Want quad tips

[Foggsy]

Pirate you really know your stuff mate. Always a pleasure reading your posts. Those pics are great.
It looks to me like the standard VE SS intake pipe from airbox to throttle body has at least one Helmholtz chamber coming off it??? Its unbelieveable they go to such lengths to wreck/quieten right down an induction note.... One of the best aspects of my car's driving experience is the massive induction roar I get out of my Duspeed OTR - it gives me a chubb every time LOL

Yeah cinchy, works a treat too. There are a few posts, threads and comments I've done over a few years here, lookup keyword helmholtz.
You could do it yourself I suppose if you can weld... lets you have a performance exhaust note (quiet or loud) without the boom and drone in the cabin.
First you find the offending frequency, then work out pipe spec, then fit it. Voila!!

 

[mtw002]

Yeah cinchy, works a treat too. There are a few posts, threads and comments I've done over a few years here, lookup keyword helmholtz.
You could do it yourself I suppose if you can weld... lets you have a performance exhaust note (quiet or loud) without the boom and drone in the cabin.
First you find the offending frequency, then work out pipe spec, then fit it. Voila!!

Awesome thanks heaps mate!
Iv got a good mate who is a welder so I'm sure it shouldn't be to hard.,,


Can you just check my thinking then;
If the ss AFM mufflers remove the drone, then could I not just use the stats from that one?
Like the one I saw pictured before?


Matt

 

[PIR4TE]

If the ss AFM mufflers remove the drone, then could I not just use the stats from that one?
Like the one I saw pictured before?

Possibly, worth a try of course, but that tuned length and diameter is for a different engine and exhaust combo, which had a drone spike at 1800rpm (+/-300), which was identified at 116hz.
To identify your sound issue you need to use an audio spectrum analyser, many are available as apps for your phone.
Be aware that with most phones you need to calibrate the mic and skew the weighting to C to get reliable results.

 

[mtw002]

So once I have the offending frequency, how do I convert that into a volume- or diameter x length equation?


Matt

 

[PIR4TE]

1100 feet/second (roughly the speed of sound outside the exhaust pipe) divided by the target frequency you're trying to eliminate (in cycles/second) gives a full wavelength in feet per cycle.
Divide this number by 4 to get a quarter wavelength (a much more convenient length to work with).
Finally, multiply this wavelength by 12 to get the chamber length in inches.
Use an aluminised or stainless pipe of this length x (a diameter 1/4" less than your exhaust axle back), then at one end make a duck mouth to weld onto the exhaust and the other end of the pipe is capped off.
Locate the attachment point somewhere convenient like mine, cut a hole to suit the duck mouth and weld it on.
There you have a Helmholtz chamber that takes the annoying frequency and bounces it back into the flow 180 degrees out of phase, knocking it out.
The results: no more drone.

 

[mtw002]

Your a hero mate, thanks heaps.


Matt

 

[bosmonaut]

i've got a stock SS system on my 6 now with the Y pipes and the quad tips at the back. no drone and looks a heap better than the single tips

 

[Tasmaniak]

1100 feet/second (roughly the speed of sound outside the exhaust pipe) divided by the target frequency you're trying to eliminate (in cycles/second) gives a full wavelength in feet per cycle.
Divide this number by 4 to get a quarter wavelength (a much more convenient length to work with).
Finally, multiply this wavelength by 12 to get the chamber length in inches.
Use an aluminised or stainless pipe of this length x (a diameter 1/4" less than your exhaust axle back), then at one end make a duck mouth to weld onto the exhaust and the other end of the pipe is capped off.
Locate the attachment point somewhere convenient like mine, cut a hole to suit the duck mouth and weld it on.
There you have a Helmholtz chamber that takes the annoying frequency and bounces it back into the flow 180 degrees out of phase, knocking it out.
The results: no more drone.

This apply to my wife?

 

[PIR4TE]

This apply to my wife?

if you can convince her to keep the goggles on then yes, you can use a J-Pipe to muffle your missus too.
When the drone gets annoying simply insert the flange in the duck mouth. Viola: