Knock Sensor: Functions and How it Works

Knock Sensor: Functions and How it Works - Knock sensor is one of the sensors used in EFI vehicles that serves to detect the occurrence of knocking. What is knocking? To find out more about knocking, you can first read knocking and its general causes.

Knocking/Detonation

Knocking is a high-frequency vibration caused by an explosion or premature combustion in the combustion chamber or combustion that is not caused by a self-ignition spark plug.

In fact, in every vehicle there are at least 9 kinds of sensors that have a function to detect environmental conditions such as temperature and pressure and engine load conditions. Where the conditions that occur are varied. One that is used is a knock sensor mounted on the cylinder block of the car. The following is a function and how the knock sensor works which has a very important role in EFI cars.

Knock Sensor Function

Knock sensors on vehicles that have carried electronic control technology in their fuel system (EFI) are sensors that function to detect the occurrence of knocking/detonation. This knocking or detonation often occurs if the ignition timing does not match the predetermined ignition degree. Various cases are found that the ignition timing is faster than it should be.

Cars that have used electronic control technology usually not only regulate the fuel flow process, but also regulate the ignition system. Because the right ignition angle will make the resulting power output to be maximum.

On EFI vehicles, the ignition timing has been set precisely according to engine speed and the detection results from the sensors. But sometimes over time there is a change in the ignition timing so that the ignition timing becomes incorrect. Improper ignition timing will cause knocking / detonation and knocking can damage engine components. The real impact felt is that the driver will realize that gradually his vehicle loses power. This is why a knock sensor is installed on the vehicle to detect a knock.

How the Knock Sensor Works

The knock sensor consists of a pizoelectric element and a diaphragm. If there is a vibration in the cylinder block caused by knocking, the diaphragm on this component (knock sensor) will vibrate and move the pizoelectric element. The vibrations received by this element will then be converted into a voltage signal and then sent to the ECU. The size of the voltage that will be sent to the control system (ECU) depends on the intensity of the vibrations that occur due to knocking.

In this condition, the ECU receiving the input signal from the knock sensor, will take a reading of the engine condition, and the ECU will slow down the ignition timing based on the knocking intensity.

After the knocking is gone, the knock sensor will detect that there is no more vibration or knocking in the engine and then the knock sensor will send a data signal to the ECU for then the ECU will advance the ignition timing if the knocking has not occurred.