Some Experiences in Analysis of Abnormal Noise of Motor Vehicles (1)

Part of the engine 1. To distinguish whether the sound of the main part or the attachment sounds to the engine, first determine whether it is the main part or the attachment. If the noise disappears after the fan belt is released, it indicates that the noise is related to the pump or the generator and its rotating parts; if the sound of all the belts is released and the sound still does not disappear, it should be considered that the main part or other parts sound. 2. To distinguish between “ringing” or “sounding” In the four-stroke engine rhythmic sound, there are “inter-ring” and “sound”. Intermittent sound means that the crankshaft oscillates once every 2 revolutions, and the continuous sound means that the crankshaft oscillates once per revolution. The noise emitted by the valve mechanism belongs to the intervening sound. The sound produced by the excessive clearance of the piston connecting rod group is generally intermittent. This is due to the impact of the piston during the working stroke. When the piston top collides with the cylinder head, the piston ring is replaced. When the cylinder or the combustion chamber enters an iron block, the percussion sound emitted is generally continuous. 3, to distinguish with the cylinder combustion status is not related to the cylinder of a diesel engine high pressure tubing release, or a short spark plug of the gasoline engine, if the sound is weakened or disappeared at this time, the cylinder noise and the combustion state in the cylinder, if the voice enhancement Is nothing to do. The sound emitted by the air distribution mechanism is generally irrelevant to the state of combustion; the sound produced by pistons, piston pins, connecting rod bushings and bearing bushes with excessive clearance is generally relevant; the piston is broken, the connecting rod bolts are loosened or the connecting rod bearings When the alloy is severely detached, the sound is often not related to the state of combustion. Sometimes when a cylinder is cut off, the abnormal sound changes from a ring to a ring, which is often a manifestation of “irrelevant”.

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