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Generator and Coach engine exhaust merging.
I have what my wife says is an oversized exhaust pipe (talking about the coach now). And the generator exhaust pipe exits just in front of the large stainless coach exhaust tip. This does not look good and the little generator pipe blocks the large stainless tip. I want to run the generator exhaust into the back of the 8″ stainless tip so they are combined. The coach has a 5″ pipe and then goes into this stainless 8″ tip so there is room at the transition from 5″ to 8″ to insert the 2″ generator pipe.
Here is my concern,,,, if I enter at 90 degrees I think the coach exhaust will produce a vacuum on the 2″ generator pipe and possibly spin the turbo on the generator when not running. I was going to enter the back of the 8″ tip and then the 2″ generator pipe will be parallel inside the 8″ coach tip. Do any of you engineers know if the exhaust flow from the coach will still produce a vacuum if the pipe is parallel ? I plan to stop the 2″ generator pipe 3″ or 4″ from the end of the 8″ pipe so it will not be seen.
If no one is sure, I will tack the 2″ pipe in place and run the coach in place to see if there is any vacuum before connecting to the rest of the generator exhaust.
Just can’t leave well enough alone.
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13 Replies
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I would leave well enough alone. Why mess with something that works now, when you don’t know what will happen if you modify it? The amount of exhaust going out of the main engine will far exceed anything you will ever produce from the generator. Who knows what the combination of wind and exhaust flow does going down the road?
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Besides the exhaust from the generator getting all over the stainless coach pipe, I think the 2″ generator pipe looks like an after thought. Just my opinion but I like the looks of one pipe. I am not taking a chance, I plan to check out the modification before welding it in for good. also plan on stainless strap clamps to connect to the rest of the generator exhaust so it can be removed for repairs. The wind is hitting the 2″ pipe now so that will actually be protected inside the large pipe, my only concern is the coach exhaust. I think running the 2″ pipe parallel inside the large pipe will prevent a vortec effect but we will see.
I know,,,,,,, too much time on my hands, but I have always tried to have something a little different than the norm.
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Robert,
I have had two coaches with Generator exhaust in the main exhaust. They were both Freightliner Truck conversions, and were both new when I bought them in 2005. The main exhaust was extended way back and came out just in front of the drive axle. 5″. The gen exhaust was plumbed into it about 6 foot before the end. The connection was on a 90 degree straight in the side of the pipe. A 45 degree toward the exit would produce vacuum. Or the other way would produce pressure. The 90 must be sort of neutral. Probably pushing a little and pulling a little out.
The Generators were both 12.5 Powertech. I had no problems with either one.
Being you don’t have much length compared to the ones mentioned above, I would worry more about back feeding the Bus more than I would the Gen. especially as far forward as the Gen is. I.E. when the generator is running, and the bus is not?
Mine runs straight out the back, maybe you could do that. I have duals, one for the aqua hot, and the other for the Gen.
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Robert, Parliament used a custom exhaust tip that contained the engine, the generator, and the Aqua Hot. They used this designe for years and never heard of any problems or issues. My new to me 05 has this exhaust and its kinda neat every thing comeing out in one place, hope this helps.
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This is going by memory so take it with a grain of salt.
I seem to recall the late Don Hoffman of Hoffman coach merged the generator exhaust into the Prevost exhaust either at the muffler or slightly ahead of the muffler with the prupose being to add the coach muffler as additional sound deadening.
Personally I really do not see a problem as long as where the two merge, both exhaust flows are aimed in the same direction so exhaust from one is not backing up or pressurizing the other. At the time Don was doing that to his conversions I don’t believe the generators he was using had turbos. I suspect the generator is not going to have enough flow to create a vacuum and spin the engine turbo (easily checked on the 8V92) but the engine might have enough to spin a generator turbo. My only concern with spinning the turbo is unless the engine is running the turbo is not getting lubrication.
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Thanks all, I was hoping for the possitive feedback.
I thought this made sense and I must not be the only one that thought of it,,,,,, just have not seen it. Glad to hear it was incorporated in some other coaches. My Webasto exits up near the middle of the coach so I am not going to change that. It would be too far, otherwise I like that idea also. I am just tired of cleaning the coach engine stainless tip every time I run the generator due to the exits being so close together.
I know the folks at Parliament, in fact that is where we bought our coach. We are only 20 miles from them so I may take a ride and see if they have any coaches with this exhaust configuration.
Hope you all have a Merry Christmas and thanks again for the conversation.
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My only concern would be the turbo spinning without lubrication. It might not be an issue, but I would make darn sure before I did any modifications. FWIW…next time you see construction equipment being hauled on the road…many if not all will have the exhaust pipes covered to prevent that very problem. I know a guy with a construction company that hauls his own, and they either let it run, or cover the pipe. He has had turbos fail because of windmilling without lube.
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Its just amazing what I learn on this forum!
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Dick, The magic trick to this forum is to figure out when we are making stuff up.
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Yes Mark, That was my concern from the start,,,, I haul my own equipment as well and that is why I know about covering the exhaust when hauling. That is also why I intend to check it out completely before final connection.
It looks much cleaner now with just one large exhaust pipe and the 2″ generator pipe coming in back under the coach. Just waiting on check valve parts for the Raycor so we can run the coach and check it out.
What is the trick for posting pictures here ? I have tried to upload pics from my computer but after the preview comes up it just sits there and does not allow me to post.
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I thought of doing the same to mine but I go to sporting events where they require you to vent thte generator up to the roof line for safety of those around you.
Good luck.
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Hey Robert
Why not consider partitioning the exhaust tip, then running the exhaust from the generator through one partition and the leaving the remaining for the bus exhaust, that way the exhaust tip looks original expect for the two partitions.
Rob
91 XL 40
Missouri
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I was originally going to run the coach and generator exhaust out the roof but my rear Cruisair is right in the way. Almost bought a Wonderlodge just because they run the exhausts out the roof where they belong. If the skin on them were stainless that would be my choice.
As far as partitioning the tip, that is a good idea but I am not running a rectangle tip,,,,, it is 8″ Round. Just finished testing today and it works great,,, no back pressure or vacuum to spin the generator turbo.
Completed the install to the rest of the generator exhaust after testing the short pipe and the generator exhaust comes straight out about 18″ above the ground so we no longer will blacken the grass from the turn down tip it had.
Wish I could post some before and after pics but still having trouble posting pics.
Thanks to all for the ideas and conversation. Have a great ho
liday season.
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