Controlling Noise and Heat in Your Classic Car
By John Gunnell
Keeping noise and heat out of a car so you could enjoy driving it was the subject of a Dynamat seminar held on Education Day at the Hot Rod & Restoration Show in Indianapolis a while back. Manufacturer seminars tend to promote specific products, but this presentation was full of good basic material as well.
One of the basic truths touched upon here was that the thicker the insulation in your car is, the better it will insulate. However, it was stressed that car insulation is different from home insulation and that R values are not a good measure of the efficiency of automotive insulating materials. You can't put a foot or two of insulation in a car like you would in your attic. Therefore, car insulation is designed differently. Chemistry comes into play and creates a thinner and lighter type of insulation that can seal out noise and heat better than in a home.
One comparison mentioned was a bowl full of golf balls and a similar bowl fill of beans. In the first instance you have dozens of golf balls with relatively large air spaces between them, as you might find in a house. In the second case you have thousands of beans packed tighter together with small air gaps between them. This denser material is like that used in cars. Automotive insulation is actually a chemical composite that converts vibration into silent energy in much the way shock absorbers convert dynamic motion into heat that is silent energy.
Typically, mat type insulation will come in 1/8-, 1/4- and 1/2-inch thicknesses for use in different places in a car body. You might be able to fit 1/2-inch material under a roof or on the firewall, but 1/4-inch might be better to use on the floor. Again, the thicker the material, the better the insulation, but the material has to fit the space. So you have to more or less map out the car and decide how thick a mat material to use in various places.
Dynamat noted that many people don't know how to measure the area of the panel they need to insulate. Unless a computerized pre-cut kit is available, it's bad practice to simply ask for enough insulation to do a '50 Mercury. To determine the area you must measure the height times the width and to express the area in square inches, you divide that number by 144. There are some guidelines, however. An early roadster will typically need 72 sq. ft. or two 36 sq. ft. bulk packs. An early coupe will require three bulk packs. A typical muscle car will use up 144 sq. ft. of Dynamat insulation in different thicknesses.
The Brookville Dynaliner Special is a sawed in half hot rod that is cutaway on the opposite side to show how to install insulation.
Each of the different insulating materials is carefully labeled to promote the product name and the purposes it is designed for.
If you want to do only partial dampening to save money on materials, you can still get an acceptable improvement by insulating at least 30 percent of any panel. That will take the basic resonate vibration out of the panel, though it's not going to give you full noise reduction from outside sounds. Using this method, you would put the insulation in the center of the panel where you get the most dynamic motion and vibration. On a panel with an area measuring six square feet, you would need to use and least two square feet of a material like Dynamat.
Dynamat has worked out a number of custom fit kits and says it is adding more of these each day. They are computer calculated for specific cars that get restored a lot like Camaros, Firebirds, Chevelles, muscle cars, some sports cars and Volkswagens The computer figures out what sizes and thicknesses each car requires and even cuts the patterns. You can lay a kit out on the floor, peel off the adhesive covering and simply stick the insulation in the proper place.
The Dynadeck flooring is a new item that resembles vintage rubber mats. The silver stuff is Extreme Dynamat and the black on the door is Dynaliner.
According to Dynamat's testing, this product can reduce cabin noise by up to eight percent or about 15 decimals at 70 mph. Through such tests, six different generations of improved insulation have been developed. Amazingly, the sixth-generation material insulates about five times better than the original, even though it is about half as thick.
This is where the chemistry of sound comes in. By using different gas-filled molecular cell structures, the degree of noise and heat insulation can be increased without upping weight or increasing mass. Temperatures come into play, too. Insulation materials in Dynamat type products operate better at higher heat ranges. This works well in a car where most parts are at temperatures above normal room temperature.
Better quality automotive insulation materials also rely on high performance lightweight insulation, used in conjunction with mat type insulation, to take advantage of a unique phenomenon. Researchers discovered that sometimes when different materials are combined, they perform better together than would be expected. The dissimilar materials benefit from something called bonding resistance or inner facial thermal resistance. Dynaliner insulation also incorporates cell block technology to lock oil and water out of the cells and prevent them from being absorbed into the material as happened years ago with the moisture-trapping open-cell insulation used in older cars.
Roofs typically take thicker insulation (1/2 inch) and quarter panels are typically done with 1/4-inch material.
Whatever insulating material you use, the seminar recommended large sheets. It was pointed out that covering a door panel with a bunch of small 12 x 12 sheets is poor practice. Larger sheets cover more area, require fewer seams and gaps and are easier to install. Larger sheets can also be trimmed smaller, but small sheets can't be trimmed larger. Typical recommended sizes are 12 x 23 inches, 18 x 32 inches, 24 x 48 inches and 12 x 36 inches for particular applications. Use only durable waterproof materials that are safe and don't support a flame. Check the internet for feedback on the supplier you use both for product quality, order fulfillment, shipping times and customer service.
One seminar attendee asked about spray-on insulating materials. Dynamat answered that it sells such products, but doesn't promote their use because of the experiences Detroit automakers have had with sprays. Sprays are production friendly in concept, but have proven to be inefficient, while adding weight and mass. According to Dynamat, no spray works as well as a constrained layer dampening material and sprays also do not reduce heat.
Another attendee asked about insulating a touring car. Dynamat pointed out that insulation in a door really helps in an open car. The inside of a car door is like a box that makes noise like a drum and has drain holes to let the noise out. If you insulate just the doors, the open car is going to feel more solid, be cooler and sound quieter. If you fully insulate it, you'll know the difference immediately. "You don't realize how much noise is in a car body until you start reducing it," said the seminar giver.
Dynamat, Dynaliner and Super Lite Dynamat are all products of Dynamic Control of North America, based in Hamilton, Ohio. To learn more about these products call (513) 860-5094 or visit www.dynamat.com. Dynamat is one of several reputable suppliers of automotive insulating materials.