Engine knocking - what is it? Causes and troubleshooting tips

During the operation of the vehicle, drivers encounter various malfunctions. If you hear a loud thump from the engine with strong vibrations, it may be detonation of the air-fuel mixture. The cause of the malfunction must be sought immediately, since continued use of the car can lead to very disastrous consequences in the form of pistons and cylinder walls destroyed by the explosion, damaged connecting rods and the crankshaft. Why does detonation occur, how to eliminate it and avoid it in the future?

Why does engine knock occur?

We have already described on our portal vodi.su the principle of operation of an internal combustion engine. Fuel, mixed in the intake manifold with air, is injected through nozzles into the combustion chambers of a four-stroke engine. Due to the movement of the pistons in the cylinders, high pressure is created, at which point a spark from the spark plug arrives and the fuel-air mixture ignites and pushes the piston down. That is, if the engine is operating normally, the gas distribution mechanism is correctly configured, and the fuel assembly combustion cycle occurs without interruption, controlled combustion of fuel occurs in it, the energy of which causes the crank mechanism to rotate.

However, under certain conditions, which we will discuss below, detonations occur prematurely. Detonation, in simple terms, is an explosion. The blast wave hits the walls of the cylinders, causing vibrations to be transmitted to the entire engine as a whole. Most often, this phenomenon is observed either at idle, or when pressure on the accelerator increases, as a result of which the throttle valve opens wider and an increased amount of fuel is supplied through it.

Detonation effects:

• a sharp increase in temperature and pressure;
• a shock wave is created, the speed of which is up to 2000 meters per second;
• destruction of engine components.

Note that due to being in a limited space, the duration of the existence of a shock wave is less than a thousandth of a second. But all its energy is absorbed by the engine, which leads to a faster development of its resource.

The main causes of detonation in the engine are the following:

1. Using fuel with a low octane rating - if according to the instructions you need to fill in AI-98, refuse to fill A-92 or 95, as they are designed for a lower pressure level, respectively, they will detonate prematurely;
2. Early ignition, changing the ignition timing - there is a prejudice that the blast wave during early ignition will give dynamics, which to some extent is true, but the consequences of such an "improvement in dynamic performance" are not the most pleasant;
3. Pre-ignition ignition - due to the accumulation of soot and deposits on the walls of the cylinders, heat removal by the cooling system worsens, the cylinders and pistons heat up so much that the fuel assembly spontaneously detonates upon contact with them;
4. Depleted or enriched fuel assemblies - due to a decrease or increase in the proportions of air and gasoline in the fuel assemblies, its characteristics change, we also considered this issue earlier in more detail on vodi.su;
5. Incorrectly selected or exhausted spark plugs.

Most often, drivers of cars with high mileage encounter knocking and knocking in the engine. So, due to deposits on the walls of the cylinders, the volume of the combustion chamber changes, respectively, the compression ratio increases, which creates ideal conditions for premature ignition of fuel assemblies. As a result of detonations, the bottom of the pistons burns out, which leads to a drop in compression, the engine begins to consume more oil and fuel. Further operation becomes simply impossible.

Methods for eliminating detonation in the engine

Knowing the cause of the malfunction, it will be much easier to eliminate it. But there are reasons beyond the control of car owners. For example, if your car was working fine, and after the next refueling at the gas station, a metallic knock of fingers began, the problem should be looked for in the fuel. If desired, the owners of gas stations through the courts can be forced to fully compensate for the damage.

If the machine is operated for a long time without significant loads, this leads to the accumulation of soot. To avoid this, at least once a week you should squeeze the maximum out of your car - accelerate, increasing the load on the engine. In this mode, more oil enters the walls and all the slag is cleaned, while blue or even black smoke comes out of the pipe, which is quite normal.

Be sure to check the settings of the ignition system, choose the right candles. In no case should you save on candles. Fill with quality oil and fuel from trusted suppliers. If these methods did not help, you need to go to the service station and undergo a complete diagnosis of the power unit.

Why Engine Detonates

Causes of engine detonation - Dmitry Yakovlev

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