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Old 04-03-2018, 12:10 AM   #1
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Brand: Thor Motor Coach
Model: ACE 29.2
State: Virginia
Posts: 22
THOR #9819
Thermo Tec Exhaust Wrap reduces sound 5db or more

We have a 2012 Thor ACE 29.2. Nice unit, but on a Ford F53 chassis, kinda noisy. We've been working on reducing sound levels, starting out at 80db upon purchase and now have it down to 66-68db while underway (60mph, freeway). The reason for the range of decibel readings quoted here is that the little app on our Android phone bounces around as it re-samples the sound ever second or so.

We installed new Bilstein shocks all around, and that helped some. We installed a steering stabilizer, and while that might not help a lot with sound, it is much more enjoyable driving. We installed Sumo Springs front and rear and that helped a good deal by taking out small "squeaks". Ride is noticeably better and the slide doesn't have an annoying rhythmic squeak anymore. We used felt and rubber pads throughout to take out other squeaks. To be able to talk, we ride with the bunk bed over the cab in the down position. We use sticky plastic pads, the kind used to keep cell phones in place, under the bunk bed supports which keeps it from rattling. In fact, we use those cell phone pads to keep lots of things in place while underway. They come in clear and black (Amazon). We like the clear ones. And we had the entire underside of the coach sprayed with sound proofing which is like double thick rust protection. Expensive ($1700), but looks great and its very unlikely to ever rust out. Unfortunately, only got 1-2 db reduction out of that.

So, we were very surprised when we obtained a 5-6 db reduction when we wrapped the exhaust pipes with Thermo Tec Graphite Wrap. Initially, we were looking for a way to reduce the possibility of vapor lock in our Onan 4000 generator. The generator location is just behind the driver's seat and the generator exhaust pipe comes out the bottom, then directly forward underneath the generator before turning to the outside. The air intake for the generator is directly above the part which turns outward, so the incoming air is pre-heated. This may be fine when driving through the North in winter, but posses problems when in the SouthWest, on a 110F degree day, on blacktop. Add to that, the fact that the Ford F53 exhaust coming off the driver's side manifold comes straight back towards the rear of the coach, making a turn to join the other pipe at just about the same place where the generator air intake is. This causes even more heating of the intake air. We bought a "heat shield" from Thor, which turned out to be a piece of sheet metal, 24"x36", with no holes, instructions or other words of mounting wisdom. When we asked Thor how to install it, the person we talked to said he didn't know. So much for that idea.

And that led us to a fellow we know at the local NAPA parts store. Unlike many in cities, this one is in the country and mostly services farmers and hot rod enthusiasts. Good thing, because he said we should use Thermo Tec's exhaust wrap, overlapping about 1/4" on each twisting turn. He assured us that he's used it for years on his rods and he races them at up to 140mph in very hot, Virginia conditions with no problems. So we tried it, and sure enough, after wrapping the generator exhaust, and running it for 30 minutes, while still running, I was able to take a hold of the exhaust pipe with my bare hand and it was just warm to the touch. Incredible, and no more pre-heating of the intake air. By the way, I used stainless radiator hose clamps every 6". They go on very easily using an impact driver and snug up much better than stainless cable ties. Further, their repositionable if needed.

After installation, I thought I noticed that the generator was running much more quietly than before. So I thought, "Why not wrap the main Ford F53 exhaust pipes which will both eliminate the pre-heated air for the generator intake and might give us a little more noise reduction?"

So I called the folks at Thermo Tec in Ohio and discussed it with them. They assured me that this is done all the time and if wrapped properly, it will not overheat the pipes. I could even start right next to the manifold if I wished.

So I bought the black graphite wrap, which is a little more flexible than the original brown wrap (which is what I used on the generator because that's what NAPA had) and the graphite makes it a little easier to apply. I later learned I could have soaked the rolls not to help make the wrap more pliable, but to keep down the small glass fibers which float everywhere. I had used a good face mask filter and very loose clothing, and I'm glad I did. I was still itchy even after a hot shower with those precautions.

