jjcold
Seattle
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Joined: 01/03/2008
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I have a '94 Gulf stream with a 5.2 KW Generac genset. It runs fine, and has about 175 hours on it. both the previous owner and I service it regullarly, and it really runs fine. However, it is a bit more noisy than I would like. Especially since I have an AC only fridge and have to run it more often than I might normally. Do you think that replacing the muffler, or doing some other mods might quiet it a few db?
I have considered a new onan microquiet, but I hate to spend 3-4k on a new genset for an older motorhome.
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Handbasket
Asheville, NC
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Joined: 01/17/2003
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_If_ they printed an 'installation manual' for it that you can find (maybe just a few pages of the owner's manual), check that.
I read the one for my Onan 2.8, and found that there were several corrections and improvements that I could make to the factory compartment & installation. The biggest one was finding that Onan only required (IIRC) 24 sq in of cooling air intake in the door; mine had over 100, since Provan had used an off-the-shelf door.... that alone cut 'way down on fan and mechanical noise. I also found that I had enough clearance on two sides and the top to add some 1" rigid f'glass insulation. That was a big help. Some 1/4" hard rubber between the box and frame at the mounting bolts did a little good. I also found some of the ways that noise was 'sneaking' out around the frame and plugged them. An Onan resonator, and a $$$ Supertrapp, and I'm down to 58 dbA at 21'... and the ST's the only thing that's not Onan-approved.
Definitely check into a resonator / 'after-muffler', even if that's all you do. But the mechanical and fan noise are a part of it too.
Jim, "Entropy never sleeps; do y'all?"
'06 Tiger CX 'C Minus' on a Silverado 2500HD 4x4, 8.1 & Allison ('Loafer's Glory'); '07 Forester 2.5 ( the 'HANDBSKT'); '95 Toyota SR5 V-6 4x4 pickup, ARB locker, Bilsteins, Warn hubs & M8000, etc;
'94 968, M030 swaybars ('DOPPLER')
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Home Skillet
Pearland Texas
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Joined: 10/21/2004
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Most generators, the noise is not emmited from the exhaust.
It's usually the motor it self.
2005 Gulf Stream Conquest 31ft
BigFoot Levelers,SmarTire,Bilstein Shocks,Trans temp guage,Lowrace iWAY
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Admiral
Lodi, Ohio
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Joined: 06/08/2003
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I have a 5kw Generac in my class A. I used a 1 1/2" soundproofing foam sheet with a fireproof face I got from an rv surplus store in Elkhart and lined the sheet metal box with it. It made the rv interior much quieter and hushed the echo part of the noise outside. There's still more noise than I care to hear coming from the bottom where the cooling air discharge comes out. There is probably alot of sound being emitted from the cooling air intakes also.
Hey, it's a 15 horse motor running wide open.
I think the only sure cure for it is to bury it with 3' of dirt.
2004 Damon Daybreak 2960F
05 Honda Element LX
In a democracy two wolves and a sheep can vote on what to have for dinner.
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tatest
Oklahoma
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I find that my genset is more quite when parked on acoustically softer ground, e.g. gravel, dirt or turf, as opposed to concrete or asphalt. Most of the noise is mechanical, not exhaust.
Tom Test
Itasca Spirit 29B
2001 Ranger Edge
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wwest
Redmond WA
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Install two 6-volt deep cycle golf cart batteries in series and purchase an inexpensive 1000-3000 watt(***) MSW(***1) DC-to-AC inverter to run the fridge.
And don't open the fridge door(s) very often when running on the batteries.
***: I use a 500 watt MSW inverter for this but my absorbtion type frig only requires ~350 watts, and only when being actively CHILLED. Your AC frig will require as much as 3 times its running current for compressor motor starting. Even 1000 watts may be overkill so check it out first.
***1: Like air conditioner compressor AC induction motors, some AC fridges will not run, the AC induction motor will stall at startup, with MSW type inverters. Even worse the fridge might work intermittently but only after the motor's overheat CB has cycled enough times that the compressor head pressure is low enough to allow an "easier", lower initial surge current, motor startup effort.
So I would test an MSW inverter first by forcing a compressor motor restart with high head pressure. Simply unplug the power when you know the motor is already running and then plug it back in within seconds to see if the motor stalls upon restart.
The alternative, using a more expensive PSW inverter, might not be cost effective depending on the fridge's startup power requirement.
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wwest
Redmond WA
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jjcold wrote:I have a '94 Gulf stream with a 5.2 KW Generac genset. It runs fine, and has about 175 hours on it. both the previous owner and I service it regullarly, and it really runs fine. However, it is a bit more noisy than I would like. Especially since I have an AC only fridge and have to run it more often than I might normally. Do you think that replacing the muffler, or doing some other mods might quiet it a few db?
I have considered a new onan microquiet, but I hate to spend 3-4k on a new genset for an older motorhome.
Convert your Onan engine to the Atkinson cycle.
Machine/mill the head(s) of the genset to get a "native" cylinder compression ratio in the range of 12:1, have a shop custom grind a cam to delay the closure of the intake long enough to reduce the "effective" compression ratio to the OEM standard (~8:1). Then put a "reed valve"(***) in the carburator throat downstream of the throttle valve to prevent reverse "surge" airflow due to the late intake valve closing.
***: Available for any 2-cycle engine.
Absent so much WASTE energy going into/out the exhaust your microquiet will not only be a LOT quieter but FE will improve dramatically, 20-25%.
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wwest
Redmond WA
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Or you could use a lathe to turn/cut the airflow impellars off of the flywheel, install a 12 volt blower to cool the cylinder head(s) with a regulating circuit to control the blower so the cyclinder head temperature rises to 180 but not above.
Lower airflow "noise" and increased engine efficiency.
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Bordercollie
Garden Grove, CA, USA
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Joined: 03/07/2002
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We had a Generac on our '79 Delta, it was loud mechanically and exhaust wise. Somebody suggested a "stinger" muffler as used on VW's, never tried it. The Onan Microquiet on our Tioga is a lot quieter but could also get on someone's nerves parked closely next to you. You'd think the RV and genset industry could improve the quietness considerably.
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jimdubya
Paducah, KY
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Joined: 05/23/2008
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A few years ago I had a Gulf Stream 36ft Class A with the generator under the bedroom and it made lots of noise, I was able to quieten it a lot with some material I bought on line called "Brown Bread". It was a dense rubber like material that came on a roll. I cut it to size to fit the compartment walls and attached it with screws and fender washers. It made a huge difference. I see from their web site that the "Brown Bread" has been replaced by a different product.
You might give them a look.
Sound Dampening Material
2004 Silverado 2500 Crew Cab 4x4 6.0L 3.73
2006 Dutchman Tundra 26RL-DSL
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