Amuse Helmholtz resonator dimensions
08-15-2011, 04:55 PM
#11
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Great info nlink! Clever and proactive way of dealing with your drone issues. I wonder if ripping off ASM with the placement of their Helmholtz near the back of the exhaust would work too?
08-15-2011, 05:39 PM
#12
I will likely lengthen the resonator and report back. Then, at least we will know how length affects the exhaust note and at which rpms. It would be nice to say that 1" longer = up 700 rpm etc.
I will report back within a few weeks.
08-15-2011, 07:03 PM
#13
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Originally Posted by mister x' timestamp='1313456104' post='20881057
Great info nlink! Clever and proactive way of dealing with your drone issues. I wonder if ripping off ASM with the placement of their Helmholtz near the back of the exhaust would work too?
I will likely lengthen the resonator and report back. Then, at least we will know how length affects the exhaust note and at which rpms. It would be nice to say that 1" longer = up 700 rpm etc.
I will report back within a few weeks.
08-16-2011, 02:57 PM
#14
OK, so I may not be adjusting the length of the resonator.
Here is a summary of where we stand:
A) With the Greddy Ti-C and silencer = not much louder than OEM, but drone city. Long drives are semi-uncomfortable due to the pressure wave inside the car. You have to keep slight throttle to keep the car out of drone, but this is not always possible. Not loud outside the car. Actually, a very nice sound outside the car.
B) With the Greddy Ti-C and no silencer = much much louder than OEM (inside the car). Seemingly too loud to drive around the neighborhood from the inside, but not horribly loud outside if easy on the gas pedal, but people will hear that you have an exhaust and know that you are coming. Under high throttle settings there is a bow wave of pressure that makes it feel like your ears will explode due to the pressure. I did a few autocross runs like this and felt my ears deafening after a 55 second run. But, it sounds outstanding outside the car and is less loud outside than inside. The pressure is what hurts.
C) With the Helmholtz resonator and Greddy Ti-C without the silencer it is like (A) above inasmuch as you can drive long distances, but there is still a drone at certain rpms. If you can keep the car between 2500 and 2800 rpm, however, there is almost no drone, and the exhaust is quiet. This is the frequency attenuated due to the Helmholtz. In addition, the very low range of idle to 1500 rpm or so is much improved with the Helmholtz. It does not require the soft pedal from idle. The in-cabin is much more comfortable, and under high throttle there is no pressure wave making your ears feel like they will explode. I could drive daily like this, but wanted more.
D) With the Helmholtz resonator and Greddy Ti-C with silencer the car sounds completely stock and had 0% drone. I only put the silencer back in because I was going to get my emmissions check today and didn't want any extra noise, and I was surprised at how quiet this thing was. I basically lost 30 lbs, and have an OEM sounding exhaust with no drone. This is what I wanted, but without the silencer's restrictions.
Result:
I may play with the Helmholtz resonator in the future, but will be attending Nationals and driving a total of about 35 hours in the car. It would have been a little annoying with the Helmholtz but no silencer, but doable. But with the silencer in, I have transformed the Greddy Ti-C into a car in which I will be able to enjoy the radio.
Another perspective:
Greddy no silencer: Radio at about 32 to hear with windows up
Greddy silencer: Radio at about 22 to hear with windows up
Greddy no silencer + Helmholtz mod: Radio at about 22 to hear with windows up
Greddy with silencer + Helmholtz mod: Radio at 12 is where I keep it with the windows up, and sometimes as low as 10.
Any further mods would be to raise the attenuation frequency to 4000 rpm so that I could have a quiet car without needing the silencer. This would be optimal since there would always be 100% power, and no fussing with a silencer for longer trips. I drove right in front of a police officer today with the silencer in, and under power, and not as much as a glance at my car.
Here is a summary of where we stand:
A) With the Greddy Ti-C and silencer = not much louder than OEM, but drone city. Long drives are semi-uncomfortable due to the pressure wave inside the car. You have to keep slight throttle to keep the car out of drone, but this is not always possible. Not loud outside the car. Actually, a very nice sound outside the car.
