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Author Topic: 6/1 silencing  (Read 4857 times)

veggie

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6/1 silencing
« on: September 01, 2020, 03:37:35 AM »
Thoughts ?
I currently have 2 large automotive mufflers in a long 25 ft exhaust system on my Roid. (20 ft of that is outdoors)
The pipe is 2" diameter all the way.
It discharges into my back yard area. Almost silent but not to my satisfaction.
I am considering adding a 3rd large muffler at the end of the run.
Would this be too much back pressure for a Lister type?

cheers
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw

mikenash

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Re: 6/1 silencing
« Reply #1 on: September 01, 2020, 08:07:33 AM »
Veg have you seen the exhaust length/diameter chart in the CS installation manuals?  Someone will be able to reference it for you.  I suspect it might want to be fatter as it gets longer?

Also the various "buried" ones?  Effectively silent

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ajaffa1

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Re: 6/1 silencing
« Reply #2 on: September 01, 2020, 09:21:41 AM »
Hi Veggie, please see the text below cut and pasted from the listeroid 6/1 installation manual:

EXHAUST SYSTEM: A standard engine is fitted with an exhaust silencer. If the exhaust piping be extended to
the out side of the building up to a length of 3 meters, the exhaust silencer can be fitted on the end of iron
pipe screw 1 1/2 BSP.
If exhaust system is longer, following pipe size is recommended.
Pipe line: Up to 3 meter 38.0mm (1 , 4) Bore
3 to 6 meter 50.8 mm (2) bore
6 to 10 meters 63.5 mm (2) bore over
10 meters 76.Omm (3) bore
However, keep the exhaust system is as short as possible with a minimum number of bends and must be erected in
easily detachable sections to facilitate cleaning during overhaul. Never embed in concrete. A faulty system
can seriously reduce the power of the engine.

Bob

ajaffa1

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Re: 6/1 silencing
« Reply #3 on: September 01, 2020, 01:38:01 PM »
Hi Veggie, when I installed my ST2 startomatic the exhaust noise was way too much for my Wife. So I went and bought a dustbin, I dug a hole and dropped the bin into it. I connected the exhaust pipe into the top of the bin and fitted another flexible pipe to the bottom of the bin. I dug a trench about 20 feet long for the bottom pipe to sit in. I then surrounded the whole thing in concrete and put the top soil back over it all.

The exhaust is now silent, more than can be said for my Wife.

Bob

veggie

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Re: 6/1 silencing
« Reply #4 on: September 02, 2020, 05:52:49 PM »
Another way of reducing gas speed and increasing sound suppression would be to split the pipe and run another one with the mufflers in parallel rather than in series.  If practical, you could cut the pipe you have in half, put in a Y section with a Muffler on each end.

That's a good idea.!
I will look into doing that.

The system is very quite as-is, but neighbors and wife can still here a puff...puff...puff.
I don't mind it of course, but non-lister humans don't necessarily like it.

Digging a hole in my back garden is not an option at this time.
- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw

veggie

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Re: 6/1 silencing
« Reply #5 on: September 04, 2020, 03:38:24 PM »
Report

Ok ... I tried a third muffler but it hardly made any difference.
The whoosh ... whoosh ... whoosh noise is still prevelent due to the restriction in the mufflers and I don't think the added back pressure is good for the system.

The next thing I am trying is a large pressure dissipation chamber much like some others have done underground but mine will be above ground.
The plan is to use a steel garbage can lined with Roxul fireproof sound insulation. This will allow the exhaust pulse cool to dissipate before leaving the can with much less force.

Design issue !
The muffler is outdoor.
One concern I have is condensation and freezing. Here in the frozen north it is very likely that the engine will be running when the outside temperatures are -15C.
Does anyone know a 'rule of thumb' for how much exhaust water is generated per liter of fuel?
I can put a layer of sand/gravel in the bottom of the chamber and drill drain holes.

cheers
veggie


- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw

veggie

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Re: 6/1 silencing
« Reply #6 on: September 11, 2020, 04:48:51 PM »
Hi Veggie, please see the text below cut and pasted from the listeroid 6/1 installation manual:

EXHAUST SYSTEM: A standard engine is fitted with an exhaust silencer. If the exhaust piping be extended to
the out side of the building up to a length of 3 meters, the exhaust silencer can be fitted on the end of iron
pipe screw 1 1/2 BSP.
If exhaust system is longer, following pipe size is recommended.
Pipe line: Up to 3 meter 38.0mm (1 , 4) Bore
3 to 6 meter 50.8 mm (2) bore
6 to 10 meters 63.5 mm (2) bore over
10 meters 76.Omm (3) bore
However, keep the exhaust system is as short as possible with a minimum number of bends and must be erected in
easily detachable sections to facilitate cleaning during overhaul. Never embed in concrete. A faulty system
can seriously reduce the power of the engine.

Bob

That's interesting.
Both mikenash and your data do in fact state that the pipe diameter should increase as the run gets longer.
My thinking was that as the outdoor run gets longer the gas would get cooler and contract along the way which would negate the need for larger diameters. I currently use 2" pipe.

I am leaning towards the Garbage Can method suggested by ajaffa1.
Here's an example from our member rbodell... and his is only half buried.
https://www.youtube.com/watch?v=v1ZJ8e3ihZg

... I am also considering this one. It's interesting if you look at what happens when he added the top 2 tires.
They start bouncing slightly. Absorbing the exhaust pulse and taking away the energy.
https://www.youtube.com/watch?v=XZBL5R47E84

- 6/1 GM90 Listeroid - Delco 33si Alternator
- Changfa R175 - Lease/Neville Alternator
- JiangDong R165 Air cooled - 2 kw