Being chicken, I started a few inches away from the manifold rather than snugging it up tight, and wrapped all the way to the catalytic converter, which took all I had, 2 rolls, 2" x 25'.

While I thought there might be a small noise level reduction, what I was not expecting was a reduction from 64-66db to 56-58db at idle in the driver's seat. Even at 2500 rpm it's still only 60db. Of course, we're not moving so there's no road noise component, which is substantial.

I have ordered 3 more rolls and intend to wrap from the catalytic converter to the muffler, the muffler, and then to the outside, i.e. virtually the entire exhaust system. Maybe I'll get another couple of db, and Thermo Tec says I may even see a small increase in horsepower because hotter gases exhaust easier.

Now, I only have left to replace the original Continental tires. I joined FMCA to get the fabulous discount on Michelin tires and hope they will provide another few decibels reduction at highway speeds, though we've put a second layer of carpet under our feet, both driver and passenger side, and that helped, again by 1 or 2 db.

My next project is to install the weBoost cell phone amplifier. We have their 4G cradle version now and while it does give a 5-15db gain (1 sometimes 2 bars), it can still be inadequate in mountainous, rural areas. The new amplifier is rated at up to 50db gain, so we're cautiously hopeful it will be much better. But that will have to wait for another post.
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Old 04-03-2018, 02:07 AM   #2
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Brand: Thor Motor Coach
Model: Outlaw 29H
State: Tennessee
Posts: 1
THOR #11152
Thermo Tec Exhaust Wrap

Jim, thank you for your in-depth tip regarding the Thermo Tec wrap. I'll be looking into getting some for my rig.
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Old 04-03-2018, 07:33 PM   #3
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THOR #2544
Thank you Jim. I may have to give it a try on my 2015 Hurricane.
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Old 04-03-2018, 07:41 PM   #4
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Model: Outlaw 29H
State: Arizona
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THOR #10400
One thing I've noticed with exhaust wrap on motorcycles is that the pipes corrode/rust under the wrap. Some report cracking pipes too due to the increased heat that isn't dissipated.
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Old 04-03-2018, 08:21 PM   #5
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Brand: Thor Motor Coach
Model: 22FE
State: New York
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THOR #5330
I agree with you 100%. I also have a friend who is an Onan generator service tech and his reply to using any type of exhaust tape or isolating the generator compartment is you will void your warranty. Now I'm going to get reamed by that statement by the RV Gods but that is what I was told. He said the only thing Onan will accept as an add on is the exhaust being extended up the side of the camper and even that they frown upon because it changed the dynamics of the backpressure.
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Old 04-03-2018, 09:45 PM   #6
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Brand: Thor Motor Coach
Model: ACE 29.2
State: Virginia
Posts: 22
THOR #9819
Your Onan generator service tech friend is probably right. "Anything" one does to make any changes to anything will likely void the warranty. It seems to be the way all companies are headed these days, and one of the two reasons we bought a gently used, 5 (now 6) year old unit. I have nothing to lose by making modifications and lots to gain.

That said, I'm willing to gamble because mine is a 2012 unit. The generator is already past the 3 years they warranty, and they won't sell an extended warranty at this point because the original period has lapsed.

One of the things I noticed while testing the unit after wrapping the pipe was that it was considerably more "steady", even with the AC on as a load. The engine firing rhythm was very regular, something that was not always true before wrapping. It may have nothing to do with wrapping, since I have recently dumped a few cans of Sea Foam into the gas tank.

