Since the beginning of hot rodding, enthusiasts have tinkered with their car’s exhaust system, particularly the mufflers, to get the “right sound.”
A muffler’s job sounds easy enough- reduce exhaust volume to tolerable levels while allowing the sweet sounds of your ride to waft through the air. But this becomes a monumental task as horsepower increases. Engines build horsepower by pushing spent exhaust out of the tailpipe as fast as possible. As pistons furiously churn, exhaust velocity increases, making your ride louder. The difficult function of performance mufflers is to keep noise where you want it, produce great sound and add horsepower.
In the golden age of muscle cars (i.e., late 1960s/early 1970s), the most popular and least costly method, was to replace the factory muffler with a glasspack muffler. Also known as a “straight-through” design, glasspack mufflers were the simplest style of muffler used on performance rides. At the heart of a glasspack muffler, is a single, perforated exhaust tube. This runs from inlet to outlet, with quieter mufflers using an angled tube and louder mufflers using a straight tube. Fiberglass or steel wool packing is wound around the tube and enclosed in a steel or aluminum shell. With their low-restriction design, glasspack mufflers are great for building more horsepower and pumping out deep exhaust tones. Sounds ranged in volume from noticeably louder-than-stock, to ear-splitting. Two widely used brands were Cherry Bomb and Thrush.
After the glasspack craze ran its course, enthusiasts turned to chambered mufflers to recapture that classic muscle car tone. With chambered mufflers, exhaust is routed through multiple chambers and around any number of angled, sound-cancelling plates, known as “baffles.” With few restrictions along the way, exhaust flow is boosted, increasing horsepower, torque and fuel economy. On top of that, they produce a rumbling, slightly metallic exhaust note that turns heads. Another plus is that chambered mufflers always sound great as the miles pile up, since they do not have packing material, like glasspacks, to blow out. A popular brand is Flowmaster.
Another type of muffler used is the turbo-muffler. It uses three or fewer tubes, so exhaust flow changes direction less. This means engine exhaust leaves the muffler faster, for an increase in horsepower and a better exhaust tone. And, turbo mufflers occasionally use additional fiberglass packing around the tubes for more sound control. For this reason, a turbo mufflers sound can vary widely in volume and tone. They work great as a “step-up” from a stock muffler and tend to be quieter than glasspack or chambered mufflers. A popular brand is Magnaflow.
When the 2008 Challenger SRT debuted, it featured dual resonators and a large “suitcase” chambered muffler at mid-chassis to control the exhaust sound of the 6.1 Hemi (5-speed automatic). SRT engineers claimed that the decibel readings coming out of the 2.75 inch exhaust pipes was the highest permitted under the law. In 2009, the suitcase muffler was replaced with two “bottle” mufflers on Challengers equipped with the new Tremac 6-speed manual.
"Suitcase" Muffler and dual resonators
Cutaway of Resonator (with packing removed)
Resonators are also an integral part of an exhaust system. As your engine’s exhaust gases leave the combustion chamber, sound waves bounce off of the walls of the pipes and ricochet all around creating both high and low frequency noise. As engineers analyzed and improved exhaust systems, they realized there were advantages to be gained in organizing and controlling these pulses and came up with the concept for the resonator. Essentially it acts like a large echo chamber that takes the exhaust pulses and optimizes their frequencies to achieve better fuel efficiency and power production.
Aside from producing the tone of your vehicle’s engine and helping move exhaust gas along its way, the resonator also plays part in controlling the volume of sound that your engine emits. By manipulating the frequency of exhaust sound waves, it can either give your car a more throaty and loud tone or silence it for smooth peaceful driving.
Resonators are often times confused for mufflers and while they may appear similar and share some of the same jobs, they play an integral part in producing optimal volume and tone from your engine. They also have an important role in the exhaust evacuating process, which helps your engine produce more power and reduce fuel consumption at the same time.
The “sweetspot” for Challengers owners came in 2015 with advent of an electronically controlled exhaust, for R/T Scat Packs and SRTs (with 392 engines). The 2.75 dual mode exhaust system produces a deep, throaty exhaust note, under acceleration, in keeping with the Challenger’s heritage and track-bred credentials. It uses a pair of electronic valves located near the rear of the vehicle to control the level of the exhaust noise. At idle and in light throttle situations, the valves are in their closed position to keep sound levels down. This also helps to reduce “drone” when cruising on the highway and won’t wake your neighbors while idling. But, when you put the hammer down, the valves open and the exhaust gets a whole lot louder! (see "Active Exhaust" article).
The sound of this exhaust system on the 2015-2016 Scat Packs and SRTs became one of the favorite features among owners (after the raw power), but buyers of the models with the 5.7L Hemi V8 were been forced to turn to the aftermarket for a similar roar. However, for the 2017, model year, the active exhaust system also became standard on performance models equipped with the 5.7L engine (i.e., R/T, R/T Plus, R/T Shaker and R/T Shaker Plus).
Dodge hit another home run!
By SRT-Tom · Mar 2, 2019 ·
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