MX-3.com

I know not too many people read the General Mazda MX-3 forum, but here's a bit of a treat for you who do. I though I'd share with you my progress and it's results.

The car:
MX-3 RS, B6DE, Flowmaster 60 series.


The goal:

Make the car as quiet as possible.

Procedure:


I'm working from the hatch forward. Hatch has been covered fully by b-quiet ultimate, two layers, 100sq ft total. Door panels have also been covered fully with several layers, both inner frame and outer panels.

Difference between soundproofed doors vs. nonsoundproofed doors.

First two taps - soundproofed
second two taps - non soundproofed

(I have two MX-3's, so I can make a valid comparison)

doorpanel.mp3 - 0.18MB




That's pretty handy dandy, cuts down on the road noise a lot

However, there is a significant amount of resonance from the muffler, the way the MX-3 is designed. Fortunately this issue can be GREATLY reduced.

I've been contemplating how to do this for quite some time and I couldn't think of a good material to use.

I ended up walking down Lowes to find the answer. When i found the answer, after years of construction, I could have slapped myself.

Cellulose insulation.



Of COURSE! It's ground up paper! Just what I needed, a paper based insulation! Great R value, NO health concerns, lightweight and CHEAP!

Paid 8 bucks for a big pack of insulation. weighs less than 30 pounds. A bag will do the whole car. You can purchase cellulose insulation that is very fire retardant as well.

Where to put it?

There is about 5 inches gap between the outer panels and inner frame in the mid and rear portions of the car, with a convenient location to stuff it all in.



Shove that stuff in EVERYWHERE. If it won't stay, I stuffed a paper towel in the way so it wouldn't fall out... then continued stuffing.



Any gap between the outer body panel and the inner frame was stuffed.

This helps several issues. Resonance, road noise, moisture, and of course, heat/cold (if you have AC)


How effective is this?

Here is an audio clip of the difference by tapping on the insulated and non insulated panels

1st, 3rd, 5th tap, insulated panel
2nd, 4th, 6th tap, noninsulated panel.
Each consecutive tap is in generally the same section, so the 1st tap will be in the same section as the 2nd, 3rd in the same as 4th, 5th same as 6th.

quarterpanel.mp3 - 0.15MB


I unfortunately didn't think ahead of recording the resonance in the cabin before insulation... but however, I created a similar scenario. With the windows down, the resonance is extremely similar to the noninsulated car with the windows up.



Here is the graph of the sound clip

I traveled about 20mph, hitting right above 2k, where resonance is some of the greatest... and traveling slow enough so noise from the front end isn't affecting the noise of the resonance of the rear hatch area (where I have insulated)
Also at 20mph, wind noise is nonexistant.
See where the frequency cuts, is where I roll the windows up. It is a SIGNIFICANT DIFFERENCE in the cabin.

Let me repeat: Resonance of a closed (windows up) cabin without insulation is VERY similar to resonance of a open (windows down) cabin with insulation.

I personally believe (I know, I drive the dang car every day) the non-insulated closed cabin is still significantly louder than the insulated, open cabin, but I don't have results for this, so therefore I count my opinion as moot.

Here is the link for the audio file of the above graph:
insulate-test.mp3 - 0.91MB

It IS messy to put in, but for 8 bucks, a couple hours of work and 30 extra pounds, the results are so EXTREMELY worth it.

*UPDATE 8/01*

I did another experiment that proved worthwhile:



I wrapped the muffler in the exhaust heat wrap insulation that's supposed to go on your headers...

Well, it's not cured yet so the results will be better yet, but it's working VERY well.
I can also touch my flowmaster after a nice summer ride down the highway and not be burned.
This means I can spray that rubberized coating on the aluminum heat shield above the muffler. That thing resonates pretty bad when you tap it, so it's an experiment that opens possibilities to other modifications.

I am also following FowlJesse's mods and am now weatherstripping the car... till I ran out...

