A glasspack is a type of automobile
muffler
A muffler (North American and Australian English) or silencer (British English) is a device for reducing the noise emitted by the exhaust of an internal combustion engine—especially a noise-deadening device forming part of the exhaust sys ...
in which the
exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...
passes straight through the center of the muffler. The basic design consists of one smaller tube centered inside of a larger outer tube that is enlarged or swollen in the middle. The gap between the swollen part of the larger outer tube and the smaller diameter center tube is packed full of
fiberglass
Fiberglass ( American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...
, hence the name.
Glasspacks are an old, simple, and relatively inexpensive muffler design that are effective at reducing
back pressure
Back pressure (or backpressure) is a resistance or force opposing the desired flow of fluid through pipes, leading to friction loss and pressure drop. The term ''back pressure'' is a misnomer, as pressure is a scalar quantity, so it has a magnit ...
, but not very effective at muffling noise. They are usually easy to identify by their simple tube design. Most are painted or powder coated red, but not all.
United States
Glasspack mufflers were originally offered in the United States by Cherry Bomb in 1968. Since then, the name of Glasspack is closely associated with this brand name, yet today that is not the only company that produces Glasspack mufflers. The distinctive features of the Glasspack mufflers are traditional red powder coating, original straight-through construction and fiberglass inner tube, and its distinctive classic sound. A longer glasspack will reduce noise to a greater extent than a shorter one. Sound is also dissipated into the fiberglass damping material. Other glasspack mufflers have perforated
louver
A louver (American English) or louvre (British English; see spelling differences) is a window blind or shutter with horizontal slats that are angled to admit light and air, but to keep out rain and direct sunshine. The angle of the sla ...
s punched into the center core which can reduce total flow capacity. The turbulence created by the perforated louvers therefore achieves greater muffling capacity at the expense of total volume of air flow. The more turbulence created, the greater the muffling & less total air flow / power production capacity. Depending on the directionality of the louvers, one can choose between slightly higher flow capacity or slightly greater muffling. This lower flow but slightly quieter design approach is commonly used in glasspack mufflers.
Some modern muffler designs are similar in principle to the glasspack, but use more sophisticated sound-absorbing materials such as
stainless steel
Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's r ...
mesh, and more advanced acoustical engineering, reducing noise while retaining the power-preserving advantages of a straight-through exhaust flow.
Outside the United States
Glasspacks and other modifications that increase the noise level of exhaust systems are illegal in the United Kingdom.
See also
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Aftermarket exhaust parts
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Exhaust system
An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall syste ...
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Modified car
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Boy racer
References
External links
Diagram of glass pack muffler{{Automotive engine , collapsed
Exhaust systems
Vehicle modifications