Detonation combustion - what is it?

Is there something knocking and rattling under the hood of your car while accelerating? Don't take these cryptic sounds lightly. It could be a knocking sound, a serious anomaly leading to serious engine damage. But what does this actually mean? More importantly, how do you avoid it? Check!

What will you learn from this post?

• What is knock combustion?
• What could be the causes of detonation ignition?
• How to prevent knocking?

TL, д-

Knocking combustion is applied to piston engines, that is, to the engines of our cars. We talk about this when the fuel-air mixture does not completely burn out in the combustion chamber, but explodes too early or too late near the spark plugs. This causes a knock chain reaction, which is audible from outside the engine as a rattling sound. The reasons for this anomaly can be many: from broken spark plugs to too high an engine temperature. However, most often it is a low-octane fuel. In any case, knocking combustion will cause serious engine damage.

What is knock combustion?

Combustion process

Detonation combustion, otherwise known as detonation, this is a very dangerous anomaly of the combustion process for the engine... With proper combustion, the fuel / air mixture is ignited by a spark plug just before the end of the compression stroke. The flame spreads at a constant speed of about 30-60 m / s in the combustion chamber, generating a large amount of exhaust gases. Consequently, a significant increase in pressure causes a corresponding movement of the piston.

Meanwhile, when detonation occurs, the mixture ignites near the spark plug, which compresses the remaining charge in the combustion chamber. At the opposite end of the chamber, a sudden, more than 1000 m / s, combustion of the mixture occurs - occurs detonation chain reactionloading the piston, connecting rod and crankshaft both thermally and mechanically. This causes a characteristic metallic clang from under the hood as the engine load increases.

Consequences of detonation combustion

The first and most obvious consequence of detonation combustion is reduced engine performance. But in the end, the effect of detonation combustion can lead to much more serious malfunctions, such as burnout of pistons, valves, damage to the head and even destruction of components of the exhaust gas treatment system.

What could be the causes of detonation ignition?

The main cause of detonation ignition: substandard fuel... As practice shows, the higher the octane number of the fuel, the slower and smoother its combustion. The low octane number makes the combustion process short-lived and violent.

Another reason too high compression ratio in the cylinder... Engines with a high compression ratio must be fired with a higher octane rating so that the combustion is not too harsh and creates no additional pressure build-up.

Ignition too early or too late also leads to detonation ignition. A defective spark plug can spark before the cylinder is depressurized or when the piston is lowered and unburned fuel remains in the chamber. To prevent spontaneous combustion in such a situation, it is also worth adjusting the ignition timing, which should be located about 10 degrees behind the piston top dead center.

As a result, spontaneous combustion can also occur. engine overheating.

What should I take care of in the car to avoid impacts?

It is installed on the engine to diagnose combustion problems. knock sensors. The task of such a sensor is to detect engine oscillations of a certain frequency, which indicate violations in the combustion process. The signals sent by the sensor are picked up by the control unit and processed. The on-board computer determines which cylinder is detonating and corrects the ignition signal or stores the error information in its memory. Then the engine malfunction indicator appears on the dashboard. However, short circuits due to corrosion or damaged wires interfere with the operation of the sensor. It also happens that it is incorrectly installed when repairing the engine. A faulty knock sensor sends erroneous signals or does not register them at all. In this case, it's time to replace it with a new one.

Daily routines such as use of quality fuels and oils... Changing the engine oil regularly in accordance with the manufacturer's recommendations will help to avoid the formation of dangerous deposits on the walls of the engine and spark plugs. As mentioned, they don't work as expected. Spark plug can cause the mixture to ignite too early or too late. Therefore, it is worth checking their condition from time to time, and also in this case, follow the recommendations of the car manufacturer.

Finally, it is a must take care of the cooling system... Engine overheating, which can be one of the causes of knocking combustion, can occur due to too low coolant level due to a leaky system or a damaged thermostat. Cooling system malfunctions lead to a myriad of serious engine problems and are known to be better prevented than treated.

Engine knocking can cause serious engine damage. As with many other car problems, in order to avoid them, you must take care of all systems on a daily basis and have your car repaired regularly.

Remember that only a serviceable car will serve you faithfully, and driving on it will be a real pleasure. Look for the highest quality parts, fluids and cosmetics at avtotachki.com!

See also:

Low-quality fuel - how can it harm?

Noises from the engine compartment. What could they mean?

Typical malfunctions of gasoline engines. What most often fails in "gasoline cars"?

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