Crusin' down the road at 65 mph in my stock (cat replaced w/ a straight glass pac) '86 2M4 at 65 mph w/ the stereo off. Sound meter held about a foot in front of the driver's headrest read 81 dB (all readings on the A scale) when pointed to the right. 83 when pointed to the left. 89 by the gas cap release lever.
Plan is to by some plain black roll roofing, a gallon can of fibered roofing cement and a can of Great Stuff expanding foam. The roofing will be cut to fit and be held in place to the metal surfaces beneath the carpeting using the roofing cement. The foam with fill any openings found prior to the roofing cement, especially in the B pillars.
Then take more readings to determine effectiveness prior to doing the lower doorskins.
Any comments or "been there, done that" advice?

[This message has been edited by 30+mpg (edited 05-10-2004).]

Not a big fan of Dynomat? I hear it does wonders....

I measured the SPL in my car with the interior stripped out (except for driver's seat, gauge pod, and door panels) with the engine at idle... 75dBA!!! The C-weighted (low-frequency) is even worse at 86dBC. This was with me holding the SPL meter about a foot above the center console, with the mic pointed forward.

I plan on doing something similar to your idea. I'm going to fill the A-pillars and B-pillars, the cavities at the bottom of the firewall, and some of the other frame members around the cabin with spray foam. I'm also going to line the floor and firewall with visco-elastic polymer sheets (doesn't stink like Dynomat). Plus I'll probably line the insides of the plastic trim pieces with foam rubber.

After stripping out the interior and poking/prodding around the frame members, I noticed that the B-pillars are big hollow chambers. There's a hole near the top for the 4x6 speaker, and a bigger hole near the bottom (for ventilation?). Noise reverberates inside, like a guitar, and is vented out the bottom into the cabin.

Also, the floor and firewall vibrate noticeably when the engine is running. So they could benefit from some mass-loading. Same goes for the center area in the roof.

[This message has been edited by Blacktree (edited 05-10-2004).]

i wouldnt complain to much idle my car was at 99db and like 120 at WOT lol...

quote Originally posted by boristheblade: Not a big fan of Dynomat? I hear it does wonders....

Yeah, I hear that too, like I wonder where all my money went.
I can get a 36" wide roll of black roofing for $13.

I put new carpet in my car and since the aftermarket carpet is kind of thin I put it right over top of the old carpet. That did wonders to quiet down my interior. The road noise is probably half what it was before.

just another Dynomat comment... Dynomat has expanded their product line over the years, and they have special types for special applications. one thing that I remember from working on a friend of mine's car (back in high school 20 years ago) is that the material can be layered, and layered, etc as you desire. The stuff is nothing short of amazing. And the price of it will give you a heart attack....

quote by Blacktree:. . . I'm going to fill the A-pillars and B-pillars, the cavities at the bottom of the firewall, and some of the other frame members around the cabin with spray foam. After stripping out the interior and poking/prodding around the frame members, I noticed that the B-pillars are big hollow chambers. There's a hole near the top for the 4x6 speaker, and a bigger hole near the bottom (for ventilation?). Noise reverberates inside, like a guitar, and is vented out the bottom into the cabin.

The B pillars are hollow for ventlation.

The opening at the bottom as a pressure relief valve that lets cabin air into the pillar. It travels up and out in back of the sail panel. If you Stuff the B pillars, your ventilation system may suffer. However if one could put a hose or tube in the B-pillar and foam around the hose or tube, that would cut noise. What dia. of tube or hose would be sufficient 1", 2" or some other size?

I'm thinking, a quiter muffler would be cheaper, and a lot less work!

But what do I know?

quote Originally posted by Lambo nut: I'm thinking, a quiter muffler would be cheaper, and a lot less work! But what do I know?

Cheaper? How? My glass pac was welded in by a muffler shop. Have you ever hassled with the muffler support springs?

Im with lambo. Louder muffler dont always mean better performance,in fact sometimes the opposite happens. Id just put a hi-po cat and a nice muffler like Spintec, Borla, etc.

Actually, my muffler IS stock. It's the CAT that's been replaced by the glass pac. Anyway, for under $30 I can sound insulate the interior.

When the Dynomat material was brought up, that's when the muffler got cheaper.
Yes I have played with the springs, so I know what you mean about those!

"My glass pac was welded in by a muffler shop."
That's where I'd take it to do the muffler. Let them mess with those springs.......

Kevin

I used a construction membrane which was like a pliable aluminum sheet with a gooey side (covered with release paper). You have to cut it as it can't be torn. The piece that got stuck to my metal shed roof is there for good too. It hugged curves very well and I don't find noise objectionable. I am running with all weather carpet on the floor in place of the heavy stock items.

Roofing paper and tar sounds awfully messy.

quote The opening at the bottom as a pressure relief valve that lets cabin air into the pillar. It travels up and out in back of the sail panel. If you Stuff the B pillars, your ventilation system may suffer. However if one could put a hose or tube in the B-pillar and foam around the hose or tube, that would cut noise.

