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Introduction

The sound/noise insulation and vibration deadening properties of almost any vehicle (except high-end luxury vehicles) can be improved through the installation of various sound insulating and vibration deadening/damping materials.

Jimnys are no exception there. They are relatively cheap vehicles, and therefore all of them have relatively poor sound insulation applied from the factory.

Factory sound insulation

In Jimny 3

The factory sound insulation which is (relatively sparsely) applied to the interior of most Jimnys 3 consists of the following:

1. Bitumen compound, glued on about 70% of the floor area;
2. Small pieces of bitumen-based mats, glued on the side door outer panels and on the side panels below rear side windows;
3. Cotton scrap material (about 15 mm thick), glued on about 80% of the underside the floor carpet;
   • This material is called by various names, like "felt", "jute", "dew" ....
4. Large rubber pad (with 5 mm thick cotton scrap underlay), just placed against the "firewall";
   • A "firewall" (in this context) is the metal wall / panel between front passengers' legs and the engine;

There is no sound insulation at all on any of the interior plastic trims (side door trim, rear door trim, rear side trim below rear side windows), nor below the roof.

In Jimny 4

Info needed ...

Installation

The general principles of choosing and installing sound insulation and vibration deadening/damping materials in a Jimny are all the same as in most other vehicles.

Also don't forget to factor in the work of dismantling the interior trim and assembling it back together.

Start educating yourself on this generic world Wikipedia article.

The good news regarding Jimnys in this process are:

1. Their interior is relatively easy to dismantle;
2. They are quite small vehicles, so they need relatively small amounts of material and relatively small amount work to apply them;

Best practices on vehicle sound proofing

Introduction

The following notes and advice represent an "abridged" knowledge and experience, which are the result of reading, watching, listening to and talking to various sources and schools of thought regarding acoustic treatments, sound proofing in general, and automotive sound proofing in particular.

Important notes on proper applications

There are numerous wrong ways to do vehicle sound proofing, and only a few correct ways.

There is a high risk to end up doing it by one of the wrong ways, especially because there is a LOT of misleading information and mis-recommendations regarding these topics on the Internet.

That is mainly for two reasons:

1. Ignorance by laymen who represent themselves as experts;
   • Many of them preach their advice and principles based on faulty experiments and thus faulty conclusions, or a mix of correct and faulty principles;
   • There is also a lot of "hearsay knowledge" which has become "common knowledge" just due to the widespread of misinformation;
2. Greedy interests by sound proofing material manufacturers and professional installers;
   • Most of them aim to sell maximum quantity and/or the most expensive materials, without the regard if such quantity is justified regarding its effectiveness, or if the type of material is actually optimal for the application.

The risk of misapplication can lead to:

1. Using excessive amounts of (usually) expensive materials with no additional gain;
   • This can also result in an excessive increase in vehicle's weight;
   • This has a lasting negative impact on vehicle's performance and its fuel economy.
2. Not achieving the desired effect, thus wasting material and effort;
3. Both of the above;

Main principles of vehicle sound proofing

General points

When approaching any sound proofing project, the first step is to determine the following:

1. Types of sounds against which an insulation is desired;
2. Sources / directions of such sounds;
3. Environment factors and risks (moisture, heat, fire, toxicity, appearance, etc.);
4. Special circumstances (accessibility to the area of application, ease of future removal in case of some repairs, etc.);

Generally, these are the types of sounds encountered in a moving vehicle:

1. Various metal and plastic panel vibrations;
   • These are usually caused by engine and transmission operation, irregular road surface, and operation of audio speakers.
2. Operating noise of an internal combustion engine;
   • Diesel engines are particularly "strong" performers in this regard;
3. Exhaust system noise;
4. Transmission operation noise;
   • This means noise caused by the rotation of various gears;
5. Rolling tyre noise;
6. Air friction noise;
   • Noise of air moving underneath the vehicle, around the vehicle and over the vehicle;
7. Rain drops hitting the vehicle (roof, hood, windows, etc.);
8. Various environmental noises and sounds;
   • Examples: other vehicles passing by, people laughing on the street, animals barking, howling, roaring and squeaking on the field, angry drivers honking, a volcano erupting nearby, mines and rockets exploding in the vicinity, etc.

All these sounds can roughly be classified in three main types:

1. Low frequency (bangs, drums, hums, etc.);
2. Medium frequency (roars, shouts, hurls, howls, etc.);
3. High frequency (pitches, screams, squeaks, etc.);

No single material can block all types of sounds, nor is applicable to every surface and in every mounting position.

