angle of rotation of the crankshaft is 30 degrees.

With different positions of the ignition timing, combustion is significantly different. With the correct UOZ, the optimal pressure is supplied to where the piston is just passing TDC. itabout 10-12 degrees.

If the UOZ is knocked down, set to a later side, then the most optimal gas pressure is in the 45-degree zone - the piston is in an even lower position here. The gases press on the descending element. The efficiency of such an engine is reduced to zero.

If the ignition timing is late, the fuel may burn out after the exhaust valves are opened. The gases formed after the explosion have a very high temperature. They can easily provoke the ignition of a new portion of the mixture that enters the cylinders. At this moment, you can hear characteristic pops in the muffler.

Early ignition is not all good. In this case, the maximum pressure is already at the piston position at TDC or earlier. The products of combustion put pressure on the piston, which has not yet reached its highest point. As a result, power drops, detonation and other unpleasant moments appear.

Signs of a downed UOZ

The process of ignition of a mixture of fuel and air in the engine chambers (delayed or advanced) can lead to various malfunctions in the engine. To determine that the ignition timing is incorrect, the following signs will help:

• Difficulty starting engine.
• The car's appetites are noticeably increasing.
• Motor loses acceleration, engine power decreases.
• You may observe erratic idling.
• When you press the gasthe responsiveness of the unit is lost, overheating is observed, as well as detonation.
• You can also hear pops - in the carburetor or intake manifold or in the exhaust system.

Consequences of an incorrect POD

Both delayed and early ignition does not have the best effect on the resource of the power unit and its operation. It should be added that not only characteristics such as engine power or fuel consumption depend on the correct ignition timing of the engine. If the spark appears earlier than necessary, then the pressure of the gases that expand will interfere with the piston. Ignition after the element has started to move down will cause the energy to catch up with the piston and then enter the exhaust tract, rather than doing useful work.

In early ignition, the rising element must make considerable efforts to compress the gases that form from the early combustion of the mixture. In this case, the load on the cylinder-piston group and the crankshaft increases significantly.

Earlier ignition is determined by the following characteristic features - you can hear metallic ringing sounds during engine operation. The idle speed will also fluctuate. After pressing the gas, there will be a dip.

Late ignition also hurts the engine. The mixture burns under reduced pressure and increased volume in the cylinder. The burning time is violated, due to which the mixture burns out during the piston stroke. The engine is losing power. To accelerate, you need to press hard on the gas pedal. There is also a high fuel consumption. Insidemotor, coke, soot and various deposits are formed. Improper combustion leads to overheating.

Therefore, it is necessary to know how to set the ignition timing. This will improve engine performance, reduce fuel consumption and protect it from premature wear.

How to determine the POP

In order to define PPH, you should know a few important concepts:

• The angle is dependent on the speed of the crankshaft. The higher the engine speed, the earlier the PTO should be. It is also affected by the temperature of the engine and the combustible mixture. The lower the temperature of the motor, the slower the combustion will be. Therefore, in this case, the adjustment of the ignition timing is done in an earlier direction. On a hot engine, the opposite is true.
• Also, the load on the engine significantly affects the UOZ. The higher the RPM, the earlier angle is needed. This is done to prevent detonation, since at high loads, increased portions of the fuel mixture are supplied to the cylinders.

Why the OOP is going astray

Such situations are quite common. The parameters recommended by the manufacturer are off. After all, they are simply not designed for the specific conditions in which the car is operated. Here you need to know what the ignition timing should be for specific conditions - it is set manually.

But first you need to make sure whether you really need to intervene and change something. You can check the UOP by ear, focusing on your feelings. To do this, the car is acceleratedin a straight section up to 40 km / h and then sharply put pressure on the gas. Fourth gear must be engaged.

If detonation sounds are heard for a short time, but at the same time acceleration is quite confident, you can do absolutely nothing with the angle. Detonation should completely disappear in a couple of seconds, after the speedometer marks 60 km / h.

When the sounds do not stop and the car does not accelerate, this indicates that the ignition is knocked down. If the detonation does not disappear, then the UOZ is too early. In the second case, the ignition is delayed.

PTO setting

Let's learn how to set the ignition timing. To do this, you need a special device - a stroboscope for ignition. But if this device is not there, then it's okay. If the ignition is contact, then it is adjusted using an ordinary light bulb. If the system is contactless, then the adjustment is carried out by ear, and the correctness of the adjustments is checked by the above method on the road.

Contactless ignition

If there is a stroboscope, then it is connected according to the instructions to the device. Usually, most devices have three power wires that connect to the battery, and a signal one. The latter is connected to the spark plug on the first cylinder.

Set the ignition timing at idle, but on a well-warmed engine. This is done in the following way. A stroboscope is connected, and its lamp is directed to the flywheel - there are marks on it. It is better to find these marks in advance by turning the engine by the wheel with the fifth turned on.transmission. The desired mark is marked with a stationery corrector. The strobe will flash and the marker will appear stationary when shine is shining on it. By rotating the distributor, they make sure that the mark is in one place opposite the ebb on the flywheel housing. The ignition timing of the VAZ according to the passport is plus or minus one degree.

It is not uncommon for an engine to run stably and well after this adjustment. Fuel consumption drops, dynamics improves. But this is not always the case. In this case, it is necessary to adjust the ignition by detonation.

UOZ and injector

Everything is much simpler here. In this case, turn on the ignition and watch the dashboard. If the lamp is on, indicating malfunctions, then they take a laptop and carry out diagnostics. Next, inspect the throttle valve. Then check the voltage in the on-board network. The damper is opened one percent. Next, sharply press the gas pedal. As a result, the damper will open 90 percent. Throttle position sensor voltage should drop to 0.45V.

With an injection engine, the factory start angle setting will suffice. Here, the electronics decides what ignition timing will be during the operation of the engine in different modes. The starting angle is set similarly to contactless ignition. Adjustment is made by turning the nuts securing the flywheel distributor.

VoZ variators

With the advent of HBO, car owners are faced with the fact that even the earliest ignition that can be seton the distributor, not enough earlier for gas fuel. The fact is that, unlike gasoline, propane-butane burns longer, which means problems appear. Since the distributor does not allow very early ignition so that the mixture can burn in the combustion chamber, ignition timing variators have appeared.

This is an electronic device whose task is to shift the SV curve. This shift is carried out according to certain algorithms for specific values. If you do not use the variator, then the ignition will not be early enough. The combustible mixture will burn out in the exhaust manifold, and this is fraught with various troubles.

In conclusion

This is how you can set and check the ignition timing. When there are failures during movement, when the engine is troiting or unstable operation is simply observed, many begin to check anything, but not the UOZ. But in vain. This parameter directly affects the stability of the internal combustion engine. A car with a properly set ignition angle will delight with its reliable and trouble-free operation.