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#31
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Re: Resinator
LOL Sorry Trevor but they are sections of exhaust pipe that expand to a larger diameter and allow the sound waves to reflect off the walls and cancel out. Hence acoustic resonator.
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#32
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Re: Resinator
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Resonance --- (Directly copied from the dictionary recorded on my Mac hard drive,) (1) Physics --- The reinforcement or prolongation of sound by reflection from a surface as a result of the synchronous vibration of a neighbouring object. (2) Mechanics --- The condition in which an object or system is subjected to an oscillating force having a frequency close to its own natural frequency. Resonant --- (Directly copied from the dictionary recorded on my Mac hard drive,) (3) Technical --- Relating to, or bringing about resonance in a circuit, atom, or other like object. Resonator --- An apparatus that increases the resonance of a sound, esp. a hollow part of a musical instrument. Physics --- A device that displays electrical or mechanical resonance. An exhaust system is most effective and is resonant, or has resonance, at a given frequency of exhaust pulses in accordance with a given engine speed, in accordance with the designed parameters. This resonance of the system can be adjusted by inserting an expansion chamber within the tract. Hence it is often called a resonator. and any application of the word “acoustic”, is particularly misleading. Whatever, it is a fact that it is an expansion chamber and it is the provision of a point of expansion within the exhaust tract which renders it effective within the system. In no way is a "reflection" or sound involved. It is surely evident why many misconstrue fact, by introducing the word “sound” as the description of the medium involved in exhaust pipe performance. The frequencies involved are certainly audible, but as I previously pointed out, “sound” as such is not involved. Sound is most certainly evident upon the exhaust gas reaching the atmosphere and or via mechanical vibrations as I have earlier explained. However sound as such, can not be related to the tuned portion of the exhaust system, having been modified on the way to the atmosphere by the muffler and even at the tip on exit. Within the muffler there is an absorption of or the softening of the gas pulses involved. At no point is there an effective reflection of sound as per (1) above. The operative feature within the exhaust tract, involves mechanics as in ( 2 & 3 ). A moving object in the form of a pulse of gas has momentum/inertia, which constitutes power and this can be utilised by taking advantage of the negative pressure or depression which follows each pulse, i.e. a source of “vacuum” as it were. It could be said that there is a slipstream behind each pulse. Nothing is reflected, backwards, sideways or forwards, there is no reflection of anything from anywhere, at any time. Nothing moves backwards. There is but a continual forwards motion of pulses of gas, starting and ending at atmospheric pressure. In respect of sound, the moving pulses become audible due moving the atmosphere on exit. N.B. The resonator or expansion chamber, does not in any way --- "allow the sound waves to reflect off the walls and cancel out."
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! Last edited by Trevor; 04-23-2010 at 08:07 PM. Reason: Typo. |
#33
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Re: Resinator
Woohoo a cut & paste war
Exhaust resonators use a harmonic balancing principle to modify an automobile's exhaust note. This concept is different from that of a muffler and is largely responsible for the signature sound of many of today's engines. Location and Appearance Resonators resemble small catalytic converters and can usually be found in a car's exhaust pipe just aft of the cats. Muffler vs. Resonator A muffler's primary job is the reduce the decibel level of exhaust noise. A resonator may not necessarily make the exhaust any quieter, since it is designed simply to alter the sound. Sound Waves The region of sound targeted by a resonator is in the higher frequency, since these notes are generally considered unpleasant. Function Whereas a muffler indiscriminately absorbs all sound waves, a resonator uses its internal shape to reflect high-frequency sound back on itself to cancel them out. Effects Resonators usually have little to no effect on exhaust flow, and make most vehicles so equipped sound as if they have a larger and more powerful engine. And: Internal combustion engines usually make a lot of noise while they are running, and this noise can