If you’ve ever ridden in a car with a performance exhaust system, it’s likely you’ve heard “the drone” – that incredibly annoying, tough-to-stomach sound that happens with certain mufflers at particular RPM levels. It can be so off-putting that it makes driving or riding in the car an exercise in endurance, and can even spoil the characteristics of the car so much that you don’t want to be in it.
Thankfully, CORSA Performance is on the hunt to eliminate the drone with their patented Reflective Sound Cancellation technology, engineered into each and every one of their muffler designs, and we are going to explain how it works.
The CORSA brand has been in existence for over 25 years, with a start in the marine category building exhaust systems for high-performance boats. They entered the automotive aftermarket in 1998, but the RSC technology had been in development for quite some time leading up to that entry. In fact, the 1998 Indianapolis 500 Corvette Pace Car showcased the technology before the company officially entered the marketplace.
This 3-inch C6 Z06/ZR1 exhaust system [PN 14164] uses the Sport sound profile and has a 45 percent flow gain over the stock muffler system. It provides an average increase of 15 horsepower and is nearly 14 pounds lighter than the factory exhaust.
The Invention Process
Aftermarket exhaust systems have always been known for providing an aggressive tone under maximum power, but some don’t offer a nice experience during the street-driving portion of a car’s life. That same ability to provide the aggressive tone when the pedal was to the wood came at the expense of cruising volume, as the designs around at that time used a variety of different technologies to round out the exhaust note, but proved ineffective for dampening sound properly at normal speeds.
Working in conjunction with a NASA scientist, the CORSA team worked to build what they consider a better mousetrap by creating an exhaust system that did three things well – maximize performance, eliminate the frequencies that create the dreaded “drone” that occurs under cruising conditions, and provide a quality driving experience for the car’s owner.
A full view of the RSC technology. Sound waves flow in on the left from the engine, and only the aggressive notes that you want to hear are transported out the back end; the other frequencies are bounced back and forth within the dampening section, eventually returning to the flowpath 180-degree out of phase – but never to be heard again.
The end result of this research became CORSA’s Reflective Sound Cancellation (RSC) technology, which they say did exactly that – mute the bad sounds while retaining the good ones and setting the stage for a consumer to have the best of both worlds because, after all, what good is a performance exhaust system if it doesn’t speak to you when you hammer the throttle?
How Does It Work?
Performance mufflers typically take certain avenues to dampen sound – reflection, absorption, or some combination of the two. The sound that travels from the exhaust is a pressure wave that’s formed from pulses of alternating high and low pressure, which make their way through the air at the speed of sound – no surprise there, right? Engines create those pulses when the exhaust valves open at different times, and the high-pressure gases escape from the cylinder and enter the exhaust system. The gases stack up with the lower-pressure molecules in the pipe, which leaves an area of lower pressure behind it in the pipe. Now multiply that by four, or six, or eight cylinders, and you have an exhaust tone as the pressure pulses reach your eardrum.
A closeup of the RSC technology in the muffler – you can see how the slots at the inlet end force the unwanted frequencies out and around the main tube in the muffler. Unwanted sound waves are subsequently cancelled out so that you can’t hear them.
Testing CORSA Exhaust Systems
Once the system particulars are nailed down, each one is tested to ensure that it flows better than a stock exhaust system and gives the expected result. On some vehicles, the CORSA team explores the application further with dyno testing to gain insight into new technologies and system designs.
Their focus on constant product improvement has enabled them to produce unique exhaust components that allow for performance gains while maintaining the enjoyable characteristics of driving the vehicle in question.
“RSC provides the unique benefit of providing a straight through design, with no restrictions to airflow to maximize performance, but at the same time enables us to create a tunable muffler to target and eliminate specific frequencies that cause drone under a variety of driving conditions. The end result is a free-flowing system, with a Jekyll and Hyde mentality of having a nice aggressive sound at idle and under acceleration yet quiet at cruise with absolutely no drone,” says CORSA’s Brent Noward.
Flip the Script
By diverting the unwanted low-frequency sound waves that cause the drone through slots in the muffler, reversing them 180 degrees, and ultimately sending them into the muffler’s packing, the RSC technology targets and eliminates the frequencies that cause the interior resonance and drone. An added benefit to the technology occurs as CORSA is able to acoustically tune the muffler design to create an aggressive sound under acceleration to match the personality of each individual application.
