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Discussion Starter #1
I've often wondered what actually makes a diesel sound like it does.


In particular when comparing the sound of say a Cummins to the Dmax. The Dmax is SO much quieter IMO.


What makes the diesel sound?


Why is one so much quieter than the other?


TIA
 

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higher compression ratios, higher combustion pressures, etc. The DMAX is so quiet due to the pre-ignition fuel spray that starts the combustion train slowly. You will notice a big difference in sound from direct injection and indirect injection.


Have fun reading...http://www.duramaxdiesel.com/
 

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Also the lack of a throttle plate like you have in a gas engine.
 

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The diesel "chatter" (even at idle
) is caused by the wave front in the burning fuel in the cylinder. As the fuel charge is compressed to the point of ignition combustion starts at random locations in the cylinder and spreads out in a wave. This wave front spreads out in a random pattern and "impacts" the piston crown, cylinder walls and head. This is one reason for the beefy lower ends on diesel engines (in addition to the increased compression) and why diesels have low-frequency vibration issues for loosening fasteners and mounted accessories that gas engines do not. The pilot injection in the HPCR systems shoots a small "initiation shot" that starts the fuel burn and when the main injection shot occurs it burns in a smoother and more uniform wave that greatly quiets the event. When rpms get too high (above 2400 to 2800) there's not enough time in the compression stroke to get in a pilot shot and injection becomes a one-shot affair with the production of the classic diesel chatter. Edited by: Idle_Chatter
 

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That makes sense, but why the massive power increase at above 2400 rpms? It feels like the truck is falling on its face until that rpm is reached--then HOLD ON! Then it shifts at like 3000 rpms--seems like with such a short rpm powerband this thing should be making power right off idle!
 

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redneck45 said:
That makes sense, but why the massive power increase at above 2400 rpms? It feels like the truck is falling on its face until that rpm is reached--then HOLD ON! Then it shifts at like 3000 rpms--seems like with such a short rpm powerband this thing should be making power right off idle!

That would be your turbo boost increasing.
 

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Not only turbo boost increase, but the stock programming has "torque management" built in that holds back power early.
 

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Oh I hope the new Juice box will cure all that when it becomes avaliable for the LLY
.
 
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