be annoying and exhaustive to your ears, especially when it is heard for a long period of time. Thus, mufflers were created to reduce the noise generated by the exhaust system. Exhaust resonators, meanwhile, further reduce the noise by making sound waves that cancel noises out. Structure 1. A typical automotive exhaust resonator is made of a hollow steel cylindrical tube and is attached to the muffler of an exhaust system. This type of resonator is designed similar to that of an acoustic resonator, which creates an "exhaust note" that gives the exhaust noise a less annoying and more pleasant tone. The sound can be enhanced by means of adjusting the exhaust note. Function 2. Exhaust resonators are usually add-on features in exhaust systems. They are placed together with the mufflers along the exhaust pipe and work primarily to decrease exhaust noise. The exhaust noise passes through the resonating chamber, which in turn tunes the sound to cause destructive interference in order to be canceled out by the opposite sound waves. Availability 3. Being an add-on device, exhaust resonators are provided by aftermarket manufacturers and can be installed on muffler systems of internal combustion systems, such as automobiles and motorcycles. Some vehicles already are equipped with tuned exhaust systems with resonators, thus making the exhaust pipes capable of pulling the combustion products out of the chamber faster with reduced sound. Most aftermarket producers improve the exhaust tuners, as these help the vehicle perform more efficiently. Advantages 4. Exhaust resonators provide a wide array of benefits to vehicle owners. Aside from reducing the noise from the engine's exhaust system, resonators also enhance overall engine performance and smoother driving because more horsepower is yielded without wasting as much fuel. Noise suppression also helps in passing fuel emission tests, as the resonator prevents chassis rattling, an effect that usually leads to contaminated fuel emissions. Support 5. Aside from exhaust resonators, catalytic converters also are part of the overall exhaust system to help the muffler perform its function of reducing exhaust noise. However, instead of canceling out each other's sound waves, their effect is to restrict the sound coming out of the exhaust pipe. Catalytic converters work hand in hand with exhaust resonators in reducing and suppressing engine noise, thus allowing the vehicle to achieve optimum engine and driving performance as compared with using mufflers alone. http://www.modified.com/tech/9912scc...ems/index.html A disadvantage to the straight-through muffler is it is louder than a reverse-flow type of muffler. Usually a straight-though muffler needs a small sub-muffler or a resonator to keep the exhaust quiet. In short, a resonator is really just another small absorption muffler that helps avoid a loud irritating drone at intermediate rpm. This drone is an unfortunate trait many straight-through absorption type mufflers exhibit. The resonator works by using its irregular spacing with the main muffler to help break up droning resonance. Army recruits are trained to break from the march step on bridges to prevent overstressing the bridge due to resonance. The irregular spacing of the resonator works in the same way to prevent droning resonance from forming in the exhaust. A resonator is usually a small, perforated core glass pack placed somewhere between the catalytic converter and the main muffler. Like the main muffler, the longer the resonator, the better for noise reduction. A Walker Magnum Glass-Pack is a good muffler to use as a resonator. Almost all of the pre-made performance exhausts feature resonators. End of my cut & paste from various sources and authors (*cough** exhaust manufactures). Also did you know that Flowmaster Mufflers are an example of true Hemholtz resonance control? And since pretty much all automotive acoustic resonators are based on Hemholtz resonance control.... see where I am going with this? With that in mind I put in an email to Flowmaster's tech center. Since they are pretty much experts in exhaust systems (we all agree on that, yeah?) I will post their reply on what an exhaust resonator is and the exact purpose it serves. http://www.rexresearch.com/helmholtz...resonators.htm Like I said you are confusing an expansion chamber (like those used on 2 stroke's) with an acoustic resonator. But hey maybe all these experts and exhaust MFG's may have it all wrong? LOL Hugs & kisses. Last edited by Bonestock; 04-24-2010 at 12:13 AM. |
#34
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Re: Resinator
You may have limited yourself to cut and pasting, by contrast I have cut and pasted only short extracts from a dictionary, specifically as a means of providing absolute references.
