Thor Forums

[Jim Jacobs]

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.