Belly Pan noise reduction - Sound Proof
 

I was wondering if you remove the sound deadening (proofing) from the vehicle.
Would you compensate the majority of the loss of sound proof by installing a belly pan (Full).?

You could save potential 40 lbs and still have more or less noise in cabin?

Maybe a very thin layer of a sound proof material (light weight of course) stuck on the belly pan. At the same time this material could be heat resistant.

? acoustic foam thin , lightweight. Not sure if they are fire proof.

Solve two problems at once maybe.

If you make significant improvement in the aerodynamic drag, then you don't have to worry so much about a 40 pound change. Forty pounds is not significant for virtually any car on the road. But if you can improve the Cd by even 0.01 you will notice a improvement in the efficiency.

Thanks for that advice although with a little road car with lower bhp, you would be surprised that 40 lbs would make a difference.

But would be nice to know the answer if you can substitute it with belly pan. 4mm corex with 6 mm acoustic foam layer.

Please prove how 40lb of removal would be a 'surprise' ?

maybe you should read some more before you question Niel's answer........

and imho, there isnt 40 lb of material in the average car sold in england.
secong, if you are dismantling the interior to find '40lbs' why not put the new isulation back on the interior? you are just creating a tin can with insulation on the outside.....there is a reason they put the sound deadening material on the inside.
And how will this insulation on the outside react to water.......?

When you drive a low powered low weight car, 40lbs is something you can feel when driving. In acceleration, braking and other handling aspects. If 40lbs was nothing to be bothered with, manufacturers wouldn't use lightweight metals to shed 40lbs. But they do.

He's not saying that 40lbs is worth 5% better gas mileage or anything like that.

I can't offer anything more than an anecdote, but when I tried the belly pan on my car, I was sure I noticed a decrease in road noise. Debatable how much was from the sound insulation properties vs. improved aerodynamics (better aero = less wind noise).

And about that 40 lbs: If I could easily take out 40 lbs from any of my vehicles without affecting my own criteria for keeping it practical, I sure would.

Perhaps surprising, but PaleMelanesian has documented a small but measurable benefit of driving with a nearly empty fuel tank vs. a full one from his vast collection of commuting data. That's in the range of ~40 lbs.

I have driven quite a few small cars and the first thing you notice is it is quite zippy when you are alone, take on a passenger and it becomes a slug, so I'm in with the 40lb weight reduction benefit, but unless you do something like pull out the rear seats I think you will have trouble finding 40lb in insulation.

@Mcrews. Please read fusion210 post.

"When you drive a low powered low weight car, 40lbs is something you can feel when driving. In acceleration, braking and other handling aspects. If 40lbs was nothing to be bothered with, manufacturers wouldn't use lightweight metals to shed 40lbs. But they do.

He's not saying that 40lbs is worth 5% better gas mileage or anything like that."

Of course weight reduction in un-sprung weight (i.e wheel/alloys) is more noticeable but every lbs counts in a smaller vehicle (75-100bhp).

But having now seen what it takes to remove some of the deadening I think it is best left. Worth questioning.

hummmmm.....
You said that there was 40lbs of deadening material.

That is just a little different than "removing 40 lbs"
maybe YOU should re-read what you wrote.
so to be clear....PLEASE SHOW ME 40lb of deadening material you can remove from YOUR car..
Let's stay on topic and not re-invent the discussion.

After all, I have documented the removal of my spare tire ('40 lbs+ of removal) from my 02 Infiniti Q45 5 yrs ago. So I am familiar with the concept of OVERALL weight removal.

I stand by my original statement.

reminds me of a management training exersice I run.

You whisper in the first persons ear a sentence. By the 6th person it has changed dramaticly.
It only took 8 posts here to change the point!

So that I am clear.
I dont believe there is 40lbs of deadening material to be found in the avg english car.
But if there were, AND you completely dismantled the interior to find it, why would you not put the (light weight) insolation INSIDE where it would work w/ 100% effecientcy (what ever that is).
If you don't put it inside then ANY inside noise (like the radio????) will sound like crap.
Remembering thwe the new material has a weight that you have to ADD to the UPTO 40lbs. THen when that material on the OUTSIDE gets wet, it gets heavier. ANd wont dry out in the closed environment of the underbelly pan. So the new weight stays.

