Engine Exhaust Through The Roof

zimmysurprise · April 06, 2016, 03:24:53 PM

Walter- although your idea is one I agree with, it's unlikely I would ever undertake the fabrication myself. That being said- it has crossed my mind. With my GM and 8V71, the exhaust manifolds terminate on the driver's side, then drop to a corkscrew around the oil filter, pop into a muffler located in an inverted barrel that I can only see 15% of, then twist back out of the hole to end within 3 feet of the exhaust manifolds. The amount of heat retained under the bus is crazy to me, especially with all the fear of rear mounted 2 strokes running hot.

In my warped mind, a thick walled steel "chimney" open on the top and bottom with a standard vertical truck muffler would stay as cool as what I have stock. Wrap the 10" pipe with fire rated insulation then build around that with a fireproof enclosure and it would be as safe (or safer) than the drum muffler I couldn't get to if it did start a fire. I'm not sure what the reasoning was for containing it underside- another passenger seat?

Lostranger · April 06, 2016, 03:52:38 PM

My exhaust exits through the roof as is has from new. Was originally parked beside the air handler, but the factory HVAC has been removed. I replaced the original muffler with an inexpensive truck muffler last spring.

As usual, TinyPic rotated my photo 90 degrees left.

Completely happy with the truck muffler, and it cost a fraction of the one sold by Gillig.

Jim in NC

DoubleEagle · April 06, 2016, 05:48:05 PM

This thread has generated more interest than I expected. It looks like there are a lot of us that would like to do it, but have not completely figured how. Don's idea of a chimney is sound, there has to be a place for the heat to rise out of the area just like Jim's Gillig setup. The transits have devoted a lot of space and hardware to set their exhaust up, but as Crabby noted, some of the heat still radiates out. There was some company that advertised in Bus Conversions years ago that had a heat insulating pipe wrap, and another company that had a manifold ceramic paint that claimed heat reduction. There might be improvements in such technology for keeping heat inside the pipe. As Tom mentioned, some have added an external pipe on the outside of the bus, but that would require some heat shielding for pedestrian protection, and since most of the buses are somewhat curved, I have the opinion that it would hurt the aesthetics of the bus. JC brought up a point that is very important and is one of the reasons I considered roof exhaust in the first place - the kicking up of dust and dirt when you go into a non-paved area. (Our radiator fans and some A/C units can as well). Passenger buses stayed on pavement most of the time, but we go everywhere. On my 8V71 05 Eagle, which had a Series III Land Rover behind it most of the time (back in the nineties) I had the dual exhaust pipes extended horizontally to each side of the coach just below the bumper with chromed curved tips. I could see the exhaust in my mirrors, they were aimed straight back so there was no dust kick-up, and the exhaust missed blasting the Land Rover. I went that route because I had two four inch pipes to work with right there, and the radiator expansion tank above the engine blocked any clean path to the roof. The newer engines have less smoke in the exhaust, but my mechanical 6V92 has plenty of smoke that chokes people if their car is behind me when I take off, so I would still like to exit the roof, but it is going to require some deep thought to pull it off safely and look good.

Scott & Heather · April 06, 2016, 07:00:21 PM

I can't say for sure we will have the time to do this, but I want to have a stack fabricated for our 102C3 this summer. Our situation is unique in that our 102 has a flat back conversion done during the roof raise. So this might help a little. The issue for us is clearing the side mounted radiator....not sure exactly how I'll do that but I'm tossing around ideas.

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DoubleEagle · April 06, 2016, 07:11:57 PM

Quote from: Scott Bennett on April 06, 2016, 07:00:21 PM
I can't say for sure we will have the time to do this, but I want to have a stack fabricated for our 102C3 this summer. Our situation is unique in that our 102 has a flat back conversion done during the roof raise. So this might help a little. The issue for us is clearing the side mounted radiator....not sure exactly how I'll do that but I'm tossing around ideas.

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Scott, looks like you have the potential of at least one vertical stack once you clear the radiator. I found a potential source of heat shield wraps at heatshieldproducts.com. One insulated pipe inside of another insulated pipe might do it.

RJ · April 06, 2016, 11:43:57 PM

GMC Fishbowl transits had a three-piece rear window. One center large section, flanked by two smaller pieces on each side. This arrangement made it easy for them to offer what was called their "Clean Air Package."

As you can see in the photo below, the RH rear small glass was replaced with the engine air intake. The LH small glass's removal allowed for the vertical exhaust. There were modifications inside the coach to accommodate these exterior changes that consisted of 90^o curved metal panels that went from the side of the coach to the engine cradle/rear window vertical support posts. These curved double panels were well insulated and sealed to prevent any type of leakage.

FWIW & HTH. . .

TomC · April 07, 2016, 12:29:23 AM

My similar exhaust through the roof on my AMGeneral.

DoubleEagle · April 07, 2016, 06:13:37 AM

Quote from: TomC on April 07, 2016, 12:29:23 AM
My similar exhaust through the roof on my AMGeneral.

Tom, you had said before that you got some soot buildup on the rear. It looks like your pipe is pretty well up over the roof, it must mean that the rear vacuum draws the exhaust down to swirl the back. I wonder whether it makes much difference where the exhaust exits as far as the soot problems go. You definitely will not stir up dust. Does the soot buildup occur evenly across the back, and is it a slow buildup over weeks or sooner?

TomC · April 07, 2016, 07:17:10 AM

Soot builds up in a matter of a few days. But-it does wipe off with a dry cloth very quickly (about once a week). I do get black smoke (even with a fuel modulator running off my turbo boost) on take off. It is pretty even in the back. I imagine there's some oil mixed in also. Good Luck, TomC