Did you know exhaust systems function like elaborate organ pipes? I always thought they were more like long megaphones or trumpets, transmitting and muting the sound of the explosions happening in the cylinders. Nope. The noise is actually generated by the rush of exhaust gasses passing—sometimes at sonic or supersonic speeds—through an exhaust valve opening, just like compressed air entering an organ pipe. This probably isn’t news to folks in the exhaust-system biz, yet Borla Performance Industries is only just now getting patent protection for tuning exhaust pipes like organ pipes.
Maybe that’s because not enough musicians design exhaust systems. David Borla, son of the performance exhaust company’s co-founders, Alex and Alyse Borla, started out in the music biz. The composer and performer held a Sony recording contract and has several IMDB movie soundtrack writing credits to his name. Now serving as the company’s sales and marketing VP, David initially riffed on the idea behind his dad’s XR1 racing-muffler patent. That concept uses a bundle of perforated tubes inside a muffler to achieve greater noise attenuation and better flow than a single large perforated tube can deliver. His experimentation with combinations of perforated and unperforated tubes resulted in the company’s line of Acoustically Tuned Applied Kinetics (ATAK) products.
Then one night David was contemplating the whole organ pipe concept and realized that “one of the things that makes an organ what it is are the polyphonic notes—playing more than one note at the same time. Harmony.” He reckoned that if pipes could be combined to engender pleasing chords like triads (a root note plus its third and fifth intervals) or perfect fifths (the kerrang of an AC/DC power chord—root plus fifth interval), the result might inherently sound more pleasing—an exhaust chorus instead of a soloist. So he visited organ pipe factories and learned how varying a pipe’s size can help it convert one note into another.
Now his team records an engine’s exhaust signature using a frequency-spectrum analyzer that helps identify pleasing and objectionable frequencies. (V-12s mostly produce the former; four-bangers generate a ton of the latter.) Pipes are then selected to enhance the sweet notes, de-emphasize or cancel the sour ones, and generate harmony. Borla has just scratched the surface of what this technology can do and is working to develop computer simulations to speed development of new systems. At press time, polyphonic pipes are available for the Focus RS, Fusion Sport, Challenger R/T, and Infiniti Q60S, soon to be joined by BMW M3/M4, Honda Civic Type R, and Kia Stinger systems.
Lessons learned so far: Location of the polyphonic pipes makes a huge difference—they’re quite close to the engine on the Focus RS system, just ahead of the tailpipe mufflers on the Fusion, and just aft of the cross-over pipe on the Challenger and Q60S systems. Polyphonics can restore much of the richness and sound character lost to turbochargers. And systems can be tuned loud or quiet—the Q60S system sings 4dB louder than stock (too loud for Euro pass-by regulations), but forthcoming Mustang EcoBoost and GT systems will be Euro-compliant.
“You’re not going to listen to it and go, ‘Oh, that’s a C triad,’” David Borla notes, “because there are harmonics and overtones. And engine speed, heat, and humidity can all affect the note. But these combinations just sound cool, and they sound different.” They also look cool. Most feature four smaller pipes spliced into the main pipe using header collectors.
Pricing for these million-mile-warranted T-304 stainless steel systems is higher-end but not crazy—$1,208 for the Focus RS cat-back system, with competitor prices ranging from $499 (MBRP’s aluminized steel) to $1,475 for a cp-e system claiming a 5 percent power boost. (Borla makes no specific performance claim for its cat-back system but does for its high-flow-catalyst downpipe.) Your choice—an exhaust that sounds like full-on AC/DC, or an Angus Young unplugged one-note solo.
Read more by Frank Markus here:
- Assessing the First Case in a Predicted Autonomy Epidemic
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- GTHO! Going in Depth with Mazda’s Brilliant Skyactiv X Engine
- Exploring the Future of EV Charging with Continental’s ALLCHARGE Concept
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