B) With the Greddy Ti-C and no silencer = much much louder than OEM (inside the car). Seemingly too loud to drive around the neighborhood from the inside, but not horribly loud outside if easy on the gas pedal, but people will hear that you have an exhaust and know that you are coming. Under high throttle settings there is a bow wave of pressure that makes it feel like your ears will explode due to the pressure. I did a few autocross runs like this and felt my ears deafening after a 55 second run. But, it sounds outstanding outside the car and is less loud outside than inside. The pressure is what hurts.
C) With the Helmholtz resonator and Greddy Ti-C without the silencer it is like (A) above inasmuch as you can drive long distances, but there is still a drone at certain rpms. If you can keep the car between 2500 and 2800 rpm, however, there is almost no drone, and the exhaust is quiet. This is the frequency attenuated due to the Helmholtz. In addition, the very low range of idle to 1500 rpm or so is much improved with the Helmholtz. It does not require the soft pedal from idle. The in-cabin is much more comfortable, and under high throttle there is no pressure wave making your ears feel like they will explode. I could drive daily like this, but wanted more.
D) With the Helmholtz resonator and Greddy Ti-C with silencer the car sounds completely stock and had 0% drone. I only put the silencer back in because I was going to get my emmissions check today and didn't want any extra noise, and I was surprised at how quiet this thing was. I basically lost 30 lbs, and have an OEM sounding exhaust with no drone. This is what I wanted, but without the silencer's restrictions.
Result:
I may play with the Helmholtz resonator in the future, but will be attending Nationals and driving a total of about 35 hours in the car. It would have been a little annoying with the Helmholtz but no silencer, but doable. But with the silencer in, I have transformed the Greddy Ti-C into a car in which I will be able to enjoy the radio.
Another perspective:
Greddy no silencer: Radio at about 32 to hear with windows up
Greddy silencer: Radio at about 22 to hear with windows up
Greddy no silencer + Helmholtz mod: Radio at about 22 to hear with windows up
Greddy with silencer + Helmholtz mod: Radio at 12 is where I keep it with the windows up, and sometimes as low as 10.
Any further mods would be to raise the attenuation frequency to 4000 rpm so that I could have a quiet car without needing the silencer. This would be optimal since there would always be 100% power, and no fussing with a silencer for longer trips. I drove right in front of a police officer today with the silencer in, and under power, and not as much as a glance at my car.
08-16-2011, 08:58 PM
#16
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I've got an idea...by using an exhaust sleeve you can have a cheap and effective adjustable helmholtz resonator! 
For example, like the Amuse one using 55mm for their helmholtz resonator diameter. you can get a 55mm exhaust sleeve, play with the length until you think its optimal.
For example, like the Amuse one using 55mm for their helmholtz resonator diameter. you can get a 55mm exhaust sleeve, play with the length until you think its optimal.
08-17-2011, 02:16 AM
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08-18-2011, 10:51 PM
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I just found out ASM S-Special 70mm Single exhaust also have a helmholtz resonator on their face-lifted version.
Does anyone know how the length/diameter of the helmholtz resonator on the ASM exhaust?
https://www.s2ki.com/s2000/topic/779...ngle-re-newed/
Does anyone know how the length/diameter of the helmholtz resonator on the ASM exhaust?
https://www.s2ki.com/s2000/topic/779...ngle-re-newed/
08-19-2011, 02:45 AM
#20
Etang,
Good post. That reminds me to tell you to make sure you weld the resonator on level or slightly downwards. There is minimal space between the resonator and the underside of the car. I was fortunate in that the shop welded it exactly to my drawn specs on the pipe. There is about 1/8" clearance, and if not adjusted properly will make noise under hard maneuvering. I noticed this at times during an autocross. Ba quick change to the hangars and it was gone. There is an indentation on the underside where the resonator fits (on the AP2 at least).
Good luck.
Good post. That reminds me to tell you to make sure you weld the resonator on level or slightly downwards. There is minimal space between the resonator and the underside of the car. I was fortunate in that the shop welded it exactly to my drawn specs on the pipe. There is about 1/8" clearance, and if not adjusted properly will make noise under hard maneuvering. I noticed this at times during an autocross. Ba quick change to the hangars and it was gone. There is an indentation on the underside where the resonator fits (on the AP2 at least).
Good luck.