Something to keep in mind. The deadening material that is attached to the sheet metal is simply vibration dampening. It is not there to block noise from entering the car, and is not dense enough to be effective at doing that.

The noise insulation in the car is the carpet padding, and in some cars the heavy vinyl/rubber and foam backed sheet that covers the firewall. To block sound, you need dense material.


The deadening in a 1996 dodge neon weighed 32 pounds, including all of the asphalt based deadening, the carpet padding, the firewall mat, and rubber hole patches that keep noise from the frame rails from entering. It will take several days, a heat gun, and scraper to get all the asphalt deadening out. If your lucky at have a butyl based deadener, you could dry ice it, and tap it out with a mallet.

Your engine noise will increase, especially with the windows closed. The closed environment will create a resonant chamber, that will drone at whatever speed your engine reaches the resonant frequency of the car.

I'll never remove sound deadening again for weight loss, unless building a strict competition car.

That's sound advice. I saw some clips where people who were putting dry ice on it, to get it to come off :D. lol

http://www.youtube.com/watch?v=uTtwg-f5YRc lol! haha

I have a belly pan and didn't notice any noise reduction. I removed the back seat, spare and parcel shelf in my hatchback for about 100 lbs of weight reduction in the VW. The downside was INCREASED noise. I added another 11 lbs on Dynamat sound deadener and still my wife would rather not ride in the car with the back seat out because of the tire noise.

Im all with toostubborn2fail advice.

I will also throw in, that over the past couple weeks since i added my revised full belly, and additional rear wheel weel inserts.
> Found Here

Mostly the rear wheel inserts have made a bigger difference than the belly in reduced road/tire/wind noise. Essentially.
Moreover added a resonent dampend material between
>Wheel:Wheel well lining/metal<
With 98% added reduction of high pressure air escaping out the wheel.

There's no easy way to reduce a prefab cars, noise level without Adding minute weight in materials specifically made for sound deadening purposes.

Makes sense, as dynamat is a vibration dampener. The seat, shelf, and spare were better at blocking noise than dynamat is. To block noise, you need a decoupled mass loaded barrier. Something like mass loaded vinyl, separated from the metal by closed cell foam, or lead with closed cell foam on both sides.

There is indeed over 30lbs of sound deadening material in a small lowly neon. If you counted the undercoating I'm sure it would hover around 40.

40lbs in a larger vehicle is absolutely believable.

For what it's worth you definitely sound like you run management training exercises mcrews.

40 lbs
 

A 1,000-lb weight addition to my Civic cost me 2-mpg at a constant 55-mph.

220 pounds of audio equipment cost me less than 1mpg at 70, per scangauge. With tolerances, it really wasn't measurable. In town might have been more, but my car doesn't get driven in town much.

Actually I'm surprised that one of our resident math/science/engineer types dont have an equation for this problem.
But we know that the issue is drag. Time is much better spent (and later enjoyed) smoothing out the shape.
That's why we always focus on:
1. increase psi (cheapest fix) worth 2mpg
2. Grill block - warmer engine & some aero gain
3. Belly pan - can improve are dramaticly AND is invisible.

All of my record setting cross country drives were done with more that 500 lbs of luggage in the car and trunk.
And back in Sacramento It was a struggle to get egual (much less better) mileage results.
so here's some math.
2002 Infiniti Q45 3800 lbs. add 500 lbs which is more than 15% of the original weight.
Get 34 mpg.
Remove the 500 lbs when i get home. Never got any better than 33mpg.
Note: went over the Great Divide......lots of down hill coasting!

your potential 30 lbs + new material 7lbs = 23 net loss. I bet it wont make a difference.
but try it your self. Get a spare tire and add it to the car. test run. Then take the tire out. test run. My gut says less that 1/2 a mpg improvement.