Wow! What a difference! When I have extra cash, I just might have to do this. 30lbs extra really isn't too bad at all either considering the RS is already slow, it doesn't really matter. With the speaker set-up you have now (close to stock I assume), did it seem clearer/more crisp or did the deadening just strickly cut down on road/car noice?

Thanks! I was going to fill everything with "GreatStuff". maybe I still will, and if there's any place I need to get to (wiring, etc..), I'll stuff that stuff. Did you se my post about putting in extra window trim? It cuts wind noise, which bothers me most.

I considered great stuff... but there are a ton of nooks and crannies you can't fill properly.
If you notice in the first picture of me insulating, I really AM shoving that stuff in there.
Also, for any reason, you cant undo what you've done, to an extent.

When I soundproofed the doors a while back, it helped out tremendously with the sound. I'm running polk momo components in the front and a 10" sub... but the sub is out of commision for the moment so I have no comment on my insulation test.

This is fantastic! lol I put a Flowmaster Super 40 Delta Series and I'm going brain dead from the sound inside the car
This is a great idea, good job.

I did a few extrarandom improvements in the 1st post.. check it out

Also, I put in the subwoofer and the sound is very crisp! Sounds more and more like my home sound system, which is very good

I learned something important about the door insulation; It shrinks. I stretched it a little, to maximize it's coverage, but it shrank so much, that I had to take it off, and put it back on, condensing it as much as I could along the way.

About the FlowMaster; I thought about wrapping mine, too, but the way it works is by the resonance inside cancelling out the incoming soundwaves, so *maybe* it will be louder out the back, but if it's quieter inside, that's what really matters. I'd love to hera the difference, if there is one, because I like the FlowMaster sound.

That's what I am aiming for i love the sound outside my car and now that i just added a subwoofer im gonna try to add some sound proofing to stop the muffler sound inside the car.

Here are my thoughts:

Exhaust/header wrap is made of woven fiberglass. I found that out after how incredibly itchy I was :S


Fiberglass, in a test between terry cloth towels (WHY!?) wood, open-cell foam, carpet and cardboard, Absorbed the most sound.

Fiberglass is commonly used in the core of sound absorption panels.

When a sound wave strikes an acoustical material the sound wave causes the fibers or particle makeup of the absorbing material to vibrate. This vibration causes tiny amounts of heat due to the friction and thus sound absorption is accomplished by way of energy to heat conversion. The more fibrous a material is the better the absorption; conversely denser materials are less absorptive. The sound absorbing characteristics of acoustical materials vary significantly with frequency

While this is on a much smaller scale, due to the fact it's a woven wrap and not loose and "fluffy" it still accomplishes some of my intended goal.

And again, the massive reduction of heat leaves more opportunities to apply more proper methods of sound reduction in the intended area.

And plus, who ELSE has wrapped their muffler? Not anyone I know. I am enjoying the "I tried it first" feeling

Also, if you wrap the whole exhaust, you may reduce more noise, and gain a couple MPG. If you keep the temp high, all the way through, it will flow faster, and more easily. I plan to wrap my sysytem before putting on the underside covering. I've read of a few guys wrapping their entire exhaust, and getting a few mpg.

Also, I have a theory about exhaust sound I'm looking forward to testing: I think that the sound is accentuated by the vibration of the exhaust pipe itself, that can be dampened by wrapping it. I'm talking about microscoping vibration, like the kind that breaks a wine glass when the "Ruebenesque" lady sings. If the pipe can be lined with a smooth, sound-absorbing material, we may not need mufflers.

I am planning on wrapping the whole pipe as well... I am expecting improvements doing so!

Are you guys running stainless exhausts, or do you have the luck of not living somewhere with road salt? I believe I have read of situations where oxidation of the exhaust pipes occurred faster due to moisture being trapped inside exhaust wrap. Regardless, I am very curious to see your results, and perhaps may try this should I upgrade my exhaust to 2.5" stainless to match my muffler.

i am curious too if wrapping the exhaust pipes and muffler will cause them to deteriorate faster. I live in south Florida so we have the humidity to worry about but not the salt.