Originally Posted by JackE
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.