RICK KRANZ

How the 2012 Camaro ZL1 got its growl

Tony Roma, Camaro program engineering manager, on the exhaust sound engineering for the 2012 Camaro ZL1: “It scares little children and annoys senior citizens. We know we have it right.”
Rick Kranz is product editor for Automotive News.
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ALTON, Va. -- The 2012 Camaro ZL1 is the most powerful production Camaro ever built and rivals the Chevrolet Corvette in overall performance.

Under the Camaro's hood is a supercharged 580-hp V-8 that produces 556 pounds-feet of torque. It's a real head snapper.

Equally important in the car's creation were the exhaust "notes," the cool sounds emitted from the exhaust system. GM's engineers worked for a year to create the right notes.

Why are these notes so important?

"The exhaust is a clue to the soul of the car. It is a character of the car," said Tony Roma, Camaro program engineering manager. "It is part of the signature of the car."

Roma said GM's engineers used the computer model that predicts engine power to create the right exhaust notes.

"It is crazy what you can do. You put in the exhaust system [data], tell it the back pressure, tell it the induction restrictions. We have a whole model of the engine -- friction, combustion, the whole thing. You tell it your parameters and it will predict how much power the engine makes.

"You can literally hit 'play,' hook up speakers to your computer, and it will play what the engine sounds like revving though the engine speeds," he said during a Camaro ZL1 event at Virginia International Raceway here, about 65 miles northwest of Raleigh, N.C.

The development team wanted the best sounding exhaust notes at cruising speed, at idle and at high and low rpms, when the car is accelerating or decelerating.

The end result was the creation of what Roma called an active exhaust system that is programmed to provide a specific sound for a specific situation.

"The sound is dramatically different" through the range, Roma said.

At the same time, the engine sound couldn't exceed noise regulations, the decibel limits set by states and municipalities.

Data were given to GM's noise and vibration team and to the automaker's exhaust system supplier to replicate several notes. They determined such things as the size of the exhaust pipes, the volume of air that will flow through the chambers, the design of the exhaust tips and the electronic controls needed to achieve the right notes within legal noise limits.

For example, "we have perforated holes inside the exhaust tips that change the frequency content of what comes out the tip," Roma said. "It gets rid of that high-frequency kind of air rush noise that would sound like a vacuum cleaner."

A year ago, the ZL1 development team spent three days on the streets in San Diego and at a nearby drag strip testing cars with the final two exhaust systems, "revving them up, just listening to them" and then making the final selection.

How does he describe the final choice?

Laughed Roma: "It scares little children and annoys senior citizens. We know we have it right."

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