Why do diesel engines have a characteristic rattle?

Asked by: Matt Nuna, Leamington Spa

In a diesel engine, the fuel/air mixture is compressed by the piston, which heats it to the point where it spontaneously ignites. This causes a very sudden increase in pressure – much more so than in a petrol engine, where the fuel is ignited at lower pressure by a spark. Modern diesel engines inject the fuel in a series of smaller pulses to smooth out the pressure rise and dampen the rattle.

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