Shutting Down Interior Heat And Road Noise With DEI

Old cars are loud, and it’s not the exhaust we’re talking about. They have the bare minimum for insulation; they don’t benefit from today’s technology when it comes to bushings and insulators, and the large, flat sheets of tin like to rattle and amplify sounds coming from the roadway. Modern cars have so much insulation that the driver usually can’t even hear the exhaust underneath the car.

While it’s true most gearheads want to hear the engine, the road, and the exhaust, those sounds can be daunting on longer drives. Without insulation, not only is the car a bit louder – which forces us to speak louder to our passenger – but the heat associated with the exhaust and other mechanical components can make the interior of the car a bit warmer as well. To combat those old school traits, we called on DEI – Design Engineering, Inc., to help help filter out unwanted noises and heat.

Whether it's the ignition wires, heat from the exhaust, or the elements that you want to shelter components from, DEI has just about everything you'll need to do the job.

Insulating fuel lines, wiring harnesses, cables, and tubing can be done with Heat Shield. The various sizes allow for as small as 1/2-inch up to 1-1/4-inch sizes, and come in three-foot lengths.

Initially, we looked to insulate some of the heat and road noise coming from under the car. But there are so many products under the DEI umbrella that you can literally go to town protecting various components from heat.

We’ve used some of its products before to protect things like harnesses and shifter cables from the exhaust heat, and the product will protect up to 500 degrees direct heat and up to 2,000 degrees radiant heat. The Heat Shroud products we used come in a variety of sizes, from closed tubing to hook and loop fasteners to ease installation, and are made from a high temperature rated glass fiber fabric with an aluminized outer facing. They can be cut easily with scissors, and it’s also fireproof.

Top: As you can see, our shifter cable is in tight quarters with the header. Without the DEI's Heat Shroud, the cable housing will melt (and did!)
Bottom: if you're installing new lines, you can slide the Heat Shield product over wires, hoses, and tubes; for protecting existing applications, the hook and loop Heat Shield wraps around the components and can be secured without removing them.

Main Floor Sound And Heat Insulation

Our main focus for reducing heat and sound is within the cabin of the vehicle. With just an existing carpet kit with its included backing, we saw temperatures on our floor reach well over 180 degrees – too hot to the touch. This heat can break down the carpeting and radiates that heat into the interior. So DEI delivered some products to help us beat the heat, and drown out some unwanted sound.

Two products that we used for the interior are Boom Mat, a self-adhesive vibration dampener for the large, flat floor surfaces, and Under Carpet Lite – a sound deadening and insulation product from DEI. However, we’re not limited to just those two products as DEI offers a multitude of products for both sound and heat insulation.

Boom Mat will help lessen vibrations in the sheetmetal, and Under Carpet Lite will insulate from heat and road noise. Both products are available in various quantities for big or small jobs.

There are other products on the market for both heat and sound insulation, and many enthusiasts have used them at one time or another. The products can be quite costly to install if you follow the “more is better” mantra that some companies would have you follow.

The curved parts of your floor pan are not where the vibration is. It’s the flat sheetmetal that causes the tinny sound, and that’s the only area that you need to apply Boom Mat. -Mike Bucca, DEI

But at DEI, the philosophy is “less is more”, and we were surprised to see how little material is actually needed for some of our insulation goals. Instead of covering every square inch of the floor with Boom Mat, for instance, DEI’s Mike Bucca told us, “The curved parts of your floor pan are not where the vibration is. It’s the flat sheetmetal that causes the tinny sound, and that’s the only area that you need to apply Boom Mat.”

This made sense, and even at shows like SEMA and MPMC we got to see how this principle works on samples that DEI shared with us. With a small piece of Boom Mat installed on a cutaway from a floor pan, it was hard to determine if the part was actually sheetmetal or a composite because the tin sound and resonance was completely gone. The sample showed only the flat portion of the sheetmetal receiving Boom Mat.

Removing the carpet shows exactly what is underneath: nothing but metal. Metal, of course, absorbs heat and resonates vibrations from the road. While our floor wasn’t completely flat, there was room for improvement.

By limiting the sound insulation to smaller, flat areas of the floor, it means less material is needed, which drastically cuts down on the costs. While some companies will provide a vehicle kit that covers nearly every square inch of the interior sheetmetal, we were able to get the job done with much less material and make a noticeable difference.

This is a perfect time to address any rust issues you might have with the floor. We had previously sealed it up with POR-15.

Out With The Old, In With The New

We began our interior project by laying out our new carpet kit in the sun to soften it, and to lay out the Under Carpet Lite from DEI. The sheet is large enough to do a couple of cars, and dwarfs our carpet kit. We cut away the insulation on the new carpet, as the product from DEI will handle all the insulation we need.

