Sound Proofing Project-Phase 1: Rear

[travisgarrison]

Phase 1: Rear storage area and rear bed
Materials:
- 1/2" Closed Cell Foam (like Ensolite)
- 1/4" Closed Cell Foam (like Ensolite)
- Spray adhesive 92
- Polyfil
- Great Stuff Spray

Tools:
- Ruler or measuring tape
- 14mm Socket
- 12mm Socket
- 10mm Socket
- Socket wrench
- Phillips Screwdriver #1
- flathead Screwdriver (w/tape over the end)
- Exacto Knife
- Scissors
- Box Knife
- Latex gloves

Goals:
- Under $100
- Under 50lbs
- Reduce road noise by 3-7dBA
- Eliminate rattles

Intro: Unfortunately Honda did not do much sound dampening with the Insight. This was probably a combination of cost saving and weight restrictions. Unfortunately this means that at highway speeds the Insight is one of the noisiest cars many of us have been in. The biggest sources of road noise in the rear of the car are coming from the wheel wells and the spare tire compartment. For this phase we will focus on damping those areas but we will do some damping in all the other areas as well.

Step 1: Prep
Remove the upholstery and everything found in the storage area. This includes the foam to the left of the IMA and the aluminum panels to the right of the IMA.

Remove the panels surrounding the hatch windows. To get access to this you will need to remove the bolt from the hatch hydraulic tube and the bolt from the seatbelt. These are both 14mm bolts. Use the flathead screwdriver to pry off the covers over the bolts.

Vaccum all surfaces, then clean all surfaces well with mild soap and warm water. Dry up any remaining moisture.



Step 2: Spray Adhesive
Using the spray upholstery adhesive spray down the left interior around the wheel well and up the walls. While that is setting spray the right side in the same way. Do not spray the spare tire compartment yet. The spray needs at least 5 minutes to set up but can have up to an hour before application.

Step 3: 1/2" Ensolite
Working with small strips (less than 12" x 6") cover the wheel well area. Before applying a strip of the foam, make sure to spray the back down with the adhesive. Apply pressure to the entire piece of foam. Take your time. You want every bit possible to be covered.



Step 4: 1/4" Ensolite
In the same fashion cover the rest of the left side with the thinner Ensolite. Again, spray the back with the adhesive.

***Repeat Steps 3 and 4 with the right side

Step 5: Great Stuff Spray
I only use great stuff where the polyfil won't easily reach. There is one place in the back for this. There is a vertical column that extends from the middle of the wheel well on both sides. It is hollow inside and while you probably could fill it with polyfil, Great Stuff expanding foam is much better in this case.

Using the applicator tube, spray the foam until it's about an inch away from the opening. The foam will expand the rest of the way. There are several holes you can use to spray in the foam.

If you accidentally use too much that's OK. Just wait an hour or so until it is semi-cured and cut away the extra... it's pretty easy to do.

***Repeat step 5 on the right side.

Step 6: Ensolite on Spare tire compartment
I used 1/4" Ensolite for the sides, front and back of the compartment. Do not put ensolite anywhere on the IMA Battery box as it needs room to breathe and the foam will only insulate heat which is bad news for the battery. I used 1/2" ensolite for the bottom of the spare tire compartment.



Step 7: Polyfil
I love this stuff. You can find it in Teddy Bears, pillows and all kinds of other plush toys. Use the polyfil liberally to the left and the right of the IMA battery. This stuff is great because it will dampen sound similarly to the Great Stuff Spray and yet it is completely removable should the IMA go bad and need to be replaced. The other benefit is that it isn't messy at all.



Step 8: Put it all back together
You may need to put holes in the Ensolite to put the plastic panels back in, but that shouldn't be difficult. Just line the panel up and note where the plastic pop-in is and there is where you need to put a hole in the ensolite.

Everything will be a tighter fit, but that isn't all that bad since it should serve to get rid of rattles.

