DD MUSIC - Rumble or Scream ? ? ?

[richardoren]

This being off topic in another thread, it seemed useful to start a dedicated thread to Detroit Diesel MUSIC. I think we can add insulation ideas, exhaust muffling and backpressure management, air intake improvements as well as blower silencers. Regarding that last point, one very savvy forum member told me in confidence that 90% of DD noise comes from the blower. Comments?

I'll kick off the thread with a quote from a DD fuel consumption post:

I didn't realize that this "blower" was actually a mechanical fuel injection. I'm all sold ever since my old mechanical injection vintage Benz which sure sounded addictive. As for the DD sound, I'll tell you after Sea Trial on Tuesday. These are the screamers - highest compression ever small sized high pitch screamers: 8V53s. They probably sound way different from 92s.

Regarding the sound, I'll probably like (love) it, but for the Admiralty I'm thinking of looking into cheap and simple measures. Some use lead barriers under the salon floor, others prefer Ensolite foam insulation. And there are those who reported success in adding Salisbury Hydro-Vac exhaust silencers to their boat - they are heat resistant neoprene or marine fiberglass elbows that attach over the exhaust outlet and redirect exhaust and noise under the surface:

Anybody here ever used these?!? Could be nice with marina neighbors that hate smoke & noise.

Otherwise there's always Don Hayward's schematic for quietening Detroits by installing a muffler immediately downstream of the exhaust manifold and upstream of the water injection.

Seems like it might be worth a shot, unless it can compromise airflow to the engine which depends a lot on the relatively open exhaust of a two stroke?

Or just tell 'em to love the noise or walk the plank!

 

[REBrueckner]

Nothing screams louder inside than 53 series Detroits. They really do sing!!!I've had 3-53 and 6V53's and both required sound deadening earmuffs when checking at cruise speed. My current 8V71TI's are much quieter inside despite being 2 or three times the HP. 71's are more deep rumble than high pitched sound. And of course they are rated at 500 less RPM which can't hurt noise levels. But the diesel compression sound is always going to be noiser than gas.

Adding Salisbury silencers will do nothing do reduce smoke at start but can reduce exhaust sound...and your ability to listen to exhaust sound for proper tone. I'd never use them myself as a suddenly loud exhaust while cruising is often the first warning you've lose saltwater flow.

Inside, if you want to try to reduce noise levels you need to add sound insulation with a lead layer suspended inside the insulation to stop the lower level frequencies. Lining the hull interior and bulkheads in the engine room to reduce sound reflections can also help.
But these are Detroits,mon, so revel in the old loud technology!!!

 

[hunshatt]

Ihad(have) 6v53n's in 41C(1964) they are loud. Can't wait to get the fresh rebuilt 6v53twin turbo's in. Probably need 2 sets of muffs to get in the bay

 

[NAN-PO 41]

One of our club members had a set of those Salisbury silencers on his boat years ago ( gas 318 Chryslers ) and when he shut down the engines after a day outing one engine rolled backwards and there was enough vacum created to overcome the small vent hole in the silencer and draw saltwater into the engine. The owner didn't know he had a problem until the next weekend when he tried to start the now seized engine. I don't think I would be a fan of underwater exhaust unless I knew there was enough open vent to prevent that possibility. (O.K. Truth be told I do love the sound of my 8v53's also)
JMHO, Fred

 

[naiad]

My 6V92 450hp reminds me of Bruce Springsteen's "Born in the USA" at full noise.

 

[Akyla]

There are many boats that run in my area with detroits. If I am at anchor on a day with standard summer haze I almost always hear them coming before I can see them. The crew boats I have run all seem to have detroits and there is nothing more mind and body numming than a long day at sea listening to them screech.... Maybe the ones I have been around had no mufflers or proper sound proofing but there is just something about the pitch and cadence that leaves me with ringing ears. I took to using a set of earmuffs even on the bridge let alone out on the deck.

That's why there are so many different manufactors - something for everyone.

 

[Trojan]

My 6/71s don't screech. I love to hear them run. So do my neighbors. There loud but not to the point of annoying. The wife loves the smell of the burnt fuel. Long live DD! Maybe you need to turn your bell-tones down. Could it be your mufflers are just shot.


BILL

 

[Mike53C]

I love the way my 12 71N sound. I love the way they start,...just push the button and you can't even hear the starter..push and they are rumbling. Underway and aboard the music is absolutely tolerable for me..or for others, no one has complained yet. From the shore, I have been told that as soon as I round the mangrove hedge in front of the marina they barley hear me. On the other hand there is a Viking, don't know what motors, that you can listen to even when about to reach open sea. It is upwind so the breeze helps the noise but we are talking a couple of miles.
Miguel

 

[newinlet]

When I fire up the DD's at the dock most give compliments and say they sound good. While underway @ 2100-2250 RPM the noise is not bad at all on the bridge .

