Ignition timing is a very important parameter that directly determines the stability and correct operation of injection and carburetor engines operating on gasoline or gas. Let's look at what the ignition timing is, what it affects, how to determine and configure it, including on gas equipment.
What is PPM
This is the moment of ignition of the air-fuel mixture inside the combustion chambers at the moment when 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 earlier or later, the gas pressure inside the system is different.
Gases press on the piston. And the force of their pressure should reach its maximum when the element begins to move down after passing the top dead center.
If the ignition is early, then the fuel-air mixture will ignite when the piston is at the beginning or middle of its path to TDC. As a result, engine efficiency is significantly reduced. Gas pressure will direct the piston down. The latter at the same time tries to move to TDC.
If the ignition is later, then the spark is supplied at the moment when the piston will move down. In this case, efficiency is also lost, and motor power is reduced.
Combustion Doctrine
Its ignition and burning is more than just a chemical process. This is a whole section of the theory. For example, if you delve a little into this area of science, it will become known that a flame front starts from a small spark discharge on a candle and spreads into the combustion chambers. It is known that the duration of the spark is not 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 is proved that the burning rate is actually low. However, as the flame increases, the burning rate also increases by 70-80 times. The remains of the mixture, which are not completely removed due to the fact that they are located near sufficiently cold cylinder walls, burn more slowly. The angle of rotation of the crankshaft is 30 degrees.
At different positions of the ignition timing, combustion is significantly different. With the correct SPL, the optimum pressure is applied to the place where the piston has just passed TDC. This is approximately 10-12 degrees.
If the UOZ is shot down, set to a later side, then the most optimal gas pressure is in the zone of 45 degrees - the piston is in an even lower position. Gases press the element that is already dropping. The efficiency of such an engine is reduced to zero.
With a late ignition timing, the fuel may burn out after the exhaust valves are opened. The gases generated after the explosion have a very high temperature. They can easily provoke ignition of a new portion of the mixture, which enters the cylinders. At this point, you can hear the characteristic popping in the muffler.
Early ignition is not all good. In this case, the maximum pressure already falls on the position of the piston in TDC or earlier. The combustion products press on the piston, which has not yet reached the highest point. As a result, power drops, detonation and other unpleasant moments appear.
Signs of a downed SPD
The process of igniting a mixture of fuel and air in the engine chambers (being late or ahead of schedule) can lead to various malfunctions in the engine. To determine that the ignition timing has been set incorrectly, the following symptoms will help:
- There are difficulties starting the engine.
- Appetites of the car significantly increase.
- The motor loses throttle response, engine power decreases.
- You may observe erratic idling.
- When you press the gas, the responsiveness of the unit is lost, overheating is observed, as well as detonation.
- You can also hear popping - in the carburetor or intake manifold or in the exhaust system.
The consequences of improper POPs
Both delayed and early ignition, not in the best way affect the resource of the power unit and its operation. It must be added that not only such characteristics as engine power or fuel consumption depend on the correct ignition timing. If the spark appears earlier than necessary, then the pressure of the gases that expand will interfere with the piston. Ignition after the element begins to move down will cause the energy to catch up with the piston and then get into the exhaust tract, and not do useful work.
With early ignition, the rising element must exert considerable effort to compress the gases that are formed from the early combustion of the mixture. In this case, the load on the cylinder-piston group and the crankshaft increases significantly.
Previously, ignition is determined by the following characteristic signs - you can hear metallic ringing sounds during engine operation. Also idle will float. After clicking on the gas will fail.
Late ignition also harms 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 stroke of the piston. The engine is losing power. To accelerate, you must press hard on the gas pedal. High fuel consumption is also noted. Coke, carbon deposits and various deposits form inside the motor. Incorrect combustion leads to overheating.
Therefore, you need to know how to set the ignition timing. This will improve the engine, reduce fuel consumption and protect it from premature wear.
How to determine the SPD
In order to determine the SPD, you should know several important concepts:
- The angle is dependent on the speed of the crankshaft. The higher the engine speed, the earlier the UOZ 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. Therefore, in this case, the ignition timing is adjusted to an earlier side. On a hot motor, the opposite is true.
- Also, the load on the engine significantly affects the UOZ. The greater the revolutions, the earlier the angle is needed. This is done to prevent detonation, since at high loads increased portions of the fuel mixture are fed into the cylinders.
Why does SPM go astray
Similar situations are quite common. The parameters recommended by the manufacturer are lost. After all, they simply are not intended 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 SPD by ear, focusing on your feelings. To do this, the car is accelerated in a straight section to 40 km / h and then sharply pressed on the gas. Fourth gear must be engaged.
If detonation sounds are briefly heard, but at the same time the acceleration is quite certain, nothing can be done with an angle. The detonation should completely disappear in a couple of seconds, after the mark on the speedometer at 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 SPM is too early. In the second case, ignition later.
SPM setup
Let's find out how to set the ignition timing. To do this, you need a special device - a stroboscope for ignition. But if this device is not, then there is nothing to worry about. If the ignition is contact, then it is configured using an ordinary light bulb. If the system is non-contact, then tuning is done by ear, and the correctness of the adjustments is checked by the method described above on the road.
Contactless ignition
If there is a strobe, then it is connected according to the instructions to the device. Typically, most devices have three power wires that connect to the battery, and a signal one. The latter is connected to a candle on the first cylinder.
Set the ignition timing at idle, but on a well-warmed engine. This is done as follows. 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 behind the wheel with fifth gear engaged. The desired label is marked with a clerical corrector. The strobe will blink, and the mark will appear motionless if shone on it. By rotating the distributor, they ensure 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.
Often after such a setting, the engine runs stably and well. Fuel consumption is falling, improving dynamics. But this does not always happen. In this case, it is necessary to adjust the ignition for detonation.
SPD and injector
Everything is much simpler here. In this case, turn on the ignition and watch the dashboard. If the lamp is lit, indicating a malfunction, then take a laptop and carry out diagnostics. Next, inspect the throttle. Then check the voltage in the on-board network. The damper is opened by one percent. Then sharply press the gas pedal. As a result, the damper will open 90 percent. The voltage at the throttle position sensor should drop to 0.45 V. If this is not the case, adjust the UOZ.
With an injection engine, setting the factory starting angle will suffice. Here, electronics decides what the ignition timing will be during the operation of the engine in different modes. The starting angle is set similar to non-contact ignition. Adjustment is made by rotating the nuts securing the flywheel distributor.
CVT variators
With the advent of HBO, car owners are faced with the fact that even the earliest ignition that can be set on the distributor is not enough earlier for gas fuel. The fact is that, unlike gasoline, propane-butane burns longer, which means problems arise. Since the distributor does not allow to obtain very early ignition so that the mixture could burn in the combustion chamber, then ignition timing variators appeared.
This is an electronic device whose task is to shift the UOZ curve. This shift is carried out according to certain algorithms to specific values. If you do not use a variator, the ignition will not be early enough. The fuel mixture will burn out in the exhaust manifold, and this is fraught with various troubles.
Finally
In this way, you can adjust and check the ignition timing. When there are dips during movement, when the engine is troit, or unstable operation is just observed, many begin to check anything, but not UOZ. But in vain. This parameter directly affects the stability of the internal combustion engine. A car with a correctly set ignition angle will please with its reliable and trouble-free operation.