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Old 10-11-2020, 06:40 PM   #21
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I can take a picture next time i am there. i think all modern transit busses are this way. do not understand why school buses are not outfitted like that.
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Old 10-11-2020, 07:16 PM   #22
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I can take a picture next time i am there. i think all modern transit busses are this way. do not understand why school buses are not outfitted like that.

at least rear engine anyway.. having hot pipes run up the outside of a bus where kids run around seems like a bad idea for a modern FE school bus.. but the transit busses the pipes run up the inside of the engine compartment.. I dont think they ever go up inside the cabin..
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Old 10-12-2020, 02:30 PM   #23
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This subject has really got me thinking. My wife has asthma and I had a significant CO exposure which has made me less tolerant to CO gasses. Getting the exhaust up out of the way would benefit both of us, and the nice paint job on the Charger I will be towing.

I'm entertaining different ideas in my head. Wondering why exhaust pipe is always round. Is there a significant difference with exhaust gasses flowing through a 4" round pipe vs a 2"x6" rectangle pipe? I'm kinda envisioning a flattened out pipe running up through the wall and out the top. With the way I'm planning on rebuilding the rear wall it wouldn't be too difficult to incorporate something like that without significant impact to the living area.
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Old 10-12-2020, 02:58 PM   #24
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Round pipe is cheaper and easy to bend/ clamp / and replace.. city busses often have square exhaust tips so I don’t see why exhaust has to be round..
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Old 10-12-2020, 03:21 PM   #25
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Originally Posted by cadillackid View Post
Round pipe is cheaper and easy to bend/ clamp / and replace.. city busses often have square exhaust tips so I don’t see why exhaust has to be round..
Round pipe is used because it is easier to bend into shape. Exhaust gas flows easier through a round pipe than a square pipe.
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Old 10-12-2020, 04:56 PM   #26
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just compare the max heated air flow through a 4 inch pipe CFM and figure out a square ducted size that will handle that cfm.
i can help with that if needed.
ductulator or duct calculator or two available online
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Old 10-13-2020, 06:02 AM   #27
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Originally Posted by JackE View Post
This subject has really got me thinking. My wife has asthma and I had a significant CO exposure which has made me less tolerant to CO gasses. Getting the exhaust up out of the way would benefit both of us, and the nice paint job on the Charger I will be towing.

I'm entertaining different ideas in my head. Wondering why exhaust pipe is always round. Is there a significant difference with exhaust gasses flowing through a 4" round pipe vs a 2"x6" rectangle pipe? I'm kinda envisioning a flattened out pipe running up through the wall and out the top. With the way I'm planning on rebuilding the rear wall it wouldn't be too difficult to incorporate something like that without significant impact to the living area.
The square and rectangular exhaust tips you see on a lot of performance vehicles are purely shaped that way for looks. For reasons already mentioned here, the actual piping throughout the lion's share of the exhaust system has always been and will always be round. While it's certainly doable to make rectangular ducts that will hold up to the abuse, it largely is counterproductive due to the turbulence it would create, although it does create an interesting means of creating backpressure for the purposes of keeping turbochargers spooled.

For those who have said to simply run a stack up the rear of the bus, here are five reasons that will not be safe or practical.

1) Potential to block emergency exit door
2) We are likely to grab on to that exhaust pipe if we have to use the emergency exit door.
3) Potential heat damage to plastic light lenses / block their visbility
4) Potential to block an RE's engine bay door
5) It likely will look tacky or cheesy -- we have enough people looking down their noses at our rigs.

Anyway, here are some crude images of the idea I have. I was looking at an image of the rear of an RE Blue Bird and noticed it had a bit of an inward slope above the window line on the rear wall that Thomas-built buses don't seem to have, at least not as prominently.

The bus pictured here also appears to have some kind of vent just forward of the slope -- not sure if this is to vent heat from the engine compartment or what. I do not believe it is a cabin air vent or intake, but if so, it should probably be blocked off with a solid steel patch panel or something.


This slope would possibly make a vertical exhaust nearly impossible to securely mount as it goes higher, as well as the other issues already mentioned. Not to exposing them to risk of damage from exhaust heat. So I came up with the following idea...

