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Why are diesel engines noisy?


RobK
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What is it exactly about a diesel engine that makes it sound so rough? With all the development that has gone on, why haven't they managed to make a smooth running one yet?

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Things are getting better.....if you compare the old dears beemer with my tractor, its sooo much smoother and quieter. The beemer engine is slightly quieter than the VW engine though.

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hmmm, i'm no specialist but i remember my dad telling me that the strengh of the explosion in the diesel engine is far, far greater than that in a petrol engine. this might explain the louder 'tractor' noise maybe? i'm sure that the rough running is something to do with the high compression. the simplest way to smooth this out is with more cylinders - hence the popularity of the V6 diesels.

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The simplest way to smooth this out is with more cylinders - hence the popularity of the V6 diesels.

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Indeed, the only negative point of the 320d is that it really does sound like a John Deere!! Why did BMW never launch the 325d - they had/have the engine in the old/new 5 series?

Ian C

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What is it exactly about a diesel engine that makes it sound so rough? With all the development that has gone on, why haven't they managed to make a smooth running one yet?

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Petrol engines use a spark to ignite the fuel/air mixture. Diesels ignite it by sheer brute force, squeezing the air/fuel mix until it spontaneously combusts. The forces involved are massive. Relatively speaking more of the resulting energy is lost as vibration/noise than a petrol. This is also the reason why diesel engines are heavier, tougher, more expensive than equivalent petrol ones. If they weren't they fly apart with a bang and a puff of smoke.

It'll be a long time before a soot-chcuker sounds like a lamborghine - unless they stick a TDi in one smile.gif Having said that, modern engine design, dampening, high cetane fuels and clever electronics make oil burners alot less noisy than ye olde models.

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