I have back tracked within the thread and have concluded that at this point, inadvertently we have become at cross purposes. We now appear to be arguing as to what is and what is not, an expansion chamber or a resonator, e.g. what is a bucket and what is a pail. An expansion chamber can be a resonator if sited within an exhaust system, for the purpose of modifying acoustics. A resonator is by its very physical nature is an expansion chamber. We are talking about the same thing, which is fact designated one way or the other, as a result of the specific purpose for which it is installed. I have correctly described an expansion chamber or resonator as this applies to the performance of an exhaust system. You have correctly described a resonator or expansion chamber as it applies to the acoustics of an exhaust system. Any reader not being fully aware of the details involving the application of an expansion chamber or a resonator, should by now have become well informed. Hopefully all has not been time wasted. In any event the exchange of ideas has been interesting and being free of antagonism, has been enjoyable.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#35
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Re: Resinator
You made your case & I countered with mine. Later I posted some information from various sources as evidence to counter your statements on post 32. So I dont know why you would think that I have "limit" myself to cut & pasting.
As I stated way back in post #2, They are typically there only to reduce the exhaust db level or to tailor the exhaust note. Every bit of info I had to verify (even if it was to confirm what I already knew) confirmed the above statement is correct. And you are right, I am glad we could discuss the matter without the bickering or insults that have become way too common on this site. Last edited by Bonestock; 04-24-2010 at 10:01 AM. |
#36
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Re: Resinator
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Cheers, Trevor.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#37
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Re: Resinator
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I suppose in the true definition of sound, Trevor is correct in inserting that there is no sound until the gases come out into the atmosphere and are detected by an ear. That is why when a tree falls in a forest, with no ears around to hear it, it is true to say that it didn't make a sound when it fell. Keith |
#38
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Re: Resinator
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This is right, the gas plug that is released when the exhaust valve opens, has a pressure of about 65psi. This gas pressure has to push the gas in the pipe in front of it. So the gas plug has a pressure front. As this plug travels away from the cylinder, it pulls a low pressure behind it that is maintained till the inlet valve opens, to start the inlet gas moving into the cylinder. It is equally important to reduce this gas plug pressure in the pipe as soon as its usefulness is over, we can’t wait till it reaches the end of the exhaust pipe, so we fit the Resonate chamber where the gas plug can expand to reduce the gas pressure, just like it reached the end of the pipe. This is the gas inertia being used, to increase the Volume Efficiency of the engine, as you say. The US have lagged behind the others by producing larger capacity engines that produce good torque at low engine speeds. So they have not had used the resonate theory like the Japanese or Europeans, to produce the torque at higher engine speeds. This has been used on engines that produce the Torque under 4500rpm. It loses it usefulness after that speed, as the gas plug only has a speed of about 300ft per sec. So as the engine revs faster, the low pressure it the cylinder, cannot be maintained till the inlet valve opens. It is occurring earlier, when the piston in rising on the exhaust stroke, so we lose the benefit of its help in increasing the VE. The SVX uses this gas plug to lower the cylinder pressure as the piston is reaching its maximum speed at about 80* ABDC. Reducing the pressure here reduces the power loss, by the piston having to push against a pressure. To get the low pressure in the cylinder that we need to start the inlet flow, we use sound waves (and just for Trevor) or acoustic waves. When the exhaust valve opens besides the gas pressure, a positive sound wave is released to travel down the pipe, at about 1600 ft per sec. When this reaches the end of the pipe, it expands into the atmosphere, to be replaced with a negative wave that travels back up the pipe, to reach the cylinder as the inlet valve opens. It then travels up the inlet tract to start the inlet sequence. As the length of the pipe affects when the negative pressure will arrive back at the cylinder, we can’t just use the end of the pipe so we use the resonator to do the same job for the sound waves, as it does for the gas plug, imitate the end of the pipe. So the SVX design uses the inertia theory to reduce pumping losses and the resonate theory to raise the VE. Best of both worlds. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#39
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Re: Resinator
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I am quite sure that Sean486 was able to glean the information he required, from the several posts which followed his query, e.g. #25, #27 & 32. If I were not, I would have as a matter of courtesy, answered him directly. Each of your posts directed my way has included nasty sarcasm and constitutes baiting. As I have previously pointed out, you repeatedly confirm the limit of your intelligence. But worse, you now insult others, by implying that they join you in being dumb. If a tree falls in the forest, it is absolutely true that there is most certainly a sound, regardless of whether it is, or is not, detected. Probably the sound of silence. Likewise your nastiness smells, whether or not the smell is detected by the monitors. It will be an arduous exercise but even so, please think on it.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#40
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Re: Resinator
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I have to agree with Kwren here, Quote:
Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#41
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Re: Resinator
Harvey, reference your post #38.
