Why are 6.5 quieter then 6.2?

[2INSANE]

I notice the 6.5 is much quieter then the 6.2. Is it the rockers? Ip? Intake?

[Robyn]

Normally the 6.5 with the electronic IP have a much harsher rattle.
They run a higher POP on the injectors.

The NA 6.2 SHOULD ACTUALLY BE A BIT QUIETER.
Now if the cold case advance is not shutting off they will rattle really hard.

[DmaxMaverick]

Age. And a turbo. New 6.2 trucks were fairly quiet. Today, 6.2 trucks rarely have the original intake plumbing intact. The 6.5TD has a turbo, so it needed less attention in this department. A turbo is a noise reducer, in both directions. Many states don't require an additional muffler (as a means of noise control) if it has a turbo. The N/A 6.5 is every bit as noisy as the N/A 6.2, all else being equal.

[More Power]

Noise, as in "combustion rattle", is largely a function of injection timing. Over time, the 6.2/6.5 timing chain will stretch to a point that it loses a degree or more in timing advance. The result is less rattle. This is/was one of the arguments in favor of the aftermarket timing gear sets.

[2INSANE]

Ok thanks for that knowledge! The 6.5 I have is much quieter then any 6.2 I have heard.