Fitsmart Fat Burner Dragons Den Uk :...
Home & Garden5 mins ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.To expand on what Clannad wrote.
Petrol engines draw in a mixture of fuel and air and then compresses them at which point it is ignited by a spark plug.
On a diesel engine only air is compressed, but has to be compressed to a very high temperature so it is red hot - diesel is then injected into the red hot air and ignites causing expansion and the noise you describe. The air to be able to reach 'red hot' requires a higher compression ratio. This means that the air from inside the cylinder is squashed (compressed) up to 20 times its volume. A petrol car is up to 10 times its volume.
I hope this helps explain matters?