As much fun as it is to prove or dispel tuning-related myths and misconceptions, we must admit: it's always more fun to put sketchy products with bold claims to the test. Sure, both set the record straight and settle arguments, but testing product marketers' mechanical "theories" usually ends in someone's feelings getting hurt-call us twisted, but that's fun to do sometimes.
Can Helmholtz Resonance Be
Utilized to Make More Power?
Having taken a break from busting fuel treatments to find that the G-Tech is surprisingly accurate (April, '10), and settle the lightweight flywheels/torque debate (May, '10), you can imagine how sadistically happy we were when we caught wind of these products from Motordyne: ART (Advanced Resonance Tuning) test pipes and resonated Shockwave V2 exhaust, designed to increase power over traditional aftermarket alternatives by using chambers that trigger Helmholtz resonance to aide in exhaust gas scavenging for increased power. Shyeah . . . and that rich Nigerian prince who keeps emailing us about cashing his inheritance check is totally legit.
Now, Helmholtz resonance is a scientifically proven phenomenon. The property can be demonstrated with a glass bottle: As air is blown across the top of the bottle, some enters it, is momentarily compressed, and then surges outward at a slightly faster rate than it went in, creating a vacuum that draws more air back into the bottle to continue the process. Proof of this oscillation of air can be heard in the tone or frequency emitted by doing so. In the case of the products at hand, exhaust gasses are blown across built-in resonance chambers, and the frequency of pressure waves created therein pushes exhaust gas through the tubing and out into the atmosphere. Now, if Motordyne has one thing working toward their credit, it's that they're by no means an upstart company. Remember the plenum spacers that have become mainstays in 350Z tuning for their simple, low-buck design and solid power gains? Turns out Motordyne owner Tony Colette was a rocket scientist in his previous profession (no, seriously-he was), and he invented those. "Not only will the resonance chambers increase scavenging and power," Tony promises about his new products, "but the titanium tips on the Shockwave exhaust also reduce pressure drop by gradually expanding the exhaust gas to recover its dynamic pressure," which, he claims, also helps increase scavenging. Exhaust tips for power? We were really looking forward to the dyno.
To test Motordyne's claims with its ART products, we gathered Ken Kojima's '06 Nissan 350Z, equipped with a reputable "Brand X" test-pipe and exhaust, to the Dynojet rollers of Yimisport Tuning in Santa Clarita, CA, where it was baselined, then tested with Motordyne's ART pipes and resonated ShockWave V2 exhaust in place of its original aftermarket vendible.
With Motordyne's ART test-pipes and resonated Shockwave V2 exhaust installed, gains as high as 9.4 whp and 17 lb-ft of torque were found throughout the '04 350Z's powerband-impressive, considering we were already testing against proven aftermarket upgrades, but Tony wasn't happy. Ken's car had been fitted with a cone filter/short-tube intake that, he suspected, was wreaking havoc on the car's MAF sensor, triggering the unusually rich air/fuel ratios throughout the duration of testing. Tony promised his products were good for even more power, and arranged an '07 Nissan 350Z (Rev-Up) as a second test car to prove it.
With its factory flat-panel air filter and box installed on the '07 350Z, testing re-commenced. Replacing the car's stock cat-back exhaust with Motordyne's Shockwave V2 produced as much as 22.7 whp and 17.9 lb-ft of torque at points in the powerband, and where the "Brand X" test-pipes produced as much as 23.3 whp and 31.8 lb-ft of torque over the stock cats at some points, Motordyne's ART test-pipes increased their output by an additional 11.2 whp and 29.7 lb-ft of torque at varying rpm. Air/fuel ratios stayed in their normal range this time, and power gains-as promised-were more plentiful.
Tested on two different cars, with two (slightly) different engines, compared to two different aftermarket manufacturers' conventional products, the gains by which Motordyne's resonance-chamber-equipped products increased power were definite. Now, you might be wondering what would happen if a different exhaust is used with the ART test-pipes, or if the Shockwave V exhaust would make power with the stock cats. Would the difference in airflow throw off the whole system and negate power gains?' "Think of blowing across that bottle," explains Tony. "If you blow harder, with more air, the frequency doesn't change but the volume or amplitude does. It's the same here. More air means even more resonance and more scavenging." Still, what happened in our first test? "350Zs have a problem with certain short-tube intakes," explains Tony. "Depending on their design, we think they direct air toward the car's MAF sensor a certain way that triggers an improper injection of fuel, which decreases power." He continues, "It's a well-documented problem, but as far as I know, no one's ever gotten to the bottom of it." Sounds like we have a topic for next month.