As their name indicates, many people consider knock sensors to detect high-frequency audible knocking sounds in car engines.
How Many Knock Sensors Does a Car Have? A car contains 1 or 2 knock sensors, usually depending on the number of engine cylinders present inside a vehicle. For example, the cars like Toyota Corolla and Honda civic have 1 knock sensor because they have only 4 cylinders, while the Ferrari and Lamborghini have 2 sensors as they comprise 8 and 12 cylinders. Furthermore, these protect the vehicle’s engine from damage by quickly sensing the knocking or unusual noise due to pre-ignition and retards the ignition process.
You can easily estimate their number in the car by looking at its interior features, like the number of cylinders.
Additionally, their task is to keep a strict check on the engine’s performance by being present on the surface of cylinders.
What are Knock Sensors?
The knock sensors recognize harsh and pinging vibrations in the engine so that the system can bring desirable changes in the vehicle to dampen the noise.
They can identify the abnormal changes in the combustion process due to pre-ignition. This premature ignition process can have a negative impact on the vehicle.
Moreover, these sensing devices contain a piezoelectric element and a resister and are present on the surface of engine blocks. Therefore, you can see them close to the head of the cylinder and intake manifold.
How many knock sensors are present in a car?
The number of knock sensors depends primarily on the number of cylinders present in a particular vehicle.
Most commonly, only one sensor is usually bolted on the top of cylinders to keep a close check on the engine’s functioning.
Vehicles with 4 or 5 cylinders require only 1 sensor to identify and analyze the knocking inside them.
Their number keeps on increasing with the cylinder count in engines. As a result, the vehicles containing V10, V8, and V6 comprise only 1 to 2 at their maximum.
Almost all the modern cars having 4 cylinders contain a single knock sensor, like Toyota Corolla, Honda Civic, Honda Accord, and Hyundai Elantra.
Furthermore, vehicles with more than four-cylinders have 2 knock sensors like Ferrari, and Lamborghini has 8 and 12 cylinders.
The first monitoring device takes notice of the 1, 2, 7, and 8 cylinders, while the second one keeps a strong check on 3, 4, 5, and 6 cylinders.
Why do cars have knock sensors?
They offer many advantages that make them essential to be present in cars. They can help improve the engine’s longevity by strictly checking its performance.
Detection of vibrations
They are present on the cylinder blocks and can detect a difference in the working of the control unit.
A self-ignition in the chamber can cause spark knock (detonation or booming sound effects) that are audible to humans.
In the absence of these sensors, the system cannot recognize the drastic changes that can lead to an explosion.
Therefore, it is essential to monitor its functions by sensing the high-frequency sound waves producing a loud noise.
Reduced fuel consumption
It ensures better acceleration and helps achieve a high speed when driving on the highway.
So, it takes less time to engine for ignition and reach a maximum speed within a short time. As a result, it positively affects fuel economy and reduces overall fuel consumption.
Furthermore, an increased torque is produced due to the better and smooth acceleration.
Detection of a malfunctioning engine
Engines can lose their function for many reasons, like the carbon and other exhaust gases that begin to accumulate on the chamber walls. It results in premature ignition in the combustion chamber.
In addition, a low octane fuel and the extreme temperature which goes beyond the optimal range can affect its normal functioning.
So, they help identify the changes in its performance and provide the maximum amount of energy.
They have a robust design having lesser sensitivity to any kind of variations. As a result, they can tolerate varying conditions and remain functional even after thousands of cycles by the engine.
Moreover, it can easily reach more than 1000 to 1400 cycles before it gets lost function.
It is close to the head gasket, quickly identifies the knocking sound, and presents a report to the ECU to make abrupt decisions.
You cannot doubt the sensing properties of these sensors because they are highly reliable and give you correct information.
You can rely on the output as they provide accurate readings to inform the computer system. So, the drivers have to replace the non-functional sensors with the intact ones to ensure safety.
Tolerate high temperature
It can tolerate a wide temperature range from -42 to 158 degrees Celsius. They do not lose their functionality at extreme temperatures and behave normally.
The temperature inside the combustion chamber keeps changing continuously from extremely low to high when fuel-burning starts and stops.
The high resistance of sensors against the fluctuating temperature makes them ideal to be present on the cylinder blocks.
What happens when knock sensors sense vibration?
When the engine starts malfunctioning and producing loud pinging sounds, these identify the abnormal changes occurring inside the combustion system.
In addition, the fuel mixes with air before reaching inside the cylinder for burning.
The piston compresses the mixture resulting in the ignition of sparks pushed back due to the expansion of gases.
It contains a piezoelectric element or a crystal that starts vibrating and producing voltage. A signal of current passes to the computer system of an engine which controls the ignition timing.
Therefore, it modulates the crankshaft’s rotational movement and minimizes the fuel consumption.
In the same way, the sensing element recognizes the shaking of crystal and identifies the changes occurring due to abnormal behavior of the engine.
The vibration initiates due to spark knock, which increases the pressure inside the cylinder up to an undesirable extent.
Accordingly, the sensors inform the ECU (Engine Control Unit) about the regular knocking.
Its controlling unit helps manage the entry of fuel and air mixture inside the motor for combustion.
The system analyzes the condition correctly and acts according to the ideal parameters. Then, it starts retarding the ignition process by allowing a lesser quantity of fuel to enter the combustion chamber.
Each vehicle contains a lot of ECUs like the causal automobiles have almost 85 to 90 ECUs inside them.
However, the luxurious vehicles have extra features that require more fuel to run smoothly, so they need more controlling units, and this number can reach up to 120 and 140 ECUs.
Therefore, the controlling units monitor the intake of fuel and air mixture and release of exhaust gases and ultimately regulate the emission of gases.
Why does knocking occur in the car engine?
Knocking can occur due to premature ignition in the engine, which means the mixture of air and fuel starts to burn before the spark plug fires.
It means that the motor starts combustion before the piston compresses the charged particles.
It can happen due to the deposition of lead and carbon particles inside the chamber.
A faulty EGR valve separates the intake and exhaust manifold. A built-in electric motor controls the opening and closing movement of the valve.
Therefore, it starts producing unusual noises when the valve gets stuck or clogged due to the accumulation of exhaust particles in the narrow seams.
So, the uneven burning of fuel mixture can damage an engine and produce loud sounds. They quickly analyze the problem and fix it to help prevent a significant loss.
Take your vehicle to a mechanic and ask him to replace the EGR valve when they are not functioning correctly.
The repairing process can cost you around $270 to $340, which involves the cost of new valves and labor.
It can help save your money because the complete replacement of an engine can cost you about $2500 to $5500.
Is it essential to replace faulty knock sensors in a car?
These are an essential component of a car, and you cannot drive safely without having such a functional device on the engine cylinders.
A bad knock sensor can not only affect the performance of the vehicle but causes damage.
Therefore, it is better to replace an out-of-order product before facing problems.
You do not have to pay a considerable amount for adding new devices, and it secures you and your vehicle by preventing an undesirable loss.
A continuous knocking and pinging effect can cause permanent damage to the head and head gasket of the cylinder.
So, it is better to fix the problem at the right time by replacing the damaged sensors before it results in a bigger problem.