That makes perfect sense. I started "nerfing" my Fiero today, and noticed that there are small square holes (maybe 1.5" wide) on the outside of the B-pillars, directly behind the 4x6 speaker holes. These square holes go right out to the sail panel glass. These are probably the sail panel vents you mentioned. So if one didn't use speakers in the B-pillars, one could conceivably leave an open area for air to vent through the speaker holes and out the sail panels. And it just so happens that I won't be using the 4x6 speaker mounts. Whatcha think?

Oh, and BTW a quieter muffler will not reduce road noise, nor will it stop driveline vibration.

quote Roofing paper and tar sounds awfully messy.

Yeah... and stinky.

You can buy visco-elastic polymer sheets (no odor, and similar performance to Dynamat) at www.partsexpress.com for about $23 per sheet (27x40").

[This message has been edited by Blacktree (edited 05-11-2004).]

Take pics!

OK

quote Originally posted by 30+mpg: Plan is to by some plain black roll roofing, a gallon can of fibered roofing cement and a can of Great Stuff expanding foam. The roofing will be cut to fit and be held in place to the metal surfaces beneath the carpeting using the roofing cement. The foam with fill any openings found prior to the roofing cement, especially in the B pillars.

Hey, just wanted to chime in - I did the same. Haven't driven it yet but it seemed to work well. I cleaned any rust on the floorboards and repainted it all with Zero Rust. I skipped the roofing cement and used a heat gun - melted the rubberized layer right to the steel. I found it worked better to lay it down in 4'x6" strips, front to rear. Much easier to apply than trying to fit one big piece in there. While you're at it, take the dash out so you can get right up the wheel tubs at the front of the cockpit. The stuff doesn't weigh a whole lot and isn't so thick it will mess with the fit of the interior panels. Don't forget to do the doors.

I haven't done the spray foam yet but as suggested the B-pillars have some ventilation functionality in them. Even if you can get a plastic hose up there to keep the airflow open, it should be fine. On the other hand, sound deadening the inside and outside of the B-pillar (as opposed to the core of it) might help to get rid of any drumming effect and still leave the opening clear for ventilation.

And yes, I would agree that Dynomat is problaly better. But if Dynomat was my only option, i wouldn't have done it - too expensive. With the light weight of this stuff I can't see it doing any harm when used in conjunction with the stock sound deadening. Mine didn't stink when I melted it with the heat gun, can't see it stinking later on down the road. Depends on the material, I guess.

Just my two cents.

quote Originally posted by jscott1: I put new carpet in my car and since the aftermarket carpet is kind of thin I put it right over top of the old carpet. That did wonders to quiet down my interior. The road noise is probably half what it was before.

That's quite interesting... any adverse affects or issues during installation when going this way?

------------------

Looking for Fiero posters?

quote FieroBUZZ: I.....Roofing paper and tar sounds awfully messy.

Pay attention BUZZ, or are you trying to drift this thread?

1. I'm going to be using roll roofing, NOT roofing paper (which is much, much thinner than roll roofing).

2. Also I'll be using fibered roofing cement NOT tar. Thus no bad odors.

quote 1. I'm going to be using roll roofing, NOT roofing paper (which is much, much thinner than roll roofing). 2. Also I'll be using fibered roofing cement NOT tar. Thus no bad odors.

OK, got it.

I'm almost finished "nerfing" the B-pillars, rear roof support, and console supports. I also plan on doing the door frames, A-pillars, and lower firewall sections. I'd post photos of my progress, but my internet connection is really crappy today. It'd take forever for the pics to load.

quote Originally posted by 30+mpg: Yeah, and it cost more than $30. Again my muffler is STOCK w/ a single dual tip on the left side. Any aftermarket muffler would probably be louder, sooooooo, tell me, why, o' why should I replace it????

Because, if it is too loud for you, then it must be worn out internally, and why in the hell would you have a glass pack where the cat is supposed to be????
If there is too much noise around the head rest area, maybe it is more of a "whine" then a road noise..at least that is what I'm hearing.....

quote nut: Because, if it is too loud for you, then it must be worn out internally, and why in the hell would you have a glass pack where the cat is supposed to be????

Hmm, interesting. I NEVER said the muffler was too loud. However, the cat had a hole in it which was way loud, thus it was replaced with a glass pac.

Does the term "hell" represent an attempt at hostility?

Take a pill, dude.

This thread is about how loud the interior is for a nearly stock 2M4, not mufflers.

[This message has been edited by 30+mpg (edited 05-12-2004).]

Just wanted to chime in...one or more of you mentioned filling up the ventilation passages..wouldn't that be VERY bad if they were sealed, and you slammed the door? Pressure would make yer ears very unhappy...?

*-pop-*

Maybe you were referring to different passages, I never tore my car apart, and thus, have never seen them "naked"...

But you started the thread about a replaced cat.........., and a muffler..............., and noise..............., what else was one to think.
And you realize that by replacing the cat with a glass pack, you have broken the law.

I do have two other ideas, turn up the radio, or get some ear plugs.
By the way, I'm just messing with you some, not really trying to piss anyone off.
I've been told I come across that way in my e-mails sometimes. That is why I usually read to get good info, instead of pipe in from time to time.
Apologies to my neighbor to the west!

