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.
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?
^^^^^^
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.
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.
Not arguing, discussing, from 2nd gen to 3rd gen the additional injector events is what made it go from sounding like a Cummins to sounding like a gas engine. Then in the 4th gens even more.
2nd gens are still my favorites.
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
Adding more injection events and higher fuel pressure via a CP4 will make the engine a lot quieter. With more injection events, instead of one big loud explosion, you get multiple smaller explosions that are a lot quieter. Common rail with electronic solenoid injectors allowed Cummins to add multiple injection events to the Cummins which is why common rail trucks were a lot quieter than the previous trucks. The new engine probably has even more injection events than the previous which is seven if I am not mistaken.
Also, with higher fuel pressure from the CP4, you are able to spray more fuel throughout the cylinder and burns quicker with a finer mist instead of a more localized spray with lower pressure that creates a hot spots burns throughout the cylinder. The combination of these two reduces NVH dramatically because there is not one big bang and instead multiple smaller bangs as the piston is traveling down with a much cleaner burn .
Edit: Correction, it is piezo injectors found on PSD's and D-max's that has up to 7 injection events. The electronic solenoid injectors on the Cummins is only quick enough to get 5 events in per combustion event.
This is one of those posts that makes me wanna do some homework. Also, I will settle for 5 combustion events but I’m assuming that by using Mobil one, I’ll get like 3 times that
Here's a clip from an article I found a while back stating that the injectors have been revised. Of course I cant find the actual source so i obviously cant verify it.
Does anyone else notice that they sound different, not just quieter? Mine has more of a "clack" to it in the 2019 model. for reference, I've had an 08,10,15,and 18. First two deleted, last two stock. This one just sounds different, not sure I like it....
I feel the exact same way. Sounds ok under a load, but when you are cruising around 35/40 and just barely on the throttle, I don’t like the sound it makes. I still have a 2016 G56 that is quiet enough for me. My new 19 sound funny. And I can hear when it’s doing a regen. I can never tell on the other truck.
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