Therefore, applying at least two types of materials (a two layer insulation) is a minimum requirement for having any hopes of achieving a comprehensive sound insulation in a vehicle. Applying three types of materials (in three layers) provides an even better solution.

Those three types of materials /layers are:

1. A "viscoelastic" material - CLD (Constrained Layer Damper);
2. A sound absorbing + decoupling material - usually a CCF (closed cell foam);
3. A sound blocking material - usually a MLV (Mass Loaded Vinyl);

Layer 1 - CLD

General info on CLD materials

• A viscoelastic material is the first layer, and it is usually the most expensive of the three types of materials.
• The main trick is in the viscoelastic adjective.
  • Such materials combine the properties of both viscous and elastic materials in one - they resist movement (viscous), and they return back to original shape after the deforming force has perished (elastic).
    • This means that such materials absorb relatively strong mechanical stress (vibration is a mechanical stress) relatively well, and they turn its mechanical energy into low level heat.
• Therefore, the main purpose of a CLD material is to dampen vibrations of a base panel to which it is applied (stuck onto).
  • What actually happens is that the vibration frequency of an underlying metal panel is reduced to a lower value, which is usually below the human hearing range.
• CLD materials have relatively poor insulation properties of airborne sounds (wind howls, engine roars, people shouting, etc.).
• Vehicle manufacturers have traditionally (ever since the dawn of automobiles) used bitumen as the CLD layer with varying amounts of application inside a vehicle (depending on the price / class of vehicle).
• A much better (and much more expensive) material for this purpose is butyl, which has gained prevalence over bitumen in the 21st century.
• For CLD applications, butyl (in its raw form) is produced with a layer of thin aluminium foil.
  • Such CLD products are usually called "alubutyl".
• All CLD materials are relatively heavy (usually between 2 kg and 4 kg per m2).

Differences between alubutyl and bitumen

Bitumen and butyl CLD sheets look and feel very similar. Therefore, a layman can not discern any practical differences between the two materials. Therefore, many people see no reason to pay a premium price for alubutyl CLDs, since they can get classic bitumen CLDs for less than a third of the price. The list below will show them all the reasons NOT to use bitumen CLDs.

Differences between alubutyl and bitumen:

1. Temperature dependency characteristics.
   • Bitumen is quite brittle when cold, and quite soft and squishy when warm.
   • Mechanical properties of butyl are much less temperature dependent than those of bitumen.
   • Therefore, bitumen has a risk of delaminating (partially separating or even falling off from a surface) when it gets really warm.
     • This is especially the risk with dark-colored vehicles on hot sunny days.
     • If the bitumen partially delaminates from a metal panel, there is a high risk of moisture getting trapped in between, rusting the metal panel.
2. Material's vibration damping performance varies significantly based on its hardness.
   • Therefore, bitumen loses a significant amount of its intended performance (because it becomes too stiff or too soft) whenever the ambient temperature is outside of its "normal" range (15-25 C).
   • Butyl, having a more consistent hardness through a wide temperature range, is a more uniform performer.
3. Installation process.
   • Bitumen (and the intended underlying surface) have to be heated up significantly with a torch or a hot air gun during installation.
     • Reason: it is the only way to make the bitumen soft and tacky enough so that there is a hope of adhering it properly to the surface.
   • Raw butyl is naturally quite "tacky" and has strong self-adhesive properties.
     • Therefore, butyl does not require any additional adhesives and does not require heating up with a hot air gun when applying.
       • Note: this is valid as long as the environment temperature during application is over approx. 12-15 degrees Celsius.
     • This difference also makes the installation of alubutyl CLDs much easier and faster than bitumen CLDs, especially in awkward and hard to reach areas (example: inside doors).
4. Risk of corrosion promotion.
   • If a CLD material partially delaminates from the underlying metal panel, moisture can get trapped in between, thus promoting unseen corrosion.
   • Bitumen carries a certain risk of delaminating in the future even if applied properly (see more above).
   • Butyl sticks so well to a surface (when applied properly with a pressure roller) that there is practically no chance of moisture ever coming in between it and the underlying surface.
5. Odor emission and toxicity.
   • Bitumen, being a type of tar, usually stinks on tar whenever it gets quite warm.
     • Apart from being quite unpleasant, tar smells are usually not exceptionally healthy.
   • Butyl never emits any kind of odor.
6. Ease of removal.
   • Butyl is much easier to remove in the future than bitumen (in case that some repairs on the bodywork are needed).
     • Only bare hands and a lot of pulling are required (plus some minor cleanup of some of the remains by bare hands).
   • It is very hard to remove bitumen on an ambient temperature (unless chiseling it off is an acceptable method).
   • There are two typical methods of removing bitumen:
     1. Hot method: Heating it up significantly with a hot air gun or a torch so it becomes super soft. Then scraping it off.
        • This is quite messy - almost like removing a hazelnut spread.
     2. Cold method: Cooling it to extreme levels (around -70 degrees Celsius) by covering it with dry ice (frozen CO2) so it becomes super brittle. Then simply shattering it with a hammer.
        • This is reported as an easiest method, but has the logistical complexity of handling the dry ice.
7. Vibration damping performance.
   • The viscoelastic performance of high quality alubutyl CLDs is usually at least twice as good as the performance of typical bitumen CLDs, even in bitumen's optimal temperature range.
   • This means that usually at least a double amount of bitumen CLD material has to be used to achieve the same vibration damping effect as a high quality alubutyl CLD.
   • This defeats bitumen CLD's cost saving advantage.
     • This is especially valid when considering the additional work of applying a double layer, as well as the weight which the double amount of bitumen CLD material adds, permanently affecting vehicle's performance and fuel economy.

