Matrix too noisy w/ rear seats out
 

Hi all,

I tried going "full hypermiler" a few years ago with my 2007 Toyota Matrix (base) and removed the rear seats and cargo area floor and spare tire a few years back. After a short while I put them all back. It was LOUD in my car, and I had problems using the cargo area w/o my shiz flying forwards.

Now, I'm trying round two. I have the spare tire, tire changing tools, and rear seats out, along with a bunch of other misc items, for 113.5 lbs of weight loss. I know from experience that my car will be louder w/ the rear seats out. I thought I might add a few pounds of Dynamat or other sound deadening material, but after removing the seats earlier this evening, I realized that there was some factory sound deadening material installed (see attached). Would adding some Dynamat on top of that help at all??...

A friend (non-hypermiler) said it sounded like I was trying to have my cake and eat it too. :( He suggested maybe Dynamatting the wheel wells.. :confused:

http://ecomodder.com/forum/attachmen...5&d=1475379832

http://ecomodder.com/forum/attachmen...6&d=1475379832

I've never used Dynamat myself, but my understanding is that it is most effective in the center of flat panels that would otherwise act as a drum-head.

And I've seen people putting Dynamat on top of Dynamat, so it probably could go over the factory stuff. At least it easier than putting it underneath. :)

A long time ago, maybe 30+ years, I used Dynamat in some car I owned and was pleased with the result. IIRC, I used a Canadian made substitute that was available at the time.

*IF* you never plan on re-installing the seats, have you thought about filling the area with expanding insulation foam (use the low-density stuff) underneath a thin sheet of plywood?

Thanks all, for your input.

So far, everything I've done to my car is reversible, should I decide to sell the car. I'm not 100% certain I want to keep the rear seats out, as my needs may change.

Old Tele Man, I've seen some pics of builds where people built a straight plywood platform, to have a level load floor. That might be OK, but I'm concerned about weight. I'm trying to lighten things - not add them back!

After a few day's contemplation, I'm trying out making the pictured area where the rear seats were as my primary cargo area; e.g., I fill that area first, when loading the car. That way (hopefully), the mass of my items helps absorb some of the sound energy. A possible issue is items sliding off the front of the seats, down to the floor, during harder stops. If this proves to be a good plan, I might cut a thin strip of plywood out as a ledge and bolt it on using the existing seat bolts & holes, and maybe even get some matching fabric to make it and the bare seat area a little more presentable.

I primarily listen to podcasts & talk radio, and it's frustrating to not be able to understand what they are saying because of road noise (and I value my hearing enough that I don't like the workaround of cranking up the volume).

If your driving is not primarily stop and go, the weight reductions will net close to zero improvement in economy. My Insight gets basically the same economy when cruising on the highway when it's completely empty as it does with 5-800lbs of cargo - which is like 33-50% additional mass, given how light the car is to begin with.

I do, perhaps, 40% stop/go city driving. I understand it'll be a marginal gain, at best. But I'll take what I can get. :thumbup:

OK... I discovered one source of noise intrusion when my car was backlit by the setting sun, parked in the garage. See attached photo. See that brightly lit hole? That's where one of the seat belt harnesses was bolted in. :D It goes clear through the bottom of the car... I'll need to plug that with something...

How about putting a layer of plastic film over the floor to protect it, then place a plywood false floor and fill the space between them with expanding foam. The plastic will give a more robust outer surface and make it release cleanly from the floor whilst still bonding to the ply. Once cured it can be trimmed up and made more presentable. Be wary of the foam leaking out the sides and filling holes in the body. A variation on this (filling a plastic bag with the foam and sitting in it) is how I made custom fitted seat inserts to minimise body movement in my go kart.

Simon

Foam ear plugs, just roll them up and put them in. A great seal and easily removable.


Have you installed a belly pan or anything in the rear wheel wells to seal them up as well? That should keep some noise out. What about installing a partition between the front and rear? That would help with things flying forward too.

It's popular to seal up all the access holes in the inner panels. I think that will help out with your noise now without adding too much weight. Aluminum flashing cut to size/shape, butyl rubber to seal it and some screws to keep it in place.