Why Do Diesel Engines Make More Noise Than Petrol Engines?


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Taylor Edgar answered
Modern diesel engines are now as quiet as petrol engined vehicles.

However, it is true to say that older types of diesel engines were much noisier, and together with low power outputs, was one of the reasons they were usually only fitted to commercial vehicles.

Older diesel engines were typically noisy especially at low speeds and when cold. The reason for this was the sudden ignition of the diesel fuel by compression, as opposed to by an electrical spark in a petrol engine. When the diesel was injected into the combustion chamber, the sudden temperature change resulting from ignition caused a knock or clattering noise. This racket was louder and more pronounced when the engine and combustion chamber were cold and operating at lower temperatures.

The use of improved engine design and fuel delivery systems has now largely eliminated the worst excesses of the noise problems with diesels. The only time you notice a modern diesel engine is when it is idling for it has its own distinctive sound quite unlike a petrol engine.

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