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Old 01-10-2016, 05:47 PM   #1
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2009 22' Interstate
Tahoe City , California
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Loud generator

I have an Airstream Interstate 2009. The generator on it is unreasonably loud! I took it to a muffler shop but the serviceman didn't think there was anything he old do. Any ideas?

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Old 01-10-2016, 06:33 PM   #2
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Had the same problem on sob mh, I didn't go to a muffler man, so I didn't know it wouldn't work when I went to Autozone and ask for the cheapest small car muffler they carried, they found one and an adapter pipe to reduce it to fit the tail pipe of the generator. Cut the sound in half, next I noticed the generator case had an input air vent about 6x12inches, and the louvered door they mounted for the enclosure had 1.5x2ft of louvers. reduced it with insulation. You could have a conversation on that side of the van after the mods

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Old 01-10-2016, 07:21 PM   #3
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My Interstate's generator was also comparatively loud when the van was new, but no louder than the van's engine at idle.

First thing is to make sure all of the exhaust connections are tight. An exhaust leak is also a sound leak. All it takes is backing over a high curb and you can snag the exhaust pipe and pull it loose. Happened to me at Fort Pickens campground; backed up just a bit too far and the wheel stop at the end of the campsite snagged the generator exhaust pipe.

Second thing is to add a resonator to the exhaust, right before the outlet. An Onan resonator provides a 3dB reduction. Which doesn't seem like much, but thanks to the logarithmic decibel scale, a 3dB reduction means the sound volume is halved.

That will help reduce the sound volume for listeners outside the van. For listeners inside the van, you're out of luck. Much of what you perceive as sound inside the van is actually vibration transmitted from the generator to the van's frame and from there to your body. There isn't enough clearance under the van to use vibration-damping motor mounts on the generator, so it's a solid bolted connection.

You have to be careful about adding more sound insulation to the generator's enclosure than it already has. It's very easy for the air-cooled Onan generator to overheat if you reduce the vent louvers at all, especially since the generator gets all of its air from under the van and vents its heat under the van as well. It's not like a larger motorhome where the generator vents are part of the van's sides or end panels.
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