Sound deadening the Challenger - Let the project begin

[EA37TS]

I'm going to start trying to reduce the noise inside the Challenger. Although the Challenger is not plagued by some of the issues experienced by others I see some areas for improvement. I hope to reduce the sound level inside the coach by 10 percent.

Today, before the project begins, I took some sound level readings while seated in the driver's seat. The readings are as follows:

Engine not running - peak level 46db. (see note below)

Engine idling at ~ 750 RPM - peak level 65db

Engine running between 1750 and 2000 RPM - peak level 75db

Based on the Galen Carol audio chart the sound level with the engine running is somewhere between a normal conversation at 3 feet and a telephone dial tone. The chart can be found at the following link

Decibel (Loudness) Comparison Chart

Today or tomorrow I will order the material to reduce sound and insulate the engine cover (doghouse) and the area under the dash which is accessible through the hood. After this I will again take the readings before moving on to phase 2 (the exterior of the floor pans).

A couple of interesting notes:

One thing I found interesting is while sitting in the driver's seat with the engine off road noise would create sound level averages of 70db and peak higher than 80db. The road noise level while standing outside my coach (standing at the front end of the coach) would average ~ 90 db and peak at 105 db (the truck guys with the magna flow exhaust systems). My coach, parked in my driveway, is 350 feet from a two lane rural road with a 45 MPH speed limit.

Due to the ticking clock in my home office, and the pendulum on the chime clock in the foyer, the sound level in my house is between 48 and 52 db. It appears to be quieter sitting in the coach than it does sitting in my house.

[EA37TS]

Decided to pull the engine cover (doghouse) and have a look see.



There is some insulation, more like heat shield, that covers the inside of the engine cover relatively well. For this area I am considering adding some Dynamat Extreme for sound deadening and then some Dynamat or FatMat 3/4 inch hood insulation. Also, I plan to swap out some screws. It is not very clear in the picture but right in the middle of the cover there are two screws that protrude through about 2 1/2 to 3 inches. I may need to pull the tray panel off the top to get access to these screws and to determine why they are there in the first place.



Looking at the engine compartment I saw a couple of interesting items. First, when looking at the vinyl flooring there appears to be some form of sound deadening material between the vinyl and the floors solid surface.

Second looking at the picture from the upper right corner of the engine bay running towards bottom center there is a bulb seal which was not installed correctly. When I tried positioning the seal I found that it is only 2/3 the length required to go around the opening.

Let the fun begin.

[EA37TS]

Materials for the project have been ordered with a delivery date of May 11. I find it interesting that it is going to take a week to deliver something 4 miles. The Amazon fulfillment center servicing this order is less than 4 miles from my front door. Unfortunately fulfillment center pickup is not an ordering option.

I decided to go with Dynamat all the way. Dynamat is designed and engineered with vertical and overhead surfaces in mind and that was the basis for my decision. I also found out that Fatmat is manufactured by the owner of a roofing company so a lot of their adhesives are designed for roofing (and thereby horizontal) applications.

The materials ordered include:

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

Amazon.com: Dynamat 10455 18" x 32" x 0.067" Thick Self-Adhesive Sound Deadener with Xtreme Bulk Pack, (Set of 9): Automotive

I am also going to stop by my local home improvement center and find some rigid foam insulation, this I will cut to the inside dimensions of the A pillars and prior to stuffing it inside I will line the outside surfaces of the foam with Dynamat Extreme. I will also pick up some rubber washers for the mounting screws that hold the engine cover in place as well as some weather stripping or bulb seal to correct Thor's inadequate attempt at the bulb seal installation along the leading edge (carpeted area) of the cover opening. I am not sure that bulb seal was the best choice for the intended purpose and I believe there are better options available.

[EA37TS]

Amazon got the shipping address wrong so the materials won't be in until tomorrow.

Today I disassembled the engine cover (removed the cup holder tray) and it was interesting what I found.



There is a 1/4 inch piece of plywood acting as a spacer. The plywood was screwed to the engine cover with 2 screws (one is visible and the hole for the other is approx. 4 inches to the left). Since the plywood was secured in an area where the engine cover changes contour (ridge running from left to right) the two screw locations caused the plywood to act as a fulcrum. After doing the inside of the engine cover I will see about placing some Dynamat between the cup holder tray and the engine cover for cushioning.

I did go to my local home improvement center and bought the rubber washers I plan on using for the screws mounting the engine cover to the floor. The rubber washers should minimize any potential noise transference through vibration

Also, I began looking at the driver's and passenger's floor pans. The passenger's side floor pan is approximately 1 1/2 to 2 inches thick. Since the bulk of this thickness is insulation I believe adding some Dynamat extreme sound deadening is all that is warranted in this location.

The driver's side is another issue.





The area immediately below the driver's seat is the same thickness and composition as the passenger's side. The area under and to the front of the driver's feet is 1/4 inch plywood resting on a 1/8 inch steel plate. This area is going to require some serious attention.

