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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.


The Verdict:
Fact
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.


Read more: http://www.importtuner.com/tech/impp_1006_nissan_350z_motordyne_fact_or_fiction/viewall.html#ixzz1bRYfnlsz

It seems legit, perhaps a similar design for the GT-R would work even better. Thoughts?
 

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This principle is very valid, but nobody has tested it on the GT-R yet.

Motordyne, along with the Japanese company Saclam, use Helmholtz Resonance principles in their design.
 

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ive always wondered why saclam exhausts look so overly complicated

good read

 

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^DING DING DING^
Helmholtz resonance can only occur under pulsed flow conditions. IE 6 manifold primaries merging into an exhaust pipe. The volume and length of the various segments can be manipulated to move the resonant frequency to a useful spot/spots in the powerband.

The inclusion of a turbocharger and the and the accompanying pre/post turbo pressure zones all but eliminates any usable pressure pulses downstream of the turbine.
 

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Yes, intakes and intake manifolds can be tuned to take advantage of the helmholtz resonance principles. But again, it will not apply to the GTR because it is a turbocharged car. On our Formula SAE car in college we used a tuned intake manifold and exhaust header to strategically place torqe peaks at particularly advantageous spots in the power band. Worked great as we ended up with a very broad and flat torque curve with tons of midrange torque (ideal for the autocross course that the car would compete on).

So yeah, it works.
 

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Yes, intakes and intake manifolds can be tuned to take advantage of the helmholtz resonance principles. But again, it will not apply to the GTR because it is a turbocharged car. On our Formula SAE car in college we used a tuned intake manifold and exhaust header to strategically place torqe peaks at particularly advantageous spots in the power band. Worked great as we ended up with a very broad and flat torque curve with tons of midrange torque (ideal for the autocross course that the car would compete on).

So yeah, it works.
Incorrect, tuned intake manifolds work well on forced induction cars. If that were not the case you would see no effort to manage plenum volume, runner lengths etc. there is a wrinkle though. One large component of Helmholtz tuning is the speed of sound IE the rate at which the pressure wave bounced off the intake valve and back into the plenum. Since the speed of sound is dependent on the density of the medium it is travelIng through, boost pressure can affect the timing of these pulses. The more dense the air in the manifold the faster they travel.
This fact can and has been used to allow an intake manifold to hit more than one resonant peak in a vehicles power bad. For example, long runners tend to favor low end torque; more air column and it takes more time for a pulse traveling x speed to clear it. Long runners then, on an NA or turbo engine would seem to be beneficial from a low RPM / per boost torque perspective. Now, push a ton of boost into the manifold and the speed of sound in the runner goes up, an the pulses now clear the runner at a higher frequency by virtue of higher speed.

Tuning for a forced induction intake is difficult though, just that many more variables.
 

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Incorrect, tuned intake manifolds work well on forced induction cars. If that were not the case you would see no effort to manage plenum volume, runner lengths etc. there is a wrinkle though. One large component of Helmholtz tuning is the speed of sound IE the rate at which the pressure wave bounced off the intake valve and back into the plenum. Since the speed of sound is dependent on the density of the medium it is travelIng through, boost pressure can affect the timing of these pulses. The more dense the air in the manifold the faster they travel.
This fact can and has been used to allow an intake manifold to hit more than one resonant peak in a vehicles power bad. For example, long runners tend to favor low end torque; more air column and it takes more time for a pulse traveling x speed to clear it. Long runners then, on an NA or turbo engine would seem to be beneficial from a low RPM / per boost torque perspective. Now, push a ton of boost into the manifold and the speed of sound in the runner goes up, an the pulses now clear the runner at a higher frequency by virtue of higher speed.

Tuning for a forced induction intake is difficult though, just that many more variables.
I guess what I meant was that it is much easier and effective to tune N/A intakes because you don't have the added variable of boost. The gains you will see from a properly tuned intake and exhaust on an N/A enigne will be much larger than that of a forced induction engine, percentage wise. For turbo cars we can just turn up the boost ;). Also, the speed of sound increases with the temperature of the gas, not the density, but in this example the IAT will increase as you increase the boost, so the end point is still valid.
 

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I guess what I meant was that it is much easier and effective to tune N/A intakes because you don't have the added variable of boost. The gains you will see from a properly tuned intake and exhaust on an N/A enigne will be much larger than that of a forced induction engine, percentage wise. For turbo cars we can just turn up the boost ;). Also, the speed of sound increases with the temperature of the gas, not the density, but in this example the IAT will increase as you increase the boost, so the end point is still valid.
don't neglect the pulse dynamics.
 

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As I said a ton of variables but it is possible, especially in a known OEM configuration to make certain optimizations that can be made. If Helmholtz tuning was not possible on the intake of a FI car why do the have runners with any length, or a plenum that is any larger than what is necessary to connect them and not cause a steady state restriction?

I do agree that larger gains can be found in a FI car than Helmholtz optimization. A good example would be a 2003-2004 Ford Mustang Cobra. They slapped a blower and intercooler on it to up the power. Packaging dictated that they could have an intercooler OR a proper inlet manifold with tuned runners. The intercooler won. The manifold is little more than a flanged box that mounts a blower, contains an A/W intercooler and belmouths to transition into the intake ports.

The GTR does not have the same packaging constraint. If you have freedom over the molds eke out any advantage you can. Especially one that will help with off boost power which is generally the Achilles heel of a motor built for forced induction.

Why optimize intake design, why put bigger cams in, why port the heads if you can just turn up the boost?;-)
 
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