Cut a length of pipe long enough to reach from below the floor to above the roof, and large enough in diameter to stick the exhaust pipe inside with about 3" diameter clearance (3-inch exhaust - use a 6-inch pipe. This will give about 1.5-inch clearance around the exhaust pipe to allow for heat wrapping the pipe -- which will keep the heat inside the pipe and minimize heat transfer to the body.

Next, cut this length of pipe in half running along its length, creating a long curved channel. A perfectly split symmetrical cut is not necessary, but will allow for a mistake the first time.

Now, measure the full width side-to-side (NOT length). Measure and cut a section matching this same width, out of the body side just forward of where this slope meets the roof, from the roof to the floor.

Next, weld the channel made from the piece of pipe in place of the removed section of body paneling. You CAN recess the channel and exhaust pipe further into the wall, just be sure to allow for enough clearance to prevent rattling / rubbing, and you'll need a bit of sheet metal to deepen the channel walls.

Make sure to cut a hole through the floor that matches the inner curve of the channel that has now been created, and properly seal all mating surfaces and welds. This will allow the exhaust to be routed from underneath the body to meet the vertical exit pipe, and prevent water and exhaust leaks. It might be a good idea to weld in a bit of extra metal with a slight angle downward at what was the floor surface to facilitate outward rainwater drainage. Better yet, create the channel all the way down to the bottom of the body skirts.

Apologies for the crudity of these images, but I was creating this on-the-fly by modifying existing images for the purposes and do not have the sophisticated editing software necessary for better results. However, I think the point should come across easily.

Here is a crude idea of what the modified area should now look like...


Now imagine a heat-wrapped vertical exhaust pipe nestled into this newly created body channel... Be sure to extend the pipe a foot or so above the top roof line to allow the exhaust to travel far enough away from the windows. Keep its height in mind when driving, however.


Also, keep in mind the image of the exhaust stack I pasted in is pointing at an awkward angle -- pointing an angled tip toward the rear or inward toward the roof center, but away from emergency hatches or A/C's would probably be best. Or, use a straight-cut pipe with an exhaust stack flap like the one shown, likely a better idea to prevent rainwater buildup in the pipes that can back up into the turbo and the engine.


Voila! You should now have a vertical exhaust exiting above the roof that solves the problems discussed in this thread, though I would probably remove and cover over the windows fore and aft of its position to prevent accidental exhaust gas entry.

Also, note that the image with the stack pasted in is inverted -- You may notice it appears to be right-hand-drive. This could be done for either side, but for hypotheticals I wanted it to appear to be on the passenger side, but it is technically on the driver's side.
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Old 10-13-2020, 07:07 AM   #28
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Quote:
Originally Posted by o1marc View Post
Round pipe is used because it is easier to bend into shape. Exhaust gas flows easier through a round pipe than a square pipe.

I did an air study for HVAC on square / rectangle vs round ducting.. and in a straight pipe the flow was equal when the same exact area and airflow / oressure was applied..



when it came to bends, round beat the square hands down.. using rounded bends in the square pipe helped greatly. the flow difference with just a couple bends in a medium static-pressure application (0.75 - 1.25 in / h20) was somewhat close when using true rounded bends (inside and outside was rounded). with low static pressure ( < 0.75 in / h20). the difference was fairly significant..



im not sure what the average exhaust pressure is in a diesel however im guessing the pressure is high enough that if you install a round baffle on the outside corner of any bend you likely can do just fine for flow.. cant be any worse than the newer engines with DPFs and multi-pass mufflers..
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Old 10-13-2020, 09:35 PM   #29
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I guess there's been enough activity today the thread dropped off the "new posts" list -- Any thoughts on my solution?
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Old 10-14-2020, 06:29 AM   #30
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When I was in Alaska school busses had a stack on the rear corner of the bus i was told they needed it for the colder climate to keep from hazing out the other cars in traffic.
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Old 10-14-2020, 04:30 PM   #31
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Well thought out. One thing to bear in mind is that if you put insulation between the exhaust pipe and the housing, you will want to have some air gap between the outside of the insulation and the housing or make sure you seal the top of the housing so that rain/snow can not get into the housing. Some sort of silicone gland like we put wires through when piercing the roof.
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Old 10-14-2020, 05:34 PM   #32
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Well thought out. One thing to bear in mind is that if you put insulation between the exhaust pipe and the housing, you will want to have some air gap between the outside of the insulation and the housing or make sure you seal the top of the housing so that rain/snow can not get into the housing. Some sort of silicone gland like we put wires through when piercing the roof.
Or possibly weld a shield onto the top stack mount where it would mount to the roof (needed to stabilize the top of the stack). And the heat wrap I feel is really necessary, otherwise you are risking a fire from overheating insulation inside the wall around where the stack is nestled in.
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Old 10-14-2020, 05:53 PM   #33
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The vent on the side up high that you reference is the intake location for the engine. Probably not a good idea to cover it up!
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Old 10-14-2020, 05:54 PM   #34
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The vent on the side up high that you reference is the intake location for the engine. Probably not a good idea to cover it up!
If that's the case, then no harm, no foul. I just mentioned that on the off chance it might be a vent or fresh air intake for the cabin.
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Old 10-15-2020, 12:37 PM   #35
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575+ views and only one person sharing their thoughts? o-0

