Remote Onan Exhaust - Extension

M

mark sawyer

New member
Aug 20, 2015
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Was considering setting up a sort of exhaust extension for the onan, to move the exhaust fumes farther from the coach to keep my wife happy. Was
thinking along the lines of welding a threaded collar onto the Onan Exhaust muffler outlet, and a female threaded collar onto a length of flex tube
similar to this:

https://www.amazon.com/Walker-40002-Exhaust-Tubing-Flex/dp/B000CQFQOM

Should be able to just screw it on like a garden hose when boondocking or whatever, then unscrew and stow when not needed.

Is anyone doing this already? Any opinions on if this is advisable?

I've considered the added backpressure that it will put on the engine, and if you go with a slightly larger tube, and keep the run below say 15', I
would imagine it would be negligible. Plan to monitor some exhaust/head temps with it uninstalled and installed to see how much it raises temps.
Would obviously also keep the tube out of leaf piles, etc. to prevent fires/heat damage to anything.


--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
There were some that have used this with success. I remember reading that here I think.

https://www.amazon.com/Camco-44461-Gen-Turi-Generator-Exhaust/dp/B000BUU5XG https://www.amazon.com/Camco-44461-Gen-Turi-Generator-Exhaust/dp/B000BUU5XG

Jared & Stefanie Kohl
Rappahannock County, VA
1973 Painted Desert "Onslow"

Was considering setting up a sort of exhaust extension for the onan, to move the exhaust fumes farther from the coach to keep my wife happy. Was
thinking along the lines of welding a threaded collar onto the Onan Exhaust muffler outlet, and a female threaded collar onto a length of flex tube
similar to this:

https://www.amazon.com/Walker-40002-Exhaust-Tubing-Flex/dp/B000CQFQOM

Should be able to just screw it on like a garden hose when boondocking or whatever, then unscrew and stow when not needed.

Is anyone doing this already? Any opinions on if this is advisable?

I've considered the added backpressure that it will put on the engine, and if you go with a slightly larger tube, and keep the run below say 15', I
would imagine it would be negligible. Plan to monitor some exhaust/head temps with it uninstalled and installed to see how much it raises temps.
Would obviously also keep the tube out of leaf piles, etc. to prevent fires/heat damage to anything.

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

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Get a piece of the silicone corrugated exhaust hose and you can coil it up and stuff it almost anywhere. Expensive, but worth it when you can use it
on the GMC exhaust if needed, working on vehicles in the garage etc.

https://smile.amazon.com/Crushproof-FLT300-Flarelock-Exhaust-Hose/dp/B004IQLRYK/ref=sr_1_2?ie=UTF8&qid=1496292188&sr=8-2&keywords=exhaust+hose

You can also find it in a smaller size, but that cuts down on usability for other temporary exhaust evacuation needs.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
The metal flexible exhaust is heavy and will not coil up into a very small space. Also, the moisture from the exhaust gets into all of the joints
(actually one long joint) and the corrodes the metal a little each time and makes the pipe stick in the shape it's in when the water finally
evaporates. It's ok for a strange bend in a fixed system, but unless it's stainless it won't last very long in that application either.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Only thing I'm concerned about with the silicone hose is the heat limit. Let me run the onan today and see what the temp at the exhaust outlet is.
I'd imagine at high load, the temps may be higher than the silicone would tolerate.

Also agree, stainless would be a better alternative to the galvanized, but I'd imagine would cost quite a bit...
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
Mark,

Have you looked up Gen-Turi?

One can be assembled for lest than the 100+ that they are sold for.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
One nice thing with the Genturi is the hot exhaust is mixed with outside air and the pipe temperature is greatly reduced. I have never use one.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> Mark,
>
> Have you looked up Gen-Turi?
>
> One can be assembled for lest than the 100+ that they are sold for.
>
> Matt

Thanks very much, Matt! No I had not heard of the Gen-Turi. Doesn't look like there's much to making one. I will definitely give this a shot.

