Engine noise: Cummings vs Volvo Penta

wawando

wawando

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Hello,
I am puzzled with the noise difference at idle between Volvo and Cummins.
At the beginning i thought it was 6 cyl vs 4 cyl but it is not... a IPS 900 (6 cyl D13) is even noisier than the D4...
I was told that when navigating cumming becames louder... is it true?
Why is there such a big difference?
ips 900: https://www.youtube.com/watch?v=yGLBG50uox8
Cummins QSD 4.2 6 cyl 320 hp: https://www.youtube.com/watch?v=VeWF_CGU8y0&t=3s (engines start at 55s of video)

The difference sounds like IPS is 5x noisier!

This is not a detail.. it impacts comfort... although of course with hatch closed it becomes much quieter...

It has nothing to do with the videos, i shot all and used the same phone. The sound in loco felt like it sounds on the videos...
 
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Er... no device to do noise readings.... just what I listen... and is "audible" in the videos... my point is that the difference is SO HUGE that I am really amazed...
 
The displacement volume difference is huge. D13 is a 10.8 litre engine! It’s bound to be louder than a 4.2.
 
Wawando, I don’t want to cause you any more confusion but the QSD 4.2 is a Cummins in name only. It’s actually an Italian engine
 
Sounds like the valve trains are different .
The Volvo sounds like they are overdue adjustment .Or if auto adjust hydraulic ( I have not googled life too short ) then there is huge “natural “ valve lash when cold .

Cummins valves sound leagues ahead in refinement ......but no surprises there .

I don’t think it’s just a displacement multiplier, it’s a different in engineering tolerance/ refinement.
Jump in a BMW 3.0 d variant diesel theses days and you can’t really tell ....feels like 3.0 petrol .
 
FARSCO said:
The displacement volume difference is huge. D13 is a 10.8 litre engine! It’s bound to be louder than a 4.2.
Click to expand...

Exactly that was my first thought , a lot more going off inside the D13 than the D4 .

Look at the D13 , 6 unit injector pumps all going bang , the D4 is common rail, no pump noise.

Also you would be surprised how much noise the IPS upper gear unit makes , Volvo don’t Bragg about that in the sales lit.
Half the transmission is inside the boat compared to a drive unit that’s immersed and outside the boat , all contributing factors to the noise level.
 
Bouba said:
Wawando, I don’t want to cause you any more confusion but the QSD 4.2 is a Cummins in name only. It’s actually an Italian engine
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Precisely.....don’t underestimate IT internal combustion tech arguably been at the top of the tree engineering wise for a while , think Ferrari and it’s historical F1 and Le Mans engine dominance , Ducati , MV Augusta , FPT , iveco + many more .
Even the humble Vespa .
They know there onions with engines .
 
Another thing that partly explain is the engineering tolerances and materials of the pistons , there rings and liners .
Diesels make a greater racket than petrols when cold because in use they run a far greater cylinder temperatures and pressures .As things warm up metals expand to seal .When cold stuff has basically shrunk .If it was the right or near enough size when cold ......the excessive thermal expansion ( compared to cooler running petrols ) would cause binding and premature wear.
So they tend to rattle when cold until things expand and fit better .
Thats why they smoke a bit when cold oils getting past the rings because they are cold and don’t fit as tight as a petrol equivalent.

How ever having said that the better refined manufacturers use less thermally active ( from a change of dims pov ) materials so less noise when cold .

There may be a difference in sound absorbing between dry liner and throw away cast blocks like the D4 and a wet liner block .
The wet liner should have an extra “ layer “ of the liner , or different material to the block to absorb certain low frequencies......Again back to Sq 1 engineering refinement , which comes at a price .
 
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...But the cummins was started from cold just like the volvos D6 and D4...
It seems the italian-build-but-silent-diesel-cummins is much better balanced or maybe uses lower pressure... it seems cummins is petrol and others are diesel but this is not the case, all diesels... maybe at higher revs things change...
 
wawando said:
...But the cummins was started from cold just like the volvos D6 and D4...
It seems the italian-build-but-silent-diesel-cummins is much better balanced or maybe uses lower pressure... it seems cummins is petrol and others are diesel but this is not the case, all diesels... maybe at higher revs things change...
Click to expand...

Yes that’s what iam saying .
Maybe this is easier to understand.....
A better set of boffins have gone through the Cummins engines than the Volvo Penta team through VP products .

But the best team of marine Diesel engine boffins work in Germany :)

Automotive in Japan .

.
 
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One overlooked issue is the sound deadening as this is crucial, each engine gives off different frequencies of noise at different revs and two totally differing engines from different manufacturers give off totally different frequencies.

You can get sound deadening material but it has to be tuned as much as possible to the engine frequencies and you can install the correct type to absorb both the engine and IPS noise and make a huge difference in dampening many of the annoying frequencies and make a nicer environment.
 
Portofino said:
Yes that’s what iam saying .
Maybe this is easier to understand.....
A better set of boffins have gone through the Cummins engines than the Volvo Penta team through VP products .

But the best team of marine Diesel engine boffins work in Germany :)

Automotive in Japan .

.
Click to expand...

The VM disguised as a Cummins is that good no one wants them and boats with them fitted are harder to sell than the VP equivalents.

As for German Diesel’s...have you read this months MBY ?
 
Boat2016 said:
The VM disguised as a Cummins is that good no one wants them and boats with them fitted are harder to sell than the VP equivalents.
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To keep things in balance, a while ago I did a lot of research into the QSD4.2 and it was hard to find a bad word against it. The problem is that it’s an orphan, for parts and maintenance do you go to VM (good luck with that one) or Mercruiser or Cummins. All have claimed ownership of the model but who has washed their hands of it?
 
It’s a complex world of corporate take overs in most utilities inc Diesel engines no exception there .Parts supply chains and dealer franchises get churned at every sale / acquisition.Thats an side show happens all the time .
This does not alter my opinion where the best “ boffins “ do or have done there stuff .Or Volvo Penta don’t do enough hard R+D , won’t do enough, don’t need to do enough, just focus on marketing and small outdrive / IPS boats .IPS being a huge research hungry rabbit hole , but a great commercial success .....it’s sells and brings in revenue agreed but engineering wise refinement, a completely different story which is the basis of this thread and the OP wondering why they sound so different.

VM like I said ( Italian ) very highly regarded academically... boffin loaded ....know there stuff .

For clarification see post #18/19 here .......

http://www.ybw.com/forums/showthread.php?301370-Cummins-Mercruiser-4-2L-270HP/page2

Aside couldn’t you not just hear the difference on the vids the OP posted ?
Theses vids where back to back cold start tick over in the ER . A perfectly good question , why does one sound so different ?
 
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