Kevin

quote Originally posted by Lambo nut: But you started the thread about a replaced cat.........., and a muffler..............., and noise..............., what else was one to think. And you realize that by replacing the cat with a glass pack, you have broken the law. I do have two other ideas, turn up the radio, or get some ear plugs. By the way, I'm just messing with you some, not really trying to piss anyone off. I've been told I come across that way in my e-mails sometimes. That is why I usually read to get good info, instead of pipe in from time to time. Apologies to my neighbor to the west! Kevin

Check again, I did NOT mention a muffler at the start of this post.

Could you please inform everyone as to which Kansas law regulates catalyic converters on automobiles?

I AM using earplugs w/ the stereo up

[This message has been edited by 30+mpg (edited 05-13-2004).]

This is kind of interesting, having too much passenger compartment sound with a 2m4

I've driven a 2m4, and frankly it wasn't bad.

Of course I have driven some other sports cars that stock were much louder. MG Midget, MGB, Austin Healey 100, Jaguar 140K, Fiat Spyder, Austin Mini, and a few others.

Of course my 85 GT will be as loud as any of them except maybe the Mini because I had a drag racing exhaust on it and it was down right loud at anything over 1000 rpm.

Bottom line to me, is that you can try to tame the beast or just enjoy it.

I think I'll take the latter.

Arn

quote Originally posted by FieroRumor: Just wanted to chime in...one or more of you mentioned filling up the ventilation passages..wouldn't that be VERY bad if they were sealed, and you slammed the door? Pressure would make yer ears very unhappy...?

FieroRumor nailed down the point that we've been touching on but nobody really said why it was important. Yeah, the "holes" are there for ventilation but that's a pretty broad term. Fresh air ventilation is one thing, pressure ventilation is another thing. Definately keep some amount of airflow through that B-pillar, IMO. Most cars and trucks have a rubber flap on the doors that will vent the pressure out when you close a door or on a hot day.

Ok, I'll drop the muffler part.I just made the generalization of the exhaust as a whole. My bad.

The replacement of the cat with a glasspac, or the removal of the cat, is illegal by federal laws, which over rides any Kansas laws. I can find that in writing for you if you would like, but a short search should find the proof you so desire.

Kevin

quote Too bad you didn't get some readings before you removed your seats and carpeting. How about a reading after you get the abatement material in place, and then another reading after your interior is reinstalled?

For some reason, I forgot about taking an SPL reading before removing the stock interior. But I will take (and post) readings with the foam installed, then with the mass-loading. I won't be re-installing the stock interior. I've decided to build a custom interior instead. Since I also have other projects going on, it could take quite some time for the whole project to be finished. Just giving you some fore-warning.

Oh, and BTW I think the 75dBA figure was a typo. I think it was actually 71dBA. I didn't write it down, because I was more interested in dBC. There's a LOT of low-frequency noise in the cabin, so I used C-weighted measurements to reflect that.

To everyone else: I'm not sure about 30+mpg, but my reasons for trying to quiet the cabin are to reduce background noise, to improve the clarity of my stereo system. In addition, I've installed a stiffer suspension in the car, which has increased road noise considerably. While I love the improved handling, I'm not so thrilled about every little crack and pebble sending a resounding echo through the frame. I want the car to have a nice, solid feel when driving over irregularities.

[This message has been edited by Blacktree (edited 05-14-2004).]

No passanger vehicle inspections in Kansas.

Also, anyone who drives faster than the posted speed limit breaks the law.

On the vent in the "B" pillars, without a way for the air to get out, your heater will not be very efficient till you roll down a window,
don't just fill 'em up without addressing the "flow through" issue.

I left the vents open. They're right behind the 4x6 speaker holes. And since I won't be using 4x6 speakers, the air can vent through there. I've already tested it, turning the vent fan to full speed and closing the doors. There is still plenty of air seeping out of the sail panels, and through the seam between the roof and the rear clip.

Did the driver's side today.
Removed the sail panel & outer vent.
Drizzled a whole can of Great Stuff into the back half and bottom of the B-pillar as well as some of the area above the outer vent and above the 4x6 speaker.
Got everything back in place.
Will run a dBA reading Monday.

Don't expect much just from filling the one B-pillar. With my B-pillars and rear roof support "nerfed", I got a noise reduction (engine at idle, C-weighted measurement) of 2dB. But the car already sounds more solid going over railroad crossings and bumps. I'm working on the door frames and A-pillars now.

BTW, it took 6 cans of "Great Stuff" to fill the B-pillars and roof support, another can for the console supports, and one more for the bottom door frames.

[This message has been edited by Blacktree (edited 05-15-2004).]

With the driver's side, footwell to behind the seat & upside the console to the rocker frame, done, I thought I had made a major improvement in making the interior quieter. Gee, it really sounds better

I'm reading about a 1 dBA improvement over all my previous readings.

Oh well, if I do the other side I ought to pick up another 1 dBA. At least I get my carpet clean. Found 2 dimes on the driver's side.