Glasspack - Wikipedia

Type of automobile muffler This article is about the auto part. For the rock band, see The Glasspack.

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A glasspack is a type of automobile muffler in which the exhaust gas passes straight through the center of the muffler. The basic design consists of one smaller tube centered inside a larger outer tube that is enlarged or swollen in the middle. The gap between the enlarged part of the outer tube and the center tube is packed with fiberglass, hence the name. A common alternate name is "cherry bomb", after an early hot rod muffler manufacturer.[1]

Design

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The glasspack is an old, simple, and relatively inexpensive muffler design that has less back pressure than other types of muffler, but is less effective at muffling noise.

A longer glasspack will reduce noise to a greater extent than a shorter one, as sound is dissipated into the fiberglass damping material. Other glasspack mufflers have perforated louvers 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.[2] The more turbulence created, the greater the muffling and 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 mesh, and more advanced acoustic engineering, reducing noise while retaining the power-preserving advantages of a straight-through exhaust flow.

Legality

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Glasspacks and other modifications that increase the noise level of exhaust systems are illegal in the United Kingdom.[3]

See also

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• Exhaust system
• Custom car
• Boy racer

References

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1. ^ Chris DeMorro (2010-10-19). "A Look Inside Cherry Bomb and How they Build Exhaust Components". Dragzine. Retrieved 2025-10-02.
2. ^ "Frequently Asked Questions (FAQ-U)". Maxima Forums. Retrieved 2023-10-11.
3. ^ "Noise from roads, trains or planes". UK Government (Crown Copyright).

External links

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• Diagram of glass pack muffler

v t e Internal combustion engine
Part of the Automobile series
Engine block and rotating assembly	Balance shaft Block heater Bore Connecting rod Crankcase Crankcase ventilation system (PCV valve) Crankpin Crankshaft Core plug (freeze plug) Cylinder (bank, layout) Displacement Flywheel Firing order Stroke Main bearing Piston Piston ring Starter ring gear
Valvetrain and Cylinder head	Flathead layout Overhead camshaft layout Overhead valve (pushrod) layout Tappet / lifter Camshaft Chest Combustion chamber Compression ratio Head gasket Rocker arm Timing belt Valve
Forced induction	Blowoff valve Boost controller Intercooler Supercharger Turbocharger
Fuel system	Diesel engine Petrol engine Carburetor Fuel filter Fuel injection Fuel pump Fuel tank
Ignition	Magneto Compression ignition Coil-on-plug Distributor Glow plug Ignition coil Spark plug Spark plug wires Capacitor discharge ignition
Engine management	Engine control unit (ECU)
Electrical system	Alternator Battery Dynamo Starter motor
Intake system	Airbox Air filter Idle air control actuator Inlet manifold MAP sensor MAF sensor Throttle Throttle position sensor
Exhaust system	Catalytic converter Diesel particulate filter EGT sensor Exhaust manifold Muffler Oxygen sensor
Cooling system	Air cooling Water cooling Electric fan Radiator Thermostat Viscous fan (fan clutch)
Lubrication	Oil Oil filter Oil pump Sump (wet, dry)
Other	Knocking / pinging Power band Redline Stratified charge Top dead centre
Portal Category