Additional notes on alubutyl CLDs

1. Beware that some CLD manufacturers do not specify the material used, and that some of them use a mix of butyl and bitumen.
   • Use CLDs only made by brand name manufacturers which clearly state to be 100% butyl (with aluminium foil) and which have good reviews.
2. The two main performance parameters of alubutyl CLDs are MLF (mechanical loss factor - vibration damping "strength") and its temperature dependency, which should be observed in correlation.
   • Therefore, when comparing two different CLDs, an ideal method would be to have the "MLF to temperature dependency" graphs for both of them.
   • If such graphs are not available, but only single MLF values, then it makes sense to compare those individual MLF values only if both are stated for the exact same temperature.
     • For example, it is invalid to compare MLF of alubutyl product A to MLF of alubutyl product B if MLF "A" is stated for 25 degrees C and MLF "B" is stated for 15 degrees C.
3. When choosing an alubutyl CLD, prefer those which have some sort of physical embossment pattern on their aluminium layer (usually repeated honeycomb or rectangles).
   • This pattern serves as an indicator during the installation.
     • When alubutyl is pressed in using a pressure roller tool during the installation, the embossed ribs in the aluminium foil largely disappear if pressed in properly.
     • This indicates that that area of the CLD has been pressed in properly for permanent and complete surface adhesion.
4. Look for the specification of aluminium foil's thickness.
   • Preferred thickness is around 100 ym, while thickness of around 60 ym usually represents a cheap / budget solution.
   • Beware that there are some specialized alubutyl CLDs with relatively thin butyl layer and relatively very thick aluminium foil (around 0,3 mm or even more).
     • These CLDs are not optimal for vibration damping of solid panels - they are too stiff.
     • These CLDs are instead meant to seal large technological holes /cavities in the bodywork and to structurally strengthen the metal panels around the hole.
     • Typical application example is when there is a high performance speaker in a door.
       • The inner door cavity serves as a "box / enclosure" for the speaker, and sealing its technological opening and strengthening the surrounds improves the acoustic performance of the speaker.

Proper application of CLDs

• In contrast to all other types and layers of sound insulation and deadening materials, it is not required to achieve 100% surface coverage with CLDs for proper effect.
• Unfortunately, covering 100% of surface area with CLDs is one of the most common (and most expensive and time consuming) mistakes.
• This misconception is mostly "powered" by instructional videos from CLD material manufacturers and from professional vehicle sound proofing installers.
  • The vast majority of such instructional videos portray full 100% surface coverage with CLD materials (for example, 100% of the floor, doors, roof, wheel arches, etc.).
  • Some CLD manufacturers and installers even have neat interactive "vehicle surface coverage" calculators, which calculate how much material packages you need to buy from them for a certain typical vehicle type (for example: a large sedan).
• There are two typical motives of their authors for promoting that misconception:
  1. Aim to sell maximum quantity of material (alubutyl CLD is usually the most expensive type of material).
  2. Fear of looking "unprofessional" or "skimpy" if they don't cover 100% of the surface.
     • Due to the widespread misconception, most customers (of which many are rich snobs who want the luxury of having premium sound proofing) expect full surface coverage as a visual indication that the sound proofing has been thoroughly done.

