What year did they reduce the noise level of the 5.9 Cummins diesel?
I am told that it made a substantial difference.

 

When the heavy duty trucks got the new body style in 2003, was when the Cummins Engine was re-worked to make it quieter. Yes, there is a significant difference.

 

THANKS!

 

I'll second that, but whats nice sounding is hearing that turbo spooling between 1600-2400rpm. . .music

however there are ways to make it louder, if you want more turbo whistle theres a damper you take out of the turbo that will be like putting an amp on a guitar and cranking it up.

the way Cummins got this engine more quiet is to do a pre-ignition dump of fuel right as the piston hits TDC, this acts as a buffer for the main charge of fuel as it enters the combustion chamber. plus the main dump is not one continous stream, it's bursts of fuel at different rates to keep the engine quiet throughout the RPM range, by doing this you are achieveing a more even and efficent burn of fuel produceing more power. I do miss the old clatter of the gen 2 engines, but when I pull side by side to a gen 2 and smoke the tires through 5th gear it makes me forget about the old clatter and the new ponies under the hood.

 

it wasnt until the 2004.5 325/600 cummins turbo diesel ,2003 had the 305/555 & kept them till 2004 ,when the 325/600 was released it was the 2004.5