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Quick Car related question

  1. Aug 22, 2003 #1
    Hi everyone I just have a very quick car related question.
    Is it possible to use sound waves to create "multiple frequency sound waves" that help charge cylinders with air? I'd just like to know because there is a product (an Air intake) that claims to do just this.
    I personally feel that these claims are just junk science and product hype. The only true way to increase air density is to lower temperature and dispel moisture IMO. Here is the link to the product:
    http://www.aempower.com/product_intake.asp it’s the AEM V2.
    Any help with this would be greatly appreciated. -S.K
     
  2. jcsd
  3. Aug 22, 2003 #2
    Atriot,
    sorry, no idea about the physics. But listen to the 2 sound samples from accelerating cars. If you listen closely, you will find that it's the same sample twice. Only put thru different sound filters so that the 2nd version sounds better. That's suspicious, isn't it?
     
  4. Aug 22, 2003 #3

    Ivan Seeking

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    Tuning the intake and exhaust so that the harmonics of these systems coincide with the desired performance range of the engine is standard for racing vehicles.
     
  5. Aug 22, 2003 #4
    Sound waves could be used to heat the air, thereby expanding it and givng an impression of greater volume.
    Looked at the site, saw no real technical data, so I would want to know lots more before I would spend a cent!
     
  6. Aug 22, 2003 #5
    Can anyone refute the claim that "accoustic waves can produce power?". Thanks for your help in this matter.
     
  7. Aug 22, 2003 #6

    LURCH

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    But that would put less O2 in the cylinder. Not really what you want. AFAIK, increasing turbulance to disrupt an airflow causes less volume to arrive where you want it, not more. The "Cold Air Induction System" should do what it says, but the V2 looks like fraud.

    Besides, any product named "V2" that isn't rocket-propelled is flagrant false advertising, IMO.
     
  8. Aug 22, 2003 #7

    Ivan Seeking

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    Unless I am misreading this, I think you are all missing the idea.

    First, cold air is denser than warm air. This means that cold air provides more oxygen per unit volume that warmer air. This is the motivation to access air from outside of the engine compartment.

    Next, when the valve(s) to a piston open and creates a vacuum relative to the ambient pressure, a pressure wave travels along the air path from the valve to the mouth of the intake manifold. This then sets up an accoustic wave in the intake system as the valves cycle open and closed. Any system will have a particular set of harmonics in this regard. Obviously the acoustical harmonics are mostly a fixed element of the topology of the intake system. However, the forcing function for the system - the action of the intake valves and pistons - change in frequency as the engine speed does.

    Therefore, we design the harmonics of the system so that when a valve opens for the intake, we insure that a pressure front is racing through the intake system to the valve to provide the maximum charge of air at just the right time. Classically, the draw back to this is that we limit the range of performance. Highly tuned racing cars run best only at one [or a couple] of points along the RPM [tach] curve. This device claims to address multiple harmonics so that we get better performance over a broader range of engine speeds.
     
  9. Aug 23, 2003 #8
    resonance of gas flow is used in every two stroke engine.
    Goal for inlet is have valves open shortest time possible. If for that moment they can arrange for such sound front that would ram air near valves into the cylinder faster, they are closer to their goal. Constantly keeping high pressure at inlet takes energy.

    If they could arrange for multiple resonant frequencies of gas flow, they made it possible to benefit from the effect at multiple rpms.
    I'd be more worried about what happens between those resonant rpms, is it possible that due to some resonant interaction some moments cylinders are starving? This would heavily increase wear of engine.
     
  10. Aug 23, 2003 #9

    Ivan Seeking

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    I work according to a principle adopted long ago. When designing anything, nothing is free. Any benefit has costs somewhere. This is especially true for automobiles. It is hard to beat a team of factory engineers for the design objective. Their objective is a balance of reliability and performance [and obviously much more]. IMO, you will almost certainly pay a price for improving performance.

    First, the darn thing may just not work as intended.

    Like Wimms pointed out, if you improve performance at one RPM using this device, you are guaranteed of lesser performance at another RPM.

    As an example, improved performance in this case means more oxygen to burn. This means more energy in the combustion of the fuel/air mixture. This means greater forces on the wrist pins, piston rings, and crankshaft bearings. This additional torque then translates throughout the drive train, transmission, and through the drive axel. At each point in the system, we may be exceeding the design criteria for the maximum torque and the other forces and heat to be managed.

    Then we might address the effects on the valves – perhaps greater temperatures are involved that will damage the valve seats. We may also change the exhaust and affect the emission control devices. The list goes on and on. Of course, if you want to go real fast for a short time, put in those cams, headers, and high rise manifolds. Just don’t expect the car to last.
     
  11. Aug 23, 2003 #10
    YOu might just do better simply by 'polishing' your present intake port, as the absence of burring in the manifold helps decrease airflow turbulence, thereby improving efficiency, volume of air.
     
  12. Aug 23, 2003 #11

    LURCH

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    Of course! Turbulance already exists in any air intake. Setting up a controlled accoustic vibration can make that turbulance conform to a predictable and organised pattern. OK, now I'm convinced; this will put more O2 in the mix, increasing horsepower.
     
  13. Aug 23, 2003 #12

    Ivan Seeking

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    Lurch I have definitely run across accepted principles in auto [racing] design that beg for critical review, but this idea of a tuned intake - historically as high rise manifolds - and of a tuned exhaust - headers - are well established. What bothers me about this product is the size and length of the tube. With the typical manifold, we have a very large bore intake about 12 inches long [usually seen sticking out of the hood]. We may then use ducts to direct the intake from the direction of motion - this to increase the intake pressure by using the air pressure caused by the car's forward motion. But this product seeks to direct the air along a rather contorted path. I think your original objection may speak to this aspect of the design. The more I think about this, the less I think this will work as claimed.
     
  14. Aug 24, 2003 #13
    So, in sound wave understanding we seek the knowledge of how pressure waves act in water as to understand how sound waves will act in the atmosphere.

    As a wave in water is a pressure wave, same as a sound wave in air, we observe that the cork that floats in water will, when encountering a (pressure) wave, travel in a small circle, and move in the direction of the wave, only slightly.

    From this we can know that sound waves travelling through the atmosphere will advance the air only slightly.

    Now, a gasoline engine works on a principle of vacuum pressure, to accelerate, and the idling of an engine is due to restrictions on the vacuum pressure as the venturi in the throttle body resticts airflow. Open the venturi, the air rushes into the intake manifold, (Because of the generated vacuum pressure ~18 to 27 ft/lbs) and the engine speeds up.

    In the use of turbo chargers, (and super chargers, sorta) the problem was the differentiation between the shift from a vacuum pressure to a positive pressure, as generated by the turbo, only as the engine gained enough speed, (~ 1800-2000 RPM) in it's exhaust, to generate the pressure required to generate a "positive" pressure.

    This problem was solved using a "butterfly valve" and/or by directly injecting a quantity of raw gasoline into the intake manifold, just as the pressure differentiation was about to occur. This stopped the hesitation that would otherwise cause a short "flat spot" in the engines RPM range, as it shifted from negative (vacuum) pressure to positive pressure.

    Why do I explain this, simple, if the generation of sound waves, in an intake manifold, can actually cause the volume of air, flowing through, to be increased, it will end up as a restriction on the amount of vacuum pressure available, and the engine will accelerate LESS quickly!

    Aside from the simple observatin that sound waves as pressure waves, do little to actually move air. Harmonizing the sound waves might help slightly to increase airflow, but only because it might slightly (and very slightly it would be) reduce the turbulence that is occuring in the intake manifold.
     
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