Food for thought, folks, exhaust, especially diesel exhaust, is known to cause asthma (and worse) as well as trigger it. I think everybody owes it to themselves to do this.
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Old 10-15-2020, 01:29 PM   #36
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As far as lining the chase (or wrapping the inner pipe) with insulation -- another approach is to leave the space open and vented to the exterior. If air can freely move through then there'll be convection currents that carry the hot air out the top. That won't prevent radiant heat transfer from the exhaust pipe to the chase wall, but I suppose the airflow would provide convective cooling to get rid of some of the heat that got into the chase wall by radiant transfer. I like the idea of designing for some air flow through there so that any moisture that gets in can easily dry out.
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Old 10-15-2020, 04:48 PM   #37
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Sorry Cheese, I am just another lazy reader! I thought of doing the same if not just to keep the dirty exhaust up and away. The Wanderlodges somehow do it but I never got into how they did it. I don't think it would be cost effective in my case and would lose a little interior space to create a metal wall for the pipe going through the corner. Like most readers on this thread, we are hoping for pictures from someone who actually completed this modification. Incidentally, I have Sarcoidosis. Need to thank my parents for many many years of them smoking in closed environments until I got migraines.
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Old 10-15-2020, 05:48 PM   #38
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Like most readers on this thread, we are hoping for pictures from someone who actually completed this modification.
I think the best we can hope for as far as pics is to hear from those who have attempted a rear stack extending from the factory pipe in or under the bumper. No offense to those who have done this, but I think most of these are risking being snagged on their surroundings or burning passersby.

And no offense, but the aesthetics on these setups leave a lot to be desired as well, and I think this method actually uses more pipe than would really be necessary. Not to mention having to get creative to avoid blocking an RE's service bay door or obscuring tail lights from view or exposing them to heat damage.

I'm interested in seeing joeblack's setup.
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Old 10-15-2020, 06:41 PM   #39
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a not so cheap option for exhaust insulation.
but is not that expensive to cover a safety issue is a fire /blanket/wrap insulation.
many manufacturers and suppliers but they all meat the intent.
look at 3m fire wrap.
it is a ceramic fibre wrapped in a jacket that is rated for high degree temps.(caint remember exact) but just research fire wrap insulation.
is normally used to wrap exhaust hoods.grease duct and i have used it in hospitals to wrap emergency/backup generator power conduit and elevator power conduit.
3M is one but of course hilti.
specseal,metacaulk meet the same specs but are cheaper because you are not paying for the name.
years ago i wrapped part of a header and a little bit of exhaust with some because the starter was getting hot and it did the job but the ASJ (all service jacket) didnt like being exposed to the weather.
if anyone chooses this route?
PPE is adamant from an experienced installer perspective.
long sleeve shirt
safety glasses
face mask
pants/not shorts
socks in your footwear that are covered by your pants.
i would say a hat or hard hat because i wear both for a living but this stuff sucks if you get it into the nooks and crannies.
it is a very fine ceramic fibre but is only exposed when you cut it to fit before resealing the blanket just before install.
read the specs for what you choose.
most i think can handle 2-3000 degrees.
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Old 10-15-2020, 08:38 PM   #40
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I was doing some welding today and went to look at my exhaust setup. Even if I wanted to run the stack through the inside corner of the bus, the air filter intake would be in the way. The exhaust and air intake are both on the same side. I don't think it would be economically feasible in my case.
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