Engine detonation. Causes and types

Detonation is one of the obvious signs of engine malfunction. All further efforts of the car owner should be aimed at its elimination. There are various reasons, when the detonation of the engine appears with the usual style of driving. It occurs when a mixture of fuel and air ignites in the combustion chamber unevenly. There are two of its types - unacceptable and permissible.

The most common causes of engine detonation are the violation of the car's operation by the driver: driving on a gear that is too high for these revolutions. Usually this happens when the driver does not think about switching to a lower one at the exit due to a turn at a low speed, when climbing into a hill at an elevated or accidental shift of the gear to the wrong position. On cars with a forced engine, engine detonation may appear after fueling with a low octane rating.

Some models of cars are sensitive to driving conditions. For example, if the car is operated for a long time in idling mode in traffic conditions, a high inlet temperature, heat from under the hood and a boost system can lead to detonation. This is especially noticeable if the air temperature sensor is located close to the beginning of the intake, and not in the intake manifold. The reasons listed above are typical.

How can you determine the detonation in such conditions?

Detonation in the engine, as a rule, is determined by the metallic sound, as if something is rapidly striking each other. It can also resemble the strumming of balls that roll in a poke. Any amount of detonation will be bad for the motor of the machine. In addition to auditory perception, detonation of the engine can be detected by means of special electronic devices. The most popular way is to use a sensor that is mounted on the engine block. He analyzes the transmitted sounds and determines the frequency of this phenomenon among many other noises.

The permissible detonation of the motor develops at low speeds, is poorly audible and lasts for a short period of time. It can happen in those cars, in the production of which the plant sought to achieve too high a torque with a small engine volume.

What are the causes of unacceptable detonation? Typically, this type is characteristic of modified machines. Here are some of the reasons:

- one way to increase the torque and sensitivity to the opening of the throttle is the process of installing the ignition advance;

- if the ignition occurs early in the cycle of piston movement, then the resulting pressure wave can ignite a mixture of fuel and air in certain parts of the combustion chamber - this is the most common cause;

- depletion of the "fuel-air ratio" in order to achieve a higher engine power (the manufacturer provides for the use of a motor on a rich mixture for one reason - control of the combustion temperature);

- heat of air at the inlet - in those cases where the air filter is installed under the hood;

- an unsuccessful design of the combustion chamber.

How does the engine detonate?

- First, make sure that there is no self-igniting mixture. To avoid errors, turn off the engine. If it stopped immediately, it means that the most likely cause of knocking is detonation combustion.

- The installation of a late ignition will help to eliminate the detonation that was caused by the use of inappropriate fuel, otherwise it is necessary to replace the fuel, which has anti-detonation requirements.

- Application of the appropriate type of gasoline.