The flex pipe starts right where the stack meets the saddle tank. From there, it is flex pipe all the way to the back of the generator. I don't forsee that as being an issue.

 

Well, my 2 cents. Everyone that I've talked to that did a pipe like yours up the back of the cab broke off pretty quick. They also had flex pipe but it's not made to be bent back and forth non stop. It's meant to turn a corner or conform to some odd angle. If you continually bend any metal it will break.

As far as the noise from your unit. Any time you increase or reduce the size of a pipe you change the sound big time. Just putting a stupid azz chrome end on your mothers Toyota muffler will make it louder because it's a bigger diameter.

If you want to make a car quiet you run a pipe as long as you can to the rear and put the muffler as close to the end as you can.

If you want to make a car sound deep and throaty you run a short pipe from the engine, then the muffler then a long pipe all the way to the rear.

If you want to make your Autsin Mini Cooper sound like a screaming banshee you run a 3" pipe from the engine down to a 2" pipe then down to a 1 1/4" pipe to the muffler. This is the same principle as strip mining.

So.....to make an APU as quiet as possible you need to run a pipe from the engine as far as you can before putting a muffler on. Also, do the change of diameter as close to the engine as possible so the rest of the pipe is the same size all the way back.

One thing I have on you Rev is my age and back in the 70's we tried everything to make our Ford Country Squire station wagon sound like a dragster. The only things at our disposal was Cherry Bomb and Thrush mufflers so we experimented with all configurations.

 

Relocating the muffler isn't an option. The diameter change is done directly behind the engine, and stays at 1 1/4" ID the entire way.

I do believe you are correct, however, about the pipe not being able to withstand the movement, because I went to fire up the generator for breakfast this morning, and found that the elbow had snapped off the muffler tail pipe right at the back of the engine. What I don't get is how the stacks for the truck's engine can handle it, but this can't. There is still plenty of tail pipe left for me to repair, however. If I have to relocate the exhaust (again), I will.

 

And one last question. Have you thought about turning a rooftop unit sideways? Doesn't matter which way it's pointed.

 

Yes, and there still isn't enough height with the wing.

 

How is exhaust mounted? Solid? The exhaust for a Pete has two sets of rubber isolating bushings. One set at the top of the muffler and one set at the bottom to reduce the vibration.

 

If you think about the exhaust like a seesaw the end moves up and down a lot and the closer you get to the center the less it moves.

 

I guess I didn't really expect that the sleeper moved all that much, but it's pretty clear to me that I need to run the exhaust along the frame somewhere, since the box is mounted to the frame. If I have to run it out under the trailer, I will - even though I don't want to. All I know is that it didn't work where I had it mounted before (on the side of the box).

 

A much better grade of flex pipe, almost always made of stainless steel, plus less movement, the pivot for the cab is at the firewall, the stacks are only a little further back, anything behind the sleeper is almost twice the distance and will then flex twice as much.

Flex pipe usually lasts maybe 2 years on the exhaust, at least for me it does.

Bigger pipe= more noise.

 

I had Meinike muffler install my muffler for $135. I don't have that much room but they bent the pipe and welded custom brackets along the way. The muffler was mounted sideways in the very back with the exhaust pointed towards the back. Keep in mind you only need like a 3" space here and there all the way back to route the pipe. Those muffler shops are masters at bending and routing.

If only you have them make a pipe your way ahead of the game. They also had to make a custom pipe to connect to my engine. There wasn't any thought at all to any of this for them. It was all second nature and they've done this type of work a million times.