My wife recently asked the question when people were filing in the campground for the weekend "why are most of the diesels so noisy?" The only real answer I could give was because they made it that way because they like it that way. I never really complain because I'm sure I have annoyed many when I was a kid with my jacked up 70 GTO with headers and straight so-called mufflers and now my no so quiet motorcycle. The point of the post is I was totally taken by surprise today. I went to the dump to get rid of some tree branches and this HUGE Caterpillar front end loader came in next to me to move the brush pile and you could barely hear it. Do you think the big "quiet" truck will catch on? Nah, big boys like noisy toys.

The newest diesels are nearly as quiet as their gas counterparts and are more quiet than big block gas engines of yesterday. It's hard to hear them until they're right next to you.

Diesels really don't have to be noisy. Little boys like their toys.

Diesels are noisy by nature, you wanna hear a Deutz air cooled on cold start up. The manufacturers have gone to great lengths to quiet them down, I am really impressed with our 05 Cummins, but there is a certain element that feels the need for straight pipes and megaphone tips.

You can't hear the new ones, especially in the cab :B

The difference between the noisy ones and the quiet ones is in the injection system. Old diesels, like the 2002 and older 5.9L Cummins for example, do one injection event per combustion cycle. Newer common rail fuel injection technology (2003+ Cummins 5.9L) allows for multiple injection events per cycle, thereby spreading the explosive power over a longer time and quieting the noise of combustion.

Diesel noise | Good Sam Community

45Ricochet
Explorer
May 29, 2013
I believe the high compression is the main reason, although the new ones are silent :H Might have to do with the higher pressures they run in the fuel delivery system for a cleaner burn of fuel.
Not sure when a valve lash is do on a newer Cummins, but the old 5.9L would really get loud when they needed to be adjusted. And the 12 valve version came loud from the factory. Never said we could sneak up on anyone :B Funny the DW would always know when I was returning home a few minutes before I arrived, yep the dog would warn her of my arrival :P
thirtydaZe
Nomad
May 29, 2013
Dont forget the long line of emissions, cats, and that dpf kill the sound on a cummins. Pull the stock system off a 2012 ram 2500, put on a 4" turbos back exhaust and you have a whole different animal.
ScottG
Nomad
May 29, 2013
Most of the noise abatement is in the new style pumps and injectors. There has also been big improvements in the architecture of blocks, heads and just about anything that involves NVH or noise vibration and harshness.
But there's always some guys that have to chop up the exhaust and intake to make the things as loud as possible.
grizz272
Explorer
May 29, 2013
My wife asked a variation on this question today on the way home. Why is our new 2013 Chevy Duramax so much quieter that our old 2003 GMC Durmax. My answer was the truck is new everything is tight and the new engine is just plain quieter. Parked my truck next to a 2000 Dodge ram Cummings and you could not hear it at all
ib516
Explorer II
May 29, 2013
The difference between the noisy ones and the quiet ones is in the injection system. Old diesels, like the 2002 and older 5.9L Cummins for example, do one injection event per combustion cycle. Newer common rail fuel injection technology (2003+ Cummins 5.9L) allows for multiple injection events per cycle, thereby spreading the explosive power over a longer time and quieting the noise of combustion.
coolbreeze01
Explorer
May 29, 2013
You can't hear the new ones, especially in the cab :B
romore
Explorer II
May 29, 2013
Diesels are noisy by nature, you wanna hear a Deutz air cooled on cold start up. The manufacturers have gone to great lengths to quiet them down, I am really impressed with our 05 Cummins, but there is a certain element that feels the need for straight pipes and megaphone tips.
Johno02
Explorer
May 29, 2013
Diesels really don't have to be noisy. Little boys like their toys.
ScottG
Nomad
May 29, 2013
The newest diesels are nearly as quiet as their gas counterparts and are more quiet than big block gas engines of yesterday. It's hard to hear them until they're right next to you.

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Diesel noise

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