You commenced your own crap game with your abusive post #26. You now excrete more of the same and continue with a continued “litany of lies” in the form of childishly worded text, devoid of sense and diction. I have correctly explained the principle involved in an exhaust system. You now make a series of wrong statements all directly misinforming readers. Quote:
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The evidence presented is completely contradictory and is self conflicting. It is stated that the system is used at higher engine speeds, but then it subsequently stated it is not suitable when 4,500 RPM is exceeded. Quote:
The speed of the gas plug is in no way limited and depends only upon, the cross section of the pipe and length before the first point of expansion; engine speed, compression ratio, and valve overlap. The principle was most widely used in the past, in engines providing power at relatively high RPM, e.g. racing engines. The limiting factor has been the width of the power band over which the action involved can be made effective. In later years greater understanding has enabled improvements, so that the system is able to be used in common road cars, with the exhaust and intake being treated as a whole. Quote:
N.B. In order to use the expression “sound waves” in this context, it is absolutely necessary to explain exactly how waves of sound, rather than pulses of gas have inertia. The explanation will be awaited by many and will provoke considerable interest. Quote:
When the inlet valve opens, a low pressure area is in existence behind the pulse/plug of gas which at that point is leaving the exhaust port and thus has inertia. That pulse in turn is assisted by the inertia of the preceding pulse, there being several travelling in unison. Quote:
For absolute confirmation in respect of my statements, as well as a simple explanations in layman’s terms, refer as below and in paricular take note of, “The Exhauxt Pulse,” as well as, “Resonators.” --- http://www.nsxprime.com/FAQ/Miscella...austtheory.htm Also here. --- http://www.sideways-technologies.co....?m-1201221799/
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#42
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Re: Resinator
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#43
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Re: Resinator
can I jump in the cat fight?!?!!?
I worked at a custom exhaust shop for years. The lack of resonator WILL not affect the driveability of your car. it is there strictly for exhaust tone. The ONLY way removing stuff from your exhaust would cause that drastic of a change would be if you took off all cats and muffler and drove it completely STRAIGHT pipe. The lack of backpressure would make it drive like a fat girl being pushed in a wheel barrel. |
#44
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Re: Resinator
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I raced cars for years. I can assure you that based on lap times recorded when racing, running a straight exhaust on a standard production car, does not "make it drive like a fat girl being pushed in a wheel barrel." The lack of back pressure is of considerable advantage.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
#45
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Re: Resinator
yer not makin any sense...
You need a space where a space once was.. If there was a resonator there once before, there should be one there when you build a new exhaust as well.
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1992 Pearl White LS-L "Ruslana" #4946 - 180k on body, 95k on engine. Mods: ECU bead crush, 15 min mod, 20 min mod, drilled/slotted rotors & Axxis ceramic brakes, SS lines, 17" Evoke F1 wheels, XS-HF137 Sony Xplod speakers, 6000k HID's (lows & fogs), resistor mod, 1½" Sleek Spoiler mod, custom exhaust by svxfiles, '02 WRX aluminum racing radiator by svxfiles, Summit Racing 400# x 300# springs w/ Koni's by svxfiles, ClassGlass fiberglass hood /w scoop, Nevin's rear sway bar, '97 grille, phenolic spacers, custom LED interior lighting, custom paint. †"War doesn't determine who is right, only who is left"† Work to be done: Tinted windows, clear/LED tail lights, tailbar mod, "Power Mode" mod, Supertone horns, clear corners & headlight lenses, 2 pc splitters or custom bumper, Alcyone side skirts, TruSpeed Stage III SVX Intake, Hydra, 4.44 tranny swap, JDM auto folding side mirrors, engine rebuild, super charger, STi seats, bone leather interior /w SVX emblem, dash overhaul, SVX decals, paint (stock color). Total cost?: 22k At least it's going down..
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