 

[luckydave215]

The noise DD's produce all depends on the muflers fitted. Mine are so quiet I can't hear them 50' down the dock when they're idling, unless the engine room hatch is open. Then it's a different story, but the audible noise comes up the hatch, not out the pipes. The up-the-hatch noise is louder when the engnes are cold, of course.
My dock mate (courageous, '68 39'C) has 8-53's and his engines are LOUD at the pipes. Mine are turbo's and his are N's, but I think the biggest difference is the muffler efficiency.
The little four stroke Yanmar's found in most sailboats are very loud when the raw water impeller (water lift muffler in other words) fails. Don't ask how I know.
If you want them to be quieter, look at the mufflers.

 

[Genesis]

I like the sound of Detroits..... goes with the smell of diesel in the morning

 

[Paul45c]

Ditto -- I can't imagine a sweeter sound than that throaty rumble of 6v92s idling. Pure sweet musclecar sound!

Once they're up over about 1800, most of what you hear seems to be turbo/blower whistling. A buddy talked me into this really expensive carpet underlay that MUST have some lead in it -- supposedly it cuts down on that high-frequency sound. I think I would have been better off saving the money. All it seemed to do was make my hatches heavier!

 

[Pete]

I have a pair of the screaming 453N's in a 48 LRC. Have already added lead cored vinyl sound reducing material to the overhead of the engine room. Also added sound reducing carpet pad to the salon. Did not cut out any hatches. This fall I will be redoing the mufflers with a pair of Centek double lift inline mufflers. These should help with the actual exhaust noise.

I would rate the current sound levels as follows: Pilothouse is very quite, sounds like a pair of sewing machines running in the salon. Salon noise level allows normal speech volume level conversations and you can even watch TV while underway. Flybridge gives no indication that any engines are running, all you hear is the water as the boat moves forward. Engine Room is a front row rock concert in front of the speakers. Have to wear ear muffs. The cockpit is loud with exhaust noise but you can talk to someone if you yell. All of these observations are at a cruise RPM of 1800 to 1900. Next time out I will get some actual sound level (dba) measurements as a base line before the muffler work.

I like the tone and overall sound of a Detroit best of any engine. I just want to turn down the volume control.

Pete

 

[Angela]

Me too!! I love the sound of my DDs and the smell of diesel! But not with engine room doors open! Too loud - need ear protection, even at idle, for me anyway.

When the tour boats come in to fuel in front of me, I always go outside to listen to them. The are DDs without a doubt. And what I love more than the sound of my DDs???? Those big honkin' horns!

 

[Traveler 45C]

Everyone at my marina knows when I crank up mine, heads turn, no way I can sneak outta there. Someone always stops by to make a comment on how nice they sound. If only I could hear them talking…

 

[Pete]

Finally did some sound measurements on our 48 LRC with 453N mains and the oem exhaust system. The results are all at 1800 RPM, which is our normal cruise speed.

Stern coaming/sound meter facing aft/on center line: 82 dba
Stern coaming/sound meter facing aft/ above each exhaust pipe: 84dba
Salon: 68 dba
Pilothouse: 60 dba
Engine room on centerline at rear of engines: 105 dba

Will take another set of measurements after changing the exhaust system and post those when available.

Pete

 

[Trojan]

Hell, sometimes I just start them up just to get a DD fix. Once you own a DD you just can't get that sound out of your head. It all started with my DD farm trucks. Then it moved along to the DD tractors. Now boats. That sound, that smell, the vibration. When will it end, I hope never. I'm going to make a CD so I can listen to the boat over coffee in the morning through the winter when it is on the hard. Love My DD. The admiral loves them to I think she is hooked.

Bill

 

[skrmetta90]

I was stoked looking at our boat for the first time when I found 8V71's in her. We were cruising at 2000 rpm's last weekend and i went in the engine room with no muffs to photo tac the motors and it wasn't that loud. I used to listen to crew boats back in Delcambre and other small cities on the bayous of Louisiana passing us on my dads shrimp boat. I don't think "screaming" gives those boats justice.

 

[Trojan]

I believe if my mind recalls correctly. That 80db is the max that you by OSHA are allowed to be around without ear protection. And that may be time limited to. Like one minute. I remember an issue with production operators using air tools and the noise that they made. But that's been long ago. Maybe someone has up to date info. just for our information.

BILL

 

[MikeP]

Here's a page with the recommended noise exposure:

http://onlinesafetysource.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=EAR

I don't know the noise level of the DDs in the eng room, having never measured them but I'd bet that at idle they are at least 95.