In physical reality, most of panel's vibrations are dampened with much less surface coverage with a CLD material, and the formula for surface coverage is not linear.

Panel surface coverage vs. vibration damping effect

% of surface coverage	% of maximum effect
25	70
50	90
75	97
100	100

The above are rough estimates, just to get the idea of the correlation. The actual correlation highly depends on the panel size, shape, orientation, any indents, points of connection with other panels, material type and thickness, etc.

So, in general terms, surface coverage between 25% and 50% will give more than adequate vibration damping effect for most panels. There is never a benefit in covering more than 75% of panel area with a CLD material. In other words, anything over 75% surface coverage is always a pure waste.

Also note that some panels hardly require any vibration damping at all. Those are usually "double skinned" panels, thick panels, curved panels (especially heavily curved ones) and heavily ribbed panels.

The best "on site" method of determining if a panel is susceptible to vibration is by tapping it with a hand and listening its response. If it sounds "hollow" and/or "echoey", then it should be dampened. Likewise, if it sounds quite solid and "dull", it may need only a little bit of vibration damping, or none at all. Usually the most susceptible to vibrations are large, flat, thin, non-reinforced metal panels.

Bitumen CLD removal techniques

Introduction

Most vehicle manufacturers still use bitumen CLD material for vibration damping on vehicle floors. The two main probable reasons for that are because (1) it is a cheaper material and (2) because they can apply it quite easily by super-heating it to a near-liquid (honey-like) state and just robotically pouring it over the floor. Since it is so squishy in that moment, the bitumen naturally conforms and settles exactly on the shapes of the underlying panels and no rolling or pressing is required.

Standard removal methods

However, the removal of this material can be quite of a hassle (to put it very mildly).

It is quite stiff / hard at regular ambient temperatures (10 - 30 C) but not brittle at all. Therefore, it is extremely difficult to remove. It is too stiff / hard to scrape off with normal effort, and not brittle at all to crack it by hammering it.

The only three possible bitumen CLD removal options at ambient temperatures are:

1. To use a very strong scraper;
   • This requires a LOT of manual power (jargon term: "elbow grease");
   • There is a high risk of scratching the underlying metal panels.
2. To use a hammer with a chisel.
   • This will certainly make a lot of scratches in the underlying metal panels.
   • There is even a significant risk of denting them.
3. To soak it with petrol, brake cleaner fluid or WD-40 (all of these fluids dissolve bitumen).
   • This will create a major mess (think of a gigantic oil tanker ocean spill) and will require LOTS of paper towels and multiple soaking iterations to dissolve all the bitumen.

Hot bitumen removal method

The scraping off method can be significantly eased (and the risk of scratching reduced) by heating up the bitumen with a hot air gun. This will soften up the bitumen, so the scraping can be done without extraordinary manual power. However, the softened bitumen behaves like a sticky and very dense cream, and thus creates a lot of mess during removal (like removing bull shit from the floor of a stable).

Cold bitumen removal method

Finally, we come to the best bitumen removal method.

The most effective method by far to remove factory bitumen vibrodamping coatings from horizontal sheet metal is to cover them with "dry ice" (frozen CO2).

Frozen C02 is so extremely cold (around -80 C) that the bitumen cracks due to rapid freezing and stiffens to a super brittle state, almost like potato chips.

It is then quite easy to scrape (or even just pull) the bitumen off without much force. Sometimes huge pieces come off in one move. If a certain section of bitumen still "holds on" when trying to pull it off or to scrape it off, it can be lightly hammered to crack it and that will release it from the metal sheet.

Usually there will be only minimal bitumen residue left on the underlying metal sheet after removing the bitumen with the dry ice method. The remains can easily be wiped off with paper towel or cotton wool soaked in petrol, WD-40 or brake cleaning fluid.

Conclusion: Dry ice method is much, much faster as well as cleaner than heating the bitumen up with a hot air gun and then messing with it, literally.