Results: Noticeably quieter back (sorry, I don't have a meter so I can't give you a dB reading), rattle in the rear hatch is gone, sweeter bass response from my sub which the spare tire compartment effectively acts as a box for. Rough roads now sound the same as smooth roads and small bumps no longer sound like the rear wheels ran over a small child.

Upcoming:
- Phase 2: Doors
- Phase 3: Front Wheel Wells
- Phase 4: Floors and firewall
- Phase 5: Rear Wheel Wells

[jf_cole]

Wow! Thanks for the guide. I'm hoping to do this to my Insight in the next month or two. Its fine on the Smooth new Motorways, but the older roads its just too loud and the stereo needs to be up high to drown it out.

Cant wait to see the rest!

[jonnyvtec]

I might try something like this aswell, that large wheel well must just act as a resonance chamber so adding mass to the panels should help. Also I imagine those rubber cargo mats serve as a good barrier to actually block sound that might be worth trying, although at 7.5kg there reasonable heavy.

[retepsnikrep]

Excellent post. Please continue the series, useful info for all members.

[freezin4]

Nice work. Great pics.
This will surely make your x-country trip more pleasurable.

Question: How do you think this mod affects the battery compartment temperature or ventillation?

[travisgarrison]

Good question about the IMA Battery temp and vent. There are probably some others on this forum that could better answer this question or the question could be answered by taking an ambient temperature reading in the area.

Honestly I'm not too concerned. The Ensolite in the wheel wells and spare tire area don't block or reduce air flow and the polyfil on the sides does not block any vents.

However, I specifically would not recommend putting polyfill in the spare tire compartment as that would reduce air flow. I also would not recommend putting ensolite (the closed cell foam) anywhere on the IMA box. Not only would it not do any good, but it would act as a heat insulator.

[travisgarrison]

Jonnyvtec,

The ensolite doesn't work the best as a "mass loader" although it does do some of that. The closed cell foam works the same way that screaming into a pillow works. It acts as a sound barrier or dampener. Mass loaders like Dynomat Extreme are meant to deaden sound by eliminating rattling. The main problem in the Insight however is outside road noise, not rattling (although I'm working on figuring out where two rattles in my dash are coming from).

I chose Ensolite because its light weight and works better than the heavy mass loaders at dampening road noise. Polyfil and Great Stuff Expanding foam have similar properties.

[jf_cole]

Question.

Given the current climate, im looking to do this on a budget. I've worked out its going to cost a good €200 to do this. Not the bargain I had hoped. However, I just came across a box of about 1000 mousemats. Foam backed. Would this stuff be a cheap alternative? Going to see how "fireproof" one is later!

[travisgarrison]

The question you will need to answer for the mats is what they are made of. If they are open cell foam (lighter and squishier) then they are susceptable to moisture and will mold if you use them in areas like the wheel wells. You want closed cell foam which is denser. My guess is that if these are door mats then you don't need to worry about moisture. Here is what I would take into consideration:

- Are they flexible? The foam you need will need to contour to the shape of what you are adhesing it to. If these are hard rubberized mats then they won't work well and will come off frequently

- Are they heavy? If it's a dense rubberized mat then it's going to add a lot of weight to the insight. Try to think how much 50 square feet (13 square meters) is going to weigh.

- How thick is it? 1/2" and 1/4" is ideal, although there are areas where you could use thicker.

I purchased my closed-cell foam locally at a rubber supply shop. You might see if you can find one in your area so you don't need to worry about shipping.

[jf_cole]

I started at this last night, I found that in the LHS & RHS Panels, between the outer skin and inner skin, the wheelarches were covered in 1/2 thick foam pads already! Im not sure if this was done at factory level or if the Honda Distributor did this (Car was owned by Honda UK, then Honda Ireland, now me).

Has anyone else noticed this?

Anyway, rear is stripped and have used the more expensive E-Dead around the wheel arches and in parts of the boot well. I got under the car and you could see how exposed some of it was to tyre noise, so I felt this was as important as the wheel arches, if not more as its so thin and shaped like a drum!

Lots more to do before I can put it back together and get results.