We removed the seats and our makeshift console, and removed the old carpeting. This is a great time to address any rust issues, or missing/cracked body plugs. We had already laid down some POR15 on some of the lightly rusted areas, and vacuumed out all the dust and debris on the floor. It was time for Boom Mat to be put into place on the bare floor.

Boom Mat is self-adhesive and we have to warn you: once you press it down, it’s not easy to remove. So be sure to place each piece exactly where you want it. It’s not going to move around once it’s in place.

As DEI stated, it’s not necessary to cover every square inch, and with our oddly shaped floor pan that was a relief. We started with pre-cut squares that came in the full car kit, and started laying them down. Although we didn’t need to cover all the curved areas, such as up the side of the console, if the product covered some of it we were fine with it because it meant less cutting.

Starting with full sheets, we removed the backing and gently laid out the sheet on the floor, being careful to not press it into place until it was lined up. Boom Mat has an adhesive property that makes it near impossible to remove once it’s pressed down. We used a small roller to make installation easier, and to help smooth it out a little. It can be cut with standard scissors or a utility knife, and is easy to cut and shape.

While you might be tempted to cover everything, we're told it's just overkill by DEI. Those curved areas on the floor won't resonate any vibrations, but the flat part of the floor will, so we covered in full sheets, then covered smaller flat areas with remnants.

We cut ‘darts’ into the Boom Mat to help cover the shape of the floor pan, and laid sheets from the front to the rear of the car, trimming where needed, and kept the product mostly to flat, smooth areas. With the floor covered with Boom Mat, we were ready to start on the Under Carpet Lite.

It’s a large sheet and more than you’ll need, and you can install it one of two ways: lay the whole sheet down and cut as necessary, or try to measure it and lay it out in smaller pieces. A little adhesive spray will help keep it in place and prevent it from shifting, but it isn’t necessary to adhere the entire sheet.

DEI states the lighter side should go down, and if your carpet has insulation, it should be removed. Under Carpet Lite is all we needed between the carpet and the floor. We laid it all out and trimmed as necessary.

We had ordered a carpet kit, and laid it out and made our cuts. One thing we can't stress enough here is to make sure you cut all of your holes for seats and seat belts. That goes for the Under Carpet Lite, and the final carpet cover.

This job is simple enough for the do-it-yourselfer, but if you have no experience with carpeting and insulation, and don’t want to tackle it yourself, many upholstery shops can do the job for you. The emphasis on this installation is to remember to mark and cut holes for seat belt bolts and seat hardware. Forget this step, and you might have to remove everything and start over.

Prior to installing Boom Mat and Under Carpet Lite, we read the floor temperature and saw close to 140 degrees on the bare sheetmetal, and 140 degrees on the carpet. With the Under Carpet Lite we saw a reduction down to the low 90s – that’s a 50 degree reduction in radiant heat inside the car.

Prior to this install, we saw 140 degrees on the bare metal, that's too much for comfort. After the installation, we dropped 50 degrees on the surface of the carpet, keeping the heat from radiating into the interior.

In addition to the reduction in radiant heat inside the car, we also had a noticeable reduction in the transfer of road noise. Prior to all of this insulation, we had our stereo cranked up to 34-40 on the volume knob just to hear the music at 70 mph (with the windows up).

After installing Boom Mat and Under Carpet Lite, we could hear the music at a volume level of 20-24 with the windows up, and traveling at 70 mph. With the windows down, we still didn’t need to go to the same level as before, with 28-30 being sufficient. And let us say, all those creaks and squeaks are now so muffled that we don’t even hear them – it was literally like stepping into a different car.

More Insulation Products From DEI

The coverage is almost endless when it comes to products from DEI to protect from heat and elements. From starter shielding to heat reflective material, you can spend hours surfing the DEI website, and a full weekend protecting your vehicle. Check out more of our installation below.

That starter is pretty close to the header, but DEI's Versa-Shield starter protector will keep the heat away. And under the floor, the radiant heat from the muffler helped to reflect some of the heat away from the interior.

Protect your spark plug wires with Protect-A-Sleeve, and if you have spark plug boots laying across your headers install Protect-A-Boot. Both products will protect from up to 1,800 degrees direct heat and up to 2,500 degrees radiant heat. As we mentioned, there's literally no end to what you can do with DEI products.

About the author

Michael Harding

Michael is a full time Power Automedia writer and automotive enthusiast who doesn’t discriminate. Although Mopar is in his blood, he loves any car that looks great and drives even faster.
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