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
Heat limit on the hose will never be exceeded by Onan or 455 under normal operating conditions. That's what it is made for. Those engines that belch
flame should probably not use exhaust "hose" :lol:
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
> Heat limit on the hose will never be exceeded by Onan or 455 under normal operating conditions. That's what it is made for. Those engines that
> belch flame should probably not use exhaust "hose" :lol:

I'll for sure keep them off my RX7s ;) Turbo rotaries especially run very hot. I see EGTs in the 1600 degree range on my 94. But I thought a piston
engine under load would still see EGTs around 1200 degrees? Always assumed those silicon hoses were more for idle and emissions testing... Not for
running extended periods under high load?

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
 
EGTs are measured in the manifold, and they are plenty high there, that's why smart designers use cast iron if they can to construct air-cooled
exhaust manifolds. A lot of heat is lost in the rest of the exhaust system.

Do not use exhaust hose for a permanent installation. It will hold up to the heat of full power exhaust from a V8 engine, but not continuously for a
long period. It will hold up to the Onan running continuously until the end of days if you use a hose larger than the exhaust pipe that will allow
extra air to enter. If you raise the output end it will draw air through just like the exhaust venturi. You don't seal the entrance end to the
tailpipe.

If the exhaust was hot enough to damage that special hose, you would never be able to run the Onan while stationary, as it would melt the pavement or
set the grass on fire.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
>
> One nice thing with the Genturi is the hot exhaust is mixed with outside air and the pipe temperature is greatly reduced. I have never use one.

The admixture of ambient air and exhaust definitely results in a cooler surface on the stack - but from a CO-poisioning perspective wouldn’t you want the stack gases to remain as hot as possible so as to be carried up and away from the coach to the greatest extent possible as they exit out the top? In cooler night conditions where there is little wind I can envision where they might come out the top and start heading back down to the ground as they are cooled by ambient air..

(Gen-turi or not, I keep two tested battery-powered CO detectors in the coach at all times for extra safety).

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
Jim,

I have to wonder which effect would dominate in the mixing of ambient air
with the CO: Temperature reduction or CO proportion reduction? And what
about the direction of the velocity vector, vertical vs horizontal?

One thing for sure: All the neighbors would appreciate it if I'd aim my
Troy-Bilt exhaust somewhere away from them! :-)

Since about the only time we fire it up is for lunch in a roadside
location, I haven't bothered to do anything beyond using two mufflers.

The detectors are unquestionably valuable in any case.

Ken H.

> >
> > One nice thing with the Genturi is the hot exhaust is mixed with outside
> air and the pipe temperature is greatly reduced. I have never use one.
>
> The admixture of ambient air and exhaust definitely results in a cooler
> surface on the stack - but from a CO-poisioning perspective wouldn’t you
> want the stack gases to remain as hot as possible so as to be carried up
> and away from the coach to the greatest extent possible as they exit out
> the top? In cooler night conditions where there is little wind I can
> envision where they might come out the top and start heading back down to
> the ground as they are cooled by ambient air..
>
> (Gen-turi or not, I keep two tested battery-powered CO detectors in the
> coach at all times for extra safety).
>
> —Jim
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
 
I grabbed a piece of scrap flexible electrical conduit from a job site I think its 1 1/2 about 5' long and slip it on the end of the tail pipe to
divert from campers next to us and from blowing dirt all over. It works perfect and you can lay it up over the rear bumper if heat concerns. We are
almost never on grass usually packed dirt so I just snake it on the ground to where ever is good. coil it up and stow. The added collar or venture to
help bring in secondary air would be a plus just haven't done that yet as I only use for short times while bringing the batteries up .
--
Tony Cook
77' Kingsley ' SuperSession 77 '
Torrance Beach,CA
 
Tony,
Look in our Onan sectio for an Air Deflector to avoid steering dust under
your unit and expelling heat away from intake.

> I grabbed a piece of scrap flexible electrical conduit from a job site I
> think its 1 1/2 about 5' long and slip it on the end of the tail pipe to
> divert from campers next to us and from blowing dirt all over. It works
> perfect and you can lay it up over the rear bumper if heat concerns. We are
> almost never on grass usually packed dirt so I just snake it on the ground
> to where ever is good. coil it up and stow. The added collar or venture to
> help bring in secondary air would be a plus just haven't done that yet as
> I only use for short times while bringing the batteries up .
> --
> Tony Cook
> 77' Kingsley ' SuperSession 77 '
> Torrance Beach,CA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
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