borla exhaust
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I have one on my RCSB also. Had to remodel the front portion of the pipes as they do not offer a kit for the short wheelbase, but the rest of it popped into place with minimal adjustment (unlike Magnaflow).
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Is there any drone?
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Yes there was at 1700 rpm highway cruise, but I put a single 26" long tube into the passenger side tailpipe in a "T" configuration and it stopped it completely. This tube is a quarter wave "Helmholtz resonator" and it is capped off on the opposite end. See some pics in my gallery. It is easy to make one yourself, and they work great to stop drone. :tu:
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You must firstly know the frequency of the drone. I guessed around 125 Hz by ear. Secondly you must calculate the wavelength of the sound using the formula:
wavelength = speed of sound / frequency.
Using 1100 feet/second as an approximate speed of sound, plug the numbers into the formula.
wavelength = 1100 / 125 = 8.8 feet.
The length of the tube should be one quarter wavelength or 2.2 feet = 26 inches.
The exhaust sound approaches the "T". Some of it turns and heads into the tube. It travels the length of the tube, reflects off the solid wall at the end, then returns back to the "T". Because the sound has travelled two quarter wavelengths in total inside the tube, it gets reversed in polarity just like if you swapped the positive and negative wires in a speaker. Once this shifted sound combines with the original sound at the "T", they cancel each other. :nod:
wavelength = speed of sound / frequency.
Using 1100 feet/second as an approximate speed of sound, plug the numbers into the formula.
wavelength = 1100 / 125 = 8.8 feet.
The length of the tube should be one quarter wavelength or 2.2 feet = 26 inches.
The exhaust sound approaches the "T". Some of it turns and heads into the tube. It travels the length of the tube, reflects off the solid wall at the end, then returns back to the "T". Because the sound has travelled two quarter wavelengths in total inside the tube, it gets reversed in polarity just like if you swapped the positive and negative wires in a speaker. Once this shifted sound combines with the original sound at the "T", they cancel each other. :nod:
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okay, now we're getting the science! I appreciate that! Do you have any more pictures?
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Not immediately brother, and in fact those two pics were from the MagnaDrone system, not the Borla. The MagnaDrone reaaalllly needed the Helmholtz tubes. :lol: The Borla was about half as bad but still enough that it bugged me on long highway trips, so when I ripped off the MagnaDrone system for the Borla I decided to put the same resonators on the Borla.
By plugging off each of the two tailpipes in sequence I noticed the bulk of the drone was caused by the passenger's side tailpipe. Therefore I only installed a single Helmholtz tube in the passenger's side tailpipe, in between the spare tire and axle. It only took half an hour to cut the hole and clamp up the tube as I had everything already fabbed from the MagnaDrones.
By plugging off each of the two tailpipes in sequence I noticed the bulk of the drone was caused by the passenger's side tailpipe. Therefore I only installed a single Helmholtz tube in the passenger's side tailpipe, in between the spare tire and axle. It only took half an hour to cut the hole and clamp up the tube as I had everything already fabbed from the MagnaDrones.
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