Knocking is one of the clear signs of engine malfunction. All further efforts of the car owner should be directed to its elimination. There are various reasons when engine detonation occurs with a normal driving style. It occurs when the mixture of fuel and air ignites unevenly in the combustion chamber. There are two types of it - unacceptable and permissible.
The most common causes of engine detonation are impaired operation of the vehicle by the driver: driving in a gear that is too high for these revolutions. Usually this happens when the driver does not think about shifting to a lower one when leaving due to a turn at a low speed, when climbing uphill at an increased speed or when a gear is accidentally shifted to the wrong position. On cars with a forced engine, engine detonation may occur after refueling with a low octane rating.
Some car models are sensitive to driving conditions. For example, if a car is operated for a long time in idle running in traffic conditions, then a high level of temperature at the inlet, heat from under the hood and 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 detonation be determined under such conditions?
Detonation in an engine is usually determined by a metallic sound, as if something is quickly hitting one another. It may also resemble the strumming of balls that roll around in a bag. Any amount of detonation will be bad for the engine of the car. In addition to auditory perception, engine detonation can be detected using special electronic devices. The most popular way is to use a sensor that is mounted on the engine block. It analyzes transmitted sounds and determines the frequency of this phenomenon among many other noises.
Permissible motor detonation develops at low speeds, is hard to hear 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 torque with a small engine size.
What are the causes of unacceptable detonation? As a rule, this type is typical for modified machines. Here are some of the reasons:
- one of the ways to increase the torque and sensitivity to the opening of the throttle valve is the process of setting the ignition timing;
- if ignition occurs early in the cycle of movement of the piston, then the pressure wave that arises can ignite the mixture of fuel and air in certain parts of the combustion chamber - this is the most common reason;
- depletion of the fuel-air ratio in order to achieve a higher engine power (the manufacturer provides for the use of the engine on a rich mixture for one reason - control of the combustion temperature);
- heat of air at the inlet - in cases where the air filter is installed under the hood;
- unsuccessful design of the combustion chamber.
How is engine detonation eliminated?
- First, make sure that there is no self-igniting mixture. To avoid errors, turn off the engine. If he stopped right away, this means that the most likely cause of knocking is detonation combustion.
- The installation of late ignition will help to eliminate detonation, which was caused by the use of an inappropriate type of fuel, otherwise it is necessary to replace fuel with antiknock requirements.
- Use of the appropriate type of gasoline.