Where does the engine noise come from? What is the reason for the rumbling of the car engine?

When a car is driving, it will produce a lot of noise, mainly from the engine. The reason why you can't feel it so loud when you are sitting in the car is mainly because of the corresponding sound insulation design. So where does the engine noise usually come from?

Where does the engine noise come from?

Common engine noises include mechanical noise, formal gear noise, intake noise, and cooling fan noise.

Mechanical noise

Piston knocking is usually most obvious in a cold engine. It is caused by the piston's rapid lateral movement and hitting the cylinder. The main knocking occurs near the top dead center.

Official gear noise.

This noise is the result of changes in the torque of the gas adaptor and the injection pump drive. In addition, when the torque amplitude exceeds the tooth side clearance of the timing gear or the additional torque of the torsional vibration exceeds the average torque of the gear, it will cause repeated knocking of the gear, thereby stimulating noise.

Intake noise

It is caused by the intermittent intake of the engine. Exhaust noise is one of the main noise sources of automobiles. According to the mechanism of noise generation in the exhaust process, exhaust noise includes: exhaust pressure pulsation sound; vortex sound generated by airflow passing through the valve and valve seat; exhaust outlet jet noise and other components.

Cooling fan noise

This noise includes: broadband noise caused by air vortex; blade passing frequency sound determined by fan speed, number of blades and angle, also known as beat sound; mechanical noise caused by vibration of fan, wind shield ring, etc.

What causes the car engine to rumble?

Engine knocking. A sound similar to metal knocking is also called cylinder knocking. The general causes of the fault are substandard fuel quality, incorrect engine timing control, and excessive carbon deposits in the engine.

Abnormal valve noise. After the car engine is ignited, it makes a "clicking" sound. This is the sound of the valve, especially after the cold car is started, because the oil pressure has not yet risen and the valve has not been lubricated in place. It will naturally get better after a while. This usually happens when the car is parked for a long time.

Engine "backfire" failure. When the car is decelerating, there is a "puff puff" sound when the accelerator is reduced. This may be an engine "backfire" failure, which is usually referred to as an engine "backfire". Too much valve carbon deposits or incorrect valve timing will produce the sound. It is recommended to clean the valve carbon or adjust the valve timing.

The engine is missing a cylinder. If one cylinder does not work, the engine will be unbalanced and produce abnormal noises, accompanied by violent engine vibrations, lack of power and other faults. This may be a fault with the ignition module, spark plug, or fuel injector. You can just replace the corresponding parts.

Engine noise sources

Mechanical noise: piston slapping, valve seat impact, vibration noise caused by transmission parts movement and impact, body surface vibration noise caused by cylinder pressure, bottom shell surface vibration noise, valve chamber surface vibration noise

Combustion noise: The size of the combustion noise depends on the rate of increase of the gas pressure in the cylinder. For example, the noise of a diesel engine is loud, and when the injection amount and injection pattern are not timely, the noise will increase significantly.

Gas flow noise: intake noise, exhaust noise, fan noise