I have also wondered if I could put a small, downward facing exhaust extension on the end of the generator exhaust pipe. As it is now, the exhaust blows straight out and is noisy, but below the 60 db federal park limit at 50 ft. In fact, ours is now 55 db at 10 ft., but it seems to me that a slightly curved, small extension which pushed the sound into the ground would make it even quieter at 10 ft., probably something like 50 db, which is pretty near normal conversation level.
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Old 04-04-2018, 09:07 PM   #7
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Model: 2013 31L
State: Florida
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THOR #908
hmmm...maybe another project for me.....
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Old 04-04-2018, 10:30 PM   #8
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Model: Tiffin Wayfarer 24 BW
State: New York
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THOR #8860
I wouldn't even mind tackling a project like this...
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Old 04-04-2018, 10:36 PM   #9
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THOR #9721
In a younger, previous life I modified cars for performance. As mentioned prior in this thread, that wrap can cause an issue where it will warp, rust and crack the pipe underneath the wrap especially closer to the engine heads.
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Old 04-04-2018, 11:01 PM   #10
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THOR #8860
So the question becomes: "How quickly will that exhaust rust out?
(And how expensive is it, to replace?")
Okay: Two questions...
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Old 04-04-2018, 11:51 PM   #11
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Brand: Thor Motor Coach
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THOR #9819
That's an excellent question. How fast will the wrap damage the pipe(s) underneath? I plan to call Thermo Tec tomorrow and ask them. They do have a spray (can) which they said helps close the pores and bind the wrap material together better, but they said it was optional. It doesn't help with heat dissipation. I asked about what happens to the wrap when going down the road and it gets wet from rain and road spray. They said the water evaporates very quickly on account of the heat and it does not damage the wrap in any way. I didn't ask about salt spray from de-icing the roads. I wouldn't be surprised if the salt clings to the wrap helping to initiate corrosion. I will see what they have to say.
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Old 04-06-2018, 03:50 PM   #12
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Brand: Thor Motor Coach
Model: ACE 29.2
State: Virginia
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THOR #9819
I called Thermo Tec this morning and asked them about corrosion and splitting of pipes.

They said that they have encountered split pipes when the wrap is put on too thickly. They recommend overlap of no more than 1/4" (and I've even suggested to them that they add a stripe using some non-combustible material such a chalk which would help gauge the wrap overlay). The overlap is necessary to keep the wrap uniformly on the pipe. The problems have arisen when people have double wrapped pipes and retained too much heat. Their instructions are very clear not to do that, but apparently some people have done it anyway.

Usually, according to them, this occurs when someone has a hole in a pipe already and tries to use their wrap to fix the hole. This, invariably, doesn't work. Keeping the extra heat at that point causes the pipe to crack even further.

As for corrosion, they have not encountered that. They have encountered light rust, which they feel does not cause any problems other than being unsightly. When I asked about water retention, they said that as long as the wrap is applied with a 1/4" overlap, most of the material is of a single thickness and dries out very quickly on account of the heat.

Their other suggestion is to spray the wrap with their high heat coating, something they list in the instructions as "optional". This both helps seal the wrap and keep it in place better. They recommend re-coating it every year or two, depending on how it looks. I will probably get a can or two of the spray and try it, though keeping it from over-spraying while crawling around under our MH in tight quarters may prove challenging. The biggest problem I'm likely to encounter is the fact that the wrap is black and the spray is black, so I will likely not get as good a coating as I would if I had used the light tan wrap and then sprayed with black.

The reason, in case I didn't mention it before, for the black wrap is that it contains graphite which allows the wrap to be more flexible. Installation is easier. Having worked with both the original tan wrap and the black graphite wrap, I can say that the black is easier to apply, though not as much easier as I had expected, i.e. the black wrap is still pretty stiff. I plan to wet it for any future applications, at least to keep down the fiberglass particles and perhaps to help make it more pliable.

I also asked them how long the wrap will last. They said 3-4 years is reasonable, especially if sprayed, but that one of the techs at their company has a pickup with wraps all the way to the manifolds and he's been using it for the last 6-7 years with no difficulties (so far). I took that to mean, "no corrosion" and "no split pipes", but I didn't specifically ask if that's what they meant.

Given what I know (and don't know) at this point, and given my mania to make the MH quiet enough to hear my wife talk to me without shouting while driving at 65mph on an interstate (which is mostly what we do), I've decided to finish wrapping the exhaust system all the way to the tailpipe.

Wish me luck.
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Old 04-06-2018, 05:30 PM   #13
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Model: Tiffin Wayfarer 24 BW
State: New York
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THOR #8860
The best of luck to you! Please let us know what the results are.
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