[Nursx2]

Sweet mod plans Dave! I look forward to the finished results as this is also on my list!

[EA37TS]

My materials arrived so I can now begin working on this project.



Dynamat Hood Liner, Dynamat Extreme, Dynamat Tape, Dynamat Roller


I had to modify the sequence of attack slightly due to environmental conditions (it's hot outside!!!) The first step is now:

Turn on AC in coach and let the interior temp drop below 85 degrees before reentering the sweat box. Even with the windows open and the attic fan running the inside temp was 95 degrees. I sure am happy I had the electrician change my shore power connection from 30 amp to 50 amp a couple weeks ago.

I did take a couple of measurements while in the coach. I wanted to know:

1. How far does the top of the engine protrude through the floor. That is 5 inches.
2. The height on the inside of the engine cover. The height of the engine cover is 8 inches. This explains why Thor could use 3 inch screws for a 1 inch job without serious side effects.

I am now positive that 3/4 inch Dynamat hood liner and a sheet of Dynamat Extreme Sound Barrier (sandwiched between the cover and hood liner) will fit inside the engine cover and still provide adequate space for air circulation around the top of the engine.

I was planning on cutting engine cover templates tonight but I was just informed that if I want dinner we are going out. The wife says she is not cooking tonight.

[EA37TS]

I was able to get a little accomplished tonight.

Here is a pic of the engine cover before I did anything. The existing insulation was full of gaps and there weren't air pockets, there were air rivers that was distorting the inside shape of the cover.



Gaps in existing insulation

The first thing I did was tape all loose areas and eliminate the air rivers.



Gaps taped and air pockets removed

I then began installing the Dynamat sound deadening sheets



I began on the sides of the engine cover

Here is a pic of the Dynamat Extreme completion. The completion took 2 sheets of the Dynamat Extreme.



After completing this two things became obvious. First when tapping on the side of the engine cover with a knuckle it no longer sounds hollow. It now sounds like hitting solid wood. Second the engine cover now weights about 5 pounds more than when I started. The Dynamat Extreme is some heavy stuff.

After completing the cover I set it over the engine and started the coach. With the installation there was a reduction in sound of 3 db at idle and 4 db at 1750 rpm. That is a 4 and 5 percent reduction respectively and I have not yet installed the hood liner and the engine cover was not secured with screws.

I am going to allow the engine cover to sit for a day or two. I want to ensure the weight of the Dynamat does not pull the existing insulation free and ruin the job. If everything stays in place I will install the hood liner later this week.

[Larry]

Good job Dave and great results.

My Axis engine noise doesn't seem to be loud enough to bother me. 85 - 90 db at 65 mph. Suppose I lucked out when they installed the insulation on my coach.

[EA37TS]

Originally Posted by Larry

Good job Dave and great results.

My Axis engine noise doesn't seem to be loud enough to bother me. 85 - 90 db at 65 mph. Suppose I lucked out when they installed the insulation on my coach.

The engine noise on my coach does not bother me either. My wife is concerned it bothers the dog (Marta). My first mod to the coach was to install a seat belt extension on the passengers seat so there are two seat belt buckles and the Marta gets hooked to one while we are travelling. She gets a little anxious while travelling and my wife believes if I can reduce the noise it may help. Personally I think she misses her travelling companion (Mandy) which we lost to cancer 2 years ago. The anxiety showed up the first trip after we lost Mandy.

What this has done is somewhat confirm my suspicion that the majority of my engine noise is not coming through the cover, but rather through the floor pans. All mechanical components of my engine, valve covers, exhaust manifolds, bell housing etc... sit below the level of the floor with the air inlet into the intake being the only component above floor level.

I believe before I waste money on installing hood liner in the engine cover I am first going to see what happens when I tackle the floor pans. I expect a large gain in reduction when I use the Dynamat on the driver's side floor pan.

[Larry]

Sorry about the loss of your dog, Mandy. They become a big part of the family. Maybe the sound reduction, as you said, will help with calm Marta.

Our Lab, Lucy, sits between us on 2 crates and bedding (so she can see out better) practically the whole time we're traveling in the RV and loves it. Gets excited over seeing cows and horses. Of course she loves travelling in any vehicle anytime.

Good luck with the future mods.

[EA37TS]

Originally Posted by Larry

Sorry about the loss of your dog, Mandy. They become a big part of the family. Maybe the sound reduction, as you said, will help with calm Marta.

Our Lab, Lucy, sits between us on 2 crates and bedding (so she can see out better) practically the whole time we're traveling in the RV and loves it. Gets excited over seeing cows and horses. Of course she loves travelling in any vehicle anytime.

Good luck with the future mods.

Marta is also a rider when it comes to the cars. She loves being in the coach but when we start rolling is when she gets anxious. We are thinking she needs another travelling companion to occupy her time. Marta is a Collie mix we rescued with Mandy. They were together with the previous owners who passed away and we decided to keep them together. Marta is now a certified therapy dog that love to work with children with reading disabilities and she loves the adventure of different campgrounds. We have up to 13 deer that graze in our back yard every evening and Marta would love to herd them up.

