Extending an exhaust system on a gas powered generator

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  #1  
Old 05-31-12, 03:47 PM
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Extending an exhaust system on a gas powered generator

Here are some images of my generator in question:

http://img.photobucket.com/albums/v70/DUNBAR/002-2.jpg

http://img.photobucket.com/albums/v70/DUNBAR/001-1.jpg



My plan with this generator is to install this securely inside of a covered trailer to provide a electrical source to fans and mist pump in a misting fan trailer.

I believe this 15 horsepower briggs & stratton motor is ported with 3/4" threads in the exhaust manifold.


My biggest concern is backpressure on the exhaust as I need to drill a hole through the floor and route this piping out of the trailer as it would never work exhausting into the closed trailer.

I'm positive that all 3/4" black iron would be a bad idea. I could use a 3/4" nipple off the exhaust manifold and increase to 1", even larger to make the first 90 downward as large as needed to be.

I was recommended this device at my termination point, unless of course this needs to be at the exhaust manifold immediately after it leaves the exhaust system.

Model 5S Mufflers


The constant moving of this generator in and out of the trailer is not going to happen. It needs to be secured to the trailer as this equipment is left at numerous events throughout the year and could easily be stolen as a result. If it is mounted into the trailer it can mist large crowds in parades which is what I'm also trying to do.

I have another generator that has a large box exhaust system that's so loud that you can hear it for a 1/4 mile and really needs to be quieted down. They make generators that do very well on the quiet front so I'm curious to know what ideas this forum might have to consider for this application.



The goal is to work this through the use of black iron pipe and fittings if it is possible without long term damage to the generator.
 
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  #2  
Old 05-31-12, 07:45 PM
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Hello DUNBAR PLUMBER,


I'm curious to know what ideas this forum might have to consider for this application.

Sorry to inform you, But that's a Generac GN410 engine you have and likely won't have threads in the exhaust port.

Any gen-set is subject to excessive vibration when running due to the rubber mounting, Adding heavy black iron pipe in long lengths can cause issues with exhaust flange mounting bolts.

I would suggest something like this guy did; Generac 7500 EXL

But, Instead of adding another muffler just add a extension pipe. I would also suggest the use of regular exhaust system tubing for lighter weight, Check with your local automotive muffler shops, They should have/be able to get and bend 1 1/2" pipe. With a extension pipe on your existing muffler you should be able to direct the exhaust from under and out the side of the trailer. Then you wouldn't need that high dollar resonator since you will still have the original spark arrestor screen.


Just my [ATTACH=CONFIG]851[/ATTACH]


Good Luck
 
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  #3  
Old 05-31-12, 07:56 PM
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My take would be to leave the extra plumbing out of it altogether and sit the unit (as OEM outfitted) so the exhaust would exit through a side panel in the trailer and use sufficient venting in to the cylinder heads and outside side to vent the heat from not only the muffler, but also from the head cooling. Since you're not talking about twenty four hour continuous operation, I would also use an auxiliary fan to help move the heat.

Really, the back pressure from the exhaust isn't as big an issue as getting rid of the engine/exhaust heat. You can just go over sized on everything. But that still isn't a tuned exhaust or one that takes into consideration the exhaust pulses relative to the intake system on the engine. The latter is what ever you take it to be in a generator engine like that. It's not like you're dealing with a performance racing engine, but those tuning aspects are still a part of the design of the engine. The type of modification you're describing would change that part of the OEM design. To say it would destroy anything would be another matter.

I would be in favor of leaving the OEM stuff in place and modify the cabinet for the generator to take care of the heat.
 
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Old 06-01-12, 05:27 AM
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marbobj pretty much covered what I was going to say. Also should be noted that if there is the slightest bit of exhaust leak or similar, you'll be now dealing with CO2 issues.

Would it be possible to run a dog house or cage outside the trailer?
I'm actually in the process of designing a dog house arrangement for my portable generator at home. It'll basically be a small enclosure that will protect it from the elements, keep it secured and reduce the noise of the unit a bit. That being said, it'll be heavily vented with grills on 3 sides.
 
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Old 06-03-12, 06:34 PM
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Thanks for all the replies.


That link was very useful, showing the exact model unit and how they extended the exhaust.


I got this far today, not very far. http://img.photobucket.com/albums/v70/DUNBAR/001-3.jpg


I'm going to pull the muffler off, weld a coupling onto outside of it, use 1.5" like the link showed and nipple out, then 90 down so it goes through the floor.

I'll probably collar the floor and figure out a way to get it through with some room to play.

I'll post my progress, hoping I don't blow massive holes into that muffler welding thick to thin.
 
  #6  
Old 06-06-12, 07:00 PM
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http://img.photobucket.com/albums/v70/DUNBAR/001-4.jpg

http://img.photobucket.com/albums/v70/DUNBAR/002-4.jpg

http://img.photobucket.com/albums/v70/DUNBAR/003-5.jpg

http://img.photobucket.com/albums/v70/DUNBAR/004-2.jpg

http://img.photobucket.com/albums/v70/DUNBAR/005-4.jpg

http://img.photobucket.com/albums/v70/DUNBAR/006-3.jpg

http://img.photobucket.com/albums/v70/DUNBAR/007-2.jpg <<< Unobstructed inside this fitting. It's 1.25" galvanized coupling. I grinded the galvanized coating off before welding.

Used a mig, I'm known for my gorilla welds but they are strong, good penetration and no leaks. I work well with thin metal, and this was a thick to thin application with no blowholes in the metal whatsoever.

I'm going to wire brush the rest of the muffler, cover it with a 5000 degree spray paint.

I bought a nipple, 90 that the inside diameter is still the same of the original opening. The plumber that I am is resorting to materials that I can easily utilize and this iron piping is pretty permanent. I don't think I'll be welding any connections, just doping up the threads and installing so I can break it all down in the future.

On the vertical, I was going to stud weld some 10-24 machine bolts, then tack one nut on the back side so it holds the 3" galvanized ductwork away from the pipe for a heat shield. It'll still get hot, just not as hot as the iron pipe.

Of course, I'm running out of time on this project. I wish I had more to do this but I work 3 businesses and my deadline is sunday to get this generator on the trailer and working.

If there's anything I need to take in consideration at this point, please let me know. I can do a lot of things now that I have a takeoff on this muffler to install anything I need to make it work.
 
  #7  
Old 06-07-12, 04:13 AM
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Hello DUNBAR PLUMBER,

Looks like your moving right along, I would suggest a rubber type automotive tail pipe hanger installed up under the trailer to help support the weight of this iron pipe.....


Good Luck
 
  #8  
Old 06-07-12, 06:27 AM
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You probably already know this, but the fitting looks like it's galvanized. Welding on that material gives off a lung damaging fume. Extra precautions need to be taken to avoid inhaling that stuff.

I know someone who did permanent damage to his lungs with it.

Take care.
 
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