“Over the years CORSA has continued to develop RSC technology, and we’ve refined the design to allow for further tunability. A variety of sound levels are possible, showcasing our three different muffler designs. The Touring systems offer slightly louder than stock sound with no drone. Sport gives a high performance sound, distinct rumble at idle, and no drone during cruise. Lastly, there’s our Xtreme muffler, which offers the most aggressive sound level, a deep growl at idle, bold sound during acceleration, screams at high RPM and still permits no drone during cruise,” Noward explains.
Today the company has three different acoustical solution patents pertaining to exhaust systems and muffler design, has multiple acoustical engineers on their staff, and uses their own proprietary software to develop new systems for many different applications.
Each system, including the muffler itself, is designed for a particular vehicle-specific application, as no two vehicle models are the same in terms of exhaust note and performance.
CORSA’s bolt-on exhaust systems are all created on vehicle-specific jigs and cut with a laser cutter for accuracy.
“A CORSA system takes into account a wide variety of variables to create the exacting requirements of each system. Every CORSA system has to deliver on its No Drone promise without exception, but before a system can be created a long list of attributes must be measured and calculated. We measure everything from the vehicle’s stock acoustical characteristics of sound to vehicle performance and record those measurements under a wide range of driving conditions,” says Noward.
TIG-welding, laser-cutting - all of the latest and greatest technologies are used by the CORSA team as they craft exhaust systems designed to fit right and sound great.
We measure everything from the vehicle’s stock acoustical characteristics of sound to vehicle performance and record those measurements under a wide range of driving conditions. – Brent Noward
Once the company establishes a baseline for a particular application, they repeat the process under the same conditions with a straight pipe to monitor and record the raw sound of the engine. After each variable is recorded, the development process begins.
CAD software is employed at the hands of the acoustical engineers to model a prototype. The research and development department fabricates the prototype and installs it onto the vehicle, where the same set of attributes as were measured previously is measured again, both under static and dynamic driving conditions. This allows them to compare the systems back-to-back for real-world results and ensure the prototype system meets all expectations for both sound and performance.
They use Spectrum Analysis equipment to measure sound output, and those results are pinpointed through the proprietary software the company employs to remove the drone, while leaving the roar intact.
A visual illustration of how the sound waves are processed by the RSC technology.
Building exhaust systems that need to fit the first time, every time, is an undertaking on a massive scale. Each tube needs to be bent properly, each weld needs to be perfect, and each hanger needs to be in the correct place, with clamps that seal properly and last for the life of the vehicle – and it needs to be a repeatable process.
“Once the system is designed and testing has been completed, the systems are then sent through a pilot production run. During this phase of the development process we ensure large scale manufacturing of the exhaust system is able to be produced efficiently and consistently. As the product continues to get honed into its final production form we are making finite adjustments all throughout the process that allow CORSA to deliver the best possible product to the market with consistency and durability,” says Noward.
The Corsa facility is massive - with both manufacturing and warehousing under one roof, they've got a little bit of something for everyone going on in Ohio.
Every one of Corsa’s systems is produced in their ISO 9001:2008 compliant manufacturing facility in Berea, Ohio. The ISO spec requires that the company adhere to specific and rigorous manufacturing, development, and business operation standards.
Here a CORSA Performance craftsman finishes up the welding on a muffler assembly. Both TIG and MIG welding are employed depending upon the situation.
Their manufacturing techniques include robotic welding, laser cutting, mandrel bending, and the use of both TIG and MIG welding operations to ensure that the systems meet not only the manufacturing standard but also their own internal standards for fitment and performance. Each CORSA exhaust component is built from heavy-gauge premium 304 stainless steel and is backed by their limited lifetime warranty.
Sounds Good to Us
Nobody wants to drop a few weeks worth of fun money on an exhaust system that in turn makes them resent turning the key to go for a cruise, and through the use of their exclusive RSC technology, CORSA Performance is out to make sure that the reality is exactly the opposite.
We’ve discussed each of the three styles of muffler that the company makes, and if you’re interested in hearing them for yourself, they have a complete gallery of sound clips on their website that you can check out. Chances are your vehicle is there, so head on over and give it a listen. Each system’s sound is presented during a variety of conditions, giving you a true sense of exactly what you’ll get once you open the box.