How'd they make it quieter? - Dodge Cummins Diesel Forum
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post #1 of 31 (permalink) Old 07-18-2019, 10:09 AM Thread Starter
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How'd they make it quieter?

I've noticed the new 2019 Cummins models are a lot quieter (outside) than the previous years--almost doesn't even sound like a diesel. Anyone have any idea how they did this?

My thoughts are by changing the injection timing. I know the graphite block is new, but I don't think that'd lend to making the engine quieter per se. Any good input would be much appreciated.

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post #2 of 31 (permalink) Old 07-18-2019, 10:12 AM
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Biggest change to perceived outside noise is going to be the hydraulic lifters. I am sure there are other changes that help, but that classic Cummins "clatter" was the from the solid tappets.


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post #3 of 31 (permalink) Old 07-18-2019, 10:20 AM Thread Starter
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Originally Posted by battlerattle View Post
Biggest change to perceived outside noise is going to be the hydraulic lifters. I am sure there are other changes that help, but that classic Cummins "clatter" was the from the solid tappets.
I'm not going to pretend to be the most well-versed engine guy, but I've tried researching exactly what the hydraulic lifters did in the engine and the information I find is still sort of vague to me. What exactly is their purpose in the engine? To lift the intake and exhaust valves? And given they are "hydraulic"--I'm guessing the fluid that controls them is the engine oil?
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post #4 of 31 (permalink) Old 07-18-2019, 10:37 AM
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Quote:
Originally Posted by ChfEngr View Post
I'm not going to pretend to be the most well-versed engine guy, but I've tried researching exactly what the hydraulic lifters did in the engine and the information I find is still sort of vague to me. What exactly is their purpose in the engine? To lift the intake and exhaust valves? And given they are "hydraulic"--I'm guessing the fluid that controls them is the engine oil?
They ride on the cam lobes and transfer that movement to the rockers that move the valves. Being "Hydraulic" means they have pressurized oil in them. This allows them to constantly and every so slightly change dimensions (overall length). This allows for constant contact against the cam and removes the need for valve lash adjustments as they take up any slack.

The previous designs (18 and earlier) use a solid tappet style design. Highly effective, strong and simple, but prone to making noise as the valvetrain does its thing. They also require the valvetrain to be periodically adjusted to account for any slack.

I am sure there is someone that can explain it much better than I can.


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Last edited by battlerattle; 07-18-2019 at 10:46 AM.
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post #5 of 31 (permalink) Old 07-18-2019, 12:21 PM
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^^^^^^
Excellent explanation.
Also adding to the quietness is the new compact graphite block, the new acoustic noise cancelling glass and sound deadening materials placed where it counts.

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post #6 of 31 (permalink) Old 07-18-2019, 01:46 PM
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Quote:
Originally Posted by battlerattle View Post
They ride on the cam lobes and transfer that movement to the rockers that move the valves. Being "Hydraulic" means they have pressurized oil in them. This allows them to constantly and every so slightly change dimensions (overall length). This allows for constant contact against the cam and removes the need for valve lash adjustments as they take up any slack.

The previous designs (18 and earlier) use a solid tappet style design. Highly effective, strong and simple, but prone to making noise as the valvetrain does its thing. They also require the valvetrain to be periodically adjusted to account for any slack.

I am sure there is someone that can explain it much better than I can.
^^^^^^Nope you did a good job!!!
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post #7 of 31 (permalink) Old 07-19-2019, 09:16 AM
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So the lifters actually shape shift a bit? Like they're pliable?

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post #8 of 31 (permalink) Old 07-19-2019, 09:54 AM
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Quote:
Originally Posted by esminbritt View Post
So the lifters actually shape shift a bit? Like they're pliable?
They are made of steel. Think more of a plunger in a tube. You crank up the pressure and the plunger moves.

https://youtu.be/_x6PIqXqLlk

Jump to about 7:30 if you don't want to watch the whole video. Its old, very old, but pretty accurate.


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post #9 of 31 (permalink) Old 07-19-2019, 11:02 AM
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Quote:
Originally Posted by battlerattle View Post
They are made of steel. Think more of a plunger in a tube. You crank up the pressure and the plunger moves.

https://youtu.be/_x6PIqXqLlk

Jump to about 7:30 if you don't want to watch the whole video. Its old, very old, but pretty accurate.
That's a great video. Is it actually from the 50's? Regardless, it's informational

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post #10 of 31 (permalink) Old 07-19-2019, 11:54 AM
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And IIRC they did add an injection pulse also
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post #11 of 31 (permalink) Old 07-19-2019, 12:50 PM
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They may have added an injector pulse, i am not 100% sure. Generally pulse timing, width and duration make more noticable changes under load. In the end its probably a combination of all the factors. I think at idle though, the biggest change to the noise level is the hydraulic lifters.


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post #12 of 31 (permalink) Old 07-19-2019, 01:14 PM
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Mostly, I enjoy the fact that it's quieter. I do miss the whine of older model turbos though. I'm not a big exhaust, black smoke guy. But I do love hearing a Turbo spool

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