[EA37TS]

No issues with the Dynamat going over the existing insulation so I continued.

I first began by remounting the piece of plywood that serves as the mounting surface for the cup holder tray. Instead of using the two wood screws that Thor used I purchased some 8 x 24 stainless steel pan head screws along with ss washers and ss nylock nuts. I then mounted the plywood to the engine cover using 4 mounting points rather than Thor's 2. The plywood is now secure and does not act like a fulcrum.



Next I began installing the Dynamat acoustic hood liner.



After the hood liner was cut to fit and installed I taped all of the seams with Dynamat foil tape and this completed the hood liner installation.

.

The hardest part of the project was locating the screws holes to reinstall the engine cover. I did install rubber washers between the mounting screw flat washers and the engine cover to reduce any vibration related noise from this mounting point. I also used some Dynamat Extreme sound deadening mat on the plywood before reinstalling the cup holder tray.



After the installation I did another sound check.

Beginning idle = 65 db
Current idle = 58 db
Reduction of noise at idle 10 percent

Beginning 1750 RPM = 75 db
Current 1750 RPM = 66 db
Reduction of noise at 1750 RPM = 12 percent

I must say I'm impressed with the Dynamat. I did not expect to get this level of noise reduction from the engine cover only. My next project will be to tackle the drivers floor pan and under the front part of the dash. Since I only ordered one sheet of the hood liner and I still have seven sheets of the Dynamat Extreme I believe I will check the results with the extreme before ordering more hood liner.

More to follow as time permits and other projects (e.g. install the missing bulb seal etc...) allow.

[gfullertx]

Dave, Thanks for posting your process. I wanted to see what the final results were regarding heat. I am considering doing basically what you did on my 2014 Outlaw but am a little concerned about keeping that much more heat inside the engine compartment and damaging the engine.

Any insight into this would be appreciated.

[gfullertx]

Dave, Thanks for posting your process. I wanted to see what the final results were regarding heat. I am considering doing basically what you did on my 2014 Outlaw but am a little concerned about keeping that much more heat inside the engine compartment and damaging the engine.

Any insight into this would be appreciated.

[EA37TS]

Originally Posted by gfullertx

Dave, Thanks for posting your process. I wanted to see what the final results were regarding heat. I am considering doing basically what you did on my 2014 Outlaw but am a little concerned about keeping that much more heat inside the engine compartment and damaging the engine.

Any insight into this would be appreciated.

I have not observed any noticeable difference in engine operating temperature as a result of adding the insulation to the engine cover.

2 points:

First, Thor did add some insulation to the engine cover although it was minimal at best.

Second, on the Challenger the majority of heat producing components of the engine (exhaust manifolds etc...) already sit below the level of the floor. The only thing that is inside the engine cover is the air plenum/hose running across the top of the intake manifold. (photo attached)



I'm not sure how point 2 will apply to the Outlaw.

[Timon]

Originally Posted by dstankov

After the installation I did another sound check.

Beginning idle = 65 db
Current idle = 58 db
Reduction of noise at idle 10 percent

Beginning 1750 RPM = 75 db
Current 1750 RPM = 66 db
Reduction of noise at 1750 RPM = 12 percent

I must say I'm impressed with the Dynamat. I did not expect to get this level of noise reduction from the engine cover only.

Interesting, however I think you percentage of sound reduction is wrong. Remember that sound level changes are not linear but are a log function. For every 3db of change you half or double the level.

If you do the math a 10db reduction is 10% of the sound level. You have 6 and 9db changes which Is about a 75% and 87.5%. That not bad at all.

[EA37TS]

Timon,

Thanks for the correction. I am happy with the results.

[Brakeman48]

Dave, great information and pictures. I was thinking of doing the same on the 2016 Hurticane 35C we just purchased. I have a large roll of FatMat I had partially used to deaden the noise in our '74 Datsun 260Z. Has anyone information on a comparison between Dynamax and FatMat in regards to noise deadening properties?

[EA37TS]

Originally Posted by Brakeman48

Dave, great information and pictures. I was thinking of doing the same on the 2016 Hurticane 35C we just purchased. I have a large roll of FatMat I had partially used to deaden the noise in our '74 Datsun 260Z. Has anyone information on a comparison between Dynamax and FatMat in regards to noise deadening properties?

If you look at post 3 in this thread you will see why I went with Dynamat instead of FatMat. That was based on information I was able to gather prior to ordering the products.

[Chance]

Nice work Dave.

Did you test engine at 1750 under load (while driving) or stationary while parked? I assume the latter. Under load the engine should be louder so improvement may be even more (on absolute basis, not sure as percent).

Have you driven the motorhome since upgrade? I'm curious how much of the reduction remains with wind and road noise in background.