Where and how to obtain dry ice:

• In some countries, dry ice can be obtained from regular shopping malls where people buy everyday consumables.
  • If not available there in your region, it is usually available from companies which deal with gasses and other chemicals (for example butane-propane bottle filling facilities).
• Alternative "ingenious" source of frozen C02 is from C02 fire extinguishers.
  • Just spray the bitumen sheets with a C02 fire extinguisher and it will spray frozen C02 all over it.
    • Beware that this is a completely imprecise application method (see more notes about that below).
• Frozen CO2 thaws quickly on ambient temperatures (it literally evaporates / sublimates directly into its gas form - hence the name "dry ice").
  • Therefore, you should at least use some portable freezer / refridgerator as the basic transportation container, if you don't have specialized storage containers for the dry ice.
    • A simple passive portable beach refridgerator filled with water ice cubes is still better than nothing.
  • Note that it is quite difficult to store frozen CO2 for longer than 24 hours even in the best ordinary household freezers (which usually don't cool below -20 C).

Additional notes:

• Dry ice can also be mixed with some alcohol, which will additionally improve the heat transfer to the bitumen.
• Dry ice usually comes in the form or snow (preferred form) or in the form of chunks or pellets.
  • If the chunks or pellets are relatively large, they should be quickly crushed into smaller fragments just before applying them to the bitumen.
• Try to avoid covering anything except bitumen with dry ice, as covering painted metal with such cold material might crack the paint as well!
• Removing bitumen CLDs from vertical surfaces with the dry ice method requires some improvisation.
  • One solution is to put dry ice in a garbage bag and press and hold the bag against the vertical bitumen with something for a minute or so.
• Beware not to touch dry ice with bare hands, or you will instantly learn how it feels to hold the most frigid woman in the universe in your arms!
  • Use heavy duty thermal insulation gloves and some metal tools like big spoons etc.

Layer 2 - sound absorbers + surface decouplers

Introduction

The primary purpose of the 2nd layer is to decouple the 3rd layer from the base surface (including the 1st layer), so that any surface vibrations (which can still occur in an (off)road going vehicle no matter how much of 1st layer is present) do not entice the heavy 3rd layer to also begin vibrating.

The secondary purpose of the 2nd layer is to provide thermal insulation.

The tertiary purpose of the 2nd layer is to absorb sounds - both those coming from outside into vehicle's cabin, and particularly those originating from inside the cabin. Absorption of interior sounds reduces reverberation and echo and therefore creates "softer" sounding interior environment when speaking, singing, yelling, listening to music, and also softens all the "technical" sounds like engine and exhaust noise. It is a similar "softening" effect as after an empty room gets filled with floor carpet and furniture.

Thermoinsulating and sound absorbing performance of the 2nd layer (for any type of layer 2 material) is directly proportional to its thickness. Unfortunately, space in vehicle's cabin is always restricted, so the thickness of layer 2 materials in most areas in vehicle's cabin can be between 3 mm and 10 mm (depending on area), 15 mm in certain places if you are lucky. Do not try to "overfill" an area with a too thick layer 2 material. You will most probably have major issues with reinstalling the carpet or the original trim back in place, and most layer 2 materials lose their sound absorbing properties when compressed anyway, so you get no additional gain, only pain.

Typical materials

The most common layer 2 materials are:

• Cotton felt (scrap);
• Open cell foam - OCF;
• Closed cell foam - CCF;
• Hydrophobic melamine foam - HMF;

Cotton felt

Cotton felt is chopped and pressed scrap material from cotton garment factories etc (analogue to wood particle boards made from wood saw chips).

Cotton felt is used by most vehicle manufacturers for three reasons:

1. The cheapest solution (scrap material);
2. Very good sound absorbing properties;
3. Very good decoupling performance;
4. Excellent thermal insulating properties;
5. Natural material, so no customer health issues or regulatory / court claims to worry about;

However, cotton scrap has one major disadvantage for certain usage scenarios - it loves soaking in water and moisture and holding for very long time. Stale moisture in it causes many small organisms (like bacteria, mold, fungi etc.) to grow and thrive and rot the material, causing decay and stench.

Therefore, cotton scrap is a potentially awful material choice for moisture-risky areas like below the carpets, inside the doors etc. However, the irony is that many vehicle manufacturers use it in those particular places more than in any other!

Another disadvantage of cotton felt is that most such materials do not like high temperatures (like those in the engine bay), are flammable and love to burn. Exception is if it is treated with some fire retardant chemicals etc., but that needs to be checked with the manufacturer and that also raises the questions of health hazards through possible emissions of VOCs (volatile organic compounds).

Open cell foam

OCF is a foam which is made up of individual cells, where every cell is partially open ("incomplete").

