I have a couple issues with the exhaust system on my bus. It all started with the tailpipe. I knew that it had fallen apart behind the rear wheels and was just tied up to the frame. I finally got under the bus and pulled the pipe out so that I could clean up the ends and have the end expanded so that I could weld it back into place. Unfortunately, as soon as the muffler shop started to expand the end of the pipe, it split! The pipe had way too much rust inside. I measured the pipe and it is 2.75" pipe. Of course I cannot find anyone with that size pipe locally, I can find 2.5" or 3". I decided to look underneath again to see how hard it would be to weld a 3" pipe onto the over-axle pipe that was still in place. Upon inspection I found that the front of that pipe, where it connects to a straight section going forward to the muffer was barely hanging on by a sliver of metal. I unbolted this section and it fell right out. Now I have no tailpipe, and no over-axle pipe on the bus. Again I found it full of rust and soft spots all over in it. This pipe was also 2.75". The strange thing is that someone replaced the straight section from the muffler towards the rear with 2.5" pipe. The muffler appears to be okay, rusty, but seems intact and no holes. The pipes from the manifolds are 2.5" pipes with rust, but again, no holes and seem okay. This leaves me with a few options:
1) Cut the pipe off at the exit of the muffler, put on a 3" elbow and 3" pipe out the left side of the bus
2) Cut the pipe off at the exit of the muffler, run 3" pipe back and out just in front of the left rear tire
3) Leave the 2.5" pipe in place and add an elbow and exit with 2.5" pipe out in front of the left rear tire or
4) Have a new over-axle pipe made and run new 3" pipe from the muffler to the rear bumper (expensive!)
The engine is a Ford 370 on Propane, so I don't want to do anything that will decrease my fuel economy. Of course with that long section of 2.5" pipe after the muffler it may be choking it off as it is. Factory pipe was all 2.75" past the muffler. I am thinking 3" pipe would be a better choice, especially if I keep a long run of pipe. Also, is it important to exit the exhaust at the rear, or is it just fine to exit out the side? I need to keep the costs down as much as possible and have been quoted about $15/foot for new 3" pipe and $14/foot for 2.5"