Properties of open cell foams:

1. Relatively cheap;
2. Very good sound absorbing properties;
3. Some thermal insulating properties;
4. Very light;
5. Can be made high-temperature tolerant and also resistant to burning;
   • Manufacturer / product dependent;
6. Easily compresses under pressure so does not carry weight on it well;
   • When compressed, its sound absorbing properties diminish;
7. Very good decoupling performance (if not under significant pressure);
8. NOT water resistant;
9. Tendency to hold in water and moisture (though not as thoroughly long as cotton scrap);
   • This induces tendency to develop mold and stench in it if left wet.

Based on the properties above, the conclusion is that OCF has the same issues with water as cotton scrap. On the other hand, if it is a high temperature fire-retardant variant, it can be used in places where cotton scrap can not, like in the engine bay or near the exhaust etc.

Closed cell foam

CCF is a foam which is made up of individual cells, where every cell is completely closed, like a bubble.

Properties of closed cell foams:

1. More expensive than OCF, as more material per volume is used (much higher density);
2. Good sound absorbing properties;
3. Some sound blocking properties;
   • Sound frequency blocking range is highly dependent on foam thickness;
4. Exceptionally good thermal insulating properties;
5. Very good decoupling performance (if not under strong pressure);
6. Quite light;
7. Can be made high-temperature tolerant and also resistant to burning;
   • Manufacturer / product dependent;
8. Compresses under pressure but not as easily as open cell foam;
   • When compressed, its sound absorbing and sound blocking properties diminish;
9. Completely water proof;
   • When it comes into contact with water, the water will just float on it - it will never penetrate into the foam.

Based on the properties above, the conclusion is that CCF has many useful properties and no particular disadvantages, for relatively high economic cost. Being waterproof is a major advantage for certain usage scenarios, like in the doors, under the floor carpet etc.

Hydrophobic melamine foam

Not much is currently known about HMF, expect that it generally has similar characteristics as CCF, only does most of those better but at a premium price.

Layer 3 - sound blockers

Introduction

The purpose of the final layer is to block the sounds.

The only thing which blocks the sounds is mass. The heavier (denser) an object is, the stronger sounds it can block. Steel and concrete for example are excellent sound blockers. However, if a material (like those two) is stiff, there is a risk with lower frequencies of a side effect contrary to sound blocking - sound enhancing. That is when a stiff sound blocker starts resonating and enhancing the vibration (strong low frequency sound), instead of blocking it. That is why concrete building apartments are notorious for transmitting every trump, bump and hit created in them throughout the other apartments in the building.

Therefore, a proper sound blocker needs to be very heavy (dense) but not stiff. Lead is a very good material which has both of these properties - extremely dense, still relatively stiff but a lot less than other metals. Lead is used as a sound blocker in many industrial applications, but is limited to uses where it is sealed off from coming into contact with living beings, because of its toxicity.

Another quite heavy and quite flexible material is mass loaded vinyl. That is vinyl which is imbued with a very dense material, usually barium sulfate. Vinyl is already relatively heavy but more importantly, is quite flexible. When combined with very heavy and non-toxic barium sulfate, the resulting material gets the best of both worlds.

Therefore, mass loaded vinyl (MLV) is the material of choice as a layer 3 material (sound blocker), especially for automotive applications.

Notes about MLV

Here are some quick notes about MLVs:

• Not all MLVs are the same - quality varies.
• Some MLVs could be toxic - double check product's technical specifications and material safety data sheet before buying.
• Some (more expensive) MLVs are made from "virgin" vinyl, while some (cheaper) are made from recycled vinyl.
  • The ones made from recycled vinyl tend to emit "plastic-like" odors for quite a while or even indefinitely (especially when warm/hot), and should therefore be avoided for automotive applications.
  • Double check with the manufacturer or the seller if the desired MLV product emits any odors before buying.
• While MLVs should have no problems enduring temperatures up to at least 80 degrees C (normal occurrence in automobiles), it is better to double-check in product's technical specifications.

• MLVs are very heavy, so don't be surprised at humongous postage fees if buying remotely.
• MLVs are made in different thicknesses which translates into different weight per surface area and therefore different sound blocking "strength".
  • Typical densities are around 2 kg / m2, around 4 kg / m2, around 6 kg / m2, 8 kg / m2, etc.
    • MLV density of 4 kg / m2 is considered "normal" density for automotive applications - it provides significant sound blocking performance, at moderate additional weight payload penalty for the vehicle.
    • Using MLV densities of 6 kg / m2 or more in automotive applications will add considerable weight payload penalty to the vehicle, and might be too thick for certain areas in the vehicle.
    • MLV density of 2 kg / m2 will provide only light to moderate sound blocking performance, but at an advantage of low additional weight penalty for the vehicle.

• Some MLVs are made pre-glued with a layer 2 material (vibration decoupler) - usually CCF.
• The thickness of pre-glued CCF depends on the product, but usually varies between 3 mm and 10 mm.
• While such "combo" CCF+MLV products are usually more expensive than separate MLV and CCF products, they can save considerable installation time, as in most cases you need to put CCF under MLV anyway (as a thermal insulator and as a vibration decoupler). When installing CCF and MLV separately, you have to cut and conform both products separately to the surface. With a combined CCF+MLV product, this (sometimes tedious) installation process is done only once.

Installing MLV

• MLV is easy to cut with strong scissors or with a blade.
• Do not try to stretch MLV - it does not like that.

• MLV has to achieve 100,00% coverage of a certain area in order to effectively block sound.
  • It's analogue to hydro insulation - even a small crack will seep water/sound through.
• Therefore, adjoining pieces of MLV should be overlapped by at least 2 cm and then glued together using a glue which is compatible with vinyl and which can endure temperatures of at least 80 C.
• If two adjoining pieces of MLV can not be overlapped (usually because they are too short), then a third "adjoining" strip of MLV (usually 3-5 cm wide) should be placed over the join and glued to both adjoining pieces, thus creating a sealed connection.

Recommended additional works

While all the vehicle's cabin interior is dismantled and removed in order to install sound insulation, you might use the opportunity to perform some additional works in the exposed cabin sections along the way.

Jimny 3 specifics

Forum user Bosanek went through the process of completely stripping the interior of his Jimny 3 and applying additional sound insulation.

This chapter will currently contain only some quick notes until more time is found later to properly "frame" all the content.

Most Jimnys 3 contain OEM bitumen vibration damping (CLD) material hot melted onto the floor on the factory production line. That material covers about 80% of the front floor section (below rear seats) and about 60% of the rear floor section (below rear seats). It also covers some sections of the front floor transmission tunnel.

The factory bitumen CLD material is known for partially delaminating from the underlying sheet metal as it gets old (perhaps 10 years or older?). In some cases it has not stuck well even from the factory.

If you decide on replacing it with a high quality alubutyl CLD, the fastest and easiest method to remove it is to cover it with dry ice (frozen C02) mixed with alcohol. This will cause extreme rapid cooling, which will shrink and stiffen the bitumen so much what it will delaminate from the underlying metal. Then just slam it slightly with a hammer and pry it off. It will come off like big chunks of chips. Beware not to cover surrounding metal sheet with dry ice, only the bitumen itself and not to use excessive amounts of dry ice. Rapid cooling of the metal sheets might cause the underbody stone chip protection to crack too!

The total weight of OEM bitumen CLD material removed from a Jimny 3 weighted around 6,5 kg (measured in two parts on a kitchen scale).

Don't be surprised of you encounter some rusty surprises under the removed bitumen!

An additional hassle which you will encounter while removing OEM bitumen CLD is the presence of underlying body seam sealer compound, which bitumen covers in certain sections (where the floor sections overlap). This compound is super difficult to remove when dry ice is not used. It is much easier to remove with dry ice, but even then more effort is required than to remove the bitumen. The strange thing is that this OEM seam sealer is generally flexible and easy to scrape off on the floor sections which are not covered with bitumen, but the part of it which was covered with bitumen is extra stiff and tough to scrape off. Even when some sections of it resist the dry ice, use of a chisel or a flat screwdriver is usually necessary to forcibly scrape of the remaining parts which were under the bitumen.

The body seams which were covered with the OEM seam sealer should then be re-sealed with a high quality polyurethane seam sealer. It is a higher quality material than the OEM seam sealer anyway.

Examples of Jimnys with applied sound insulation

Most of these examples have been stumbled upon on the Internet. No evaluation of the quality or purposefulness of the work in them has been performed!

• Example 1 on a Jimny 3 from Russia;

References

Until this article gets properly written, gather some more knowledge at the following forum topics:

• Bonnet insulation;
• Sound deadening;
• Vaxxi's sound proofed Jimny;

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Page last edited on 17/01/2021 by user Bosanek